A method for separating and extracting glycyrrhizin from liquorice

Abstract

The present invention discloses a method for separating and extracting glycyrrhizin from the plant licorice, comprising the following steps: extracting the licorice residue with water, then concentrating it by soaking it in ethanol; adsorbing the concentrated solution on a macroporous resin column, and concentrating the eluate to obtain a crude flavonoid powder; treating the crude flavonoid powder with solvent I and solvent II, stirring to obtain a turbid solution, filtering, heating the filtrate to volatilize solvent I, and then cooling the filtrate to a low temperature at a rate of 1 to 3°C / min. After complete crystallization, filtering to obtain the glycyrrhizin product. The heating temperature is 30 to 60°C, and the ratio of solvent I to solvent II is 1:2 to 1:15. The present invention provides a high-purity glycyrrhizin separation and extraction method with simple process conditions, low equipment requirements, low material costs, high product quality, and ease of industrialization.

Description

Technical Field

[0001] The invention relates to the technical field of separation and purification of natural active substances in plants, in particular to a method for separating and extracting a flavonoid compound glycyrrhizin from liquorice. Background Art

[0002] Licoricidin is a flavonoid active ingredient in licorice, with the molecular formula C 26 H 32 O5, molecular weight is 424.53, structural formula is as follows:

[0003]

[0004] Studies have shown that glycyrrhizin exhibits significant antibacterial activity against oral disease pathogens such as Porphyromonas gingivalis and Streptococcus mutans, while having no obvious cytotoxicity to oral epithelial cells and gingival fibroblasts; glycyrrhizin can significantly scavenge ABTS free radicals (2,2-azo-bis(3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt) and ROS free radicals (reactive oxygen species); glycyrrhizin has the potential to treat characteristic dermatitis and periodontitis. Not only that, glycyrrhizin can also inhibit the migration and expression of mouse breast cancer cells, human prostate cancer cells, and human colorectal adenocarcinoma cells. The latest research found that it promotes energy consumption and induces beigeization of white fat by activating the cAmp-PKA signaling pathway; it can inhibit the activity of tyrosine protein phosphatase, and play a certain role in combating the new coronavirus COVID-19 by inhibiting proteases.

[0005] Licoricecillin has great market potential and development prospects in the pharmaceutical and health product sectors. However, licorice's complex composition, with multiple active ingredients having similar physical properties to glycyrrhizin, makes separation difficult, making it difficult to efficiently isolate glycyrrhizin. Licorice contains a very low concentration of glycyrrhizin, approximately 0.08%, and is high in impurities, requiring complex steps or equipment to separate it. Licoricecillin extracts with a purity greater than 95% currently cost hundreds of thousands of yuan per gram, making them expensive. Therefore, there is a significant market demand for high-purity glycyrrhizin extracts prepared from inexpensive licorice residue.

[0006] A search revealed few literature and patents on the preparation of high-purity glycyrrhizin. Most methods utilize silica gel column separation, a complex process. For example, Chinese patent application number CN201910379619.0, "A method for extracting isopentenyl flavonoids from licorice using ionic liquids," mixes licorice with pure ionic liquid and then ultrasonically extracts it, yielding glycyrrhizin at a concentration of 224.5 μg / g in the supernatant. This process requires a high reaction temperature, and the synthesis of the ionic liquid is complex, resulting in high costs and a complicated subsequent recovery process. Chinese patent application number CN201510918824.1, "New medical uses of a class of isopentenyl isoflavones from licorice," uses ethanol and ethyl acetate extractions, followed by silica gel column chromatography, ethanol-water gradient elution, polyamide column chromatography, and dichloromethane-methanol gradient elution to obtain glycyrrhizin. The resulting glycyrrhizin concentration is 900 mg / 35 kg. This complex preparation process is costly and yields are low. The document "Study on Isopentenyl Flavonoids from the Roots of Ural Licorice" uses ethyl acetate and petroleum ether for extraction, followed by silica gel column gradient separation, and then polyamide chromatography column separation and semi-preparative separation. Silica gel column chromatography is difficult to meet market demand in terms of product quality, has a low yield, and complex steps; semi-preparative liquid chromatography preparation is small and difficult to meet industrial requirements. The Chinese patent application number CN200880023333.9, "Antimicrobial and Anti-inflammatory Isolates of Licorice Extracts," uses supercritical CO2 extraction to extract glycyrrhizin. This method extracts licorice after loading CO2 into a supercritical state, which has the characteristic of CO2 being recyclable. However, it has high requirements for extraction conditions, expensive equipment, and certain safety risks in high-temperature or high-pressure experimental conditions.

[0007] Furthermore, the yields of glycyrrhizin products obtained in existing technologies are low. For example, Chinese patent CN201910379619.0, "A method for extracting isopentenyl flavonoids from licorice using ionic liquids," has a total yield of 0.02%; Chinese patent CN201510918824.1, "New medical uses of a class of isopentenyl isoflavone compounds from licorice," has a total yield of 0.005%; and the document "Study on the chemical composition of flavonoids from the root of Glycyrrhiza glabra," has a total yield of 0.0004%. Summary of the Invention

[0008] The invention aims to make full use of liquorice residue and provide a method for separating and extracting high-purity glycyrrhizin with simple process conditions, low equipment requirements, low material cost, high product yield and easy industrialization.

[0009] The present invention first extracts licorice residue through alcohol extraction, then removes some impurities from the alcohol extract using a macroporous resin to obtain a crude flavonoid product. High-purity glycyrrhizin is then isolated using an improved crystallization method. Reaction conditions are controlled to enhance the crystallization effect, ultimately yielding a product with a purity exceeding 95% through a single crystallization step. The specific technical solutions of the present invention are as follows:

[0010] A method for separating and extracting glycyrrhizin from liquorice comprises the following steps:

[0011] Step 1): weighing licorice residue, soaking it with deionized water at room temperature, and filtering to obtain water-extracted licorice residue; soaking the water-extracted licorice residue with anhydrous ethanol at room temperature, wherein the material-liquid ratio of the licorice residue (before soaking) to anhydrous ethanol is 1:10 to 1:15 (g / mL), and the extraction time is 10 to 16 hours; collecting the soaking liquid, and concentrating it under reduced pressure to obtain an anhydrous ethanol concentrate;

[0012] Step 2): The anhydrous ethanol concentrate obtained in step 1) is diluted with deionized water and adsorbed on a macroporous resin column at a sample loading flow rate of 1 BV / h, wherein the macroporous resin is a non-polar or weakly polar resin; after the column loading is completed, gradient elution is performed with a 50% to 85% ethanol aqueous solution, the elution volume of the ethanol aqueous solution gradient elution is 8 to 10 BV, and the flow rate is 1 to 1.5 BV / h; the final eluate is concentrated to obtain a crude flavonoid powder;

[0013] Step 3): using solvent I and solvent II to treat the crude flavonoid powder obtained in step 2), stirring to obtain a turbid liquid; filtering the turbid liquid, heating the filtrate to volatilize the solvent I, and then cooling the filtrate to a low temperature condition at a rate of 1 to 3°C / min. After crystallization is complete, filtering to obtain the glycyrrhizine product; the solvent I is any one of acetone, ether, and dichloromethane, and the solvent II is any one of cyclohexane, n-hexane, petroleum ether, and carbon tetrachloride; the heating temperature is 30°C to 60°C, and the volume ratio of solvent I to solvent II is 1:2 to 1:15; the low temperature condition is 4°C to -15°C.

[0014] As an optimization method for treating the crude flavonoid powder obtained in step 2) with solvent I and solvent II, there are two schemes:

[0015] ① Solvent I and solvent II are mixed in a certain proportion, and then the crude flavonoid powder is dissolved. After sufficient stirring, the turbid liquid is filtered, and the filtrate is heated at a certain temperature to volatilize solvent I. The solution is then cooled to a low temperature condition at a rate of 1 to 3°C / min. After complete crystallization, the glycyrrhizin product is filtered.

[0016] ② First, dissolve the crude flavonoid powder in solvent I, then add solvent II and stir thoroughly to obtain a turbid solution. Filter the turbid solution, heat the solution at a certain temperature to evaporate solvent I, and cool the solution to low temperature at a rate of 1-3°C / min. Once crystallization is complete, filter to obtain the glycyrrhizine product.

[0017] Further optimization, the deionized water soaking material-liquid ratio in step 1) is 1:5-1:15 (g / mL), and the soaking time is 5-14 hours.

[0018] Furthermore, the normal temperature is 18-25°C.

[0019] Furthermore, the non-polar or weakly polar resin in step 2) is of model LSA-10, D101, LX-T28, D101B or AB-8, and the amount of the resin is 200 to 300 g.

[0020] Furthermore, the anhydrous ethanol concentrated solution in step 2) is diluted with deionized water to a volume fraction of ethanol of 45% to 55%, and then applied to a macroporous resin column for adsorption.

[0021] Furthermore, in step 3), the concentration of the crude flavonoid powder in solvent I is 80-400 mg / mL.

[0022] Furthermore, in step 3), the cooling rate of the solution is 1°C / min.

[0023] Beneficial effects of the present invention:

[0024] 1) The present invention combines alcohol extraction, macroporous resin decontamination, and crystallization to separate and purify glycyrrhizine from the plant licorice. This technical combination of separation and extraction is an innovation of the present invention. By improving the crystallization method, the crystallization effect is enhanced, the time required for separation and purification is greatly shortened, and the yield and purity of the glycyrrhizine preparation process are improved.

[0025] 2) The present invention utilizes liquorice residue as a raw material to extract glycyrrhizin, thereby fully utilizing liquorice resources and saving costs.

[0026] 3) The present invention uses a non-polar or weakly polar macroporous resin to purify the licorice concentrate, effectively removing impurities with a polarity significantly different from that of glycyrrhizin. The resin is environmentally friendly and easy to regenerate for recycling. An ethanol aqueous solution is used as an eluent, which has low toxicity and low cost.

[0027] 4) The purification route of the present invention is simple, and the crystallization process is used for the first time to separate and purify glycyrrhizin, avoiding the silica gel column gradient separation method currently used for separating glycyrrhizin. It has low equipment requirements, short cycle, and is easy to expand industrial production.

[0028] 5) The crystallization method of the present invention utilizes the difference in the solubility of glycyrrhizin in different solvents, and precisely controls the temperature change to optimize the crystallization method. A glycyrrhizin product with a purity of >95% can be obtained with only one crystallization. Compared with ordinary crystallization methods, the present invention uses two solvents for crystallization; the present invention controls the temperature of the heating process to volatilize one solvent in the mixed solution, and at the same time controls the cooling rate to precipitate glycyrrhizin crystals to the maximum extent. The whole process greatly improves the purity and yield, achieving a better purification effect. Referring to the comparative example, using only one solvent for crystallization does not achieve a good purification effect. By adjusting the above conditions, a large amount of high-purity target compound crystals can be obtained in a relatively short period of time, and there is no need for long-term drying afterwards.

[0029] 6) The total yield of the present invention can reach more than 0.7%, which is much higher than the yield reported in the prior art.

[0030] Total yield = (mass of pure glycyrrhizine obtained after crystallization / mass of licorice residue) * 100%

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a technical flowchart of the method of the present invention;

[0033] Figure 2 This is a liquid chromatogram of the soaking liquid after soaking liquorice residue in deionized water in Example 3;

[0034] Figure 3 This is a liquid chromatogram of the soaking liquid after the liquorice residue is soaked in ethanol in Example 3;

[0035] Figure 4 This is the liquid chromatogram of the macroporous resin sample solution in Example 3;

[0036] Figure 5 This is the liquid chromatogram of the last eluate of the macroporous resin in Example 3;

[0037] Figure 6 This is a liquid chromatogram of the glycyrrhizine product obtained after crystallization in Example 3;

[0038] Figure 7 This is a liquid chromatogram of the product obtained in Comparative Example 1;

[0039] Figure 8 This is a liquid chromatogram of the product obtained in Comparative Example 2;

[0040] Figure 9 This is a liquid chromatogram of the product obtained in Comparative Example 3;

[0041] Figure 10This is the liquid chromatogram of the product obtained in Comparative Example 6. DETAILED DESCRIPTION

[0042] Example 1

[0043] A method for separating and extracting glycyrrhizin from liquorice comprises the following steps:

[0044] Step 1) 500 g of licorice residue was added to 6 L of deionized water at room temperature and soaked for 5 h, and the deionized water was filtered to obtain a water-extracted licorice residue; 5 L of anhydrous ethanol was added to the residue and soaked for 14 h at room temperature, and the residue was concentrated under reduced pressure to obtain an anhydrous ethanol concentrate.

[0045] Step 2) The obtained anhydrous ethanol concentrate was diluted with deionized water to a volume fraction of 45% ethanol, and adsorbed on D101 macroporous resin at a sample flow rate of 1 BV / h; gradient elution was performed with 55% to 75% ethanol aqueous solution with 10 column volumes at a flow rate of 1.5 BV / h and an elution volume of 10 BV; the last eluate was collected and concentrated by vacuum distillation to obtain a crude flavonoid dry powder.

[0046] Step 3) The dry powder was dissolved in dichloromethane to a concentration of 400 mg / mL, and cyclohexane was then added to the dichloromethane solution. The volume ratio of dichloromethane to cyclohexane was 1:7. The turbid liquid was filtered after sufficient stirring. The filtrate was heated at 38 ° C, and the temperature was slowly increased. After the dichloromethane was essentially volatilized, the solution was cooled to 4 ° C at a rate of 1 ° C / min. After crystallization for 24 hours, the glycyrrhizin product was filtered. HPLC detection showed that the product purity was 96.7%, and the yield of this step was 51.66%. The total yield of this embodiment was 0.736%.

[0047] The HPLC analysis conditions used in the experiments were as follows: Shimadzu LC-15C analytical system, Agela Venusil XBP C18(L) column (4.6×250 mm, 5 μm), mobile phase consisting of acetonitrile-0.1% acetic acid aqueous solution (60:40), flow rate 1 mL / min, column temperature 35°C, and UV detection at 282 nm. The same applies to the following examples.

[0048] Example 2

[0049] A method for separating and extracting glycyrrhizin from liquorice comprises the following steps:

[0050] Step 1) 400 g of licorice residue was added to 4 L of deionized water at room temperature and soaked for 8 h, and the deionized water was filtered to obtain a water-extracted licorice residue; 4 L of anhydrous ethanol was added to the residue and soaked for 16 h at room temperature, and the residue was concentrated under reduced pressure to obtain an anhydrous ethanol concentrate.

[0051] Step 2) The obtained concentrated solution was diluted with deionized water to a volume fraction of ethanol of 50%, and adsorbed on D101-B macroporous resin at a sample flow rate of 1 BV / h; eluted sequentially with 10 column volumes of 60% to 70% ethanol aqueous solution at an elution flow rate of 1.5 BV / h and an elution volume of 9 BV; the last eluate was collected and concentrated by vacuum distillation to obtain a crude flavonoid dry powder.

[0052] Step 3) Acetone and petroleum ether are mixed in a volume ratio of 1:10, and the crude powder is dissolved in the mixed solution (the concentration of the crude powder in acetone is 80 mg / mL). After sufficient stirring, the turbid liquid is filtered, and the filtrate is heated at 55 ° C, and the temperature is slowly increased. After the acetone is substantially volatilized, the solution is cooled to -2 ° C at a rate of 2 ° C / min, and filtered after crystallization for 4 hours to obtain the glycyrrhizin product. HPLC detection shows that the product purity is 95.9%, and the yield of this step is 53.33%. The total yield of this embodiment is 0.743%.

[0053] Example 3

[0054] A method for separating and extracting glycyrrhizin from liquorice comprises the following steps:

[0055] Step 1) 500 g of licorice residue was added to 5 L of deionized water at room temperature and soaked for 12 h, and the deionized water was filtered to obtain water-extracted licorice residue; 5 L of anhydrous ethanol was added to the residue and soaked for 16 h at room temperature, and the residue was concentrated under reduced pressure to obtain an anhydrous ethanol concentrate.

[0056] Step 2) The obtained anhydrous ethanol concentrate was diluted with deionized water to a volume fraction of 55% ethanol, and adsorbed on AB-8 macroporous resin at a sample flow rate of 1 BV / h; gradient elution was performed with 60% to 80% ethanol aqueous solution with 10 column volumes at a flow rate of 1 BV / h and an elution volume of 8 BV; the last eluate was collected and concentrated by vacuum distillation to obtain a crude flavonoid dry powder.

[0057] Step 3) The dry powder was dissolved in ether to a concentration of 200 mg / mL, and cyclohexane was then added to the ether solution at a volume ratio of 1:15. The turbid liquid was stirred thoroughly and filtered. The filtrate was heated at 34°C and the temperature was slowly raised. After the ether was substantially evaporated, the solution was cooled to -5°C at a rate of 2°C / min. After crystallization for 2 hours, the glycyrrhizin product was filtered. HPLC analysis showed a product purity of 95.1%, and the yield of this step was 49.76%. The total yield of this embodiment was 0.729%.

[0058] Example 4

[0059] A method for separating and extracting glycyrrhizin from liquorice comprises the following steps:

[0060] Step 1) 600 g of licorice residue was added to 5 L of deionized water at room temperature and soaked for 12 h, and the deionized water was filtered to obtain a water-extracted licorice residue; 5 L of anhydrous ethanol was added to the residue and soaked for 16 h at room temperature, and the residue was concentrated under reduced pressure to obtain an anhydrous ethanol concentrate.

[0061] Step 2) The obtained anhydrous ethanol concentrate was diluted with deionized water to a volume fraction of 50% ethanol, and adsorbed on AB-8 macroporous resin at a sample flow rate of 1 BV / h; gradient elution was performed with 55% to 70% ethanol aqueous solution with 10 column volumes at an elution flow rate of 1 BV / h and an elution volume of 10 BV; the last eluate was collected and concentrated by vacuum distillation to obtain a crude flavonoid dry powder.

[0062] Step 3) Diethyl ether and petroleum ether are mixed in a volume ratio of 1:6, and the crude powder is dissolved in the mixed solution (the concentration of the crude powder in diethyl ether is 150 mg / mL). After sufficient stirring, the turbid liquid is filtered, and the filtrate is heated at 34 ° C, and the temperature is slowly increased. After the diethyl ether is substantially volatilized, the solution is cooled to -2 ° C at a rate of 1.5 ° C / min, and filtered after crystallization for 2 hours to obtain the glycyrrhizin product. HPLC detection shows that the product purity is 96.3%, and the yield of this step is 47.83%. The total yield of this embodiment is 0.702%.

[0063] Example 5

[0064] A method for separating and extracting glycyrrhizin from liquorice comprises the following steps:

[0065] Step 1) taking 800 g of licorice residue, adding 6 L of deionized water at room temperature and soaking for 10 hours, filtering the deionized water to obtain a water-extracted licorice residue; adding 10 L of anhydrous ethanol and soaking for 16 hours at room temperature, and concentrating under reduced pressure to obtain an anhydrous ethanol concentrate;

[0066] Step 2) diluting the obtained anhydrous ethanol concentrate with deionized water to a volume fraction of 50% ethanol, and adsorbing the concentrate on LSA-10 macroporous resin at a flow rate of 1 BV / h; gradient eluting with 70% to 80% ethanol aqueous solution over 10 column volumes at a flow rate of 1 BV / h and an elution volume of 10 BV; collecting the final eluate and concentrating it by vacuum distillation to obtain a crude flavonoid dry powder;

[0067] Step 3) The dry powder was dissolved in dichloromethane to a concentration of 200 mg / mL, and then n-hexane was added to the dichloromethane solution. The volume ratio of dichloromethane to n-hexane was 1:6. After sufficient stirring, the turbid liquid was filtered. The filtrate was heated at 38 ° C, and the temperature was slowly increased. After the dichloromethane was essentially volatilized, the solution was cooled to 2 ° C at a rate of 1.5 ° C / min. After crystallization for 24 hours, the glycyrrhizin product was filtered. HPLC detection showed that the product purity was 97.5%, and the yield of this step was 50.47%. The total yield of this embodiment was 0.719%.

[0068] Comparative Example 1

[0069] This comparative example is a comparative example of Example 1, and compared with Example 1, only the low-temperature crystallization operation in step 3) is missing. Other operations are the same as in Example 1.

[0070] In step 3), the dry powder was dissolved in dichloromethane to a concentration of 400 mg / mL, and cyclohexane was then added to the dichloromethane solution at a solvent ratio of 1:7. After thorough stirring, the turbid liquid was filtered. The filtrate was heated at 38°C with the temperature slowly increased. After the dichloromethane was substantially evaporated, it was filtered and dried to obtain the product. HPLC analysis revealed a product purity of 50.07%, and the yield for this step was 9.52%.

[0071] Comparative Example 2

[0072] This comparative example is a comparative example of Example 3. Compared with Example 3, the cooling rate is not controlled. Other operations are the same as Example 3.

[0073] In step 3), the dry powder was dissolved in ether to a concentration of 200 mg / mL, and then cyclohexane was added to the ether solution at a solvent ratio of 1:15. After sufficient stirring, the turbid liquid was filtered. The filtrate was heated at 34°C and the temperature was slowly increased. After the ether was substantially evaporated, the solution was cooled to -5°C and crystallized for 2 hours before filtration to obtain the glycyrrhizine product. HPLC analysis showed that the product purity was 89.39%, and the yield of this step was 15.37%.

[0074] Comparative Example 3

[0075] This comparative example is a comparative example of Example 1. Compared with Example 1, no solvent II was added, and single solvent crystallization was performed. Other operations were the same as in Example 3.

[0076] In step 3), the dry powder was dissolved in dichloromethane to a concentration of 400 mg / mL. After stirring, the solution was placed in a 38°C water bath and refluxed. The solution was then cooled to 4°C at a rate of 1°C / min. After crystallization for 24 hours, the glycyrrhizine product was filtered. HPLC analysis revealed a glycyrrhizine purity of 24.10%, and the yield for this step was 45.45%.

[0077] Comparative Example 4

[0078] This comparative example is a comparative example of Example 2. Compared with Example 2, the added solvent II is not within the preferred range. Other operations are the same as Example 2.

[0079] Step 3) Acetone and benzene were mixed in a volume ratio of 1:10, and the crude powder was dissolved in the mixture (the concentration of the crude powder in acetone was 80 mg / mL). After thorough stirring, the turbid solution was filtered, and the filtrate was heated at 55°C with the temperature slowly increased. After the acetone was substantially evaporated, the solution was cooled at a rate of 2°C / min to -2°C. No glycyrrhizine crystals were observed.

[0080] Comparative Example 5

[0081] This comparative example is a comparative example of Example 4. Compared with Example 4, the added solvent I is not within the preferred range. Other operations are the same as those in Example 4.

[0082] Step 3) Ethanol and petroleum ether were mixed in a volume ratio of 1:6, and the crude powder was dissolved in the mixture (the concentration of the crude powder in ethanol was 150 mg / mL). After thorough stirring, the turbid solution was filtered, and the filtrate was heated at 34°C, slowly increasing the temperature. The solution was then cooled to -2°C at a rate of 1.5°C / min. No glycyrrhizine crystals were observed.

[0083] Comparative Example 6

[0084] This embodiment is a comparative example of embodiment 5. Compared with embodiment 5, the only difference is the water bath temperature in step 3). Other operations are the same as those in embodiment 5.

[0085] Step 3) The dry powder was dissolved in dichloromethane to a concentration of 200 mg / mL. Then, n-hexane was added to the dichloromethane solution at a solvent ratio of 1:6. After thorough stirring, the turbid liquid was filtered. The filtrate was heated at 25°C, then cooled to 2°C at a rate of 1.5°C / min. After crystallization for 24 hours, the glycyrrhizine product was filtered. HPLC analysis showed a purity of 39.93%, and the yield of this step was 15.47%.

[0086] Comparative Example 7

[0087] This example is a comparative example of Example 2, except for the choice of macroporous resin. All other aspects are the same as Example 2. The selected macroporous resin is LXD-762. HPLC analysis revealed a yield of only 3.58%, and the glycyrrhizin purity in the concentrated flavonoid powder was only 9.81%. Therefore, the preferred resin should be used for processing, otherwise it will affect subsequent crystallization.

[0088] The above embodiments are only partial embodiments of the present invention and cannot cover the entire present invention. Based on the above embodiments and drawings, those skilled in the art can obtain more implementation methods without paying any creative work. Therefore, these implementation methods obtained without paying any creative work should be included in the scope of protection of the present invention.

Claims

1. A method for separating and extracting glycyrrhizin from liquorice, characterized in that: The following steps are involved: Step 1): Weigh the licorice residue, soak it with deionized water at room temperature, and filter it to obtain the water-extracted licorice residue; soak the water-extracted licorice residue with anhydrous ethanol at room temperature, the material-liquid ratio of the licorice residue before soaking to anhydrous ethanol is 1:10-1:15, and the extraction time is 10-16 hours; collect the soaking liquid, and concentrate it under reduced pressure to obtain an anhydrous ethanol concentrate; Step 2): The anhydrous ethanol concentrate obtained in step 1) is diluted with deionized water and applied to a macroporous resin column for adsorption at a sample loading flow rate of 1 BV / h, wherein the macroporous resin is a non-polar or weakly polar resin; after the column loading is completed, gradient elution is performed with a 50% to 85% ethanol aqueous solution, the elution volume of the ethanol aqueous solution gradient elution is 8 to 10 BV, and the flow rate is 1 to 1.5 BV / h; the last eluate is concentrated to obtain a crude flavonoid powder; Step 3): The crude flavonoid powder obtained in step 2) is treated with solvent I and solvent II, and stirred to obtain a turbid liquid; the turbid liquid is filtered, the filtrate is heated to volatilize solvent I, and then the filtrate is cooled to a low temperature condition at a rate of 1 to 3°C / min. After crystallization is complete, the glycyrrhizine product is filtered; the solvent I is any one of acetone, ether and dichloromethane, and the solvent II is any one of cyclohexane, n-hexane, petroleum ether and carbon tetrachloride; the heating temperature is 30°C to 60°C, and the volume ratio of solvent I to solvent II is 1:2 to 1:15; the low temperature condition is 4°C to -15°C.

2. The method for separating and extracting glycyrrhizin from liquorice according to claim 1, wherein: The deionized water soaking material-liquid ratio in step 1) is 1:5-1:15, and the soaking time is 5-14 hours.

3. The method for separating and extracting glycyrrhizin from liquorice according to claim 1, characterized in that: The normal temperature is 18-25°C.

4. The method for separating and extracting glycyrrhizin from liquorice according to claim 1, wherein: The non-polar or weakly polar resin described in step 2) is of model LSA-10, D101, LX-T28, D101B or AB-8.

5. The method for separating and extracting glycyrrhizin from liquorice according to claim 1, wherein: The anhydrous ethanol concentrate in step 2) is diluted with deionized water to a volume fraction of ethanol of 45% to 55%, and then applied to a macroporous resin column for adsorption.

6. The method for separating and extracting glycyrrhizin from liquorice according to claim 1, characterized in that: In step 3), the specific operation of using solvent I and solvent II to treat the crude flavonoid powder obtained in step 2) is as follows: solvent I and solvent II are mixed, and then the crude flavonoid powder is added and stirred to obtain a turbid liquid.

7. The method for separating and extracting glycyrrhizin from liquorice according to claim 1, characterized in that: In step 3), the specific operation of using solvent I and solvent II to treat the crude flavonoid powder obtained in step 2) is as follows: first dissolve the crude flavonoid powder with solvent I, then add solvent II to the solution, and stir to obtain a turbid solution.

8. The method for separating and extracting glycyrrhizin from liquorice according to claim 6 or 7, characterized in that: In step 3), the concentration of the crude flavonoid powder in solvent I is 80-400 mg / mL.

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