Method for efficiently extracting radix puerariae essential oil by using deep eutectic solvent assisted resin chromatography

Abstract

The invention discloses a method for extracting radix puerariae essential oil by using deep eutectic solvent assisted resin chromatography. According to the method, non-polar macroporous resin is utilized to enrich volatile components of radix puerariae, a choline chloride deep eutectic solvent (DES) with a specific molar ratio is screened as an eluent, and efficient analysis is realized by utilizing the specific affinity of the DES to hydrophobic terpene components. Based on the physical characteristic that DES is extremely difficult to volatilize, volatile essential oil is directly separated from elution fraction by adopting reduced pressure distillation, and kettle residue DES is recycled. According to the method, solute evaporation is creatively used for replacing the step of solvent evaporation in traditional ethanol elution, and azeotropic entrainment loss and heat-sensitive component damage of low-boiling-point head incense components are effectively avoided. The obtained radix puerariae essential oil is high in yield, heat-sensitive terpene components and terpene characteristic components are completely reserved, no organic solvent is left, and green and low-carbon preparation of the essential oil is achieved.

Description

Technical Field

[0001] This invention belongs to the field of natural plant active ingredient extraction and separation technology, specifically relating to a green preparation process for plant essential oils. It involves a method for efficiently enriching and separating volatile essential oils from kudzu root (Pueraria lobata) using non-polar macroporous adsorption resin chromatography with deep eutectic solvents (DESs) and vacuum distillation. This method combines resin adsorption enrichment technology with the non-volatile properties of deep eutectic solvents, achieving efficient retention and extraction of heat-sensitive terpenoid components under conditions free of organic solvent residues. Background Technology

[0002] Kudzu root (Pueraria lobata), the dried root of a plant in the genus Pueraria of the legume family, is often called "Asian ginseng." Besides being rich in isoflavones, its volatile essential oil also has significant medicinal and application value, exhibiting remarkable effects in lowering blood lipids, anti-oxidation, and improving microcirculation. The bioactivity and unique aroma of kudzu root essential oil mainly originate from its terpenoids, which not only give the plant its unique aroma but also synergistically enhance its medicinal effects through the "adaptive effect." However, these terpenoids, especially low-boiling-point monoterpenes and some structurally unique sesquiterpenes, are extremely sensitive to heat. Under high-temperature or prolonged heating conditions, they are easily oxidized, isomerized, or volatilized, leading to a deterioration in the essential oil's aroma and a reduction in its bioactivity.

[0003] Currently, the main extraction technologies for kudzu root essential oil include steam distillation, supercritical CO2 extraction, and resin adsorption, but all have significant technical bottlenecks. While steam distillation uses simple equipment, the raw material is exposed to high temperatures for extended periods during extraction, leading to the decomposition of a large amount of heat-sensitive terpenes, and the extraction rate is typically low (only about 0.1%-0.5%). Supercritical CO2 extraction (such as the kudzu root essential oil extraction method disclosed in patent CN104017653A) can better preserve heat-sensitive components, but the equipment is expensive and the operating pressure is extremely high (usually above 20 MPa), making it difficult to promote on a large scale in conventional industrial production. Furthermore, while traditional macroporous resin adsorption can effectively enrich essential oils using non-polar resins, ethanol is typically used as the eluent after the resin becomes saturated. The process faces two major challenges in the subsequent vacuum concentration to remove ethanol: first, "azeotropic entrainment loss," which means that when a large amount of ethanol solvent is evaporated, low-boiling-point terpenes will form an azeotrope with the ethanol vapor and evaporate together, resulting in a bland aroma and reduced yield of essential oils; second, "high energy consumption and residues," which means that evaporating a large amount of solvent consumes a lot of energy and it is difficult to avoid trace amounts of organic solvent residues, which does not meet the requirements of green manufacturing.

[0004] Deep eutectic solvents (DESs), as a novel green solvent, possess advantages such as low vapor pressure, strong solubility, and biodegradability, and have attracted much attention in the extraction of plant active ingredients in recent years. Existing technologies mostly use DES as a direct extraction solvent to assist steam distillation (e.g., patent CN117946810A for agarwood essential oil extraction and CN113549497A for perilla essential oil extraction). However, these methods mainly utilize DES to disrupt cell walls or increase solubility, and there are few reports on using DES as an eluent in resin chromatography combined with its low volatility for essential oil separation. In summary, developing a green extraction process that can efficiently enrich terpenes using resins, eliminate ethanol elution, and utilize the high boiling point of DES to avoid the loss of heat-sensitive terpenes and solvent residue by "evaporating the solute" rather than "evaporating the solvent," is a key technical challenge for improving the quality and yield of kudzu root essential oil. Summary of the Invention

[0005] The purpose of this invention is to provide a method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography. This method aims to solve the technical problems existing in current kudzu root essential oil extraction technologies, such as low extraction rate, difficulty in removing organic solvent residues, and the easy loss or pyrolysis of heat-sensitive terpenoid components by azeotropic reaction with low-boiling-point solvents during traditional heating and concentration processes.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A method for extracting kudzu essential oil using deep eutectic solvent-assisted resin chromatography is characterized by the following steps: (1) Kudzu pretreatment and extraction: dried kudzu root is pulverized, subjected to ultrasonic-assisted water extraction and filtration to obtain kudzu extract; (2) Resin adsorption enrichment: the extract is passed through a non-polar macroporous adsorption resin column, utilizing the hydrophobic interaction between the resin skeleton and essential oil molecules to adsorb volatile components, and then washed with water to remove water-soluble impurities; (3) DES elution: deep eutectic solvent is used as the eluent to elute the essential oil components on the resin, and the DES elution fraction is collected; (4) Vacuum distillation separation: The DES elution fraction is placed in a vacuum distillation apparatus, and the vacuum and temperature are controlled to distill the kudzu root essential oil from the DES and collect it by condensation.

[0007] Conventional processes use ethanol for elution, followed by heating to remove over 95% of the ethanol solvent by volume to obtain the essential oil. Because ethanol (boiling point 78℃) has a relatively close boiling point to many monoterpenes and sesquiterpenes (such as alkenes and alcohols) in essential oils, and readily forms azeotropes during gas-liquid phase transitions, a large amount of volatile top notes are lost along with the ethanol vapor through azeotropic entrainment during solvent removal. Unlike conventional processes where ethanol solvents suffer from drawbacks such as the loss of top notes due to their boiling point (78°C) being close to that of essential oil terpenoids and the tendency to form azeotropes, this invention utilizes the "extremely low vapor pressure" and "wide liquid range" characteristics of deep eutectic solvents (DES), which are characterized by hydrogen bond acceptors and donors linked by a dense hydrogen bond network. Specific DES types (quaternary ammonium salts such as choline chloride as hydrogen bond acceptors and polyols as hydrogen bond donors) were creatively selected and their molar ratios precisely controlled (typically 1:2 to 1:5), constructing a unique supramolecular solvent system. This system utilizes a strong hydrogen bond network to lock the solvent... While preventing the volatile components from evaporating, the molecular mechanism cleverly adjusts the affinity between the solvent and essential oil molecules. This allows the essential oil components to easily overcome the interaction forces between them and the solvent molecules and "escape" through distillation under mild vacuum distillation conditions below 80°C. Meanwhile, the DES solvent itself remains at the bottom of the vessel due to its extreme evaporation rate. This reverse separation strategy of "evaporating the solute and retaining the solvent" effectively avoids high-temperature thermal decomposition and azeotropic entrainment losses. As a result, it significantly improves the extraction rate of essential oils while fully preserving the characteristic aroma components and minimizing the damage and loss of heat-labile terpenoid components in the essential oils, achieving unexpected technical results.

[0008] To achieve the aforementioned technical effects, the technical solution adopted by this invention includes: A method for extracting kudzu essential oil using deep eutectic solvent-assisted resin chromatography is characterized by the following steps: (1) Kudzu pretreatment: Take dried kudzu root, crush and sieve it to obtain kudzu root powder; (2) Ultrasonic-assisted extraction: Mix kudzu root powder with water, extract under ultrasonic assistance, filter to remove filter residue, and obtain kudzu root aqueous extract; (3) Resin adsorption enrichment: Pass the kudzu root aqueous extract obtained in step (2) through a chromatography column packed with non-polar macroporous adsorption resin, and control the flow rate so that the volatile essential oil components and hydrophobic components in the extract are adsorbed by the resin; (4) Impurity removal: Use pure water or low-concentration alcohol solution to rinse the adsorbed resin column to remove polar water-soluble impurities such as polysaccharides, proteins and inorganic salts, and discard the washing liquid; (5) DES elution: Use deep eutectic solvent (DES) as eluent, pass it through the resin column at a specific flow rate, and analyze and collect the deep eutectic solvent elution fraction containing kudzu root essential oil; (6) Vacuum distillation separation: The elution fraction collected in step (5) is placed in a vacuum distillation apparatus. Taking advantage of the boiling point difference between the essential oil and the deep eutectic solvent, the kudzu essential oil is distilled out and collected under negative pressure and low temperature conditions. The residue in the reactor is a recyclable deep eutectic solvent.

[0009] Preferably, in step (3), the non-polar macroporous adsorption resin selected is one or a combination of several of D101, HPD-100, HPD-400, HPD-500, D1300, DM130, HP20, and AB-8. Particularly preferred are D101 or AB-8 type non-polar macroporous adsorption resins. These resins have suitable specific surface area and pore structure, and their adsorption capacity for volatile components of kudzu root and their DES desorption rate are superior to other types of resins. Preferably, in step (5), the deep eutectic solvent (DES) is prepared by hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD) in a molar ratio of 1:2 to 1:5; the hydrogen bond acceptor is selected from choline chloride or betaine; the hydrogen bond donor is selected from polyols or organic acids with high boiling point and strong essential oil dissolving ability, specifically including one or more of 1,3-butanediol, 1,2-propanediol, 1,3-propanediol, glycerol, lactic acid, and citric acid. To ensure that the solvent does not evaporate during vacuum distillation in step (6) and that the eluted essential oil is dissolved to the maximum extent, the present invention further screened the DES formulation as a particularly preferred option: Preferred formulation A: choline chloride (HBA) and 1,3-butanediol (HBD) in a molar ratio of 1:3 to 1:4; Preferred formulation B: choline chloride (HBA) and 1,2-propanediol (HBD) in a molar ratio of 1:2 to 1:4; Preferred formulation C: choline chloride (HBA) and lactic acid (HBD) in a molar ratio of 1:2 or 3:2.

[0010] Furthermore, in step (6), the specific process parameters for vacuum distillation are: vacuum degree controlled at -0.08 MPa to -0.1 MPa, and distillation temperature controlled at 50℃ to 80℃. Preferably, the distillation conditions are controlled at a vacuum degree of -0.095 MPa to -0.1 MPa and a temperature of 50℃ to 55℃. Under these extreme process conditions, utilizing the extremely low volatility of DES (boiling point much higher than 200℃), reverse separation of "solute distillation and solvent retention" is achieved, minimizing the pyrolysis of heat-sensitive components. Attached Figure Description

[0011] Figure 1 Flowchart for the extraction and preparation of kudzu root essential oil; Figure 2 The response surface plots are for key process parameters of ultrasound-assisted extraction and low-pressure distillation recovery. Detailed Implementation

[0012] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0013] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

[0014] To screen for a deep eutectic solvent (DES) suitable for elution with non-polar macroporous resins and capable of efficient separation of kudzu root essential oil via vacuum distillation, this section of the examples investigated the effects of different hydrogen bond donor (HBD) types and molar ratios on essential oil yield and terpene component retention (evaluated by the physical shape and aroma of the extract). General experimental procedures (as shown in the attached diagram) were followed. Figure 1 As shown below: 1. Pretreatment of kudzu root (step S1): Take dried kudzu root, crush it and pass it through an 80-mesh sieve, and use it as raw material for later use.

[0015] 2. Extraction and column loading (steps S2-S4): Mix kudzu root powder with water at a ratio of 1:15, and perform ultrasonic-assisted extraction (300W, 40℃, 30min). Filter to obtain the extract. Pass the extract through a D101 macroporous adsorption resin column. After adsorption saturation, rinse with pure water until the effluent is colorless and set aside.

[0016] 3. DES Preparation and Elution (Step S5): Hydrogen bond acceptor (HBA) choline chloride is mixed with different hydrogen bond donors (HBD) in specific proportions and stirred at a constant temperature of 60-80°C until a homogeneous, transparent liquid is formed. The prepared DES is used as the eluent and passed through a resin column at a flow rate of 1 BV / h, and the eluent is collected.

[0017] 4. Vacuum distillation (step S6): Place the eluent in a rotary evaporator, control the vacuum degree to -0.09 MPa and the temperature to 65℃-75℃, and collect the condensed oil, which is kudzu root essential oil.

[0018] Example 1: Screening of different types of hydrogen bond donors (HBD)

[0019] In this embodiment, the hydrogen bond acceptor was fixed as choline chloride, and the molar ratio was fixed at 1:3. The effects of different types of HBD on the elution and separation of kudzu root essential oil were investigated.

[0020] 1. DES solvent preparation: ① Experimental group 1-1: Choline chloride + glycerol (molar ratio 1:3); ② Experimental group 1-2: choline chloride + 1,2-propanediol (molar ratio 1:3); ③ Experimental groups 1-3: choline chloride + 1,3-butanediol (molar ratio 1:3); ④ Experimental groups 1-4: choline chloride + citric acid (molar ratio 1:3).

[0021] 2. Experimental Results and Analysis: Table 1

[0022] 3. Conclusion: Experimental group 1-1 (glycerol) had low elution efficiency because its viscosity was too high, making it difficult to diffuse within the resin column.

[0023] Although the acidic environment of experimental groups 1-4 (citric acid) helps stabilize some components, the viscosity is still high at a 1:3 ratio.

[0024] Experimental groups 1-2 (1,2-propanediol) and 1-3 (1,3-butanediol) performed best. In particular, 1,3-butanediol, with a boiling point (207℃) significantly higher than that of the main terpenoid components in essential oils under negative pressure (which are highly volatile), and also much higher than that of water, can serve as an excellent "non-volatile substrate" during vacuum distillation, "forcing" out the essential oils while not being distilled out itself, thus ensuring the purity of the essential oils.

[0025] Therefore, 1,3-butanediol and 1,2-propanediol are initially preferred as preferred alcohol hydrogen bond donors.

[0026] Example 2: Optimization of the ratio of the choline chloride-alcohol system (preferred formulations A and B)

[0027] Based on the results of Example 1, the molar ratio of choline chloride to 1,3-butanediol (Formula A) and 1,2-propanediol (Formula B) was further optimized to determine the optimal ratio range.

[0028] 1. Experimental Design: Series A (1,3-Butanediol): Molar ratios are 1:2, 1:3, 1:4, and 1:6.

[0029] Series B (1,2-propanediol): molar ratios of 1:1, 1:2, 1:4, and 1:5.

[0030] 2. Experimental Results: Series A (choline chloride-1,3-butanediol): 1:2: The system is relatively viscous, and the resin resolution is low; 1:3: Moderate viscosity, high resin resolution; 1:4: Optimal fluidity, highest resin resolution; 1:6: Although it has good fluidity, it has poor affinity for certain terpenes due to the reduced concentration of hydrogen bond acceptors.

[0031] Conclusion: The preferred formulation A is determined to be choline chloride and 1,3-butanediol in a molar ratio of 1:3 to 1:4.

[0032] Series B (choline chloride-1,2-propanediol): 1:1: Easily precipitates crystals at room temperature and is unstable; 1:2: Forms a stable homogeneous liquid, stable at room temperature; 1:4: Forms a stable, homogeneous liquid that is stable at room temperature; 1:5: The effect is not significantly different from 1:4, but the amount of solvent used increases, and the cost rises.

[0033] This experiment used kudzu root powder that had passed through an 80-mesh sieve as raw material. Choline chloride was used as the hydrogen bond acceptor. Homogeneous and transparent deep eutectic solvents (DES) were prepared by stirring at 80℃ with 1,3-butanediol (Formula A series) and 1,2-propanediol (Formula B series) at specific molar ratios. Kudzu root powder was directly mixed with the prepared DES solvent at a ratio of 1:20 and ultrasonically assisted extraction was performed at 450W and 55℃ for 30 minutes. After extraction, the supernatant was collected by centrifugation. The total terpene content in the extract was finally determined by the vanillin-glacial acetic acid colorimetric method. The table below shows the detection results of the total terpene content for different formulations.

[0034] Table 2

[0035] Conclusion: The preferred formulation B is determined to be choline chloride and 1,2-propanediol in a molar ratio of 1:2 to 1:4.

[0036] Example 3: Screening of specific ratios for the choline chloride-lactic acid system (preferred formula C)

[0037] Considering the advantages of acidic DES in extracting specific alkaloids or phenolic substances, and the literature reports that the choline chloride-lactic acid system has excellent extraction effect on agarwood essential oil (containing a large amount of sesquiterpenes), this example specifically examines the application of the lactic acid system in elution of kudzu resin.

[0038] 1. Experimental Design: The molar ratio of choline chloride to lactic acid was set at 1:1, 1:2, 2:1, and 3:2. This experiment used kudzu root powder that had passed through an 80-mesh sieve as raw material. Choline chloride was used as the hydrogen bond acceptor, and it was mixed with lactic acid (formula C series) at a specific molar ratio (1:1, 1:2, 2:1, 3:2) at 80℃ with constant temperature stirring to prepare a homogeneous and transparent deep eutectic solvent (DES). The kudzu root powder was directly mixed with the prepared DES solvent at a ratio of 1:20, and ultrasonic-assisted extraction was performed at 450W and 55℃ for 30 minutes. After extraction, the supernatant was collected by centrifugation. Finally, the total terpene content in the extract was determined using the vanillin-glacial acetic acid colorimetric method. The table below shows the detection results of the total terpene content for different formulations: 2. Experimental Results: Table 3

[0039] Results analysis: Choline chloride and lactic acid can form a homogeneous and transparent deep eutectic solvent (DES) at 60°C under different molar ratios. However, viscosity is a key factor affecting the elution efficiency of resin column chromatography.

[0040] When the molar ratio is 1:1 and 2:1, the system viscosity is relatively high, especially at the 2:1 ratio where the viscosity increases significantly after cooling. This increases the flow resistance of the eluent within the resin channels, reduces the mass transfer rate, and is detrimental to industrial operation. In contrast, systems with molar ratios of 1:2 and 3:2 exhibit better flowability, facilitating the penetration of solvent molecules into the microporous structure of the macroporous resin, thereby more efficiently desorbing the adsorbed essential oil components.

[0041] Considering the hydrodynamic properties of the elution operation and the quality of the essential oils, the preferred formulation C is determined to be choline chloride and lactic acid, with an optimal molar ratio of 3:2 or 1:2 (emphasizing rapid elution and ease of operation).

[0042] Example 4: Screening of Resin Types and DES Solvent Systems Based on Orthogonal Design

[0043] Considering the advantages of acidic DES in extracting specific alkaloids or phenolic substances, and the literature reporting that the choline chloride-lactic acid system has excellent extraction effects on agarwood essential oil (containing a large amount of sesquiterpenes), this embodiment specifically introduces a horizontal comparison between the lactic acid system and the alcohol system. The table below shows the comparative experimental results of the extraction effects of different hydrogen bond donors on kudzu root essential oil: Table 4

[0044] Results analysis: Experiment 4 (AB-8 resin, choline chloride-1,3-butanediol, molar ratio 1:4) achieved the highest total terpene content of 9.68 mg / g and the best sensory evaluation, and was established as the optimal process. The data showed that 1,3-butanediol, due to its suitable viscosity and high boiling point, effectively avoided solvent evaporation and azeotropic loss during low-temperature vacuum distillation, which was significantly better than the volatile 1,2-propanediol system. AB-8 and D101 resins showed similar and excellent adsorption performance. Finally, the AB-8 resin combined with choline chloride-1,3-butanediol (1:3 to 1:4) system was determined to be the core preferred technical solution of this invention.

[0045] For the choline chloride-lactic acid system, when the molar ratio is 3:2 (Experiment No. 2), the system exhibits good fluidity at 60℃, and the obtained essential oil aroma is closest to the natural original fragrance. This is consistent with the excellent extraction effect of agarwood essential oil (sesquiterpenes) reported in the literature. However, considering that lactic acid has a high boiling point and is acidic, subsequent vacuum distillation requires equipment with high corrosion resistance; therefore, it is considered an alternative for the extraction of specific functional essential oil components.

[0046] Example 5: Response surface optimization of key process parameters for ultrasound-assisted extraction and low-pressure distillation recovery

[0047] To further explore the synergistic effect of the two key steps of ultrasonic-assisted extraction and DES elution-reduced vacuum distillation in this invention, and to determine the optimal process window, this embodiment adopts Box-Behnken Design (BBD) response surface methodology. Ultrasonic power (A), distillation temperature (B), and vacuum degree (C) are selected as the factors to be investigated, and the yield of kudzu essential oil (Y1) and total terpene content (Y2) are used as the response values ​​for the experiment. The following table shows the Box-Behnken experimental design and results.

[0048] Table 5

[0049] Conclusion: The optimal extraction and separation conditions were determined to be: ultrasonic power 450W-600W, distillation temperature 50℃-55℃, and vacuum degree -0.095 MPa to -0.10 MPa. Under these optimized conditions, the yield of kudzu root essential oil reached 0.65%, and the total terpene content was as high as 9.68 mg / g. Compared with the traditional steam distillation method (yield of approximately 0.11%-0.43%) and the ethanol elution-thermal concentration method, this invention utilizes DES-assisted resin chromatography combined with low-temperature vacuum distillation technology, which significantly improves the essential oil yield, effectively preserves the characteristic terpene components with biological activity, and leaves no organic solvent residue, thus achieving efficient and green preparation of kudzu root essential oil.

[0050] like Figure 2 The response surface methodology analysis of key process parameters for ultrasonic-assisted extraction and low-pressure distillation recovery shows (this figure visually illustrates the interaction between ultrasonic power (A) and distillation temperature (B) on essential oil yield (Y1) when the vacuum degree is fixed at -0.09 MPa): the highest point of the surface (orange-yellow area) is concentrated between ultrasonic power of 450-600W and temperature of 60-70℃. This verifies that the present invention achieves maximum extraction efficiency while protecting the active ingredients of essential oil through the synergistic effect of "high-power ultrasonic enhancement" and "medium-low temperature vacuum distillation".

Claims

1. A method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography, characterized in that, Includes the following steps: (1) Take dried kudzu root, crush it, and sieve it to obtain kudzu root powder; (2) The kudzu root powder is mixed with water and extracted under ultrasonic assistance. The residue is removed by filtration to obtain kudzu root aqueous extract. (3) Load the kudzu root aqueous extract obtained in step (2) onto a chromatography column packed with non-polar macroporous adsorption resin so that the essential oil components and hydrophobic components in the extract are adsorbed by the resin. (4) Use rinsing solution to rinse the adsorbed resin column to remove impurities, and discard the rinsing solution; (5) Use deep eutectic solvent as eluent to elute through a resin column and collect the eluent containing kudzu root essential oil; (6) The eluent is separated by vacuum distillation, and the distilled kudzu essential oil is collected. The residue in the kettle is a recyclable deep eutectic solvent.

2. The method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 1, characterized in that, In step (3), the non-polar macroporous adsorption resin is selected from one or more of D101, HPD-100, HPD-400, HPD-500, D1300, DM130, HP20, and AB-8.

3. The method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 2, characterized in that, The non-polar macroporous adsorption resin is selected from D101 or AB-8.

4. The method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 1, characterized in that, In step (5), the deep eutectic solvent is composed of hydrogen bond acceptors and hydrogen bond donors, and the molar ratio of the hydrogen bond acceptors to the hydrogen bond donors is 1:2~5.

5. The method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 4, characterized in that, The hydrogen bond acceptor is selected from choline chloride or betaine; the hydrogen bond donor is selected from one or more of 1,3-butanediol, 1,2-propanediol, 1,3-propanediol, glycerol, lactic acid, and citric acid.

6. A method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 4, characterized in that, The deep eutectic solvent is selected from any of the following formulations: Formula A: Choline chloride and 1,3-butanediol in a molar ratio of 1:2 to 6; preferably, the molar ratio of choline chloride to 1,3-butanediol is 1:3 to 4. Formula B: Choline chloride and 1,2-propanediol in a molar ratio of 1:1 to 6; preferably, the molar ratio of choline chloride to 1,2-propanediol is 1:2 to 4. Formula C: Choline chloride and lactic acid in a molar ratio of 1:1~2 or 3:1~2; preferably, the molar ratio of choline chloride to lactic acid is 1:2 or 3:

2.

7. The method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 1, characterized in that, In step (2), the particle size of the kudzu root powder is 80~300 mesh; the power of the ultrasonic-assisted extraction is 250W~600W, the time is 20~60min, the temperature is 30~50℃, and the mass-volume ratio of the material to the liquid is 1:10~30g / mL.

8. The method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 1, characterized in that, In step (6), the vacuum degree of the reduced pressure distillation is -0.08MPa to -0.1MPa, and the distillation temperature is 50℃ to 80℃.

9. The method for extracting kudzu root essential oil using deep eutectic solvent-assisted resin chromatography according to claim 1, characterized in that, The total terpene content of the kudzu root essential oil prepared by the method described above is 5.15 mg / g to 9.68 mg / g.

Images