Plant extract purification method based on eutectic solvent

Abstract

The invention belongs to the technical field of plant active component extraction and purification, and particularly provides a plant extract purification method based on a deep-eutectic solvent. A plant extract purification method based on a deep-eutectic solvent comprises the following steps: firstly, crushing and grinding a plant to be extracted to obtain fine powder, then heating and uniformly mixing choline chloride, modified amino acid and lewis acid to prepare the deep-eutectic solvent, then mixing the fine powder, the deep-eutectic solvent and water according to a certain solid-to-liquid ratio, and uniformly mixing to obtain the plant extract based on the deep-eutectic solvent. And carrying out ultrasonic extraction at a certain temperature to obtain an extracting solution, and finally purifying. According to the method, the saponin component in the soapberry can be effectively extracted, the saponin yield is high, and the purity is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plant active component extraction and purification, and particularly relates to a plant extract purification method based on a low eutectic solvent. BACKGROUND

[0002] Saponins are a kind of natural active ingredients composed of sugar groups connected by glycosidic bonds and triterpene or steroidal aglycones. Due to the different degrees of lipophilicity of aglycones and the strong hydrophilicity of sugar chains, this special and complex structure endows saponins with amphiphilicity, and the aqueous solution of saponins can produce soap-like foam. Therefore, saponins have washing, solubilizing, emulsifying and foaming properties, and are often used to manufacture emulsifiers, detergents and foaming agents, etc.

[0003] At present, the commonly used extraction methods of saponins are alcohol extraction and water extraction. The alcohol extraction method has the advantages of simple operation, recyclable solvent and high purity of extracted saponins. However, a large amount of methanol or ethanol is required, which may cause solvent residue risk. In addition, high-temperature reflux has high energy consumption and may also destroy the activity of saponins. Moreover, the volatilization of organic solvents will also cause environmental pollution. Although the water extraction method is environmentally friendly, it has many impurities and low purity of saponins.

[0004] A low eutectic solvent is a new type of green solvent, which is usually composed of a hydrogen bond acceptor and a hydrogen bond donor. The preparation process is simple, no waste is generated, it is friendly to the environment, has adjustable polarity and unique hydrogen bond network structure, and therefore can be used for the extraction of natural plant active ingredients.

[0005] The patent application with the publication number CN115887578A discloses a natural low eutectic solvent and a method for sustainable extraction of plant saponins. The natural low eutectic solvent synthesized by butyric acid-urea is used as an extractant to extract plant saponins. In the extraction process, ferric chloride is added to promote cell wall fragmentation. The natural low eutectic solvent has the characteristic that its solubility in water changes greatly with ionic strength. Sodium chloride is added to the natural low eutectic solvent extract. Saponins are recovered into water, and the natural low eutectic solvent is separated from water and continues to be used for extracting new plant powder to be extracted. The method is green, simple and sustainable, and has been successfully applied to the sustainable extraction of plant saponins. However, the saponin yield is relatively low when the extraction method is used for saponin extraction. SUMMARY

[0006] In view of the above problems, in order to further improve the yield and purity of saponins, the application provides a plant extract purification method based on a low eutectic solvent.

[0007] The application first provides a plant extract purification method based on a low eutectic solvent, which comprises the following steps: S1: crushing, grinding and sieving the plant to be extracted to obtain fine powder; the plant to be extracted is soapberry; S2: Choline chloride, modified amino acids, and Lewis acids are heated and stirred to obtain a eutectic solvent; the modified amino acids are prepared by reacting amino acids with alkylethylenediamine; the alkylethylenediamine is prepared by reacting ethylenediamine with alkyl haloalkanes. S3: After mixing the fine powder, eutectic solvent and water, perform ultrasonic extraction and centrifugation to obtain the extract; S4: Adsorb the extract with AB-8 macroporous resin, then elute, evaporate and concentrate, and dry.

[0008] Furthermore, in step S2, the amino acid is one or more selected from glycine, tryptophan, glutamic acid, aspartic acid, histidine, and lysine. And / or, in step S2, the alkylethylenediamine is one or more of dodecylethylenediamine, octylethylenediamine, and isooctylethylenediamine; And / or, in step S2, the Lewis acid is one of ferric chloride, aluminum chloride, and zinc chloride.

[0009] Furthermore, in step S2, the mass ratio of choline chloride, modified amino acids, and Lewis acids is 1:(0.5-3):(0.5-3).

[0010] Furthermore, in step S2, the molar ratio of amino acid to alkylethylenediamine is 1:(1-2).

[0011] Furthermore, in step S2, the modified amino acid is processed by a method including the following steps: reacting the amino acid with alkylethylenediamine, mixing the resulting reaction product with sulfuric acid solution, reacting, and then vacuum drying; the mass ratio of the modified amino acid to sulfuric acid is 1:(0.3-0.6).

[0012] Furthermore, in step S3, the mass ratio of the eutectic solvent to water is 1:(0.2-1).

[0013] Furthermore, in step S3, the mass ratio of the sum of the masses of fine powder, eutectic solvent and water is 1:(10-50).

[0014] Furthermore, in step S3, the extraction temperature is 40-70℃ and the extraction time is 30-120 min.

[0015] Furthermore, in step S4, the AB-8 macroporous resin is treated as follows: first soaked in anhydrous ethanol, then washed with water, then soaked in an alkaline solution and washed with water until neutral, and finally soaked in an acidic solution and washed with water until neutral. And / or, in step S4, the elution step is as follows: first, elute with distilled water, 0.1% sodium hydroxide solution, and distilled water in sequence, and then elute with 70% ethanol.

[0016] Compared with the prior art, this application has the following beneficial effects: 1. The alkyl ethylenediamine modified amino acid in the eutectic solvent of this application improves the hydrogen bond network strength of the eutectic solvent. At the same time, the introduction of hydrophobic alkyl groups is beneficial to improving the interaction with saponin aglycones. Therefore, it has a strong dissolution ability for saponins and can obtain higher saponin yield and purity.

[0017] 2. In this application, the modified amino acids are acid-treated, which improves the solubility of the eutectic solvent, thereby increasing the yield and purity of saponins.

[0018] 3. The eutectic solvent of this application also contains Lewis acids, which can promote the dissolution of plant cell walls, thereby making it easier for the active saponin components to dissolve. It can also improve the stability of the eutectic solvent structure, thereby further improving the saponin yield. Attached Figure Description

[0019] Figure 1 The yield and purity of saponins in Examples 1-2 and Control Groups 1-3 of this application are shown. Detailed Implementation

[0020] To make the inventive objectives, technical solutions, and beneficial technical effects of this application clearer, the following detailed description is provided in conjunction with embodiments, clearly and completely describing the technical solutions in the embodiments of this application. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0023] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0024] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0025] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0026] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0028] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0029] In this application, room temperature refers to 0-40°C, including but not limited to 10-40°C, or further to 20-30°C.

[0030] Based on extensive experimental research, this application provides a method for purifying plant extracts using a eutectic solvent, comprising the following steps: S1: The plant to be extracted is crushed, ground, and sieved to obtain a fine powder; the plant to be extracted is Sapindus mukorossi; S2: Choline chloride, modified amino acids, and Lewis acids are heated and stirred to obtain a eutectic solvent; the modified amino acids are prepared by reacting amino acids with alkylethylenediamine; the alkylethylenediamine is prepared by reacting ethylenediamine with alkyl haloalkanes. S3: After mixing the fine powder, eutectic solvent and water, perform ultrasonic extraction and centrifugation to obtain the extract; S4: Adsorb the extract with AB-8 macroporous resin, then elute, evaporate and concentrate, and dry.

[0031] In some embodiments of this application, choline chloride is used as a hydrogen bond acceptor and alkyl ethylenediamine-modified amino acids are used as hydrogen bond donors to prepare eutectic solvents. After modification with alkyl hexamethylenediamine, the ability of the amino acids to provide hydrogen atoms is enhanced, thereby increasing the strength of the formed hydrogen bonds and strengthening the hydrogen bond network. Furthermore, since the aglycone in the saponin structure has a certain degree of hydrophobicity, the introduction of alkyl groups can improve the interaction with the hydrophobic aglycone of the saponin, thereby improving the dissolution capacity of the saponin and reducing the extraction of other highly polar substances. Additionally, the hydrogen bond strength formed between amino and hydroxyl groups is higher; therefore, the modified amino acids can disrupt cell walls, further improving the dissolution of the active components of the saponin.

[0032] In some embodiments of this application, in step S2, the amino acid can be one or more of glycine, tryptophan, glutamic acid, aspartic acid, histidine, and lysine. And / or, in step S2, the alkylethylenediamine can be one or more of dodecylethylenediamine, octylethylenediamine, and isooctylethylenediamine; And / or, in step S2, the Lewis acid can be one of ferric chloride, aluminum chloride, and zinc chloride. Lewis acids, in synergy with modified amino acids, enhance the destructive effect on the cell walls of Sapindus mukorossi plants, making the active saponin components easier to dissolve, thereby increasing the saponin yield. Furthermore, the metal ions in the Lewis acid can form coordination compounds with hydrogen bond acceptors or hydrogen bond donors, making the eutectic solvent structure more stable, thus enhancing the eutectic solvent's ability to dissolve saponins.

[0033] In some specific embodiments of this application, in step S2, the mass ratio of choline chloride, modified amino acid, and Lewis acid is 1:(0.5-3):(0.5-3), for example, it can be 1:0.5:0.5, 1:0.5:1, 1:0.5:1.5, 1:0.5:2, 1:0.5:2.5, 1:0.5:3, 1:1:0.5, 1:1:1, 1:1:1.5, 1:1:2, 1:1:2.5, 1:1:3, 1:2:0.5, 1:2:1, 1:2:1.5, 1:2:2, 1:2:2.5, 1:2:3, 1:3:0.5, 1:3:1, 1:3:1.5, 1:3:2, 1:3:2.5, 1:3:3.

[0034] In some embodiments of this application, in step S2, the molar ratio of amino acid to alkylethylenediamine is 1:(1-2), for example, it can be 1:1, 1:1.5, or 1:2.

[0035] In some embodiments of this application, in step S2, the modified amino acid is treated by a method including the following steps: after reacting the amino acid with alkylethylenediamine, the resulting reaction product is mixed with sulfuric acid solution, reacted, and then vacuum dried; after treatment, the modified amino acid not only improves the ability of hydrogen bond donors to provide hydrogen atoms, thus increasing the strength of the formed hydrogen bonds and strengthening the hydrogen bond network, but also enhances the acidity of the eutectic solvent, which is beneficial to improving the extraction of saponins.

[0036] In some embodiments of this application, the mass ratio of the modified amino acid to sulfuric acid is 1:(0.3-0.6), for example, it can be 1:0.3, 1:0.4, 1:0.5, or 1:0.6.

[0037] In some specific embodiments of this application, in step S3, the mass ratio of the eutectic solvent to water is 1:(0.2-1), for example, it can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, or 1:1.

[0038] In some specific embodiments of this application, in step S3, the mass ratio of the sum of the mass of fine powder, eutectic solvent and water is 1:(10-50), for example, it can be 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, or 1:50. When the mass ratio of the sum of the mass of fine powder, eutectic solvent and water is 1:30, the saponin yield is higher.

[0039] In some embodiments of this application, in step S3, the extraction temperature is 40-70℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, or 70℃. When the extraction temperature is 60℃, the saponin yield is the highest. The extraction time is 30-120 min, for example, it can be 30 min, 45 min, 60 min, 75 min, 90 min, 105 min, or 120 min. As the extraction time is extended, the saponin yield increases. When the extraction time exceeds 120 min, the saponin yield tends to stabilize.

[0040] In some embodiments of this application, in step S4, the AB-8 macroporous resin is treated as follows: first soaked in anhydrous ethanol, then washed with water, then soaked in an alkaline solution and washed with water until neutral, and finally soaked in an acidic solution and washed with water until neutral. And / or, in step S4, the elution step is as follows: first, elute with distilled water, 0.1% sodium hydroxide solution, and distilled water in sequence, and then elute with 70% ethanol.

[0041] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0042] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0043] Example 1 The plant extract purification method based on eutectic solvent in this embodiment includes the following steps: S1: After drying the soapberry fruit at room temperature, crush and grind it using a high-speed pulverizer, and pass it through a 40-mesh sieve to obtain fine powder; S2: Weigh 10g of choline chloride, 20g of modified amino acids and 10g of zinc chloride respectively, place them in a three-necked flask, and stir magnetically at 90℃ for 2h until a homogeneous liquid is formed to obtain a eutectic solvent. S3: Weigh 1g of fine powder, 20g of eutectic solvent and 10g of water, mix them evenly, and then perform ultrasonic extraction at 60℃ for 120min. Then centrifuge at 4000rpm for 10min to obtain the extract. S4: Treat the AB-8 macroporous resin as follows: first soak it in anhydrous ethanol, then wash it with water, then soak it in a 5% sodium hydroxide solution and wash it with water until neutral, and finally soak it in a 5% hydrochloric acid solution and wash it with water until neutral; dilute the extract with 10 times pure water, adsorb the extract with the treated AB-8 macroporous resin, and then elute it sequentially with distilled water, a 0.1% sodium hydroxide solution, distilled water, and a 70% ethanol solution. Finally, evaporate, concentrate, and dry. The modified amino acid in this embodiment was prepared using the following method: Weigh out 0.1 mol of tryptophan and 0.1 mol of isooctylethylenediamine, dissolve them separately in methanol solution, react them at room temperature, and then dry them to obtain the product. The isooctylethylenediamine in this embodiment was prepared by the following method: Weigh 0.1 mol of 1-bromoisooctane and slowly add it dropwise to 0.5 mol of ethylenediamine. The mixture is stirred and refluxed. Throughout the reaction, the pH of the reaction system is adjusted to be no lower than 8.0 using sodium hydroxide solution. After reacting for 10 hours, the upper layer is separated while hot and washed repeatedly with hot water until the pH is neutral. Then, the mixture is vacuum dried and cooled to room temperature to obtain the final product.

[0044] Example 2 The purification method for plant extracts based on eutectic solvents in this embodiment is the same as that in Example 1; The modified amino acids in this embodiment are processed using the following method: Weigh out 0.1 mol of tryptophan and 0.1 mol of isooctylethylenediamine, dissolve them separately in methanol solution, and react them at room temperature. Dry the reaction product, weigh out 10 g of the dried reaction product, add 10 g of 50% sulfuric acid solution, mix well, stir the reaction at 60 °C for 2 h, and then dry it under vacuum at 80 °C to obtain the product. The preparation method of isooctylethylenediamine in this embodiment is the same as that in Example 1.

[0045] Control group 1 The purification method for plant extracts in this control group includes the following steps: S1: After drying the soapberry fruit at room temperature, crush and grind it using a high-speed pulverizer, and pass it through a 40-mesh sieve to obtain fine powder; S2: Weigh 1g of fine powder and 30g of 70% ethanol, mix them evenly, and then perform ultrasonic extraction at 60℃ for 120min. Then centrifuge at 4000rpm for 10min to obtain the extract. S3: Treat the AB-8 macroporous resin as follows: first soak it in anhydrous ethanol, then wash it with water, then soak it in a 5% sodium hydroxide solution and wash it with water until neutral, and finally soak it in a 5% hydrochloric acid solution and wash it with water until neutral. Dilute the extract with 10 times pure water, adsorb the extract with the treated AB-8 macroporous resin, and then elute it sequentially with distilled water, a 0.1% sodium hydroxide solution, distilled water, and a 70% ethanol solution. Finally, evaporate, concentrate, and dry.

[0046] Control group 2 The purification method for plant extracts based on eutectic solvents in this control group includes the following steps: S1: After drying the soapberry fruit at room temperature, crush and grind it using a high-speed pulverizer, and pass it through a 40-mesh sieve to obtain fine powder; S2: Weigh 10g of choline chloride and 20g of tryptophan, place them in a three-necked flask, and stir magnetically at 90℃ for 2 hours until a homogeneous liquid is formed to obtain a eutectic solvent. S3: Weigh 1g of fine powder, 20g of eutectic solvent and 10g of water, mix them evenly, and then perform ultrasonic extraction at 60℃ for 120min. Then centrifuge at 4000rpm for 10min to obtain the extract. S4: Treat the AB-8 macroporous resin as follows: first soak it in anhydrous ethanol, then wash it with water, then soak it in a 5% sodium hydroxide solution and wash it with water until neutral, and finally soak it in a 5% hydrochloric acid solution and wash it with water until neutral. Dilute the extract with 10 times pure water, adsorb it onto the treated AB-8 macroporous resin, and then elute it sequentially with distilled water, a 0.1% sodium hydroxide solution, distilled water, and a 70% ethanol solution. Finally, evaporate, concentrate, and dry.

[0047] Control group 3 The purification method for plant extracts based on eutectic solvents in this control group includes the following steps: S1: After drying the soapberry fruit at room temperature, crush and grind it using a high-speed pulverizer, and pass it through a 40-mesh sieve to obtain fine powder; S2: Weigh 10g of choline chloride, 20g of tryptophan and 10g of zinc chloride respectively, place them in a three-necked flask, and stir magnetically at 90℃ for 2 hours until a homogeneous liquid is formed to obtain a eutectic solvent. S3: Weigh 1g of fine powder, 20g of eutectic solvent and 10g of water, mix them evenly, and then perform ultrasonic extraction at 60℃ for 120min. Then centrifuge at 4000rpm for 10min to obtain the extract. S4: Treat the AB-8 macroporous resin as follows: first soak it in anhydrous ethanol, then wash it with water, then soak it in a 5% sodium hydroxide solution and wash it with water until neutral, and finally soak it in a 5% hydrochloric acid solution and wash it with water until neutral. Dilute the extract with 10 times pure water, adsorb it onto the treated AB-8 macroporous resin, and then elute it sequentially with distilled water, a 0.1% sodium hydroxide solution, distilled water, and a 70% ethanol solution. Finally, evaporate, concentrate, and dry.

[0048] Performance testing 1. Saponin yield and purity: The yield and purity of saponins in Sapindus mukorossi from Examples 1-2 and Control Groups 1-3 were determined using the vanillin-sulfuric acid colorimetric method. The results are as follows: Figure 1 As shown.

[0049] contrast Figure 1 Data from Example 1 and Control Group 1 show that using a eutectic solvent to extract saponin active components from Sapindus mukorossi results in higher yield and purity compared to ethanol extraction; Figure 1 Data from Example 1 and Control Group 2 show that the yield and purity of saponins increased after modification of amino acids in the eutectic solvent. This may be because modified amino acids are more likely to bind with saponins, thus facilitating their dissolution and potentially reducing the extraction of other substances. (Comparison) Figure 1 Data from Example 1 and Control Group 3 show that the addition of zinc chloride is beneficial to increasing the saponin yield. This may be because zinc chloride can catalyze the degradation of cellulose and lignin in the cell walls of Sapindus mukorossi plants, thereby facilitating the penetration of the eutectic solvent and making the active saponin components easier to dissolve. (Comparison) Figure 1 The data from Examples 1 and 2 show that the modified amino acids have higher saponin yield and purity after acid treatment, possibly because the eutectic solvent has stronger solubility after acid treatment.

[0050] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for purifying plant extracts based on a eutectic solvent, characterized in that: Includes the following steps: S1: The plant to be extracted is crushed, ground, and sieved to obtain a fine powder; the plant to be extracted is Sapindus mukorossi; S2: Choline chloride, modified amino acids, and Lewis acids are heated and stirred to obtain a eutectic solvent; the modified amino acids are prepared by reacting amino acids with alkylethylenediamine; the alkylethylenediamine is prepared by reacting ethylenediamine with alkyl haloalkanes. S3: After mixing the fine powder, eutectic solvent and water, perform ultrasonic extraction and centrifugation to obtain the extract; S4: Adsorb the extract with AB-8 macroporous resin, then elute, evaporate and concentrate, and dry.

2. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S2, the amino acid is one or more of glycine, tryptophan, glutamic acid, aspartic acid, histidine, and lysine. And / or, in step S2, the alkylethylenediamine is one or more of dodecylethylenediamine, octylethylenediamine, and isooctylethylenediamine; And / or, in step S2, the Lewis acid is one of ferric chloride, aluminum chloride, and zinc chloride.

3. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S2, the mass ratio of choline chloride, modified amino acids, and Lewis acids is 1:(0.5-3):(0.5-3).

4. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S2, the molar ratio of amino acid to alkylethylenediamine is 1:(1-2).

5. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S2, the modified amino acid is processed by a method including the following steps: reacting the amino acid with alkylethylenediamine, mixing the resulting reaction product with sulfuric acid solution, reacting, and then vacuum drying; the mass ratio of the modified amino acid to sulfuric acid is 1:(0.3-0.6).

6. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S3, the mass ratio of the eutectic solvent to water is 1:(0.2-1).

7. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S3, the mass ratio of the sum of the masses of fine powder, eutectic solvent and water is 1:(10-50).

8. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S3, the extraction temperature is 40-70℃ and the extraction time is 30-120 min.

9. The method for purifying plant extracts based on a eutectic solvent according to claim 1, characterized in that: In step S4, the AB-8 macroporous resin is treated as follows: first soaked in anhydrous ethanol, then washed with water, then soaked in an alkaline solution and washed with water until neutral, and finally soaked in an acidic solution and washed with water until neutral. And / or, in step S4, the elution step is as follows: first, elute with distilled water, 0.1% sodium hydroxide solution, and distilled water in sequence, and then elute with 70% ethanol.

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