A method for preparing total flavonoids rich in glycyrrhizin from licorice residue at low temperature

Abstract

This invention relates to a method for preparing total flavonoids rich in glycyrrhizin from licorice residue at low temperature. The specific steps of this method are as follows: licorice residue is extracted with an ethanol-water solution; the extract is concentrated; the concentrate is then subjected to resin enrichment, decolorization, purification, further concentration, and low-temperature drying to obtain high-purity total flavonoids (total flavonoid content ≥92%, of which glycyrrhizin content ≥40%). The process provided by this invention is simple, controllable, and environmentally friendly; the extraction and purification process uses only ethanol as the organic solvent, which can be recycled and reused; simultaneously, the separation materials can be reused repeatedly, significantly reducing the production cost per unit product; this process has a high product transfer rate, stably and efficiently enabling large-scale preparation and industrial production.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical technology, specifically relating to a method for low-temperature extraction and preparation of total flavonoids rich in glycyrrhizin from the residue of Glycyrrhiza glabra. Background Technology

[0002] Licorice is the dried root and rhizome of *Glycyrrhiza uralensis* Fisch., *Glycyrrhiza inflata* Bat., or *Glycyrrhiza glabra* L., all belonging to the legume family. *Glycyrrhiza glabra*, also known as European licorice, is mainly distributed in the Xinjiang Uygur Autonomous Region of China. Licorice is not only a traditional Chinese medicine but also one of the substances listed by the Ministry of Health as having both medicinal and edible properties. It mainly contains flavonoids, triterpenoids, and polysaccharides. While glycyrrhizic acid, the main triterpenoid component, is widely used, the utilization rate of flavonoids in licorice is not high. *Glycyrrhiza glabra* residue is the residue remaining after extracting glycyrrhizic acid or licorice extract from licorice. This residue contains a large amount of glycyrrhizin flavonoids. my country consumes tens of thousands of tons of *Glycyrrhiza glabra* annually, and the residue is usually treated as waste, resulting in significant resource waste. Efficiently recovering the flavonoids from licorice residue has become an important measure to solve the problem of comprehensive utilization of licorice resources.

[0003] The total flavonoids in the residue of Glycyrrhiza glabra mainly include flavonoids with low polarity such as glycyrrhizin, glycyrrhizin, and isoglycyrrhizin. Glycyrrhizin is a unique flavonoid chemical component of Glycyrrhiza glabra, accounting for about 0.2% in Glycyrrhiza glabra and is also one of the main components of the total flavonoids in Glycyrrhiza glabra. Glycyrrhizin is currently recognized as the safest whitening and spot-removing ingredient in cosmetics. The standard specification for adding glycyrrhizin to cosmetics on the market is 40%. However, due to the low content of the target component in the raw materials and the complexity of the extraction and purification process, the production cost of glycyrrhizin prepared by the existing technology remains high, and the market price is comparable to that of gold. Therefore, it is known as "whitening gold".

[0004] Glycyrrhiza flavonoids have good pharmacological activity, and many scholars have conducted extensive research on their pharmacological activity. A Chinese invention patent (publication number: CN107510710A, application number: 201710946065.9) discloses a method for enriching type 2 diabetes target inhibitors from licorice residue and their medicinal uses. The results show that the licorice flavonoids extracted from licorice residue have significant inhibitory effects on two important targets in the prevention and treatment of type 2 diabetes: α-glucosidase and PTP1B. In particular, the inhibitory effect on α-glucosidase is more than 10 times stronger than that of the clinical hypoglycemic drug acarbose. This result provides a theoretical basis for the potential use of licorice flavonoids as an α-glucosidase inhibitor. There are many reports on the pharmacological activity of licorice flavonoids in the literature. For example, Yang Xiaolu et al. (Study on the in vitro anti-inflammatory activity and mechanism of licorice flavonoids and their components [J]. Chinese Journal of Traditional Chinese Medicine, 2013, 38(01): 99-103.), and Muhebuli... ▪ Abuliz et al. (Antioxidant activity of flavonoids from Glycyrrhiza glabra in Xinjiang [J]. Chinese Pharmaceutical Journal, 2008, 43(21): 1617-1620.), Hua Bing (Study on the lipid-lowering effect and mechanism of total flavonoids from Glycyrrhiza glabra [D]. Ningxia Medical University, 2015.), Zheng Jun et al. (Study on the inhibition of gastric mucosal gland atrophy in rats with chronic atrophic gastritis by total flavonoids from Glycyrrhiza glabra [J]. Chinese Pharmacology Bulletin, 2013, 30(01): 113-117.), reported that total flavonoids from Glycyrrhiza glabra have significant pharmacological activities such as anti-inflammatory, antioxidant, lipid-lowering, and repair of chronic atrophic gastritis, providing a good research and development direction for the development of new Chinese medicines, cosmetics, and health products.

[0005] In recent years, there have been numerous reports in literature and patents regarding the preparation of total flavonoids from licorice and glycyrrhizin. Chinese invention patent (publication number: CN112724155B, application number: 202011486009.X) discloses a method for preparing white glycyrrhizin using subcritical technology. This method involves the use of organic solvents and silica gel in the separation process, resulting in numerous separation steps, high separation costs, and a glycyrrhizin content of only 30%–40%. Chinese invention patent (publication number: CN113813300A, application number: 202111287796.X) discloses a method for preparing and using licorice extract, which uses petroleum ether and ethyl acetate as organic solvents in the separation process. This separation method is only suitable for laboratory research and not for the industrial production of licorice. Chinese invention patent (publication number: CN117362308A, application number: 202311323339.0) discloses a method for preparing ultra-high purity glycyrrhizin. The preparation process involves repeated acid-base adjustment, with the pH value adjusted to greater than 13. Glycyrrhizin is extremely unstable in this environment. Although high purity glycyrrhizin was obtained in the process, the transfer rate of glycyrrhizin is unknown, making industrialization impossible. Wu Hao et al. (Subcritical water extraction of licorice residue to co-extract total flavonoids and oligosaccharides from licorice [J]. Journal of Nanjing University of Technology, 2021, 43 (1): 25-31.) only reported an extraction rate of 2.81% for total licorice flavonoids, without detecting its content and purity. The above reports mostly use small-scale laboratory separation and purification methods, which are difficult to industrialize. Meanwhile, Shi Yue et al. (Study on the Large-Scale Preparation and Stability Influencing Factors of Glycyrrhizin [D]. Huazhong University of Science and Technology, 2011.) pointed out that glycyrrhizin undergoes significant thermal decomposition upon heating above 60℃, destroying the original structure of flavonoids. This method conducts a targeted preparation process study on the total flavonoid components in the residue of Glycyrrhiza glabra. The preparation process is simple, easy to implement, and environmentally friendly. It employs low-temperature treatment, reducing energy consumption, and can achieve large-scale preparation and industrial production. This provides feasibility for its development as a new drug, cosmetic, and health product, and has good market application prospects. Summary of the Invention

[0006] This invention provides a method for preparing total flavonoids rich in glycyrrhizin from the residue of Glycyrrhiza glabra at low temperature. The residue of Glycyrrhiza glabra is extracted with an ethanol-water solution. The extract is enriched by macroporous adsorption resin column and decolorized by ion exchange resin column to obtain crude total flavonoids. The crude product is then purified using a purification resin to obtain high-purity total flavonoids of licorice, wherein the total flavonoid content is not less than 92% and the glycyrrhizin content is not less than 40%.

[0007] This invention focuses on the targeted preparation process of total flavonoids from licorice root residue. The extraction and purification process is simple, environmentally friendly, and utilizes low-temperature processing technology to effectively reduce energy consumption, enabling large-scale industrial production. This process does not use any acid or alkali treatment, effectively utilizing licorice root residue to obtain high-purity total flavonoids. The organic solvent used is only ethanol, which is easily recovered and reused, further improving product safety. The licorice root extract prepared using this process significantly reduces the production cost per unit product, providing a feasible technical path for its widespread development and industrial application in new drugs, cosmetics, and health products, with broad market prospects and economic benefits.

[0008] This invention relates to a method for extracting, separating, and preparing total flavonoids rich in glycyrrhizin from the residue of Glycyrrhiza glabra, comprising the following steps:

[0009] 1) Take an appropriate amount of licorice residue and extract it with 50%~95% ethanol aqueous solution at a material-liquid ratio of 1:6~1:30. Extract 1~4 times, each time for 2~24 hours. Concentrate the extract to a material-liquid ratio of 1:0.5~1:4 (w / v) for later use.

[0010] 2) The concentrate obtained in step 1) is passed through a macroporous adsorption resin column and eluted first with 3 to 8 column volumes of 10% to 50% ethanol aqueous solution, and then with 4 to 10 column volumes of 60% to 90% ethanol aqueous solution. The 60% to 90% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of 1:1 to 1:6 (w / v).

[0011] 3) The concentrate obtained in step 2) is passed through an ion exchange resin column and eluted with 4 to 7 column volumes of 50% to 90% ethanol aqueous solution. The 50% to 90% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of about 1:0.5 to 1:2 (w / v). The concentrate is then set aside for later use.

[0012] 4) The concentrate obtained in step 3) is passed through a purification column and eluted first with 3 to 8 column volumes of 20% to 50% ethanol aqueous solution, and then with 60% to 90% ethanol aqueous solution. The 60% to 90% ethanol eluent is collected, concentrated, dried, and ground to obtain total flavonoids rich in glycyrrhizin, wherein the total flavonoid content is not less than 92% and the glycyrrhizin content is not less than 40%.

[0013] The extraction, concentration and drying temperatures described in steps 1), 2), 3) and 4) should be controlled below 60°C.

[0014] The extraction method in step 1) is one of ultrasound, cold soaking, or percolation.

[0015] The macroporous adsorption resin type mentioned in step 2) is one or two of X-5, HPD-100, ADS-17, D-101, AB-8, and DM-301 used in combination, wherein the ratio of licorice residue to resin is 1:0.5~1:3 kg / L.

[0016] The ion exchange resin mentioned in step 3) is one or two of D318, D280, D951, D941, D201, and KA98Cl, and the ratio of licorice residue to resin is 1:0.3~1:1.5 kg / L.

[0017] The separating material mentioned in step 4) is one or two of polyamide, LK1300S, LK1200S, LK1200, chromatogram 5, and MCI, and the ratio of licorice residue to resin is 1:0.2~1:0.8 kg / L.

[0018] Step 4) yields high-purity total flavonoids. The total flavonoids content is greater than 92% as determined by ultraviolet spectrophotometry, and the content of glycyrrhizin is greater than 40% as determined by high-performance liquid chromatography.

[0019] The steps of ultraviolet-visible spectrophotometry include:

[0020] Preparation of reference solution: Accurately weigh 10 mg of glycyrrhizin reference standard, place it in a 25 ml volumetric flask, add an appropriate amount of ethanol, sonicate to dissolve, then dilute with ethanol to the mark, shake well, and you will get (each 1 ml contains 0.4 mg of glycyrrhizin reference standard).

[0021] Preparation of standard curve: Accurately measure 0.0 ml, 1.0 ml, 2.0 ml, 3.0 ml, 4.0 ml, and 5.0 ml of the reference solution into 10 ml volumetric flasks, dilute to the mark with ethanol, and shake well. Use the corresponding reagents as blanks. Measure the absorbance at 286 nm using ultraviolet-visible spectrophotometry (Chinese Pharmacopoeia 2025 Edition, Part IV, General Chapter 0401). Plot the standard curve with absorbance as the ordinate and concentration as the abscissa.

[0022] Preparation of the test solution: Accurately weigh 10 mg of this product, place it in a 25 ml volumetric flask, add an appropriate amount of ethanol, sonicate to dissolve, then dilute with ethanol to the mark, shake well, accurately measure 3 ml, place it in a 50 ml volumetric flask, dilute with ethanol to the mark, shake well, and the test solution is ready.

[0023] Determination method: Determine the absorbance according to the law, read the amount of glycyrrhizin equivalent in the test solution from the standard curve, and calculate to obtain the result.

[0024] The HPLC detection method includes the following steps:

[0025] Chromatographic conditions and system suitability tests were performed using octadecylsilane-bonded silica gel as the stationary phase; acetonitrile was used as mobile phase A, and 0.05% phosphoric acid as mobile phase B. From 0 to 5 min, the volume fraction of mobile phase A was 30%–45%, and that of mobile phase B was 70%–55%; from 5 to 20 min, the volume fraction of mobile phase A was 55%, and that of mobile phase B was 45%; from 20 to 25 min, the volume fraction of mobile phase A changed from 55% to 80%, and that of mobile phase B changed from 45% to 20%. A DAD detector was used with a detection wavelength of 280 nm, a flow rate of 0.8 ml / min, and a column temperature of 35 °C. The theoretical plate number, calculated based on the peak determination of *Glycyrrhiza glabra*, should not be less than 5000.

[0026] Preparation of reference solution: Weigh approximately 20 mg of glycyrrhizin reference standard accurately, place it in a 100 ml volumetric flask, dissolve and dilute to the mark with ethanol to prepare a solution containing 0.2 mg per ml.

[0027] Preparation of the test solution: Weigh approximately 20 mg of this product accurately, place it in a 100 mL volumetric flask, add ethanol, sonicate to dissolve and dilute to the mark, filter, and collect the filtrate to obtain the test solution.

[0028] Determination method: Accurately pipette 10 μl of the reference solution and the test solution into the liquid chromatograph and determine the result. Attached Figure Description

[0029] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings, in which:

[0030] Figure 1 Full-wavelength scans of the total flavonoids test solution and the glycyrrhizin reference solution;

[0031] Figure 2 The HPLC chromatogram of glycyrrhizin reference standard;

[0032] Figure 3 The image shows the HPLC detection results of glycyrrhizin obtained in Example 1.

[0033] Figure 4 This is a chromatogram of the HPLC detection results of glycyrrhizin obtained in Example 2;

[0034] Figure 5 This is a chromatogram of the HPLC detection results of glycyrrhizin obtained in Example 3;

[0035] Figure 6 This is a chromatogram of the HPLC detection results of glycyrrhizin obtained in Example 4;

[0036] Figure 7 This is a chromatogram of the HPLC detection results of glycyrrhizin obtained in Example 5; Detailed Implementation

[0037] The present invention will be further described in detail below with reference to embodiments. Those skilled in the art can refer to the content of the present invention and appropriately modify the relevant parameters according to the specific actual equipment to achieve the invention. The present invention has described total flavonoids in detail. Those skilled in the art can modify or appropriately change and combine the methods described in the present invention without departing from the content and scope of the present invention to achieve and apply the methods of the present invention. However, the scope of protection of the present invention is not limited to the content described. Unless otherwise specified, the methods in the embodiments are conventional methods, and the reagents used are conventional commercial reagents or reagents prepared according to conventional methods unless otherwise specified. The information of each embodiment is summarized in Table 1, and the total flavonoid detection results are shown in Table 2.

[0038] Example 1

[0039] 1) Take 30 kg of licorice residue, add 20 times the amount of the medicinal material in 50% ethanol aqueous solution and extract by percolation for 24 hours, collect the percolate, concentrate it to a material-to-liquid ratio of 1:4 (w / v) and set aside.

[0040] 2) The concentrated solution 1 obtained in step 1) is passed through an ADS-17 macroporous adsorption resin column with a licorice residue:resin ratio of 1:0.5 kg / L. It is eluted with 8 column volumes of 10% ethanol aqueous solution and discarded. Then it is eluted with 10 column volumes of 60% ethanol solution, and the 60% ethanol eluent is collected and concentrated to a material-to-liquid ratio of 1:6 to obtain concentrated solution 2 for later use.

[0041] 3) The concentrate 2 obtained in step 2) is passed through a D941 ion exchange resin column with a licorice residue:resin ratio of 1:1 kg / L. It is eluted with 6 column volumes of 70% ethanol solution. The 70% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of approximately 1:2 (w / v) to obtain concentrate 3 for later use.

[0042] 4) The concentrated solution 3 obtained in step 3) was purified by passing it through an MCI purification column with a licorice residue:resin ratio of 1:0.5 kg / L. It was eluted with 4 column volumes of 40% ethanol solution and discarded. Then, it was eluted with 80% ethanol solution, and the 80% ethanol eluent was collected, concentrated, freeze-dried, and ground to obtain 111.49 g of high-purity total flavonoids, i.e., sample 1. UV detection showed a total flavonoid purity of 100.03%, and HPLC detection showed a glycyrrhizin purity of 47.56% and a moisture content of 3.10%.

[0043] Example 2

[0044] 1) Take 30 kg of licorice residue, add 8 times the amount of 85% ethanol aqueous solution for cold soaking and extraction, extract 3 times, each time for 3 hours, filter the extract, concentrate to a material-to-liquid ratio of 1:2, and obtain concentrated solution 1 for use.

[0045] 2) The concentrate 1 obtained in step 1) is passed through an HPD-100 macroporous adsorption resin column with a licorice residue:resin ratio of 1:1 kg / L. It is eluted with 5 column volumes of 30% solution and discarded. Then it is eluted with 7 column volumes of 80% ethanol solution. The 80% ethanol eluent is collected and concentrated to a material-to-liquid ratio of 1:5 to obtain concentrate 2 for later use.

[0046] 3) The concentrate 2 obtained in step 2) is passed through a D280 ion exchange resin column with a licorice residue:resin ratio of 1:1.5 kg / L. It is eluted with 7 column volumes of 50% ethanol solution. The 50% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of approximately 1:2 (w / v) to obtain concentrate 3 for later use.

[0047] 4) The concentrated solution 3 obtained in step 3) was purified by chromatography using column No. 5 with a licorice residue:resin ratio of 1:0.5 kg / L. It was eluted with 4 column volumes of 30% ethanol solution and discarded. Then, it was eluted with 70% ethanol solution, and the 70% ethanol eluent was collected, concentrated, freeze-dried, and ground to obtain 128.15 g of high-purity total flavonoids, i.e., sample 2. UV detection showed a total flavonoid purity of 92.75%, and HPLC detection showed a glycyrrhizin purity of 41.87% and a moisture content of 2.86%.

[0048] Example 3

[0049] 1) Take 30 kg of licorice residue, add 6 times 80% ethanol aqueous solution for ultrasonic extraction, extract 4 times, 2 hours each time, filter the extract, concentrate to a material-to-liquid ratio of 1:2, and obtain concentrated solution 1 for later use.

[0050] 2) The concentrated solution 1 obtained in step 1) is passed through a D-101 macroporous adsorption resin column with a licorice residue:resin ratio of 1:2 kg / L. It is eluted with 4 column volumes of 40% ethanol aqueous solution and discarded. Then it is eluted with 6 column volumes of 85% ethanol solution. The 85% ethanol eluent is collected and concentrated to a material-to-liquid ratio of 1:4 to obtain concentrated solution 2 for later use.

[0051] 3) The concentrate 2 obtained in step 2) is passed through a D951 ion exchange resin column with a licorice residue:resin ratio of 1:1 kg / L. It is eluted with 5 column volumes of 80% ethanol solution. The 80% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of approximately 1:1.5 (w / v) to obtain concentrate 3 for later use.

[0052] 4) The concentrated solution 3 obtained in step 3) was purified by passing it through an LK1200S purification column with a licorice residue:resin ratio of 1:0.8 kg / L. It was eluted with 8 column volumes of 20% ethanol solution and discarded. Then, it was eluted with 60% ethanol solution, and the 60% ethanol eluent was collected, concentrated, dried under reduced pressure at 60℃, and ground into a fine powder to obtain 118.65 g of high-purity total flavonoids, i.e., sample 3. UV detection showed a total flavonoid purity of 94.83%, and HPLC detection showed a glycyrrhizin purity of 42.19% and a moisture content of 3.05%.

[0053] Example 4

[0054] 1) Take 30 kg of licorice residue, add 15 times 90% ethanol aqueous solution for cold soaking and extraction, extract twice, each time for 5 hours, filter the extract, concentrate to a material-to-liquid ratio of 1:1, and obtain concentrated solution 1 for use.

[0055] 2) The concentrate 1 obtained in step 1) is passed through an HPD-100 macroporous adsorption resin column with a licorice residue:resin ratio of 1:2 kg / L. It is eluted with 6 column volumes of 20% ethanol aqueous solution and discarded. Then it is eluted with 4 column volumes of 90% ethanol solution. The 90% ethanol eluent is collected and concentrated to a material-to-liquid ratio of 1:3 to obtain concentrate 2 for later use.

[0056] 3) The concentrate 2 obtained in step 2) is passed through a D201 ion exchange resin column with a licorice residue:resin ratio of 1:0.8 kg / L. It is eluted with 4 column volumes of 85% ethanol solution. The 85% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of approximately 1:1 (w / v) to obtain concentrate 3 for later use.

[0057] 4) The concentrated solution 3 obtained in step 3) was purified by passing it through an LK1300S purification column with a licorice residue:resin ratio of 1:0.2 kg / L. It was eluted with 3 column volumes of 50% ethanol solution and discarded. Then, it was eluted with 90% ethanol solution, and the 90% ethanol eluent was collected, concentrated, dried under reduced pressure at 60℃, and ground finely to obtain 123.20 g of high-purity total flavonoids, i.e., sample 4. UV detection showed a total flavonoid purity of 92.42%, and HPLC detection showed a glycyrrhizin purity of 44.23% and a moisture content of 3.51%.

[0058] Example 5

[0059] 1) Take 30 kg of licorice residue, add 6 times 95% ethanol aqueous solution for percolation extraction for 8 hours, concentrate the percolate to a material-to-liquid ratio of 1:0.5, and obtain concentrated solution 1 for later use.

[0060] 2) The concentrate 1 obtained in step 1) is passed through an AB-8 macroporous adsorption resin column with a licorice residue:resin ratio of 1:3 kg / L. It is eluted with 3 column volumes of 50% ethanol aqueous solution and discarded. Then it is eluted with 4 column volumes of 90% ethanol solution and the 90% ethanol eluent is collected. The 90% ethanol eluent is concentrated to a feed-to-liquid ratio of 1:1 to obtain concentrate 2, which is used for later use.

[0061] 3) The concentrate 2 obtained in step 2) is passed through a D318 ion exchange resin column with a licorice residue:resin ratio of 1:0.3 kg / L. It is eluted with 6 column volumes of 90% ethanol solution. The 90% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of approximately 1:0.5 to obtain concentrate 3 for later use.

[0062] 4) The concentrated solution 3 obtained in step 3) was purified by passing it through an LK1200S purification column with a licorice residue:resin ratio of 1:0.5 kg / L. It was eluted with 4 column volumes of 40% ethanol solution and discarded. Then, it was eluted with 80% ethanol solution, and the 80% ethanol eluent was collected, concentrated, dried under reduced pressure at 60℃, and ground finely to obtain 112.50 g of high-purity total flavonoids, i.e., sample 5. UV detection showed a total flavonoid purity of 103.63%, and HPLC detection showed a glycyrrhizin purity of 47.64% and a moisture content of 2.95%.

[0063]

[0064]

Claims

1. A method for preparing total flavonoids rich in glycyrrhizin from the residue of Glycyrrhiza glabra, characterized in that... Includes the following steps: 1) Take an appropriate amount of licorice residue and extract it with 50%~95% ethanol aqueous solution at a material-liquid ratio of 1:6~1:

30. Extract 1~4 times, each time for 2~24 hours. Concentrate the extract to a material-liquid ratio of 1:0.5~1:4 (w / v) for later use. 2) The concentrate obtained in step 1) is passed through a macroporous adsorption resin column and eluted first with 3 to 8 column volumes of 10% to 50% ethanol aqueous solution, and then with 4 to 10 column volumes of 60% to 90% ethanol aqueous solution. The 60% to 90% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of 1:1 to 1:6 (w / v). 3) The concentrate obtained in step 2) is passed through an ion exchange resin column. The ion exchange resin material is one or a combination of two of D318, D280, D951, D941, and D201, wherein the ratio of licorice residue to resin is 1:0.3~1:1.5 kg / L. It is eluted with 4~7 column volumes of 50%~90% ethanol aqueous solution, and the 50%~90% ethanol eluent is collected and concentrated to a feed-to-liquid ratio of 1:0.5~1:2 (w / v). The concentrate is then used for future reference. 4) The concentrated solution obtained in step 3) is passed through a purification column, first eluted with 3 to 8 column volumes of 20% to 50% ethanol aqueous solution, then eluted with 60% to 90% ethanol aqueous solution. The 60% to 90% ethanol eluent is collected, concentrated, dried, and ground to obtain total flavonoids rich in glycyrrhizin, wherein the total flavonoid content is not less than 92% and the glycyrrhizin content is not less than 40%. The extraction, concentration, and drying temperatures described in steps 1), 2), 3), and 4) are controlled below 60°C.

2. The method for preparing total flavonoids rich in glycyrrhizin from licorice residue according to claim 1, characterized in that, The extraction method in step 1) is one of ultrasound, cold soaking, or percolation.

3. The method for preparing total flavonoids rich in glycyrrhizin from the residue of Glycyrrhiza glabra according to claim 1, characterized in that, The macroporous adsorption resin type mentioned in step 2) is one or two of X-5, HPD-100, ADS-17, D-101, AB-8, and DM-301 used in combination, wherein the ratio of licorice residue to resin is 1:0.5~1:3 kg / L.

4. The method for preparing total flavonoids rich in glycyrrhizin from licorice residue according to claim 1, characterized in that, The purification material mentioned in step 4) is one or a combination of two of LK1300S, LK1200S, LK1200, and Chromatography No. 5, wherein the ratio of licorice residue to resin is 1:0.2~1:0.8 kg / L.

5. The method for preparing total flavonoids rich in glycyrrhizin from the residue of Glycyrrhiza glabra according to claim 1, wherein the total flavonoids obtained in step 4) are detected by ultraviolet spectrophotometry and have a total flavonoid content greater than 92%, and the glycyrrhizin content is detected by high performance liquid chromatography and has a content greater than 40%.

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