Method for extracting tea saponin based on oil tea cake and application thereof

Abstract

The application belongs to the technical field of surfactant preparation, and particularly relates to a method for extracting tea saponin from oil tea cake and modifying tea saponin. First, the integrated process of eutectic solvent-ultrasonic extraction and macroporous resin purification is used to extract tea saponin; then the extracted tea saponin is modified to obtain tea saponin modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine. The extraction method has high selectivity for tea saponin, simplifies the purification process, and the purity of the obtained tea saponin is greater than or equal to 97.5%. The prepared tea saponin modified surfactant significantly improves its decontamination ability in a high-oil high-temperature environment, foam stability and cleaning efficiency. The salt resistance, hard water resistance and emulsification capacity of the tea saponin modified surfactant are significantly improved, and the tea saponin modified surfactant is a green surfactant and is suitable for high-end daily chemical or washing and protecting products.

Description

Technical Field

[0001] This invention belongs to the technical field of surfactant preparation, specifically relating to a method for preparing modified tea saponin surfactant based on tea saponin extracted from camellia oil cake. Background Technology

[0002] Camellia oleifera is an important woody oilseed crop in southern my country. During the processing of camellia oil, a large amount of byproduct—camellia oil cake—is generated. Statistics show that for every ton of camellia oil produced, approximately 4-5 tons of camellia oil cake are generated. my country is the world's largest producer of camellia seeds, with annual production of camellia oil cake reaching millions of tons. For a long time, due to a lack of high-value utilization technologies, camellia oil cake has mostly been discarded directly or used as low-value fertilizer or fuel, resulting not only in enormous resource waste but also serious environmental problems. Camellia oil cake contains 10%-15% tea saponin. Tea saponin is a pentacyclic triterpenoid saponin composed of hydrophilic sugars and hydrophobic aglycones. It possesses good surface activity, emulsifying, dispersing, and foaming properties, and also has pharmacological effects such as bactericidal, anti-permeability, anti-inflammatory, and analgesic effects.

[0003] The main extraction methods for tea saponins include: 1) Water extraction: This method is simple, but the extraction rate is low and the extraction time is long. Furthermore, because tea saponins are hygroscopic, concentration and drying consume extremely high energy. The extract also contains a large amount of water-soluble proteins and polysaccharides, resulting in low product purity and a darker color. 2) Organic solvent extraction: This method uses organic solvents such as methanol and ethanol. Although the extraction rate is improved, the use of organic solvents increases production costs and safety risks. Since methanol is expensive and toxic, ethanol is mostly used for extraction. While ethanol has the advantage of short extraction time, its purity is still not high enough, and both yield and purity need further improvement. 3) Enzymatic hydrolysis: This method uses cellulase, pectinase, etc., to break down cell walls and promote the release of tea saponins. It is a green and efficient method, but the current enzymatic hydrolysis process parameters have not been fully optimized, and the separation and purification of the post-hydrolysis solution remains challenging.

[0004] Chinese Patent Publication No. CN112110979B discloses a method for extracting tea saponins. The method includes the following steps: (1) extracting tea meal raw material by contacting it with an extraction solvent, collecting the extract and drying it to obtain crude tea saponins; (2) mixing the crude tea saponins obtained in step (1) with water to obtain a tea saponin solution, separating the tea saponin solution using a macroporous adsorption resin column, eluting with an eluent and collecting the eluent, wherein the eluent contains water and an organic solvent; (3) removing the organic solvent from the eluent, mixing it with a flocculant for flocculation, separating the solid and liquid, collecting the clarified liquid, and drying the clarified liquid. The extraction method of this invention not only improves the purity of the final obtained tea saponins but also increases the yield of tea saponins. The extraction solvent used in this patent is a lower fatty alcohol selected from at least one of the monohydric alcohols of C1-C4. The advantage of this method is that it is quick and the lower fatty alcohols have good solubility and permeability to tea saponins, resulting in high extraction efficiency. However, it will also extract a variety of impurities such as sugars, pigments, polyphenols and caffeine, and the purity is not high enough. The subsequent purification steps are more complicated.

[0005] Research and application of tea saponin extraction from camellia oil cake still face some challenges. The yield and purity of the extracted tea saponin are both low. In particular, the removal of oil from the camellia oil cake requires multiple steps, purification techniques need improvement, and extraction costs need to be reasonably reduced. Therefore, there is an urgent need for a method to extract tea saponin from camellia oil cake that achieves high yield, fewer processing steps, and higher purification levels.

[0006] The extracted natural tea saponins are nonionic surfactants. Although they possess good biodegradability and low toxicity, they still lag behind synthetic surfactants in terms of hard water resistance, temperature resistance, compatibility with other ionic surfactants, and stability under extreme pH conditions. To expand the application areas of tea saponins and increase their added value, chemical modification of tea saponins is currently a research hotspot. By introducing different functional groups through chemical means, they can be converted into cationic or amphoteric surfactants. Currently, the technology for preparing such surfactants using biomass resources is still under development. In particular, the systematic cationization and amphoteric modification of tea saponins derived from camellia seed cake, and the formation of a complete industrial production process, possess enormous market potential and social value.

[0007] Tea saponin molecules contain numerous modifiable groups such as hydroxyl groups, which can be chemically modified to expand their application range and overcome shortcomings in their use. Currently, research on the chemical modification of tea saponin is increasing. Chinese patent CN103819526B discloses a method and product for preparing tea saponin stearate surfactants. The method involves adding a catalyst, tea saponin, and stearyl chloride to an organic solvent for esterification until complete; post-treatment yields the tea saponin stearate surfactant. This invention also provides a surfactant prepared by the above method. The preparation process of this invention is simple and environmentally friendly. The tea saponin stearate surfactant prepared by this method has better surface activity and a promising market prospect. Chinese patent CN106693830B discloses a method for preparing a benzyloxymethyl ether-type modified tea saponin surfactant, comprising: adding an acid-binding agent, tea saponin, and benzyl chloride methyl ether to an organic solvent for heterogeneous etherification; post-treatment yields the benzyloxymethyl ether-type modified tea saponin surfactant. The patent also provides a surfactant prepared by the above-described method. The preparation process of this patent is simple and environmentally friendly. The benzyloxymethyl ether-type modified tea saponin surfactant prepared by this method has better surface activity and foaming properties, and has good market prospects.

[0008] However, the modified tea saponin surfactants prepared by the two methods mentioned above cannot meet the diverse needs of current surfactants, especially the problems of poor foaming power and foam stability in high-temperature and heavily oily environments. Therefore, developing a multifunctional, high-performance, and environmentally friendly modified tea saponin surfactant is of great significance. Summary of the Invention

[0009] In order to overcome the shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a method for efficiently, greenly and at low cost extracting high-purity tea saponins from camellia oil cake.

[0010] Another objective of this invention is to provide a method for preparing extracted tea saponins into modified surfactants, which significantly improves their surface activity and application performance, solves the problem of poor foaming power and foam stability in high temperature and heavy oil environments, and improves their detergency. This method can be applied in the fields of detergents, shampoos and other personal care products.

[0011] To improve the purity of tea saponins and avoid the extraction of tea saponins containing large amounts of impurities such as proteins and polysaccharides, this invention employs an integrated process of "eutectic solvent-ultrasonic extraction and macroporous resin purification" to extract tea saponins. The process includes the following steps:

[0012] S1. Dry the camellia oil cake and pulverize it, pass it through a 40-80 mesh sieve to obtain camellia oil cake powder, dry it and store it in a cool place for later use;

[0013] S2, add ethyl acetate to camellia oil cake powder, the mass ratio of camellia oil cake powder to ethyl acetate is 1:3-5, stir for 20-30 minutes, centrifuge and dry to obtain defatted camellia oil cake powder;

[0014] S3. Add a eutectic solvent to defatted camellia seed cake powder, raise the temperature to 50-60℃, then ultrasonically extract for 50-100 minutes, separate, and take the upper filtrate to obtain tea saponin extract.

[0015] S4. The resin was soaked in ethanol, hydrochloric acid solution and sodium hydroxide solution respectively, and washed until neutral after each soaking. The tea saponin extract was added to the treated macroporous adsorption resin for adsorption, washed with deionized water, and then eluted with ethanol solution. The eluent was collected, concentrated and freeze-dried to obtain high-purity tea saponin.

[0016] The eutectic solvent is choline chloride, acetamide, glycerol and deionized water in a molar ratio of 1:1 to 2:2 to 3:0.5, and the mixing temperature is 50 to 60°C.

[0017] The frequency of the ultrasound is 10-50 kHz, and the treatment time is 20-40 minutes, followed by a 5-minute interval before repeating. The treatment temperature is 50-60℃.

[0018] The mass ratio of defatted camellia seed cake powder to eutectic solvent is 1:3-4, and the macroporous adsorption resin is at least one of DM301, NKA-9, and DA201.

[0019] The hydrochloric acid solution has a mass fraction of 5%, the sodium hydroxide solution has a mass fraction of 5%, the soaking time is 2 to 6 hours, and the ethanol solution used for elution has a mass concentration of 70%.

[0020] The concentration temperature is 40-50℃, the rotation speed is 30-50 r / min, the freeze-drying temperature is -58 to -38℃, the vacuum degree is 10-15 Pa, and the drying time is 6-20 hours.

[0021] In the preparation of eutectic solvents, although glycerol is a liquid component exhibiting good flowability, it still has a high viscosity at room temperature. Compared to water and 80% ethanol, its high viscosity limits its practical application. To reduce viscosity, a certain amount of water is usually added, but excessive water addition may disrupt the supramolecular structure of the eutectic solvent. Therefore, a small amount of water and acetamide are added during the preparation of the eutectic solvent to balance viscosity and stability. This combination has a lower viscosity than the choline chloride-glycerol system, and the acetamide, acting as a strong hydrogen bond donor, forms strong hydrogen bonds and dipole interactions with the glycosidic bonds and hydroxyl sites of tea saponin molecules, improving the selectivity and solubility of tea saponin. The resulting tea saponin extract has fewer impurities and a higher yield.

[0022] Tea saponins belong to the triterpenoid saponin class of compounds. Their molecules dissolve in water through hydrogen bonding with water molecules, and they hardly ionize after dissolution, making them a nonionic surfactant. Structurally, tea saponins exhibit the typical structure of surfactants—a polar hydrophilic group and a nonpolar hydrophobic group. The hydrophilic portion consists of strongly electronegative oxygen-containing groups such as organic acids, sugars, and glycosidic bonds (-O-), hydroxyl groups (-OH), ester groups (-COO-), carboxyl groups (-COOH), and aldehyde groups (-CHO) at the aglycone linkage. The nonpolar pentacyclic triterpenoid hydrocarbon ring structure of the aglycone moiety exhibits hydrophobic and lipophilic properties. When tea saponin molecules are adsorbed at the gas-liquid interface, the aglycone portion lies flat on the water surface under the influence of the hydrophilic groups in the molecule. The smaller hydrophilic groups (carboxyl groups, hydroxyl groups, etc.) connected to the aglycone interact with each other through hydrogen bonds or cross-entanglement, giving the surface film formed by tea saponin a certain strength. However, due to the rigidity of the pentacyclic triterpenoid structure in the aglycone, it cannot be arranged very tightly. At the same time, the electronegative hydrophilic groups repel each other, resulting in certain gaps between the hydrophobic groups and poor cohesion. This reduces the strength of the surface film. Natural tea saponin has strong foaming properties, but the foam durability is relatively poor. Because the interfacial film formed by tea saponin has gaps and poor cohesion, its mechanical strength is low and its elasticity is poor. When the foam liquid film is subjected to gravity or external disturbances, the stability of the film is limited and it is easy to break. In practice, although it can emulsify quickly, the resulting emulsion is not stable enough and is prone to droplet aggregation, flocculation, and even stratification. This is because the tea saponin molecules cannot be tightly arranged on the surface of the oil droplets due to the rigid structure and repulsive force, and the protective film formed is relatively "loose" and "fragile". When the oil droplets collide with each other due to Brownian motion, this weak film is easily penetrated, resulting in weak detergency and poor foam stability in high-oil and high-temperature environments.

[0023] To address the issues of low water solubility and rapid foam drainage of natural tea saponins, a modified cationic-nonionic surfactant was obtained by grafting long-chain alkyl-polyethylene glycol-amine onto tea saponins.

[0024] First, the primary hydroxyl groups (-CH2OH) at the ends of the tea saponin sugar chains are oxidized to carboxyl groups (-COOH), while retaining the triterpenoid skeleton and double bonds. Specifically:

[0025] S01, Dissolve the extracted natural tea saponin in water, stir evenly, and then add NaBr and NaHCO3 in sequence to obtain a tea saponin pre-reaction solution, and adjust the pH to 8-9.

[0026] S02, add the catalyst 2,2,6,6-tetramethylpiperidine-1-oxy free radical to the tea saponin pre-reaction solution, slowly add NaClO solution dropwise in an ice bath at 0℃, keep the pH at 8-9 during the dropwise addition, stir at room temperature for 1-2 hours after the dropwise addition is completed to obtain a mixed solution;

[0027] SO3 was quenched with isopropanol to remove excess NaClO from the mixture. The pH was slowly adjusted to 2-3 with dilute hydrochloric acid. After acidification for 30-50 minutes, the mixture was extracted with ethyl acetate and dried to obtain a light yellow paste, which is carboxylated tea saponin.

[0028] The mass ratio of natural tea saponin, NaBr and NaClO is 1:0.01~0.02:0.25~0.35, the catalyst 2,2,6,6-tetramethylpiperidine-1-oxy radical is 0.1% of the total mass, the mass ratio of isopropanol to NaClO is 1:1, and ethyl acetate is added at a volume ratio of 1:1 to the aqueous phase.

[0029] Furthermore, carboxylated tea saponin was grafted with long-chain alkyl-polyethylene glycol-amine to obtain a tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine.

[0030] The preparation method of the tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine is as follows:

[0031] S001, carboxylated tea saponin was dissolved in 0.1M MES buffer, pH controlled at 5.0-6.0, N-hydroxysulfosuccinimide was added, and the mixture was stirred until homogeneous. Then 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added, and the mixture was stirred at 300-400 rpm and reacted at room temperature in the dark for 15-60 minutes to obtain an activated solution. At this point, the carboxyl groups on the carboxylated tea saponin were activated, and this was referred to as activated carboxylated tea saponin.

[0032] S002, first slowly add dilute NaOH solution dropwise to the activation solution while stirring to adjust the pH of the reaction system to 7.2-7.8. Then dissolve the long-chain alkyl-polyethylene glycol-amine in 30% ethanol solution and slowly add it at room temperature. Stir gently for 2-6 hours. After the reaction is complete, dialyze with deionized water for 48-72 hours, changing the water 4-5 times to completely remove small molecule impurities and excess polyethylene glycol. After the purified solution is concentrated under reduced pressure to 1 / 3 of the original volume, freeze-dry to obtain a white, loose, flaky solid, which is the tea saponin modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine.

[0033] This tea saponin-modified surfactant, grafted with long-chain alkyl-polyethylene glycol-amine, significantly enhances the hydration of the entire molecule, resulting in improved solubility and stability in hard water. Polyethylene glycol, a strongly hydrophilic unit, forms a dense, highly hydrated "brush-like" protective layer at the interface after grafting. This effectively prevents droplet polymerization or flocculation, enhancing emulsion stability. Simultaneously, it strengthens the surface viscoelasticity of the liquid film, leading to more stable and finer foam. Furthermore, the polyethylene glycol chain physically shields the irritating hydrophobic portion of the tea saponin aglycone, reducing irritation to skin and mucous membranes, making it more suitable for use in high-end daily chemical or personal care products.

[0034] To avoid affecting the surface activity of tea saponin due to the significantly increased hydrophilicity of the resulting substance after introducing polyethylene glycol chains, the chain length of polyethylene glycol must be controlled within a molecular weight range of 500–2000. At the same time, long-chain alkyl groups are introduced, which introduces a strong hydrophobic tail on the basis of the polyethylene glycol hydrophilic chain, forming a unique amphiphilic structure of tea saponin hydrophobic head-polyethylene glycol hydrophilic chain-alkyl hydrophobic tail, which greatly enhances the surface activity of the modified product.

[0035] The polyethylene glycol is polyethylene glycol with a molecular weight of 500 to 2000, and the long-chain alkyl group is a C16 to C18 long-chain alkyl group;

[0036] The modified tea saponin surfactant, grafted with long-chain alkyl-polyethylene glycol-amine, exhibits excellent cleaning performance at the macroscopic level primarily due to its surface activity, which reduces liquid surface tension, and its solubilizing effect, which promotes the dissolution of poorly soluble substances. Foam is essentially a bilayer formed by the attraction of hydrophilic groups between two surfactant molecules, while the lipophilic groups remain in the air. Therefore, foam easily forms in high-volume air environments such as spraying. The key is to ensure the rapid collapse of the formed foam. When the foam formation rate is lower than the collapse rate, the macroscopic manifestation is low-foaming performance. Therefore, selecting an appropriate ratio of hydrophilic to lipophilic groups is crucial for controlling the foam formation and collapse rates, achieving good foam stability.

[0037] The mass ratio of carboxylated tea saponin, N-hydroxysulfosuccinimide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is 10:1.3-1.8:3-4.0; the mass ratio of activated carboxylated tea saponin and long-chain alkyl-polyethylene glycol-amine is 1:2.2-2.8.

[0038] The cleaning process is essentially the process by which surfactants penetrate and diffuse into impurity particles, causing the particles to swell, soften, and loosen. When the surfactant concentration in the cleaning solution exceeds the critical micelle concentration, the impurity particles are solubilized to varying degrees and then rapidly removed. During cleaning, oil stains are also emulsified by the surfactants in the cleaning agent. The contaminants are dispersed and suspended in the aqueous solution under mechanical force or the action of some water-soluble polymers. They are then adsorbed or enriched at the oil-water interface under hydrophobic driving forces. Therefore, the entire cleaning process is synergistically accomplished through the wetting, penetration, and emulsification effects of surfactants. The modified surfactant by grafting tea saponin has both hydrophobic and hydrophilic groups. On the one hand, the strong adsorption and film-forming properties of the cationic groups can act quickly on the oily surface, accelerating the penetration. Polyethylene glycol is a strong hydrophilic unit and can form a dense, highly hydrated "brush-like" protective layer at the interface. Its hydrophilic groups can insert between the groups on the micelle surface, thereby reducing the electrostatic repulsion between the groups. On the other hand, the surfactant molecules can form intermolecular hydrogen bonds, which promotes the micellization process and significantly reduces the surface tension, thus improving the speed and efficiency of the entire cleaning process.

[0039] On the other hand, cationic groups also possess excellent antibacterial properties, offering the following advantages compared to small-molecule surfactants: Due to the presence of tea saponin and amine groups in their molecular structure, they can form a more stable antibacterial film, exhibiting a strong affinity for bacterial cell membranes, resulting in longer surface retention and a lasting bactericidal effect. More importantly, they possess good biodegradability and low toxicity, preventing pollution and harm to the environment and human body. Therefore, the prepared tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine effectively solves the problem of natural tea saponin molecules failing to tightly arrange themselves on oil droplet surfaces due to their rigid structure and repulsive forces, resulting in a relatively "loose" and "fragile" protective film. This significantly improves its detergency, foam stability, and cleaning efficiency in high-oil, high-temperature environments.

[0040] The present invention also provides a cleaning agent comprising 5-8% by weight of a tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine; further comprising 5-8% sodium fatty alcohol polyoxyethylene ether sulfate, 0.1-1% sodium chloride, 2-5% cocoyl monoethanolamide, 0.05-0.4% fragrance, 0.2-0.4% citric acid, 0.5-4% cocamidopropyl betaine, 1-2% sodium polyaspartate, 0.1-0.2% phenoxyethanol, and the balance being deionized water.

[0041] Compared with existing technologies, the beneficial effects of this invention are as follows:

[0042] 1) This invention utilizes an integrated process of eutectic solvent extraction, ultrasonic extraction, and macroporous resin purification to extract tea saponins. By adjusting the combination of hydrogen bond donors and acceptors, a eutectic solvent with high selective solubility for the target molecule, tea saponin, is tailored, thereby improving the extraction rate and enhancing selectivity. This significantly simplifies the extraction process, especially the purification process, and yields tea saponins with high purity and good usability. The eutectic solvent has a stronger hydrogen bond forming ability than traditional solvents, effectively breaking down cellulose and hemicellulose in the cell walls of tea seeds and penetrating into the matrix, promoting the leaching of tea saponins from within plant cells. It can selectively dissolve saponins while having relatively low solubility for macromolecular impurities such as proteins and polysaccharides. This helps to obtain a crude extract with less impurity content, decomposes and purifies interfering components, and after adsorption by macroporous resin, high-purity tea saponins can be obtained through a one-step elution. The purity of tea saponins obtained by this method is ≥97.5%, which can be directly applied in the daily chemical and other fields.

[0043] 2) This modification method first utilizes the hydroxyl active sites in the tea saponin molecule to oxidize the primary hydroxyl groups (-CH2OH) at the ends of the tea saponin sugar chains to carboxyl groups (-COOH), while retaining the triterpenoid skeleton and double bonds. Then, long-chain alkyl-polyethylene glycol-amine is grafted onto the carboxylated tea saponin to obtain a cationic-nonionic modified surfactant. The introduction of the long-chain alkyl group introduces a strongly hydrophobic tail onto the hydrophilic polyethylene glycol chain, forming a unique amphiphilic structure of tea saponin hydrophobic head-polyethylene glycol hydrophilic chain-alkyl hydrophobic tail, greatly enhancing the surface activity of the modified surfactant. The tea saponin modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine significantly improves the hydration of the entire molecule, and its solubility and stability in hard water are also significantly enhanced. After grafting, a dense, highly hydrated "brush-like" protective layer forms at the interface, which more effectively prevents droplet aggregation or flocculation, enhancing emulsion stability. Simultaneously, it also enhances the surface viscoelasticity of the liquid film, resulting in more stable and delicate foam. The polyethylene glycol chain can also physically shield the irritating hydrophobic portion of tea saponin aglycones, reducing irritation to skin or mucous membranes, making it more suitable for use in high-end daily chemical or personal care products.

[0044] 3) The tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine effectively solves the problem that natural tea saponin molecules cannot tightly arrange themselves on the surface of oil droplets due to their rigid structure and repulsive forces, resulting in a relatively "loose" and "fragile" protective film. This significantly improves its detergency, foam stability, and cleaning efficiency in high-oil, high-temperature environments. Its water solubility is greatly enhanced, its HLB value is increased, its foaming ability and foam stability are strengthened, its salt and hard water resistance are significantly improved, and its emulsification ability with oils is enhanced. It is also gentler to use, making it a green surfactant. Attached Figure Description

[0045] Figure 1 Comparison of infrared spectra of natural tea saponin extracted in Example 1 and tea saponin standard sample;

[0046] Figure 2 The comparison curve of the scavenging rate of ·OH by the tea saponin modified surfactant prepared in Example 1 and the natural tea saponin extracted in Comparative Example 4.

[0047] Figure 3 The tea saponin-modified surfactant prepared in Example 1 and the natural tea saponin extracted in Comparative Example 4 are compared with O2. － The comparison curve of clearance rate. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0049] Example 1

[0050] A method for extracting tea saponins from camellia seed cake involves first employing an integrated process of "eutectic solvent-ultrasonic extraction and macroporous resin purification" to extract tea saponins, specifically:

[0051] 100 portions of camellia seed cake were dried, pulverized, and passed through an 80-mesh sieve to obtain camellia seed cake powder. The powder was then dried and stored in a cool place for later use.

[0052] Add 150 parts of ethyl acetate to 50 parts of camellia seed cake powder, stir for 30 minutes, centrifuge and dry to obtain defatted camellia seed cake powder;

[0053] Choline chloride, acetamide, glycerol, and deionized water were prepared in a molar ratio of 1:1:2:0.5 and stirred evenly at 50°C to obtain a eutectic solvent. 30 parts of the eutectic solvent were added to 10 parts of defatted camellia seed cake powder, the temperature was raised to 60°C, and then ultrasonically extracted for 100 minutes at a frequency of 20 kHz with 5-minute intervals. The extract was then centrifuged, filtered, and the supernatant was collected to obtain the tea saponin extract.

[0054] The macroporous resin DM301 was soaked in ethanol, 5% hydrochloric acid solution, and 5% sodium hydroxide solution for 3 hours each, and washed until neutral after each soaking. The tea saponin extract was added to the treated macroporous adsorption resin DM301 for adsorption, and then washed with two column volumes of deionized water. It was then eluted with 70% ethanol solution, and the eluent was collected and concentrated in a rotary evaporator under reduced pressure at 50°C and 40 r / min. Finally, it was freeze-dried at -50°C under a vacuum of 12 Pa for 12 hours to obtain tea saponin.

[0055] Furthermore, the primary hydroxyl groups (-CH2OH) at the ends of the sugar chains of the extracted natural tea saponins are oxidized to carboxyl groups (-COOH) to prepare carboxylated tea saponins, specifically as follows:

[0056] Dissolve 10 parts of extracted natural tea saponin in 100 parts of deionized water, then add 0.1 parts of NaBr, stir well, and then add NaHCO3 to adjust the pH to 8.5 to obtain tea saponin pre-reaction solution.

[0057] Add 0.15 parts of the catalyst 2,2,6,6-tetramethylpiperidine-1-oxy free radical to the tea saponin pre-reaction solution, and slowly add 2.5 parts of NaClO solution dropwise in an ice bath at 0°C, maintaining the pH at 8-9 during the dropwise addition. After the dropwise addition is complete, stir at room temperature for 1-2 hours to obtain a mixed solution.

[0058] Excess NaClO in the mixture was quenched with 2.5 parts isopropanol, the pH was slowly adjusted to 2.5 with dilute hydrochloric acid, and after acidification for 40 minutes, it was extracted with ethyl acetate and dried to obtain a light yellow paste, which is carboxylated tea saponin.

[0059] Furthermore, carboxylated tea saponin was modified to obtain a tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine, specifically...

[0060] Ten parts of carboxylated tea saponin were dissolved in 100 parts of 0.1M MES buffer, with the pH controlled at 5.5. 1.3 parts of N-hydroxysulfosuccinimide were added and stirred until dissolved. Then, 4 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride were added and stirred at 350 rpm. The mixture was reacted at room temperature in the dark for 50 minutes to obtain the activated solution. At this point, the carboxyl groups on the carboxylated tea saponin were activated, and this was referred to as the activated carboxylated tea saponin.

[0061] First, slowly add dilute NaOH solution dropwise to the activation solution while stirring to adjust the pH of the reaction system to 7.5. Dissolve 22 parts of C18 alkyl-polyethylene glycol-amine in 50 parts of 30% ethanol solution and slowly add it to the activation solution at room temperature. Stir at 60 r / min for 2 to 6 hours. After the reaction is complete, dialyze with deionized water for 72 hours, changing the water 5 times to completely remove small molecule impurities and excess polyethylene glycol. Concentrate the purified solution under reduced pressure to 1 / 3 of the original volume and then freeze-dry to obtain a white, loose, flaky solid tea saponin modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine.

[0062] Finally, by mass fraction, weigh out 8% of the tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine, 5% of sodium fatty alcohol polyoxyethylene ether sulfate, 2% of cocoyl monoethanolamide, 0.2% of fragrance, 0.2% of citric acid, 4% of cocamidopropyl betaine, 1% of sodium polyaspartate, 0.1% of phenoxyethanol, and the remainder of deionized water. Heat to 60°C, stir evenly, and finally add 0.5% sodium chloride and stir evenly to obtain the cleaning agent.

[0063] Example 2

[0064] A method for extracting tea saponins from camellia seed cake involves first employing an integrated process of "eutectic solvent-ultrasonic extraction and macroporous resin purification" to extract tea saponins, specifically:

[0065] 100 portions of camellia seed cake were dried, pulverized, and passed through an 80-mesh sieve to obtain camellia seed cake powder. The powder was then dried and stored in a cool place for later use.

[0066] Add 250 parts of ethyl acetate to 50 parts of camellia seed cake powder, stir for 20 minutes, centrifuge and dry to obtain defatted camellia seed cake powder;

[0067] Choline chloride, acetamide, glycerol, and deionized water were prepared in a molar ratio of 1:2:2:0.5 and stirred evenly at 50°C to obtain a eutectic solvent. 40 parts of the eutectic solvent were added to 10 parts of defatted camellia seed cake powder, the temperature was raised to 60°C, and then ultrasonically extracted for 100 minutes at a frequency of 50 kHz with a 20-minute ultrasonic interval of 5 minutes. The extract was then centrifuged, filtered, and the supernatant was collected to obtain the tea saponin extract.

[0068] The NKA-9 resin was soaked in ethanol, 5% hydrochloric acid solution, and 5% sodium hydroxide solution for 3 hours each, and washed until neutral after each soaking. The tea saponin extract was added to the treated macroporous adsorption resin NKA-9 for adsorption, then washed with two column volumes of deionized water, and eluted with 70% ethanol solution. The eluent was collected and concentrated in a rotary evaporator under reduced pressure at 50°C, 40 r / min, and 0.2 MPa. Finally, it was freeze-dried at -50°C, 10 Pa, and for 18 hours to obtain tea saponin.

[0069] Furthermore, the primary hydroxyl groups (-CH2OH) at the ends of the sugar chains of the extracted natural tea saponins are oxidized to carboxyl groups (-COOH) to prepare carboxylated tea saponins, specifically as follows:

[0070] Dissolve 10 parts of extracted natural tea saponin in 100 parts of deionized water, then add 0.2 parts of NaBr, stir well, and then add NaHCO3 to adjust the pH to 9.0 to obtain tea saponin pre-reaction solution.

[0071] Add 0.15 parts of the catalyst 2,2,6,6-tetramethylpiperidine-1-oxy free radical to the tea saponin pre-reaction solution, and slowly add 3.5 parts of NaClO solution dropwise in an ice bath at 0°C, maintaining the pH at 8-9 during the dropwise addition. After the dropwise addition is complete, stir at room temperature for 2 hours to obtain a mixed solution.

[0072] Excess NaClO in the mixture was quenched with 3.5 parts isopropanol, the pH was slowly adjusted to 3 with dilute hydrochloric acid, and after acidification for 40 minutes, it was extracted with ethyl acetate and dried to obtain a light yellow paste, which is carboxylated tea saponin.

[0073] Furthermore, carboxylated tea saponin was modified to obtain a tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine, specifically...

[0074] Ten parts of carboxylated tea saponin were dissolved in 100 parts of 0.1M MES buffer, with the pH controlled at 5.8. 1.8 parts of N-hydroxysulfosuccinimide were added and stirred until dissolved. Then, 3.5 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride were added and stirred at 350 rpm. The mixture was reacted at room temperature in the dark for 50 minutes to obtain the activated solution. At this point, the carboxyl groups on the carboxylated tea saponin were activated, and this was referred to as the activated carboxylated tea saponin.

[0075] First, dilute NaOH solution was slowly added dropwise to the activation solution while stirring to adjust the pH of the reaction system to 7.7. 28 parts of C18 alkyl-polyethylene glycol-amine were dissolved in 60 parts of 30% ethanol solution and slowly added to the activation solution at room temperature. The mixture was stirred at 60 r / min for 4 hours. After the reaction was completed, the mixture was dialyzed with deionized water for 72 hours, with the water changed 5 times to completely remove small molecule impurities and excess polyethylene glycol. The purified solution was concentrated under reduced pressure to 1 / 3 of its original volume and then freeze-dried to obtain a white, loose, flaky solid tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine.

[0076] Finally, by mass fraction, weigh out 5% of the modified surfactant of tea saponin grafted with long-chain alkyl-polyethylene glycol-amine, 8% of sodium fatty alcohol polyoxyethylene ether sulfate, 4% of cocoyl monoethanolamide, 0.2% of fragrance, 0.2% of citric acid, 1% of cocamidopropyl betaine, 1% of sodium polyaspartate, 0.1% of phenoxyethanol, and the remainder of deionized water. Heat to 60°C, stir evenly, and add 0.5% sodium chloride to obtain the cleaning agent.

[0077] Example 3

[0078] A method for extracting tea saponins from camellia seed cake involves first employing an integrated process of "eutectic solvent-ultrasonic extraction and macroporous resin purification" to extract tea saponins, specifically:

[0079] 100 portions of camellia seed cake were dried, pulverized, and passed through an 80-mesh sieve to obtain camellia seed cake powder. The powder was then dried and stored in a cool place for later use.

[0080] Add 200 parts of ethyl acetate to 50 parts of camellia seed cake powder, stir for 20-30 minutes, centrifuge and dry to obtain defatted camellia seed cake powder;

[0081] Choline chloride, acetamide, glycerol, and deionized water were prepared in a molar ratio of 1:2:3:0.5 and stirred evenly at 50°C to obtain a eutectic solvent. 35 parts of the eutectic solvent were added to 10 parts of defatted camellia seed cake powder, the temperature was raised to 60°C, and then ultrasonically extracted for 100 minutes at a frequency of 40 kHz with a frequency of 20 minutes followed by 5 minutes intervals. The extract was then centrifuged, filtered, and the supernatant was collected to obtain the tea saponin extract.

[0082] Resin DA201 was soaked in ethanol, 5% hydrochloric acid solution, and 5% sodium hydroxide solution for 3 hours each, and washed until neutral after each soaking. The tea saponin extract was added to the treated macroporous adsorption resin DA201 for adsorption, then washed with two column volumes of deionized water, and eluted with 70% ethanol solution. The eluent was collected and concentrated in a rotary evaporator under reduced pressure at 50°C and 40 r / min. Finally, it was freeze-dried at -40°C under a vacuum of 12 Pa for 20 hours to obtain tea saponin.

[0083] Furthermore, the primary hydroxyl groups (-CH2OH) at the ends of the sugar chains of the extracted natural tea saponins are oxidized to carboxyl groups (-COOH) to prepare carboxylated tea saponins, specifically as follows:

[0084] Dissolve 10 parts of extracted natural tea saponin in 100 parts of deionized water, then add 0.2 parts of NaBr, stir well, and then add NaHCO3 to adjust the pH to 8.5 to obtain tea saponin pre-reaction solution.

[0085] Add 0.15 parts of the catalyst 2,2,6,6-tetramethylpiperidine-1-oxy free radical to the tea saponin pre-reaction solution, and slowly add 3.0 parts of NaClO solution dropwise in an ice bath at 0°C, maintaining the pH at 9 during the dropwise addition. After the dropwise addition is complete, stir at room temperature for 2 hours to obtain a mixed solution.

[0086] Excess NaClO in the mixture was quenched with 3.0 parts isopropanol, the pH was slowly adjusted to 3 with dilute hydrochloric acid, and after acidification for 50 minutes, it was extracted with ethyl acetate and dried to obtain a light yellow paste, which is carboxylated tea saponin.

[0087] Furthermore, carboxylated tea saponin was modified to obtain a tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine, specifically...

[0088] Ten parts of carboxylated tea saponin were dissolved in 100 parts of 0.1M MES buffer, with the pH controlled at 6.0. 1.5 parts of N-hydroxysulfosuccinimide were added and stirred until dissolved. Then, 3.5 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride were added and stirred at 350 rpm. The mixture was reacted at room temperature in the dark for 50 minutes to obtain the activated solution. At this point, the carboxyl groups on the carboxylated tea saponin were activated, and this was referred to as the activated carboxylated tea saponin.

[0089] First, dilute NaOH solution was slowly added dropwise to the activation solution while stirring to adjust the pH of the reaction system to 7.5. 24 parts of C16 alkyl-polyethylene glycol-amine were dissolved in 50 parts of 30% ethanol solution and slowly added to the activation solution at room temperature. The mixture was stirred at 60 r / min for 4 hours. After the reaction was completed, the mixture was dialyzed with deionized water for 72 hours, with the water changed 5 times to completely remove small molecule impurities and excess polyethylene glycol. The purified solution was concentrated under reduced pressure to 1 / 3 of its original volume and then freeze-dried to obtain a white, loose, flaky solid tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine.

[0090] Finally, by mass fraction, weigh out 7% of the modified surfactant of tea saponin grafted with long-chain alkyl-polyethylene glycol-amine, 6% of sodium fatty alcohol polyoxyethylene ether sulfate, 4% of cocoacid monoethanolamide, 0.2% of fragrance, 0.3% of citric acid, 0.5% of cocamidopropyl betaine, 2% of sodium polyaspartate, 0.2% of phenoxyethanol, and the balance of deionized water. Heat to 60°C, stir evenly, and add 0.3% sodium chloride to obtain the cleaning agent.

[0091] Comparative Example 1: The eutectic solvent was replaced with an equal amount of 50% ethanol aqueous solution. The mixture was heated at 90°C for 2 hours. The extraction process was repeated twice, with extraction times of 1 hour and 1 hour respectively. The three extracts were mixed, centrifuged, and filtered to obtain tea saponin extract. Other extraction processes were the same as in Example 1.

[0092] Comparative Example 2: The eutectic solvent was replaced with an equal amount of 80% ethanol aqueous solution. The mixture was heated at 60°C and ultrasonically extracted for 2 hours. The extraction process was repeated twice, with ultrasonic extraction times of 1 hour and 1 hour each time. The three extracts were mixed, centrifuged, and filtered to obtain tea saponin extract. Other extraction processes were the same as in Example 1.

[0093] Comparative Example 3: Choline chloride and glycerol were mixed in a molar ratio of 1:3 to obtain a eutectic solvent that replaced the eutectic solvent in Example 1 in equal amounts. Other extraction processes were the same as in Example 1.

[0094] Comparative Example 4: The natural tea saponin extracted in Example 1 was directly formulated into a cleaning agent without modification, and the rest was the same as in Example 1;

[0095] Comparative Example 5: The extracted natural tea saponins were modified by replacing C18 alkyl-polyethylene glycol-amine with polyethylene glycol-amine, and the rest was the same as in Example 1;

[0096] Comparative Example 6: The extracted natural tea saponins were modified with C18 alkyl-polyethylene glycol-amine, wherein the selected polyethylene glycol had a molecular weight of 5000, and the other conditions were the same as in Example 1.

[0097] Comparative Example 7: The extracted natural tea saponin was modified with the EO / PO block polyether in formulation 2 of Example 2 (patent number CN111592944B) to obtain a tea saponin-modified surfactant grafted with EO / PO block polyether. The preparation method of the detergent was the same as in Example 1.

[0098] Experimental data and results analysis

[0099] 1. Spectroscopic identification of tea saponins

[0100] The natural tea saponin extracted in Example 1 was subjected to Fourier transform infrared spectroscopy using the reflectance method, and compared with the infrared spectrum of the tea saponin standard sample. (See figure) Figure 1 ,from Figure 1 The infrared spectra of tea saponin extracted in Example 1 and the tea saponin standard sample can be seen. Figure 1 To. Both are 3390cm -1 The largest absorption peak at this point is generated by the superposition of several hydroxyl groups (-OH), and its in-plane bending vibration peak is located at 1384 cm⁻¹. -1 The characteristic absorption peak of the C-OH bond is at 1073 cm⁻¹. -1 and 1263cm -1 The saturated CH bond vibration peak is located at 2932 cm⁻¹. -1 Its in-plane bending vibration is located at 1608 cm. -1 The carbonyl (C=O) stretching vibration peak appears at 1654 cm⁻¹. -1 and 1718cm -1 The presence of two carbonyl groups in the molecule indicates the presence of both an ester group and a carboxyl group (or an aldehyde group). The out-of-plane bending vibration peak of the unsaturated CH bond is visible at 642 cm⁻¹. -1 This is due to the C=C bonds on the triterpenoid rings in the molecule. In addition, the symmetric and asymmetric stretching vibrations generated by the COC bonds connecting the various sugar rings appear at 1131 cm⁻¹. -1 and 1049cm -1 Place.

[0101] Therefore, the infrared absorption peak positions of the sample in Example 1 completely correspond to those of the tea saponin standard, with the characteristic peaks from the hydroxyl region to the glycosidic bond region all overlapping. This proves that the core structure of the substance extracted in Example 1 is tea saponin, and the purity and structural consistency of the target product of the process meet the standards. Meanwhile, the sample in Example 1 shows absorption peaks in the range of 3500–3000 cm⁻¹. -1 The hydroxyl absorption peak is broader and more intense, in the range of 1500–500 cm⁻¹. -1 The fingerprint region peak is slightly slower, which may be due to the stronger molecular hydrogen bonding of tea saponin in the Example 1 sample, the presence of trace amounts of glycosylated side chain modified impurities or water.

[0102] 2. Tea saponin extraction rate and purity test

[0103] Quantitative detection of natural tea saponins extracted in Examples 1-3 and Comparative Examples 1-3 was performed using high-performance liquid chromatography (HPLC). 10 mg of tea saponin standard was accurately weighed, dissolved in chromatographic-grade methanol to prepare a 1 mg / mL tea saponin standard solution, and then diluted with methanol to prepare solutions of 0.4, 0.2, and 0.1 mg / mL, respectively. The standard solutions of different concentrations were filtered through a 0.45 μm microporous membrane and analyzed by chromatographic injection. A C18 column was used at 30 °C. The mobile phase was methanol (A):water (B), with isocratic elution (35:65, V / V), a flow rate of 1.0 mL / min, a detection wavelength of 265 nm, and an injection volume of 10 μL. Chromatograms were recorded, and linear regression was performed with the peak area (Y) of tea saponin (X, mg / mL) as the ordinate and the injection concentration (X, mg / mL) as the abscissa. The above samples were subjected to chromatographic injection analysis, and the tea saponin content was calculated by the sum of the chromatographic peak areas of tea saponin. The extraction rate and purity of tea saponin are shown in Table 1.

[0104] Table 1. Extraction rate and purity record of tea saponin

[0105]

[0106] As shown in Table 1, the extraction rate is relatively low when using a eutectic solvent obtained by mixing choline chloride and glycerol in a molar ratio of 1:3 as the extraction solvent. This is mainly because the solvent is highly polar during extraction, resulting in weak interaction between the solvent and tea saponin. Furthermore, the solvent forms a highly stable hydrogen-bonded complex, making effective separation difficult. Additionally, the high viscosity of the choline chloride and glycerol system slows down the permeation rate, significantly impacting extraction efficiency. Comparative Examples 1-2, using traditional ethanol solutions as extraction solvents, have limited extraction rates and introduce a large amount of polysaccharide and protein impurities, affecting purity. In contrast, Examples 1-3 provide a eutectic solvent composition of choline chloride, acetamide, glycerol, and deionized water. This composition forms strong hydrogen bonds with tea saponin, significantly improving solubility. Additionally, the low viscosity of this combination enhances mass transfer efficiency. Moreover, it exhibits relatively low solubility for large molecular impurities such as proteins and polysaccharides, contributing to a crude extract with lower impurity content. This also decomposes and purifies interfering components, leading to high purification levels when combined with macroporous resins.

[0107] 3. Surface activity test

[0108] The critical micelle concentration and surface tension of the tea saponin-modified surfactants grafted with long-chain alkyl-polyethylene glycol-amines prepared in Examples 1-3 were determined using the platinum plate method at 25°C. The critical micelle concentration and surface tension of the natural tea saponin in Comparative Example 4 and the other modified tea saponins in Comparative Examples 5-7 were also determined, and the results are shown in Table 2.

[0109] Table 2 Test Record of Surface Activity

[0110]

[0111] As shown in Table 2, in Comparative Example 6, as the molecular weight of polyethylene glycol increases, the longer the chain, the stronger its hydrophilicity, and the higher the CMC (Cellular Molecular Weight). However, the surface tension also increases because the longer polyethylene glycol chains are more loosely arranged at the interface, resulting in lower removal efficiency for heavy oil stains. Compared to Example 1, Comparative Example 5 shows a significant reduction in CMC due to the introduction of long-chain alkyl groups, which increases hydrophobicity and makes the molecules more easily oriented, aggregating at the interface to form micelles. Compared to Comparative Example 5, the introduction of long-chain alkyl groups in Comparative Example 6 further reduces both CMC and surface tension. However, because of the introduction of long polyethylene glycol chains in Comparative Example 6, the reduction in surface tension is not significant.

[0112] Surface tension measurements revealed that, starting from lower concentrations, the surface tension of each surfactant decreased relatively rapidly with increasing solution concentration. After reaching the critical micelle concentration, the surface tension remained essentially stable with further increases in concentration. The surface tension of several modified surfactants, including those in Example 1 and Comparative Examples 5-7, decreased. The decrease in surface tension was most significant in Example 1, demonstrating the excellent surface activity of the tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine. The surface activity of the tea saponin-modified surfactant grafted with EO / PO block polyether in Comparative Example 7 was not significantly different from that of the examples.

[0113] 4. Cleaning efficiency test

[0114] The glass test slides contained typical contaminants such as grease, syrup, dust, pigments, and proteins. Specifically, the composition was: 20.0g kerosene, 20.0g soy sauce, 20.0g cooking oil, 20.0g mud ash, and 20.0g brown sugar syrup. The mud ash was derived from ordinary yellow clay and pretreated before the experiment by drying it to constant weight in a (55±2)℃ constant temperature drying oven and then passing it through an 80-mesh sieve. The specific preparation steps for the glass test slides were as follows: a clean glass slide was evenly coated with the prepared oil ash and placed flat on a clean enamel dish. It was then placed in a (55±2)℃ constant temperature drying oven for 10 hours, removed, and cooled and aged in a desiccator for 2 hours.

[0115] Transmittance measurement: In a V-1200 UV-Vis spectrophotometer, place a glass sample, select air as the reference, and set the measurement wavelength range to 400-750 nm. Measure the transmittance of the glass sample before and after cleaning.

[0116] The cleaning ability of the cleaning agent is characterized by a gravimetric method. The glass test piece coated with oil is cleaned with the prepared cleaning agent, dried and weighed, and the cleaning efficiency is calculated according to the following formula.

[0117] Cleaning efficiency = (C0 - C) / C0 100%

[0118] Where C0 is the total mass of the glass slide and the oil stain, in grams;

[0119] C represents the weight after cleaning, in grams.

[0120] The cleaning agents of Examples 1-3 and Comparative Examples 4-7 were prepared into aqueous solutions with a mass fraction of 1% and used to spray and clean glass test pieces uniformly coated with oil stains. The cleaning efficiency of the cleaning agents in Examples 1-3 and Comparative Examples 4-7 was calculated, and the transmittance of the cleaned glass test pieces was measured. Since the cleaning efficiency is also related to the temperature, the cleaning efficiency was measured at 25°C, 50°C and 70°C for 5 minutes, and the corresponding transmittance of the cleaned glass test pieces was measured. See Table 3.

[0121] Table 3 Cleaning efficiency and light transmittance

[0122]

[0123] Table 3 shows that the cleaning efficiency of Examples 1-3 and Comparisons 5-6 all increased with increasing temperature. The cleaning efficiency of Examples 1-3 did not change significantly with temperature, exhibiting excellent cleaning efficiency at both low and high temperatures, with high-temperature cleaning efficiencies exceeding 98%. This is because the prepared tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine has strong emulsifying ability and good penetration and dispersibility, easily decomposing and removing oil stains from glass, especially at high temperatures. Furthermore, the light transmittance of the glass in Examples 1-3 remained excellent from 25°C to 70°C, slightly increasing with further temperature, essentially approaching the maximum transmittance of ordinary glass. This is because the tea saponin-modified surfactant prepared in this invention has both hydrophilic and lipophilic groups in its structure, resulting in excellent cleaning ability for both hydrophilic and lipophilic substances on glass, thus providing excellent cleaning effects at different temperatures. In Comparative Example 7, the tea saponin-modified surfactant grafted with EO / PO block polyether has a cloud point of 54℃. Therefore, it will precipitate as the temperature increases. The block copolymer in the surfactant has strong adhesion and easily adsorbs and penetrates the glass surface, resulting in a decrease in light transmittance. In Comparative Example 4, the natural tea saponin shows improved solubility at high temperatures, but its stability decreases at high temperatures, thus exhibiting an initial increase followed by a decrease in cleaning efficiency.

[0124] While the modified Comparative Example 7 has similar surface tension and critical micelle concentration to the examples, exhibiting excellent cleaning capabilities, its cleaning ability decreases significantly at high temperatures due to its high-temperature stability. This is because the cloud point is closely related to the number of ethylene oxide units in the molecule. A decrease in the EO number means a reduction in ethylene oxide units in the molecule, leading to weakened hydrophilicity. This not only lowers the cloud point but also increases viscosity, surface tension, and emulsification performance. A lower cloud point results in more precipitation, making it easier to accumulate on the glass surface. Increased surface tension weakens surface activity and reduces emulsification performance, further exacerbating the deterioration of cleaning efficiency, ultimately leading to poorer cleaning results and reduced light transmittance.

[0125] Therefore, the prepared tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine effectively solves the problem that natural tea saponin molecules cannot be tightly arranged on the surface of oil droplets due to rigid structure and repulsive force, resulting in a relatively "loose" and "fragile" protective film. It significantly improves its detergency, foam stability and cleaning efficiency in high-oil and high-temperature environments.

[0126] 5. Antibacterial and antioxidant capabilities

[0127] The Oxford cup method was used to verify the antibacterial effects of tea saponin on *Escherichia coli*, *Staphylococcus aureus*, and *Bacillus subtilis* using the newly prepared tea saponin-modified surfactant from Example 1 and the natural tea saponin from Comparative Example 4. The test strains were aseptically inoculated onto test tube slant agar plates and incubated at 37°C for 20 hours. After bacterial growth, sterile distilled water was added to dissolve and shaken to form a suspension. Sterile solid culture medium was melted and poured into sterile petri dishes, and 15 ml of the prepared suspension was added to each dish. The medium was gently shaken to a thickness of 2.0-2.5 mm. Sterile Oxford cups were quickly placed on plates containing the respective strains (4 cups per plate). A 100 g / L tea saponin solution was injected into each plate, and the plates were incubated at 37°C for 20 hours. The bactericidal effect was observed, and the diameter of the inhibition zone produced by each strain was measured. Each inhibition zone was measured three times, and each concentration was replicated three times. The average value was taken. The results are shown in Table 4.

[0128] Table 4. Antibacterial effect against different bacterial species (inhibition zone diameter in mm)

[0129]

[0130] Table 4 shows that the tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine exhibited better antibacterial effects against the three bacteria than the unmodified natural tea saponin. This is mainly because the modified tea saponin incorporates cationic groups, making it a cationic-nonionic surfactant. Cationic surfactants themselves possess antibacterial capabilities and can synergistically enhance the antibacterial effect with tea saponin molecules, forming a more stable antibacterial film. This film forms a strong affinity with the cell membrane of bacteria, resulting in a longer retention time on the surface and a more lasting antibacterial effect.

[0131] Compare the antioxidant capacity of the tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine prepared in Example 1 with that of the natural tea saponin in Comparative Example 4, see [reference needed]. Figure 2 and Figure 3 ,Depend on Figure 2 and Figure 3 It can be seen that as the mass concentration of the solution increases, the tea saponin-modified surfactant in Example 1 has a greater effect on ·OH and ·O2. － The scavenging effect gradually increased, and the scavenging rate of free radicals was higher than that of natural tea saponin at the same mass concentration. When the mass concentration of the tea saponin-modified surfactant was 1.0 g / L, its scavenging effect on ·OH and ·O2 was measured. － The removal rates reached 63.8% and 74.9% respectively, which were significantly higher than those of natural tea saponins of the same mass concentration, indicating that the antioxidant capacity of the modified product was significantly improved compared with that of natural tea saponins.

[0132] 6. Foam stability test and hard water resistance test

[0133] The modified tea saponins of Examples 1-3 and Comparative Examples 4-7 were prepared into aqueous solutions with a mass fraction of 1%. The foam height of the solution after 30 minutes of circulation at 25°C was tested using a foam meter with a 1000ml graduated cylinder and a circulation pump. The foam stability refers to the height of the foam in the graduated cylinder after the foam meter stops circulating and remains still for 5 minutes. The results are shown in Table 5.

[0134] Table 5 Foaming and Foam Stability

[0135]

[0136] Generally, the lower the surface tension, the less work is required to generate foam with the same total surface area, and the stronger the foaming ability of the surfactant. Furthermore, foam stability is mainly related to the strength of the interfacial adsorption film. Stronger hydrophobic interactions between surfactants result in tighter adsorption on the adsorption film surface, leading to a stronger adsorption film and thus more stable foam. As shown in Table 5, under the same conditions, the foaming and foam stability of Examples 1-3 are significantly improved compared to the natural tea saponin in Comparative Example 4. This is because the tea saponin-modified surfactant, grafted with long-chain alkyl-polyethylene glycol-amine, greatly enhances the hydration of the entire molecule, significantly improving its solubility and stability in hard water. After grafting, a dense, highly hydrated "brush-like" protective layer forms at the interface, more effectively preventing droplet polymerization or flocculation and enhancing emulsion stability. Simultaneously, the hydrophobic association of the long-chain alkyl groups synergistically interacts with the hydrophilic interactions of polyethylene glycol and amine, resulting in a more compact molecular arrangement at the gas-liquid interface and enhanced surface viscoelasticity of the liquid film, leading to more stable and finer foam. In Comparative Example 5, the modified tea saponin exhibits enhanced spreading at the gas-liquid interface due to the hydrophilic effect of polyethylene glycol, while the polar effect of the amine groups improves the interfacial film strength. Therefore, its foaming and foam-stabilizing properties are higher than those of the unmodified natural tea saponin in Comparative Example 4. In contrast, the modified tea saponin in Comparative Example 7, while possessing hydrophilicity in its EO segment and hydrophobic rigidity in its PO segment, enhances the interfacial film strength but also reduces foaming properties, resulting in low foaming performance after grafting.

[0137] Therefore, as shown in Tables 1-5, the tea saponin modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine provided in the examples has significantly improved high-temperature stability, cleaning efficiency, foaming and foam stability compared with natural tea saponin and other modified tea saponins. Its antioxidant capacity and antibacterial capacity are also enhanced compared with natural tea saponin.

[0138] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit it. Equal modifications and variations made by those skilled in the art to the technical solution of the present invention, as long as they do not depart from the overall concept of the present invention, shall still fall within the scope of the present invention.

Claims

1. A method for preparing a tea saponin-modified surfactant, characterized in that, Tea saponins were extracted using an integrated process of eutectic solvent-ultrasonic extraction and macroporous resin purification; the extracted tea saponins were then modified to obtain a tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine. The specific preparation method is as follows: S001, carboxylated tea saponin was dissolved in 0.1M MES buffer, pH controlled at 5.0-6.0, N-hydroxysulfosuccinimide was added, and the mixture was stirred until homogeneous. Then 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride was added, and the mixture was stirred at 300-400 rpm and reacted at room temperature in the dark for 15-60 minutes to obtain an activated solution. At this point, the carboxyl groups on the carboxylated tea saponin were activated, and this was referred to as activated carboxylated tea saponin. S002, first slowly add dilute NaOH solution to the activation solution while stirring to adjust the pH of the reaction system to 7.2-7.

8. Then dissolve the long-chain alkyl-polyethylene glycol-amine in 30% ethanol solution and slowly add it at room temperature. Stir gently for 2-6 hours. After the reaction is complete, dialyze with deionized water for 48-72 hours, changing the water 4-5 times to completely remove small molecule impurities and excess polyethylene glycol. Concentrate the purified solution under reduced pressure to 1 / 3 of the original volume and then freeze-dry to obtain a white, loose, flaky solid, which is the tea saponin modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine. The carboxylated tea saponin is obtained by oxidizing the primary hydroxyl group (-CH2OH) at the end of the sugar chain of the extracted natural tea saponin to a carboxyl group (-COOH), while retaining the triterpenoid skeleton and double bond; The eutectic solvent is a mixture of choline chloride, acetamide, glycerol and deionized water in a molar ratio of 1:1 to 2:2 to 3:0.

5. The polyethylene glycol is polyethylene glycol with a molecular weight of 500 to 2000, and the long-chain alkyl group is a C16 to C18 long-chain alkyl group.

2. The method for preparing the tea saponin-modified surfactant according to claim 1, characterized in that, The carboxylated tea saponin specifically refers to: S01, Dissolve the extracted natural tea saponin in water, stir evenly, and then add NaBr and NaHCO3 in sequence to obtain a tea saponin pre-reaction solution, and adjust the pH to 8-9. S02, add the catalyst 2,2,6,6-tetramethylpiperidine-1-oxy free radical to the tea saponin pre-reaction solution, slowly add NaClO solution dropwise in an ice bath at 0℃, keep the pH at 8-9 during the dropwise addition, stir at room temperature for 1-2 hours after the dropwise addition is completed to obtain a mixed solution; SO3 was quenched with isopropanol to remove excess NaClO from the mixture. The pH was slowly adjusted to 2-3 with dilute hydrochloric acid. After acidification for 30-50 minutes, the mixture was extracted with ethyl acetate and dried to obtain a light yellow paste, which is carboxylated tea saponin.

3. The method for preparing the tea saponin-modified surfactant according to claim 1, characterized in that, The mass ratio of carboxylated tea saponin, N-hydroxysulfosuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is 10:1.3-1.8:3-4.0; the mass ratio of activated carboxylated tea saponin and long-chain alkyl-polyethylene glycol-amine is 1:2.2-2.

8.

4. The method for preparing the tea saponin-modified surfactant according to claim 1, characterized in that, An integrated process for extracting tea saponins using eutectic solvent-ultrasonic extraction and macroporous resin purification includes the following steps: S1. Dry the camellia oil cake and pulverize it, pass it through a 40-80 mesh sieve to obtain camellia oil cake powder, dry it and store it in a cool place for later use; S2, add ethyl acetate to camellia oil cake powder, the mass ratio of camellia oil cake powder to ethyl acetate is 1:3-5, stir for 20-30 minutes, centrifuge and dry to obtain defatted camellia oil cake powder; S3, add a low eutectic solvent to defatted camellia cake powder, raise the temperature to 50-60℃, then ultrasonically extract for 50-100 minutes, separate, and take the upper filtrate to obtain tea saponin extract; S4. The resin was soaked in ethanol, hydrochloric acid solution and sodium hydroxide solution respectively, and washed until neutral after each soaking. The tea saponin extract was added to the treated macroporous adsorption resin for adsorption, washed with deionized water, and then eluted with ethanol solution. The eluent was collected, concentrated and freeze-dried to obtain high-purity tea saponin.

5. The method for preparing the tea saponin-modified surfactant according to claim 4, characterized in that, The mixing temperature of the eutectic solvent is 50-60℃; the mass ratio of defatted camellia seed cake powder to eutectic solvent is 1:3-4; and at least one of the macroporous adsorption resins DM301, NKA-9, and DA201 is used.

6. The method for preparing the tea saponin-modified surfactant according to claim 4, characterized in that, The hydrochloric acid solution has a mass fraction of 5%, the sodium hydroxide solution has a mass fraction of 5%, the soaking time is 2 to 6 hours, and the ethanol solution used for elution has a mass concentration of 70%. The concentration is carried out using a vacuum rotary evaporator at a temperature of 40–50°C and a rotation speed of 30–50 r / min; the freeze-drying temperature is -58–-38°C, the vacuum degree is 10–15 Pa, and the drying time is 6–20 hours.

7. The tea saponin-modified surfactant grafted with long-chain alkyl-polyethylene glycol-amine obtained by the preparation method of the tea saponin-modified surfactant according to any one of claims 1 to 6 is used in daily chemical products.

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