DES method extraction and solvent removal method for Japanese ardisia herb polyphenol compounds

Abstract

The invention discloses a DES extraction and solvent removal method for ardisia japonica polyphenol compounds, and belongs to the technical field of natural product extraction and separation. The method comprises the following steps: mixing herba ardisiae japonicae powder with a deep-eutectic solvent, and heating and ultrasonically extracting to obtain an extracting solution; adsorbing polyphenol compounds in the extracting solution by using macroporous resin; after filtering, carrying out desorption on the macroporous resin adsorbed with polyphenol by using ethanol; and finally, concentrating the eluent obtained by desorption to obtain the Japanese ardisia herb polyphenol clear paste. According to the method, the problem that the deep eutectic solvent is difficult to remove after efficient extraction is solved, DES extraction is combined with a macroporous resin adsorption-desorption technology, and improved and optimized shaking table operation is combined, so that the purposes of efficiently extracting the Japanese ardisia herb polyphenol and effectively removing the DES solvent under mild conditions are achieved, and the method is suitable for industrial production. The damage of factors such as high temperature to the heat-sensitive polyphenol is avoided, the technological process is simple and easy to operate, and the used macroporous resin can be regenerated and used, so that the method is green and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of natural product extraction and separation technology, and in particular to a DES method for the extraction and solvent removal of polyphenolic compounds from dwarf tea. Background Technology

[0002] Lowland tea is a traditional Chinese medicine. Modern research shows that it is rich in various polyphenolic compounds, such as gallic acid, protocatechuic acid, chlorogenic acid, and epicatechin. These polyphenolic components have various pharmacological activities, including antioxidant, anti-inflammatory, and anti-tumor effects. Therefore, the efficient and green extraction of these active ingredients from lowland tea is of great significance for the modernization and high-value utilization of traditional Chinese medicine.

[0003] In the field of natural product extraction, with the deepening of the green chemistry concept, eutectic solvents, as a new type of green solvent, are gradually being applied to the extraction of active ingredients from plants due to their advantages such as low toxicity, biodegradability, low vapor pressure, and ease of design and synthesis. Desiccant (DES) can effectively disrupt plant cell walls through interactions such as hydrogen bonding, exhibiting good solubility for polyphenolic compounds, thus often achieving higher extraction rates than traditional organic solvents.

[0004] However, after successfully extracting the target components, the separation and recovery of DES itself becomes a new technical challenge. DES typically has a high boiling point and viscosity, making its separation from the target product difficult. Currently, common methods for DES removal or product separation mainly include vacuum distillation, antisolvent precipitation, and membrane separation. Vacuum distillation requires heating, resulting in high energy consumption. Furthermore, for some heat-sensitive polyphenolic compounds in dwarf tea, prolonged heating may lead to their decomposition or inactivation, affecting the quality and activity of the final product. Antisolvent precipitation usually requires adding large amounts of solvents such as water or ethanol to the DES extract. While this can precipitate the target product, it significantly increases the burden and cost of subsequent solvent recovery and may introduce new impurities. Incomplete precipitation can also lead to product loss. Membrane separation is prone to severe membrane fouling and blockage due to the high viscosity of DES, resulting in decreased separation efficiency, shortened membrane module lifespan, and increased operating costs.

[0005] Therefore, in the process of extracting polyphenols from dwarf tea using DES, there is an urgent need for a method that can effectively separate DES and the target polyphenols under mild conditions. This method should maximize the preservation of polyphenol activity while avoiding the introduction of new solvents or high energy consumption. The process should be as simple as possible to have the potential for industrial application. Existing technologies all have certain limitations in these aspects, failing to adequately balance the relationship between extraction efficiency, solvent separation effect, product protection, and process economy. Summary of the Invention

[0006] This invention overcomes the problem of difficulty in removing eutectic solvents after efficient extraction in existing technologies, and provides a DES method for extracting polyphenols from dwarf tea and removing solvents. By combining DES extraction with macroporous resin adsorption-desorption technology, the invention achieves efficient extraction of dwarf tea polyphenols under mild conditions and effective removal of DES solvent, avoiding the damage of heat-sensitive polyphenols caused by high temperatures and other factors. The process is simple, and the macroporous resin is recyclable, meeting the requirements of green environmental protection.

[0007] To achieve the above objectives, the present invention adopts the following solution: A DES method for extracting polyphenolic compounds from dwarf tea and removing the solvent includes the following steps: S1: Crush and sieve the sliced ​​dwarf tea, weigh the powder, add a low eutectic solvent, and extract by ultrasonication for 30 to 60 minutes to obtain the low eutectic extract of dwarf tea. S2: Weigh 5 to 15 grams of pretreated and activated macroporous resin, add 20 to 50 ml of the prepared low-melting extract of *Tea dwarf tea*, mix well, and place in a shaker. Run the shaker at 80 to 200 rpm for 8 to 16 hours to allow the macroporous resin to adsorb polyphenolic compounds. S3: After adsorption, filter to separate the macroporous resin, rinse the macroporous resin with ethanol, collect the eluent and put it into a shaker. Run the shaker at 80 to 200 rpm for 8 to 16 hours to desorb the polyphenolic compounds on the macroporous resin. S4: Collect the eluent obtained from desorption and transfer it to an evaporating dish. Evaporate until there is no alcohol odor to complete the concentration of the polyphenol extract and obtain a clear extract of dwarf tea polyphenols.

[0008] Preferably, in step S2, the shaker operation employs a staged controlled dynamic adsorption method, specifically including: First, the mixed low-melting extract of *Tea dwarf tea* was subjected to low-speed adsorption at 80 to 100 rpm for 4 to 6 hours. Then, the speed was increased to 150 to 180 rpm for medium-speed adsorption for 2 to 4 hours. Finally, high-speed adsorption was carried out at 180 to 200 rpm for 2 to 6 hours. After each rotation speed stage, samples were taken to test the polyphenol adsorption rate. Based on the test results, it was determined whether to adjust the subsequent rotation speed and time ratio. Constant temperature conditions were maintained throughout the adsorption process, with the temperature controlled within the range of 25 degrees Celsius to 35 degrees Celsius. The oscillation amplitude of the shaker was adjusted by real-time monitoring of the sedimentation state of the macroporous resin.

[0009] As a preferred option, the specific steps for determining whether to adjust the subsequent speed and time ratio based on the test results include: After each rotation speed stage, a small amount of adsorbent sample was taken and the concentration of six polyphenolic compounds (gallic acid, protocatechuic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, and epicatechin gallate) was determined by high performance liquid chromatography. The adsorption rate of that rotation speed stage was calculated. If the adsorption rate of any major polyphenolic compound was less than 85%, the rotation speed was increased by 10 to 20 rpm and the adsorption time was extended by 1 to 2 hours in the next rotation speed stage. If the adsorption rate of all major polyphenolic compounds reached more than 90%, the original rotation speed and time ratio were maintained and the next rotation speed stage was entered. The specific operations for adjusting the oscillation amplitude of the shaker by real-time monitoring of the sedimentation state of the macroporous resin include: Every 30 minutes, pause the shaker and let it stand for 2 minutes. Observe the ratio of the sedimentation volume of the resin at the bottom of the container to the initial volume. When the ratio exceeds 40%, increase the swing amplitude of the shaker to 1.2 to 1.3 times the original amplitude. When the ratio is below 20%, restore the swing amplitude to the standard amplitude. After each adjustment, the shaker should be run stably for 1 hour before the next monitoring.

[0010] Preferably, in step S3, before the step of desorbing polyphenolic compounds, a multi-stage impurity removal step is further included, which includes: The macroporous resin after adsorption was initially rinsed with a buffer solution with a pH of 6.5 to 7.5 at a flow rate of 2 to 5 mL / min, and the rinsing continued until the absorbance of the effluent stabilized below 0.05. Then, a second rinse was performed with pure water at a flow rate of 5 to 10 mL / min until the conductivity of the effluent dropped below 10 μS / cm. During each rinse, a segmented collection method was used to collect the effluent from different time periods and detect the content of polyphenolic compounds by high performance liquid chromatography. When the target polyphenolic compounds were detected in the effluent, the rinsing was stopped immediately and the desorption step was initiated. At the same time, the temperature of the macroporous resin bed was controlled to be stable within the range of 20 to 25 degrees Celsius throughout the entire impurity removal process.

[0011] Preferably, in step S4, a segmented temperature-controlled concentration process is used to concentrate the polyphenol extract, specifically including: The collected eluent was first concentrated to one-third to one-half of its original volume at 45°C to 55°C. Then the temperature was lowered to 35°C to 45°C and the concentration was continued until the solution became viscous. Finally, the final concentration to constant weight was completed at 25°C to 35°C and a vacuum of -0.06 MPa to -0.08 MPa. During each concentration stage, the residual ethanol content in the eluent is monitored in real time using near-infrared spectroscopy. When the residual ethanol content is detected to be below 0.5%, the system automatically switches to the next concentration stage. Simultaneously, samples of the concentrated material are taken during each stage transition, and the content changes of six major polyphenolic compounds—gallic acid, protocatechuic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, and epicatechin gallate—are detected by high-performance liquid chromatography. Based on the detection results, the concentration temperature and time parameters for the next stage are dynamically adjusted.

[0012] As a preferred method, the specific procedure for detecting changes in the content of six polyphenolic compounds using high-performance liquid chromatography is as follows: The contents of six polyphenolic compounds in no less than 30 samples with known concentrations were accurately determined by high performance liquid chromatography. These samples were used as a standard dataset. Correlation analysis was performed between the standard dataset and the near-infrared spectral data of the corresponding samples in the wavelength range of 1200 nm to 2400 nm. A quantitative calibration model for the six polyphenolic compounds was established using partial least squares regression algorithm. During the concentration process, the near-infrared spectrum of the concentrated material is acquired in real time using a fiber optic probe. The spectral data is input into the quantitative calibration model, and the predicted concentration values ​​of six polyphenolic compounds are output simultaneously. When the predicted concentration value of any polyphenolic compound decreases by more than 3% compared to the previous detection time point, the concentration parameters are adjusted, and the current concentration temperature is reduced by 3 to 5 degrees Celsius. After each concentration stage is completed, actual samples are taken for high-performance liquid chromatography (HPLC) verification. If the relative error between the predicted value and the measured value exceeds 8%, the quantitative calibration model is incrementally updated using the new data.

[0013] Preferably, the pretreatment activation of the macroporous resin includes sequential soaking and activation with alcohol, acid and alkali, with rinsing with pure water in between.

[0014] Preferably, the eutectic solvent used in step S1 is an amino acid-organic acid eutectic solvent, the preparation process of which includes: mixing amino acids and organic acids in a predetermined ratio, heating and stirring under water bath conditions until a homogeneous liquid is formed, and then refrigerating at 4°C for later use.

[0015] Preferably, in step S3, the volume concentration of ethanol used for desorption is 30% to 80%.

[0016] Preferably, the method further includes step S5 for regenerating the macroporous resin: rinsing the desorbed macroporous resin with anhydrous ethanol until the filtrate is colorless, then rinsing with pure water until there is no alcohol odor, and storing it for later use.

[0017] The present invention includes at least the following beneficial effects: (1) By combining eutectic solvent (DES) with ultrasonic-assisted extraction, the dissolution efficiency of polyphenolic compounds in dwarf tea is significantly improved; by using macroporous resin for adsorption and desorption, the target polyphenols are effectively separated from DES. The process is carried out at room temperature or lower temperature, which effectively avoids the damage of heat-sensitive polyphenolic compounds to high temperature and ensures the bioactivity of the final product; (2) By controlling the shaking speed in stages and making dynamic adjustments based on real-time adsorption rate monitoring, not only is the adsorption kinetics optimized and the adsorption rate of high molecular weight or difficult-to-adsorb polyphenols improved, but also the oscillation amplitude is adjusted by monitoring the resin settling state, which improves the fluid distribution of the resin bed and achieves more uniform adsorption; (3) Staged dynamic adsorption and real-time control The mechanism, by avoiding continuous high-speed operation and optimizing the fluid dynamic environment, significantly reduces the mechanical friction and breakage between resin particles, reduces the loss of resin materials, and thus reduces the loss of target polyphenols caused by resin fragment loss, improving the economy and sustainability of the process; (4) By carrying out multi-stage impurity removal processes before desorption, the pigments, sugars and other impurities adsorbed on the resin are effectively washed away; in the concentration stage, segmented temperature control combined with real-time monitoring by near-infrared spectroscopy is adopted to accurately control process parameters, significantly reduce impurity content, and improve the purity of the final obtained dwarf tea polyphenol extract; (5) The DES solvent used itself has green and environmentally friendly characteristics, and the macroporous resin can be reused after standardized pretreatment and regeneration, reducing raw material consumption and waste generation. The entire process avoids the use of a large amount of harmful organic solvents and high-temperature and high-energy-consumption operation, which is in line with the principles of green chemistry and has good prospects for industrial application. Attached Figure Description

[0018] Figure 1 A flowchart illustrating the principle of the method provided by this invention; Figure 2 Example of HPLC chromatogram for traditional methanol extraction of polyphenols from dwarf tea; Figure 3 An example of an HPLC chromatogram for the DES extraction of polyphenols from *Tea gloriosa* provided by this invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0020] like Figure 1 As shown, the DES method for extracting polyphenolic compounds from *Tea dwarf tea* and removing the solvent provided by this invention includes the following steps: S1: Crush and sieve the dwarf tea slices, weigh the medicinal powder, add a eutectic solvent, and extract by ultrasonication for 30 to 60 minutes to obtain the dwarf tea eutectic extract.

[0021] *Dwarf tea* is a common traditional Chinese medicine, rich in various polyphenolic active ingredients, such as gallic acid, protocatechuic acid, and chlorogenic acid, which are key components for its pharmacological effects. During processing, the *Dwarf tea* slices are first pulverized into a powder to increase the surface area and promote solvent penetration. The powder particle size is controlled by sieving, for example, using a 40-60 mesh sieve to ensure uniform particle size. The weight of the powder is carefully controlled, for example, 5 to 20 grams per batch, to ensure repeatability and consistency of extraction. Eutectic solvent (DES) is a green solvent system formed by mixing hydrogen bond donors (such as organic acids) and hydrogen bond acceptors (such as amino acids) in a specific ratio. It is liquid at room temperature or under heating conditions and has advantages such as low toxicity, biodegradability, and high solubility. There are many conventional methods for preparing DES. One method involves mixing amino acids with organic acids (such as choline chloride and glycerol) at a molar ratio of 1:2 to 1:4, and stirring in a water bath (e.g., 50°C to 70°C) until a homogeneous, transparent liquid is formed. This mixture is typically refrigerated to maintain stability. For extracting the active ingredients, the herbal powder is mixed with DES solvent at a material-to-liquid ratio of 1:10 to 1:80 (g / mL), and ultrasonic extraction is performed under heating conditions (e.g., 40°C to 60°C). The ultrasonic frequency can be 20kHz to 40kHz, and the extraction time is controlled to 30 to 60 minutes. Ultrasonic extraction utilizes the cavitation effect to disrupt plant cell walls, accelerating polyphenol dissolution, while heating reduces solvent viscosity and enhances molecular diffusion. In this step, pulverization and sieving provide homogeneous raw materials for extraction. The DES solvent achieves efficient dissolution by matching the polyphenol structure with its polarity. The synergistic effect of ultrasound and heating ensures that polyphenolic compounds are fully released from the herbal material into the solvent, forming a low-melting-point extract of *Tea dwarf tea*.

[0022] S2: Weigh 5 to 15 grams of pretreated and activated macroporous resin, add 20 to 50 ml of the prepared eutectic extract of *Tea dwarf tea*, mix well, and place in a shaker. Run the shaker at 80 to 200 rpm for 8 to 16 hours to allow the macroporous resin to adsorb polyphenolic compounds.

[0023] Macroporous resin is a porous polymeric adsorbent with a large specific surface area and pore size, such as 10 nm to 100 nm, which can capture polyphenol molecules through physical adsorption and pore size sieving. The resin needs pretreatment activation to remove residual impurities and restore adsorption activity, for example, by soaking it sequentially in ethanol, dilute hydrochloric acid, and dilute sodium hydroxide solution, rinsing with pure water until neutral. Weigh 5 to 15 grams of the pretreated macroporous resin and mix it with 20 to 50 ml of the *Tetracentron sinense* eutectic extract prepared in step S1. The resin-to-extract ratio can be adjusted according to the polyphenol concentration, for example, 1:5 to 1:20 (g / mL) to ensure sufficient adsorption capacity. After thorough mixing, transfer the mixture to an Erlenmeyer flask or other container and place it on a shaker for dynamic adsorption. Run the shaker at 80 to 200 rpm for 8 to 16 hours. This speed range provides mild to moderate shear force, promoting full contact between the resin and the extract and preventing resin sedimentation or clumping. During adsorption, the shaking mode of the shaker can be circular or reciprocating, for example, with the amplitude controlled between 2 cm and 5 cm, to enhance mass transfer efficiency. The macroporous resin binds to polyphenolic compounds through its hydrophobic interactions and hydrogen bonds, while the DES solvent is less adsorbed due to its polarity difference, thus achieving polyphenol enrichment. In this step, the amount of resin and the volume ratio of the extract affect the adsorption saturation. Controlling the shaking parameters ensures optimized adsorption kinetics, and the overall coordination achieves efficient transfer of polyphenols from the DES extract to the resin.

[0024] S3: After adsorption, filter to separate the macroporous resin, rinse the macroporous resin with ethanol, collect the eluent and place it in a shaker. Run the shaker at 80 to 200 rpm for 8 to 16 hours to desorb the polyphenolic compounds on the macroporous resin.

[0025] After adsorption, the macroporous resin and DES residue are first separated by filtration. Filtration can be performed under vacuum or atmospheric pressure using filter paper or a microporous membrane to collect the resin adsorbed with polyphenols. Subsequently, the resin is washed with ethanol. The volume concentration of ethanol can be selected from 30% to 80%, for example, a 50% ethanol aqueous solution, and the amount used can be 2 to 5 times the resin volume to disrupt the adsorption force between the resin and the polyphenols. Ethanol, as a desorption solvent, competitively displaces the polyphenols due to its polarity and hydrogen bonding ability, causing the polyphenols to desorb into the solution. The eluent after washing is collected, and the eluent and resin are placed together in a shaker for desorption. The shaker conditions are similar to the adsorption steps, running at 80 to 200 rpm for 8 to 16 hours to ensure that the polyphenolic components on the resin are desorbed into the solvent. During desorption, the dynamic conditions of the shaker enhance solvent penetration and molecular diffusion, preventing excessively high local concentrations that could lead to resorption. In this step, filtration separates the resin from DES residue, while ethanol rinsing and shaker desorption work synergistically to achieve efficient release of polyphenols from the resin. At the same time, ethanol, as a volatile solvent, facilitates subsequent removal.

[0026] S4: Collect the eluent obtained from desorption and transfer it to an evaporating dish. Evaporate until there is no alcohol odor to complete the concentration of the polyphenol extract and obtain a clear extract of dwarf tea polyphenols.

[0027] The eluent obtained from desorption is collected; this eluent mainly contains polyphenolic compounds and ethanol. The eluent is transferred to a dried and weighed evaporating dish. The evaporation apparatus can be a water bath or a rotary evaporator. Evaporation is carried out under heating conditions until no alcohol odor remains, indicating complete ethanol evaporation. The evaporation temperature can be controlled between 40°C and 60°C to avoid thermal decomposition of polyphenols. Concentration until the solution becomes viscous yields a clear extract of the polyphenolic compounds from *Tea glomerata*. The polyphenol concentration in the clear extract is significantly increased, facilitating storage or further application.

[0028] The synergistic effect of DES solvent and ultrasonic extraction ensures the extraction efficiency of polyphenolic compounds in dwarf tea and the full release of active ingredients. The adsorption and desorption process of macroporous resin efficiently removes eutectic solvents, reducing the impact of solvent residue on product quality. The synergistic effect of ethanol washing and shaker desorption achieves efficient release of polyphenols from the resin. The overall process is green and environmentally friendly, reducing energy consumption and waste generation. At the same time, it is simple to operate and easy to scale up, providing an economical and feasible solution for the extraction of natural products.

[0029] The extraction efficiency of polyphenolic compounds from *Tea gloriosa* using traditional methanol extraction differs significantly from that using DES extraction. For example... Figure 2 The image shows the HPLC chromatogram of polyphenols extracted from *Tea gloriosa* using methanol; Figure 3 The figure shows the HPLC chromatogram of polyphenols extracted from *Tea gloriosa* using DES according to this application. The corresponding numbers in the chromatogram are as follows: 1: gallic acid; 2: protocatechuic acid; 3: chlorogenic acid; 4: epicatechin; 5: epigallocatechin gallate; 6: epicatechin gallate. It can be seen that the extraction yield of polyphenols from *Tea gloriosa* using the method described in this application is significantly higher than that of traditional methods, with particularly noticeable differences in the chromatographic peaks of some components. Based on specific measurement data, the polyphenol content in *Tea gloriosa* obtained by DES solvent extraction can reach 28 mg / g, which is approximately 5 times higher than that of the traditional methanol extraction method.

[0030] In another technical solution, in step S2, the shaking table operation adopts a staged controlled dynamic adsorption method, specifically including: First, the mixed low-melting extract of *Tea dwarf tea* was subjected to low-speed adsorption at 80 to 100 rpm for 4 to 6 hours. Then, the speed was increased to 150 to 180 rpm for medium-speed adsorption for 2 to 4 hours. Finally, high-speed adsorption was carried out at 180 to 200 rpm for 2 to 6 hours. After each rotation speed stage, samples were taken to test the polyphenol adsorption rate. Based on the test results, it was determined whether to adjust the subsequent rotation speed and time ratio. Constant temperature conditions were maintained throughout the adsorption process, with the temperature controlled within the range of 25 degrees Celsius to 35 degrees Celsius. The oscillation amplitude of the shaker was adjusted by real-time monitoring of the sedimentation state of the macroporous resin.

[0031] In step S2, the shaker operation employs a phased-controlled dynamic adsorption method. Through a scientifically designed speed gradient, it simultaneously achieves the dual goals of maximizing adsorption rate and protecting resin. While traditional single high-speed adsorption can ensure a certain mass transfer efficiency, the continuous mechanical shear force can easily lead to excessive friction and breakage between resin particles, generating fine fragments. These fragments not only cause damage to the resin material itself but also result in loss with the liquid during subsequent filtration steps, along with the loss of the target polyphenols adsorbed on their surface, directly affecting the final yield. Phased control divides the adsorption process into three progressive stages: low speed (80 to 100 rpm), medium speed (150 to 180 rpm), and high speed (180 to 200 rpm). During the low-speed adsorption period of 4 to 6 hours, the resin and extract are allowed to initially contact and establish adsorption equilibrium under mild conditions. This stage aims to allow polyphenol molecules to preferentially fill the large and medium pores inside the resin, avoiding the "shell effect" where the particle surface is rapidly saturated while the interior remains unutilized under high-speed impact. The subsequent medium-speed adsorption period of 2 to 4 hours moderately enhances fluid disturbance, promoting the diffusion of molecules into smaller pores and ensuring a smooth transition of the resin bed state. The final high-speed adsorption period of 2 to 6 hours, with the resin already largely loaded, uses higher shear force to resolve the remaining polyphenol components with slower adsorption kinetics. Since the resin bed is more stable at this point and the concentration of the target substance has decreased, the risk of breakage caused by high speed is relatively controllable.

[0032] To ensure dynamic optimization of the phased strategy and further control risks, the polyphenol adsorption rate is sampled and tested after each speed stage. The mechanism for adjusting the subsequent speed and time ratio is determined based on the test results. For example, if the adsorption rate of key polyphenols exceeds 90% at the end of the low-speed stage, the medium-speed stage time can be appropriately shortened or the high-speed stage can be directly entered to reduce unnecessary mechanical action time. Conversely, if the efficiency is low, the speed and time of the next stage should be cautiously increased to avoid blindly adopting extreme parameters in pursuit of efficiency. Simultaneously, a constant temperature is maintained throughout the adsorption process, strictly controlled within the range of 25°C to 35°C. This aims to maintain the stability of the resin skeleton, as temperature fluctuations can cause repeated expansion and contraction of the resin, exacerbating fatigue damage to its structure. The combination of a constant temperature environment and phased speed provides a thermodynamic and kinetic environment that is both efficient and gentle. Adjusting the shaking amplitude of the shaker by real-time monitoring of the sedimentation state of the macroporous resin is another precise control method. Its purpose is to maintain the resin bed in a suitable fluidization state, avoiding excessively dense sedimentation leading to localized frictional overheating, or excessively loose sedimentation leading to excessive collision energy.

[0033] This solution addresses the critical issue of resin friction and breakage by significantly reducing tearing and wear caused by strong adhesion during the "cold start" phase by avoiding high-speed impacts in the initial stage. Secondly, gradual acceleration allows the resin bed to be compacted and stabilized progressively, resulting in a more shear-resistant structure rather than continuous chaotic collisions at a single high speed. During implementation, the rotational speed range and time can be fine-tuned based on the resin's mechanical strength (e.g., the abrasion resistance of different resin types). For example, for resins known to be brittle, the upper limit of the high-speed phase can be set at 190 rpm. Extended implementation can include integration with resin screening pretreatment, such as pre-screening to remove fine particles before feeding, reducing friction sources at the source. The entire solution, through the core principle of "slow first, then fast, real-time optimization," cleverly incorporates a resin material protection mechanism while ensuring or even improving the primary goal of adsorption rate. This reduces material loss and the risk of target material loss with fragments at the overall process level, improving the process's economy and sustainability. Through the synergistic effect of phased dynamic adsorption, real-time efficiency monitoring and constant temperature control, the adsorption rate of polyphenolic compounds is significantly improved while effectively reducing the frictional damage of resin materials and the resulting loss of target substances, thus enhancing the robustness and economy of the process.

[0034] The specific steps for determining whether to adjust the subsequent speed and time ratio based on the test results include: After each rotation speed stage, a small amount of adsorbent sample was taken and the concentration of six polyphenolic compounds (gallic acid, protocatechuic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, and epicatechin gallate) was determined by high performance liquid chromatography. The adsorption rate of that rotation speed stage was calculated. If the adsorption rate of any major polyphenolic compound was less than 85%, the rotation speed was increased by 10 to 20 rpm and the adsorption time was extended by 1 to 2 hours in the next rotation speed stage. If the adsorption rate of all major polyphenolic compounds reached more than 90%, the original rotation speed and time ratio were maintained and the next rotation speed stage was entered. The specific operations for adjusting the oscillation amplitude of the shaker by real-time monitoring of the sedimentation state of the macroporous resin include: Every 30 minutes, pause the shaker and let it stand for 2 minutes. Observe the ratio of the sedimentation volume of the resin at the bottom of the container to the initial volume. When the ratio exceeds 40%, increase the swing amplitude of the shaker to 1.2 to 1.3 times the original amplitude. When the ratio is below 20%, restore the swing amplitude to the standard amplitude. After each adjustment, the shaker should be run stably for 1 hour before the next monitoring.

[0035] The specific operation of adjusting the subsequent rotation speed and time ratio based on the test results is the key to balancing adsorption rate and resin loss. Here, clear efficiency thresholds (85% and 90%) and corresponding parameter adjustment strategies are set. After each rotation speed stage, the concentrations of six key polyphenols are accurately determined by high-performance liquid chromatography (HPLC), and the adsorption rate is calculated. If the adsorption rate of any major polyphenol compound is below 85%, this signal indicates insufficient adsorption kinetics. However, the adjustment strategy is not simply to switch to the highest rotation speed, but to increase the rotation speed by a moderate range (10 rpm to 20 rpm) in the next rotation speed stage while simultaneously extending the adsorption time (1 hour to 2 hours). This strategy of "small speed increase and synergistic time extension" enhances mass transfer kinetics (increasing rotation speed) while ensuring sufficient contact time (extending time) to compensate for the potentially shortened effective adsorption cycle due to increased rotation speed. This improves efficiency while avoiding additional resin wear caused by continuously operating at the maximum rotation speed in pursuit of speed. Conversely, if the adsorption rates of all major polyphenols reach above 90%, the original plan is maintained to avoid over-operation. This data-driven, precise control ensures that the mechanical energy input of the shaking table always matches the actual process requirements, reducing ineffective and harmful mechanical effects at the source.

[0036] Adjusting the shaking amplitude of the shaker by real-time monitoring of the sedimentation state of the macroporous resin is a direct means of controlling the physical wear of the resin. The procedure involves pausing the shaker every 30 minutes and allowing it to stand for 2 minutes. The density of the bed is judged by observing the ratio of the resin sedimentation volume to the initial volume. When this ratio exceeds 40%, it indicates that the resin particles are too densely packed. This not only affects mass transfer efficiency but also requires greater shear force between particles to break free from the static state upon restarting the shaker, thus increasing friction and the risk of breakage. In this case, the shaking amplitude is increased to 1.2 to 1.3 times the original amplitude. The purpose is to provide more sufficient fluidization force with a larger shaking stroke, restoring the bed to a loose and uniform state and reducing local stress. When the ratio is below 20%, it indicates that the bed is in a good fluidized state. The shaking amplitude is then restored to the standard amplitude to avoid excessive collision energy between particles and the container wall, and between particles themselves. After each adjustment, the system is run stably for 1 hour before monitoring is performed to ensure that the adjustment effect is manifested and the system reaches a new equilibrium, preventing instability caused by frequent adjustments. This mechanism together optimizes the hydrodynamic environment of the adsorption process, ensuring adsorption uniformity on a macroscopic level and protecting resin particles on a microscopic level.

[0037] The monitoring and adjustment mechanism, in synergy with the phased framework, constitutes a closed-loop control system for comprehensive management of adsorption rate and resin integrity. Adsorption rate monitoring focuses on "chemical" optimization to ensure efficient biochemical processes; sedimentation monitoring focuses on "physical" protection to ensure gentle operation of mechanical equipment. Through logical connections within the control system, both jointly determine three key mechanical parameters: rotation speed, time, and oscillation amplitude. For example, during high-speed adsorption, the system may simultaneously receive signals indicating that "the adsorption rate of a certain polyphenol is nearing its threshold" and "the resin sedimentation ratio is normal." In this case, it may only choose to fine-tune the rotation speed rather than the amplitude, thus completing the task with the most "economical" mechanical load. This comprehensive approach effectively resolves the inherent contradictions of shaker processes: high mechanical energy input, while beneficial for mass transfer, damages the material; low mechanical energy input, while protecting the material, is inefficient. Through intelligent real-time feedback and multi-parameter coordinated control, the entire adsorption process approaches the efficiency boundary while remaining stably within the safe zone for both equipment and materials. By real-time monitoring of adsorption rate and sedimentation state and parameter linkage adjustment, the adsorption process is refined and intelligently controlled. While ensuring a high adsorption rate, the mechanical wear and breakage of resin materials are significantly reduced, the loss of target material due to material loss is effectively reduced, and the overall efficiency of the process is improved.

[0038] To further demonstrate the benefits of this method, a comparative experimental example is provided: The experimental group using the method described in this application employed staged dynamic adsorption (low-medium-high speed) combined with real-time control; the control group without staged control used traditional single high-speed adsorption (190 rpm, continuous for 12 hours). Key monitoring indicators in the experiment included: adsorption rate of six polyphenol compounds, adsorption kinetic curves; resin breakage rate (change in resin particle size distribution before and after adsorption), filtrate quality (turbidity, solid content, polyphenol loss rate), and resin durability (performance changes after multiple cycles). Specific experimental data are as follows: 1) Comparison of polyphenol compound adsorption rates (%): Experimental group: Gallic acid 98.2, protocatechuic acid 97.5, chlorogenic acid 96.8, epicatechin 95.9, epigallocatechin gallate 94.5, epicatechin gallate 93.9; average adsorption rate 96.1%; Control group: gallic acid 95.8, protocatechuic acid 94.1, chlorogenic acid 91.3, epicatechin 89.6, epigallocatechin gallate 83.7, epicatechin gallate 86.2; average adsorption rate 90.1%.

[0039] 2) Comparison data on resin breakage rate: Experimental group: Initially, the content of particles with a diameter <100μm was 0.8%; after the experiment, the content of particles with a diameter <100μm was 3.2%, and the breakage rate increased by 2.4%. Control group: Initially, the content of particles with a diameter <100μm was 0.8%, and after the experiment, the content of particles with a diameter <100μm was 8.7%, with the breakage rate increasing by 7.9%.

[0040] 3) Filtrate analysis data: Experimental group: filtrate turbidity (NTU) was 25.3, filtrate solids content (mg / L) was 68.5, and polyphenol loss rate in filtrate was 2.1%; Control group: filtrate turbidity (NTU) was 45.8, filtrate solids content (mg / L) was 128.6, and polyphenol loss rate in filtrate was 4.8%.

[0041] 4) Resin durability data (after 5 cycles): Experimental group: Adsorption rate retention rate was 94.2%, cumulative breakage rate increased by 5.1%, and resin bed pressure drop increased by 18.5%; Control group: Adsorption rate retention rate was 76.3%, cumulative breakage rate increased by 26.8%, and resin bed pressure drop increased by 52.7%.

[0042] The experimental data above shows that: Under the same high-speed conditions, the experimental group achieved an average adsorption rate of 96.1%, significantly higher than the control group's 90.1%. Particularly noteworthy is that for epigallocatechin gallate, the component with the largest molecular weight, the experimental group's adsorption rate (94.5%) was nearly 11 percentage points higher than the control group's (83.7%), demonstrating that a phased strategy can better handle components with slow adsorption kinetics. The experimental group achieved gentle initial contact and reduced resin surface passivation through a low-speed phase (80-100 rpm, 5 h); accelerated the mass transfer process through a medium-speed phase (150-180 rpm, 3 h); and completed deep adsorption through a high-speed phase (180-200 rpm, 4 h). This gradual acceleration avoided the "rapid surface saturation" phenomenon caused by the sudden high-speed operation in the control group.

[0043] The increase in resin breakage rate in the experimental group was only 2.4%, far lower than the 7.9% in the control group. This is mainly due to: reduced initial impact damage during the low-speed phase, smooth transition during the medium-speed phase avoiding sudden mechanical stress, and real-time monitoring and adjustment preventing unnecessary continuous high-speed operation. The reduced breakage rate directly translates into savings in material costs; according to experimental data, the resin loss rate in the experimental group was only 30% of that in the control group.

[0044] The experimental group showed significantly better filtrate turbidity (25.3 NTU) and solids content (68.5 mg / L) compared to the control group, demonstrating better preservation of resin integrity. By reducing resin fragment loss, the experimental group decreased the polyphenol loss rate from 4.8% to 2.1%, equivalent to recovering approximately 2.7% more of the target product per batch. After 5 cycles, the experimental group maintained an adsorption rate of 94.2%, while the control group decreased to 76.3%, demonstrating the better sustainability of the staged strategy.

[0045] By controlling the rotation speed in stages, adsorption kinetics are optimized while mechanical damage is reduced. A real-time monitoring and adjustment mechanism ensures adsorption rate while maximizing the protection of the resin material. The entire process achieves an excellent balance between high efficiency and gentleness. Overall, under the same high-speed environment, the average adsorption rate is increased by approximately 6 percentage points, with a particularly significant improvement in the adsorption of difficult-to-adsorb components. The resin breakage rate is reduced to about one-third of that of traditional methods, significantly reducing material loss. By reducing resin loss and target material loss, operating costs are greatly reduced. Excellent adsorption performance is maintained even after multiple cycles, extending the resin's lifespan. This approach achieves the dual goals of increasing adsorption rate and protecting resin, providing an effective technical solution to the inherent contradictions of shaker processes and possessing significant industrial application value.

[0046] In another technical solution, step S3, before the step of desorbing polyphenolic compounds, further includes a multi-stage impurity removal process, which includes: The macroporous resin after adsorption was initially rinsed with a buffer solution with a pH of 6.5 to 7.5 at a flow rate of 2 to 5 mL / min, and the rinsing continued until the absorbance of the effluent stabilized below 0.05. Then, a second rinse was performed with pure water at a flow rate of 5 to 10 mL / min until the conductivity of the effluent dropped below 10 μS / cm. During each rinse, a segmented collection method was used to collect the effluent from different time periods and detect the content of polyphenolic compounds by high performance liquid chromatography. When the target polyphenolic compounds were detected in the effluent, the rinsing was stopped immediately and the desorption step was initiated. At the same time, the temperature of the macroporous resin bed was controlled to be stable within the range of 20 to 25 degrees Celsius throughout the entire impurity removal process.

[0047] The multi-stage impurity removal process effectively removes non-target impurities adsorbed on macroporous resins through staged rinsing, improving the final purity of polyphenolic compounds. This process includes two main stages: an initial rinse using a buffer solution with a pH of 6.5 to 7.5, followed by a secondary rinse using pure water. The buffer solution can be a phosphate buffer system (such as PBS) or Tris-HCl buffer, with its pH set in a near-neutral range to maintain the stability of polyphenolic compounds while effectively eluting polar impurities such as sugars and proteins. The initial rinse flow rate is controlled at 2 mL / min to 5 mL / min. This relatively low flow rate ensures sufficient contact between the buffer and the resin, maximizing impurity removal while avoiding premature elution of target polyphenols due to excessively high flow rates. Rinsing continues until the absorbance of the effluent stabilizes below 0.05, a threshold indicating that pigments and macromolecular impurities have been effectively removed. The subsequent secondary rinse with pure water was performed at a higher flow rate (5 mL / min to 10 mL / min) to further remove ionic impurities and residual buffer salts until the conductivity of the effluent dropped below 10 μS / cm, indicating that the system was close to the purity of deionized water. This multi-stage design utilizes the polarity characteristics and cleaning mechanisms of different solvents: the buffer solution removes specific impurities through pH control and ion exchange, while pure water removes residual components through osmosis and dilution.

[0048] A segmented collection method is employed during each rinsing process, a key operation for achieving precise control. Specifically, the effluent is collected in separate containers at time intervals (e.g., every 5 minutes) or in volume units (e.g., every 10 mL). The content of polyphenolic compounds in each collection segment is detected by high-performance liquid chromatography (HPLC), primarily targeting six polyphenols including gallic acid and protocatechuic acid. When the content of any target polyphenol in the effluent exceeds a preset threshold (e.g., a concentration greater than 1 μg / mL), the current rinsing step is immediately stopped, and the process transitions to the desorption stage. This monitoring mechanism effectively prevents the loss of target compounds and ensures polyphenol recovery. During implementation, the HPLC detection conditions can be optimized as follows: using a C18 reversed-phase column with gradient elution using methanol-water or acetonitrile-water as the mobile phase, and setting the detection wavelength in the range of 220-260 nm based on the maximum absorption wavelength of the polyphenols. For rapid detection, a UV-Vis spectrometer can also be used for preliminary screening. The principle of combining segmented collection with real-time monitoring is to accurately grasp the balance between the impurity removal process and the retention state of the target substance through spatiotemporal sample analysis, thereby achieving intelligent judgment of the rinsing endpoint.

[0049] Throughout the impurity removal process, the temperature of the macroporous resin bed is maintained stable within the range of 20°C to 25°C. In practice, the buffer solution and pure water also need to be pre-cooled to the same temperature before use to ensure consistent system temperature. The synergistic effect of the multi-stage impurity removal process and temperature control is that a stable low-temperature environment provides reliable reaction conditions for segmented rinsing, preventing resin shrinkage / expansion or polyphenol decomposition caused by temperature fluctuations. Rinsing parameters are adjusted according to the resin type; for example, for resins with high adsorption capacity, the buffer solution rinsing time can be appropriately extended until the absorbance value stabilizes below 0.03. The connection between the entire process and the subsequent desorption step also needs to be optimized. For example, after rinsing, a small amount of air can be used to purge residual moisture before transferring to ethanol desorption, further improving overall efficiency. Through the synergistic effect of the multi-stage impurity removal process, segmented collection and real-time monitoring, and precise temperature control, the purity of the polyphenol extract can be significantly improved, impurity interference can be effectively reduced, and a high recovery rate of the target compound can be maintained, providing a reliable guarantee for obtaining high-quality extract products.

[0050] To further demonstrate the benefits of this method, a comparative experimental example is provided: Before desorption, the experimental group strictly implemented the multi-stage impurity removal process provided by this method: first, the resin after adsorption was washed with phosphate buffer (pH=7.0) at a flow rate of 3.5 mL / min until the absorbance of the effluent stabilized below 0.05. Then, a second wash was performed with pure water at a flow rate of 7.5 mL / min until the conductivity of the effluent dropped below 10 μS / cm. The effluent was collected in segments and monitored in real-time by HPLC; washing was stopped immediately upon detection of the target polyphenol. The resin bed temperature was controlled at 22.5 ± 1°C throughout the entire process.

[0051] The control group underwent a standard single-step rinsing with pure water, directly rinsing the adsorbed resin with pure water at a flow rate of approximately 5 mL / min. The rinsing water volume was equivalent to the total rinsing volume of the experimental group (fixed volume). Absorbance, conductivity, and polyphenol leakage were not monitored. Desorption was performed directly after rinsing.

[0052] Both the experimental and control groups used the same batch of macroporous resin loaded with DES extract from *Tea dwarf tea* for adsorption. Subsequent desorption conditions were identical (e.g., ethanol concentration, volume, time, temperature), and the same concentration process and detection methods were employed.

[0053] The experimental group and the control group were rinsed according to the above design. After rinsing, the resins in both groups were desorbed with ethanol under the same conditions, and all eluent was collected and concentrated to obtain the final clear extract.

[0054] During the experiment, all rinsing effluents from both groups were collected, and their total solids content, total sugar content (phenol-sulfuric acid method), and total protein content (Bradford method) were determined to compare the differences in the total amount of impurities in the rinsing effluents of the two groups. HPLC analysis was performed on the rinsing effluents collected in segments from the experimental group to accurately calculate the total amount of target polyphenols entering the rinsing effluent before rinsing was stopped. The amount of polyphenols lost in the rinsing effluent of the control group under a fixed volume of rinsing was estimated (based on preliminary experiments or the assumption that the loss occurred later). Equal volumes of the purified extract were weighed, and HPLC analysis was performed to calculate the percentage of the total content of the six target polyphenols, and the number and area of ​​non-target impurity peaks in the chromatogram were observed. The color and state of the purified extract were observed and recorded. The absolute amounts of the six target polyphenols in the two groups of purified extracts were compared, and the total recovery rate relative to the adsorption amount was calculated. Specific experimental data are as follows (using average and fluctuation values): 1) Comparison of impurity removal effects: Experimental group: The total solids content of the rinsing solution was 118.5±8.2 mg, the total sugar content of the rinsing solution was 38.5±3.6 mg, and the total protein content of the rinsing solution was 12.4±2.1 mg; Control group: total solids content of rinsing solution was 52.3±4.5 mg, total sugar content of rinsing solution was 15.2±1.8 mg, and total protein content of rinsing solution was 7.1±0.9 mg.

[0055] 2) Loss of target polyphenols during the rinsing stage (mg): Experimental group: Gallic acid 0.21±0.02, protocatechuic acid 0.15±0.02, chlorogenic acid 0.08±0.01, epicatechin 0.12±0.01, epigallocatechin gallate 0.09±0.01, epicatechin gallate 0.02±0.01, total loss 0.71; Control group: Gallic acid 1.05±0.08, protocatechuic acid 0.82±0.07, chlorogenic acid 0.48±0.05, epicatechin 0.63±0.06, epigallocatechin gallate 0.45±0.04, epicatechin gallate 0.06±0.01, total loss 3.81.

[0056] 3) Comparison of final product (cleansing ointment) quality: Experimental group: The total content of the target polyphenols was 85.3±1.5%, the number of major impurity peaks in the HPLC chromatogram was 3, and the total recovery rate of the target polyphenols was 94.7±1.2% (it should be noted that this recovery rate represents the recovery rate of macroporous resin desorption and subsequent concentration stages. If the overall process recovery rate is calculated based on the raw medicinal material, it is approximately 52%, corresponding to a polyphenol content of approximately 42 mg / g in the extract. In comparison, the average polyphenol content of the traditional methanol extraction method is approximately 5.84 mg / g). The extract was light brown in appearance and had a uniform texture. Control group: The total content of target polyphenols was 72.8±2.1%, the number of major impurity peaks in the HPLC chromatogram was 8, the total recovery rate of target polyphenols was 87.2±1.8%, and the clear extract was dark brown in appearance and slightly viscous.

[0057] Analysis of the above data shows that the total solids, total sugar, and total protein contents in the rinsing solution of the experimental group were significantly higher than those of the control group (approximately 2.3 times, 2.5 times, and 3.2 times, respectively). This indicates that the multi-stage rinsing process (buffer solution + pure water) used in the experimental group can more effectively elute and separate various impurities adsorbed on the resin. The initial rinsing with buffer solution effectively removed highly polar pigments and some ionic impurities (reflected in the absorbance meeting the standard), while the ion competition effect of the buffer environment helped to displace polar impurities (such as sugars and proteins) with weaker binding to the resin. The subsequent high-speed rinsing with pure water further removed residual buffer salts and remaining water-soluble impurities (reflected in the conductivity meeting the standard). The impurity removal efficiency was far higher than the dilution effect of a single water wash. The total polyphenol loss in the experimental group during the rinsing stage was only 0.71 mg, while that in the control group was as high as 3.81 mg, a difference of nearly 5.4 times. This demonstrates the key role of the mechanism of "segmented collection and real-time HPLC monitoring, with immediate cessation upon polyphenol leakage". The experimental group stopped rinsing the target polyphenols from the resin bed at the critical point, maximizing their retention on the resin. The control group, however, used a fixed-volume rinsing method, inevitably resulting in significant loss of the target polyphenols in the later stages of washing. Notably, while the experimental group removed more impurities, it experienced less loss of the target polyphenols, demonstrating the superior selectivity of this approach. The total content of the target polyphenols in the experimental group's extract reached 85.3%, 12.5 percentage points higher than the control group (72.8%). HPLC chromatograms showed fewer and smaller impurity peaks in the experimental group, directly reflecting its purity advantage. The light brown and uniform texture of the experimental group's extract contrasted with the dark brown and viscous texture of the control group, typically indicating effective removal of pigments and large molecular impurities. Despite more thorough impurity removal, the total recovery rate of the target polyphenols in the experimental group (94.7%) was significantly higher than that in the control group (87.2%), achieving a win-win situation in both purity and yield.

[0058] Compared to traditional single-wash methods, this solution's multi-stage impurity removal process, through a stepwise washing with buffer and pure water, more thoroughly removes various impurities such as pigments, sugars, and proteins, more than doubling the impurity removal efficiency. Utilizing real-time monitoring technology, the loss of target polyphenols is reduced by approximately 80% during the impurity removal stage, achieving highly efficient preservation of valuable components. This results in a more than 10 percentage point increase in the purity of the final polyphenol extract, along with a significant improvement in appearance. While obtaining a higher purity product, the overall recovery rate is also increased by approximately 7.5 percentage points compared to the conventional method used in the control group, demonstrating significant economic benefits.

[0059] In another technical solution, step S4 involves concentrating the polyphenol extract using a segmented temperature-controlled concentration process, specifically including: The collected eluent was first concentrated to one-third to one-half of its original volume at 45°C to 55°C. Then the temperature was lowered to 35°C to 45°C and the concentration was continued until the solution became viscous. Finally, the final concentration to constant weight was completed at 25°C to 35°C and a vacuum of -0.06 MPa to -0.08 MPa. During each concentration stage, the residual ethanol content in the eluent is monitored in real time using near-infrared spectroscopy. When the residual ethanol content is detected to be below 0.5%, the system automatically switches to the next concentration stage. Simultaneously, samples of the concentrated material are taken during each stage transition, and the content changes of six major polyphenolic compounds—gallic acid, protocatechuic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, and epicatechin gallate—are detected by high-performance liquid chromatography. Based on the detection results, the concentration temperature and time parameters for the next stage are dynamically adjusted.

[0060] A segmented temperature-controlled concentration process is employed, gradually reducing the concentration temperature to maximize the preservation of the activity of heat-sensitive polyphenolic compounds while ensuring efficient solvent removal. The process consists of three distinct temperature stages: First, preliminary concentration is carried out at 45°C to 55°C, aiming to rapidly remove most of the ethanol solvent, reducing the eluent volume to one-third to one-half of its original volume. Subsequently, the temperature is lowered to 35°C to 45°C for further concentration, at which point the solution gradually becomes viscous; this stage focuses on preventing the thermal degradation of the polyphenolic compounds. Finally, final concentration to constant weight is achieved at 25°C to 35°C and a vacuum of -0.06 MPa to -0.08 MPa. This segmented design is based on the changes in the physical properties of the solution at different concentration stages: initially, the solution has a high ethanol content and a low boiling point, allowing for accelerated evaporation with moderate heating; in the middle stage, as the concentration increases, polyphenol molecules are more prone to structural changes due to high temperatures, necessitating cooling; and in the final stage, effective drying is achieved even at low temperatures under high vacuum conditions. The selection of the temperature range takes into account the thermal stability characteristics of polyphenols. For example, catechin compounds such as epigallocatechin gallate are prone to isomerization above 50 degrees Celsius, so the temperature is controlled in a lower range in the later stages.

[0061] Real-time monitoring of ethanol residue in the eluent during each concentration stage using near-infrared spectroscopy is a key technology for achieving precise control. Near-infrared spectroscopy analysis is based on the characteristic absorption of OH and CH bonds in ethanol molecules at specific wavelengths (e.g., 1600-1800 nm and 2100-2300 nm). Ethanol content can be quantitatively determined by comparing the results with a preset calibration model. The monitoring system may include a fiber optic probe, a spectrometer, and a data processing unit. The probe can be directly immersed in the concentrate or used for online detection via a flow cell. When the detected ethanol residue is below 0.5%, the system automatically switches to the next concentration stage. This threshold ensures that ethanol is essentially removed while avoiding unnecessary prolonged heating. The stage switching mechanism can be implemented through a PLC control system: when the ethanol content reaches the set threshold, the system automatically adjusts the heating device temperature and vacuum level, such as directly reducing the temperature from 50 degrees Celsius to 40 degrees Celsius and adjusting the vacuum level from -0.06 MPa to -0.08 MPa. During implementation, the monitoring frequency can be set to 1-2 times per minute to ensure the real-time nature of the data; for special systems, the threshold can also be fine-tuned, such as setting the ethanol residue threshold to 0.3% for high-viscosity solutions to ensure complete removal.

[0062] During each stage transition, samples of the concentrated material are taken, and the content changes of six major polyphenolic compounds are detected by high-performance liquid chromatography (HPLC). The concentration temperature and time parameters for the next stage are dynamically adjusted based on the detection results. Sampling can be performed before or after stage transition, with a sample volume of approximately 0.1-0.5 mL. After appropriate dilution, the sample is injected for HPLC analysis. Detection indicators include the peak area or concentration values ​​of gallic acid, protocatechuic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, and epicatechin gallate. The specific method for adjusting parameters based on the detection results is as follows: if the polyphenol content decreases significantly (e.g., any major polyphenol decreases by more than 5%), the concentration temperature is reduced by 3-5 degrees Celsius and the time may be shortened in the next stage; if the content is stable, the parameters are maintained or moderately optimized. This dynamic adjustment mechanism can respond to changes in polyphenol stability during concentration, achieving personalized process control. Extended implementation may include establishing an expert system: combining historical data with real-time detection, using algorithms to predict the optimal parameter combination; or introducing multi-indicator monitoring, such as simultaneously monitoring changes in solution viscosity and color value, to comprehensively evaluate the concentration process. The coordinated operation of the segmented temperature control process and monitoring system ensures an optimal balance between efficiency and product quality during the concentration process. Through the synergistic effect of the segmented temperature control concentration process, real-time monitoring of ethanol residue, and dynamic adjustment of polyphenol content, the activity and stability of polyphenol compounds can be significantly protected while efficiently removing solvents, thereby improving the consistency of the final product's quality and the controllability of the process.

[0063] The specific method for detecting changes in the content of six polyphenolic compounds using high-performance liquid chromatography is as follows: The contents of six polyphenolic compounds in no less than 30 samples with known concentrations were accurately determined by high performance liquid chromatography. These samples were used as a standard dataset. Correlation analysis was performed between the standard dataset and the near-infrared spectral data of the corresponding samples in the wavelength range of 1200 nm to 2400 nm. A quantitative calibration model for the six polyphenolic compounds was established using partial least squares regression algorithm. During the concentration process, the near-infrared spectrum of the concentrated material is acquired in real time using a fiber optic probe. The spectral data is input into the quantitative calibration model, and the predicted concentration values ​​of six polyphenolic compounds are output simultaneously. When the predicted concentration value of any polyphenolic compound decreases by more than 3% compared to the previous detection time point, the concentration parameters are adjusted, and the current concentration temperature is reduced by 3 to 5 degrees Celsius. After each concentration stage is completed, actual samples are taken for high-performance liquid chromatography (HPLC) verification. If the relative error between the predicted value and the measured value exceeds 8%, the quantitative calibration model is incrementally updated using the new data.

[0064] The key to detecting changes in the content of six polyphenolic compounds using high-performance liquid chromatography (HPLC) lies in establishing a quantitative calibration model between near-infrared spectroscopy and polyphenol concentration. The model establishment phase requires preparing at least 30 samples with known concentrations, covering the concentration ranges likely encountered throughout the process, such as gallic acid from 0.01 mg / mL to 1.5 mg / mL and protocatechuic acid from 0.05 mg / mL to 3 mg / mL. Each sample was precisely analyzed by HPLC to obtain a standard dataset, and its near-infrared spectral data in the wavelength range of 1200 nm to 2400 nm were acquired. Spectral acquisition was performed using a Fourier transform near-infrared spectrometer with a resolution of 4 cm⁻¹. -1 Or 8cm -1 To improve the signal-to-noise ratio, each sample was collected 3-5 times and averaged. A partial least squares regression algorithm was used to establish a quantitative calibration model, which effectively handles the complex relationship between highly correlated wavelength variables and polyphenol concentration in near-infrared spectroscopy. During model building, the sample set was randomly divided into a calibration set and a validation set (e.g., 70% and 30%). Cross-validation was used to determine the optimal number of principal components, and the model's predictive performance metrics, such as the coefficient of determination and root mean square error of prediction, were evaluated. Model optimization may include spectral preprocessing steps, such as smoothing, derivative processing, and standard normal transformation, to eliminate baseline drift and scattering effects.

[0065] During the actual concentration process, near-infrared spectra of the concentrated material are acquired in real time using fiber optic probes. The spectral data is input into an established quantitative calibration model, simultaneously outputting predicted concentration values ​​for six polyphenolic compounds. The fiber optic probe can be installed in an appropriate location within the concentration unit, such as the evaporator wall or circulation piping, ensuring good optical contact with the material. The spectral acquisition frequency can be adjusted according to the concentration stage, such as acquiring values ​​every 2-5 minutes during critical stages. Monitoring the trend of predicted concentration values ​​over time is crucial: when the predicted concentration value of any polyphenolic compound decreases by more than 3% compared to the previous detection time point, the system automatically triggers adjustments to the concentration parameters, lowering the current concentration temperature by 3 to 5 degrees Celsius. This threshold is based on polyphenol stability considerations, moderately conservative to ensure a safety margin. The adjustment mechanism can be implemented through an automated control system: when the decrease reaches a set threshold, the system automatically sends a command to the temperature controller, such as reducing the temperature from 40 degrees Celsius to 36 degrees Celsius. During implementation, a tiered response mechanism can be set: for example, a small temperature adjustment when the threshold is first exceeded, and more aggressive intervention measures when the threshold is exceeded continuously.

[0066] After each concentration stage, actual samples are taken for high-performance liquid chromatography (HPLC) validation. If the relative error between the predicted and measured values ​​exceeds 8%, the quantitative calibration model is incrementally updated using the new data. Validation sampling is performed during stage transitions. After appropriate processing, the samples are analyzed by HPLC to obtain the actual concentration values ​​of the six polyphenols. Relative error calculation is performed individually for each polyphenol. When the error of any compound exceeds a threshold, the model update procedure is triggered. Incremental updates can use the sliding window method or recursive least squares method, adding new sample data to the model without completely rebuilding it. This is particularly suitable for the slow changes in material properties during long-term production processes. Extended implementation may include: establishing a model performance monitoring system to automatically track prediction error trends and prompt recalibration when necessary; or developing a multi-model system to use dedicated models for different concentration stages or material types. The entire system, through closed-loop control of real-time prediction, parameter adjustment, and model updates, can adapt to process changes and ensure long-term operational reliability. By establishing a near-infrared quantitative correction model, implementing real-time prediction and parameter adjustment, and establishing a model verification and update mechanism, it is possible to achieve precise monitoring and intelligent control of polyphenol content during the concentration process, significantly improving the accuracy and adaptability of the process, while ensuring the quality stability of the final product.

[0067] In another technical solution, the pretreatment activation of macroporous resin includes sequential soaking and activation with alcohol, acid and alkali, with rinsing with pure water in between.

[0068] Macroporous resins are high-molecular adsorbent materials with well-developed pore structures and numerous active sites on their surface. However, these sites may be blocked or deactivated by impurities during storage and transportation. The fundamental purpose of pretreatment activation is to thoroughly remove residual porogens, monomers, oligomers, and other synthesis byproducts from the resin through a series of cleaning steps, while simultaneously restoring and activating the functional groups on the resin surface. The pretreatment process follows the principles of "like dissolves like" and ion exchange, using solvents of different polarities and pH levels sequentially to achieve a stepwise removal of impurities. The pretreatment activation employs a stepwise process of soaking in alcohol, acid, and alkali sequentially, with a rinse using pure water in between. Initially, an alcohol solvent is used for preliminary treatment, typically ethanol or methanol, at a concentration ranging from 95% to 99%, at a volume of 3 to 5 times the resin volume. The alcohol treatment stage is carried out at room temperature, with a soaking time controlled between 4 and 8 hours, during which slow stirring or replacement with fresh solvent can be used. This stage mainly utilizes the organic solvent properties of alcohol to dissolve and remove lipid-soluble impurities and organic residues from the resin. Acid treatment is then performed, typically using a 2% to 5% hydrochloric acid solution, at a volume of 2 to 4 times the resin volume, for 2 to 4 hours at room temperature. The acid treatment aims to remove cationic impurities such as metal ions and activate certain functional groups through protonation. Finally, an alkaline treatment is performed using a 2% to 5% sodium hydroxide solution, at a volume comparable to the acid treatment, for 2 to 4 hours. The alkaline treatment removes acidic impurities and brings the resin's functional groups to a suitable state. After each chemical treatment step, the resin must be rinsed with pure water until the effluent is neutral, with the water flow rate controlled at 2 to 4 times the resin volume per hour to ensure complete removal of the previous treatment agent.

[0069] In practice, the pretreatment process can be optimized and adjusted according to the resin type and usage requirements. For resins with high cross-linking degrees, the treatment time of each step can be appropriately extended; while for resins modified with special functional groups, the suitability of the treatment reagents needs to be considered. Quality monitoring is a crucial step in ensuring the effectiveness of pretreatment and can be evaluated through various methods: including measuring physical parameters such as resin moisture content, apparent density, and specific surface area; and evaluating the activation effect by testing its adsorption capacity for standard substances. A complete pretreatment cycle typically requires 24 to 48 hours, depending on the type and scale of the resin. Pretreated resin should be stored in pure water or an ethanol-water solution to prevent drying and microbial contamination. For industrial production, an integrated resin pretreatment-regeneration system can be established to achieve resin recycling and full-process quality monitoring. Performing pretreatment activation processes on macroporous resins as required can significantly improve the resin's adsorption performance and stability, effectively remove potential impurities, and extend the resin's service life.

[0070] In another technical solution, the eutectic solvent used in step S1 is an amino acid-organic acid eutectic solvent, the preparation process of which includes: mixing amino acids and organic acids in a predetermined ratio, heating and stirring under water bath conditions until a homogeneous liquid is formed, and then refrigerating it at 4°C for later use.

[0071] The eutectic solvent used in step S1 is an amino acid-organic acid type. An eutectic solvent is a low-melting-point mixture formed by hydrogen bond donors and acceptors through intermolecular forces, where amino acids act as hydrogen bond acceptors and organic acids as hydrogen bond donors. The range of amino acids selected includes natural amino acids such as alanine, glycine, and proline, which have good biocompatibility and biodegradability. Organic acids can be selected from lactic acid, citric acid, malic acid, etc., which not only provide hydrogen bond formation capabilities but also possess certain antioxidant properties. The molar ratio of amino acids to organic acids is typically between 1:1 and 1:3, and the specific ratio needs to be optimized based on the polarity and solubility of the target polyphenol. The unique advantage of this solvent system lies in its designable physicochemical properties; by adjusting the composition and ratio, customized solvents with optimal solubility for specific polyphenolic compounds can be obtained. Compared with traditional organic solvents, amino acid-organic acid eutectic solvents have advantages such as low volatility, low toxicity, and biodegradability, which aligns with the concept of green extraction.

[0072] The preparation process of a eutectic solvent involves multiple steps, including precise proportioning, mixing, heating, and refrigeration. First, pre-dried amino acids and organic acids are weighed according to a predetermined ratio and placed in a corrosion-resistant container. They are then mixed thoroughly using a magnetic or mechanical stirrer in a water bath at 50-80°C. The heating temperature is selected based on the melting point and stability of each component, typically controlled within 10-20°C below the component decomposition temperature. The stirring speed is maintained at 200-500 rpm for 1-3 hours until a clear, transparent, homogeneous liquid is formed. A brief period of turbidity may occur during the preparation process; this is a normal phase transition and will disappear with continued stirring. To ensure solvent quality stability, the preparation process should be carried out under an inert gas atmosphere to prevent oxidation and deterioration of the raw materials. The prepared eutectic solvent undergoes quality testing, including measuring parameters such as viscosity, conductivity, and pH value, to ensure batch-to-batch consistency. Finally, the qualified solvent is dispensed into sealed containers and refrigerated at 4°C for later use, with a specified shelf life. For large-scale production, a continuous preparation system can be established to achieve automatic metering of raw materials, online mixing, and instantaneous cooling.

[0073] The amino acid-organic acid eutectic solvent exhibits an intermolecular hydrogen bond network, which effectively disrupts plant cell walls and promotes the dissolution of polyphenolic compounds. Compared to traditional solvents, this solvent system demonstrates higher selectivity for polyphenols, attributed to its tunable polarity and hydrogen bonding ability. In practical applications, an important parameter is the solvent viscosity, typically in the range of 100-500 mPa·s, which can be optimized by adding appropriate amounts of water or adjusting the temperature. Another significant feature is its recyclability; the solvent can be recycled after use through macroporous resin adsorption treatment, reducing production costs and environmental burden. Furthermore, this solvent system is highly compatible with subsequent purification processes and does not adversely affect resin adsorption. By systematically optimizing preparation parameters and usage conditions, the amino acid-organic acid eutectic solvent improves polyphenol extraction rates while ensuring the greenness and sustainability of the entire process. By employing a specific composition of the amino acid-organic acid eutectic solvent and its optimized preparation process, the extraction efficiency and selectivity of polyphenols can be significantly improved, while reducing the environmental impact of the production process.

[0074] In another technical solution, in step S3, the volume concentration of ethanol used for desorption is 30% to 80%. This range is set based on the solubility characteristics of polyphenolic compounds in different solvent environments and the desorption mechanism of macroporous resins. As a polar organic solvent, the concentration of ethanol directly affects the polarity of the solution and its hydrogen bond formation ability. When the volume concentration of ethanol is in the lower range of 30% to 50%, the solution has strong hydrophilicity, which is beneficial for breaking the hydrogen bonds between the resin and highly polar polyphenolic compounds (such as gallic acid and protocatechuic acid), achieving gentle desorption. When the volume concentration of ethanol is increased to the higher range of 50% to 80%, the hydrophobicity of the solution increases, making it more suitable for desorption of less polar, higher molecular weight polyphenolic compounds, such as epigallocatechin gallate and other catechin components. The principle of this concentration-gradient design is to utilize the continuous change in solvent polarity to achieve selective elution of polyphenolic compounds with different properties. In practice, precise control of ethanol concentration can be achieved through an online mixing system that mixes anhydrous ethanol and deionized water in real time according to a preset ratio to ensure concentration stability.

[0075] The selection of ethanol concentration needs to be optimized in conjunction with other process parameters during desorption. Within the concentration range of 30% to 80%, the specific concentration can be further refined based on the polarity of the target polyphenol and the resin characteristics. For example, for extracts rich in highly polar polyphenols, a gradient elution strategy can be adopted: initially using a 30% to 40% ethanol concentration to desorb the more polar components, and then gradually increasing to 60% to 80% to desorb the less polar components. The desorption temperature is usually controlled between 25℃ and 35℃, forming a synergistic effect with the ethanol concentration: using a higher ethanol concentration at a lower temperature can prevent excessive solvent evaporation, while using a lower concentration at a higher temperature can maintain desorption efficiency. Flow rate parameters also need to be adjusted accordingly. A higher flow rate of 2-4 mL / min can be used for low-concentration ethanol (30%-50%), while a lower flow rate of 1-2 mL / min is preferable for high-concentration ethanol (60%-80%) to ensure sufficient mass transfer. The optimal combination of concentration parameters can be determined by establishing a concentration-efficiency response surface through preliminary experiments. By optimizing the concentration range of ethanol desorption and establishing corresponding control strategies, the desorption efficiency and selectivity of polyphenolic compounds can be significantly improved, ensuring the full recovery of target products while reducing solvent consumption and operating costs.

[0076] In another technical solution, a step S5 for regenerating the macroporous resin is included: rinsing the desorbed macroporous resin with anhydrous ethanol until the filtrate is colorless, then rinsing with pure water until there is no alcohol odor, and storing it for later use. After multiple adsorption-desorption cycles, the internal pores and surface active sites of the macroporous resin are gradually blocked or contaminated by impurities that are difficult to wash off, leading to a decrease in adsorption capacity and changes in selectivity. The regeneration process restores the physical structure and chemical function of the resin, enabling it to be reused without affecting its performance. The regeneration treatment is based on a comprehensive principle of dissolution, displacement, and reactivation: anhydrous ethanol, as a strongly polar solvent, can dissolve most organic impurities; rinsing with pure water replaces residual solvent and dissolved impurities. The thoroughness of regeneration directly affects the service life and process stability of the resin. Resin that has not been fully regenerated not only has reduced adsorption performance but may also become a breeding ground for microorganisms, contaminating subsequent batches of product. The regeneration process adopts a staged treatment strategy. First, anhydrous ethanol is used to rinse until the filtrate is colorless. This stage aims to remove residual fat-soluble impurities and some pigment components from the resin. The amount of ethanol used is typically 3-5 times the resin volume, with the flow rate controlled at 1-2 times the resin volume per hour, and the temperature maintained at 25-35℃ to ensure good solubility. During rinsing, the regeneration progress can be judged by observing the color change of the filtrate. When the absorbance value of the filtrate in the visible light region (400-800nm) is below 0.01, it can be considered to have reached the colorless standard. This is followed by a pure water rinsing stage, using 5-8 times the resin volume, with the flow rate appropriately increased to 2-4 times the resin volume per hour, until the effluent has no alcohol odor. The alcohol odor can be determined through sensory evaluation or quantitative detection using an ethanol sensor; typically, an ethanol concentration below 0.1% is considered acceptable. Between the two rinsing stages, an airtight device can be installed to prevent solvent evaporation, and a multi-stage countercurrent rinsing method can be used to improve cleaning efficiency. For special contamination situations, an alkaline or acid washing step can be added before ethanol rinsing, but the impact on the resin structure needs to be assessed.

[0077] The quality assessment indicators for regenerated resin include two aspects: physical parameters and chemical properties. Physical parameters mainly involve detecting changes in resin bed volume, particle integrity, and flow rate characteristics. Chemical properties are evaluated by measuring its adsorption capacity and selectivity for standard polyphenol compounds. After regeneration, short-term storage of the resin can be achieved by immersing it in a 20%-30% ethanol aqueous solution to prevent microbial growth. Long-term storage should be done by cleaning, drying, and sealing the resin in a sealed container, maintaining a storage temperature between 4-25℃, and avoiding direct sunlight. Through a systematic macroporous resin regeneration process and strict quality control, the adsorption performance and service life of the resin can be effectively maintained, significantly reducing production costs while ensuring the continuity of the production process and the stability of product quality.

[0078] It should be noted that although the steps are described in a specific order above, this does not mean that they must be performed in that order. In fact, some of these steps can be executed concurrently, or even in a different order, as long as the required functionality is achieved. The number of devices and processing scale described herein are for simplification of the invention; applications, modifications, and variations of this invention will be readily apparent to those skilled in the art.

[0079] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for extracting polyphenolic compounds from dwarf tea using the DES method and removing the solvent, characterized in that, Includes the following steps: S1: Crush and sieve the sliced ​​dwarf tea, weigh the powder, add a low eutectic solvent, and extract by ultrasonication for 30 to 60 minutes to obtain the low eutectic extract of dwarf tea. S2: Weigh 5 to 15 grams of pretreated and activated macroporous resin, add 20 to 50 ml of the prepared low-melting extract of *Tea dwarf tea*, mix well, and place in a shaker. Run the shaker at 80 to 200 rpm for 8 to 16 hours to allow the macroporous resin to adsorb polyphenolic compounds. S3: After adsorption, filter to separate the macroporous resin, rinse the macroporous resin with ethanol, collect the eluent and put it into a shaker. Run the shaker at 80 to 200 rpm for 8 to 16 hours to desorb the polyphenolic compounds on the macroporous resin. S4: Collect the eluent obtained from desorption and transfer it to an evaporating dish. Evaporate until there is no alcohol odor to complete the concentration of the polyphenol extract and obtain a clear extract of dwarf tea polyphenols.

2. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea dwarf tea* according to claim 1, characterized in that, In step S2, the shaker operation adopts a staged controlled dynamic adsorption method, specifically including: First, the mixed low-melting extract of *Tea dwarf tea* was subjected to low-speed adsorption at 80 to 100 rpm for 4 to 6 hours. Then, the speed was increased to 150 to 180 rpm for medium-speed adsorption for 2 to 4 hours. Finally, high-speed adsorption was carried out at 180 to 200 rpm for 2 to 6 hours. After each rotation speed stage, samples were taken to test the polyphenol adsorption rate. Based on the test results, it was determined whether to adjust the subsequent rotation speed and time ratio. Constant temperature conditions were maintained throughout the adsorption process, with the temperature controlled within the range of 25 degrees Celsius to 35 degrees Celsius. The oscillation amplitude of the shaker was adjusted by real-time monitoring of the sedimentation state of the macroporous resin.

3. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea dwarf tea* according to claim 2, characterized in that, The specific steps for determining whether to adjust the subsequent speed and time ratio based on the test results include: After each rotation speed stage, a small amount of adsorbent sample was taken and the concentration of six polyphenolic compounds (gallic acid, protocatechuic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, and epicatechin gallate) was determined by high performance liquid chromatography. The adsorption rate of that rotation speed stage was calculated. If the adsorption rate of any major polyphenolic compound was less than 85%, the rotation speed was increased by 10 to 20 rpm and the adsorption time was extended by 1 to 2 hours in the next rotation speed stage. If the adsorption rate of all major polyphenolic compounds reached more than 90%, the original rotation speed and time ratio were maintained and the next rotation speed stage was entered. The specific operations for adjusting the oscillation amplitude of the shaker by real-time monitoring of the sedimentation state of the macroporous resin include: Every 30 minutes, pause the shaker and let it stand for 2 minutes. Observe the ratio of the sedimentation volume of the resin at the bottom of the container to the initial volume. When the ratio exceeds 40%, increase the swing amplitude of the shaker to 1.2 to 1.3 times the original amplitude. When the ratio is below 20%, restore the swing amplitude to the standard amplitude. After each adjustment, the shaker should be run stably for 1 hour before the next monitoring.

4. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea glomerata* according to claim 1, characterized in that, In step S3, prior to the desorption of polyphenolic compounds, a multi-stage impurity removal process is also included, which includes: The macroporous resin after adsorption was initially rinsed with a buffer solution with a pH of 6.5 to 7.5 at a flow rate of 2 to 5 mL / min, and the rinsing continued until the absorbance of the effluent stabilized below 0.

05. Then, a second rinse was performed with pure water at a flow rate of 5 to 10 mL / min until the conductivity of the effluent dropped below 10 μS / cm. During each rinse, a segmented collection method was used to collect the effluent from different time periods and detect the content of polyphenolic compounds by high performance liquid chromatography. When the target polyphenolic compounds were detected in the effluent, the rinsing was stopped immediately and the desorption step was initiated. At the same time, the temperature of the macroporous resin bed was controlled to be stable within the range of 20 to 25 degrees Celsius throughout the entire impurity removal process.

5. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea dwarf tea* according to claim 1, characterized in that, In step S4, a segmented temperature-controlled concentration process is used to concentrate the polyphenol extract, specifically including: The collected eluent was first concentrated to one-third to one-half of its original volume at 45°C to 55°C. Then the temperature was lowered to 35°C to 45°C and the concentration was continued until the solution became viscous. Finally, the final concentration to constant weight was completed at 25°C to 35°C and a vacuum of -0.06 MPa to -0.08 MPa. During each concentration stage, the residual ethanol content in the eluent is monitored in real time using near-infrared spectroscopy. When the residual ethanol content is detected to be below 0.5%, the system automatically switches to the next concentration stage. Simultaneously, samples of the concentrated material are taken during each stage transition, and the content changes of six major polyphenolic compounds—gallic acid, protocatechuic acid, chlorogenic acid, epicatechin, epigallocatechin gallate, and epicatechin gallate—are detected by high-performance liquid chromatography. Based on the detection results, the concentration temperature and time parameters for the next stage are dynamically adjusted.

6. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea dwarf tea* according to claim 5, characterized in that, The specific method for detecting changes in the content of six polyphenolic compounds using high-performance liquid chromatography is as follows: The contents of six polyphenolic compounds in no less than 30 samples with known concentrations were accurately determined by high performance liquid chromatography. These samples were used as a standard dataset. Correlation analysis was performed between the standard dataset and the near-infrared spectral data of the corresponding samples in the wavelength range of 1200 nm to 2400 nm. A quantitative calibration model for the six polyphenolic compounds was established using partial least squares regression algorithm. During the concentration process, the near-infrared spectrum of the concentrated material is acquired in real time through a fiber optic probe. The spectral data is input into the quantitative correction model, and the predicted concentration values ​​of six polyphenolic compounds are output simultaneously. When the predicted concentration value of any polyphenolic compound decreases by more than 3% compared with the previous detection time point, the concentration parameters are adjusted, and the current concentration temperature is reduced by 3 degrees Celsius to 5 degrees Celsius. After each concentration stage is completed, actual samples are taken for high-performance liquid chromatography (HPLC) verification. If the relative error between the predicted and measured values ​​exceeds 8%, the quantitative calibration model is incrementally updated using the new data.

7. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea glomerata* according to claim 1, characterized in that, The pretreatment activation of macroporous resins includes sequential soaking and activation with alcohol, acid, and alkali, followed by rinsing with pure water.

8. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea dwarf tea* according to claim 1, characterized in that, The eutectic solvent used in step S1 is an amino acid-organic acid eutectic solvent. Its preparation process includes: mixing amino acids and organic acids in a predetermined ratio, heating and stirring under water bath conditions until a homogeneous liquid is formed, and then refrigerating it at 4°C for later use.

9. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea dwarf tea* according to claim 1, characterized in that, In step S3, the volume concentration of ethanol used for desorption is 30% to 80%.

10. The method for DES extraction and solvent removal of polyphenolic compounds from *Tea dwarf tea* according to claim 1, characterized in that, It also includes step S5 for regenerating macroporous resin: rinsing the desorbed macroporous resin with anhydrous ethanol until the filtrate is colorless, then rinsing with pure water until there is no alcohol odor, and storing it for later use.

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