Method for extracting phenolic compounds from boxthorn leaves and application of phenolic compounds

Abstract

The invention discloses a method for extracting phenolic compounds from boxthorn leaves and application thereof. The method comprises the following steps: (1) preparing boxthorn leaf powder; (2) ultrasonic-assisted deep-eutectic solvent extraction; (3) macroporous resin separation and purification; and (4) concentrating and freeze-drying. According to the method, choline chloride-lactic acid is used as the eutectic solvent, and the highest extraction rate of the boxthorn leaf phenolic compounds can reach 18.62 mg / g. After the crude extract is purified and separated by using XAD7HP type macroporous resin, the obtained boxthorn leaf phenolic compound is rich in rutin, chlorogenic acid, quercetin and the like, has the biological activities of resisting oxidation, reducing blood sugar, protecting liver and the like, and has a great application prospect in the fields of functional foods, medicines and the like.

Description

Technical Field

[0001] The present invention belongs to the field of comprehensive utilization of agricultural waste, and particularly relates to a method for extracting phenolic compounds from wolfberry leaves and the evaluation of their biological activities. The prepared products can be widely applied in the fields of food, medicine, cosmetics, etc. Background Art

[0002] Wolfberry leaves are called Tianjingcao, and it is recorded in "Compendium of Materia Medica" that they have the effects of tonifying deficiency and benefiting essence, strengthening tendons and bones, clearing heat, quenching thirst, dispelling wind and improving eyesight. However, currently only a small amount of young leaves are used as vegetables or functional tea, and most wolfberry leaves are used as soil fertilizers or cheap feed raw materials, resulting in the waste of high-value resources and seriously hindering the high-quality development of the wolfberry industry. Existing research shows that wolfberry leaves are rich in phenolic compounds, among which flavonoids and phenolic acids are particularly abundant in wolfberry leaves. The contents of phenolic acids and total flavonoids in them are not only significantly higher than those in wolfberry fruits, but also have advantages compared with some common vegetables. These phenolic compounds have been widely proven to have activities such as antioxidant, anti-aging and antibacterial, and have attracted much attention in the fields of food, medicine and cosmetics. Therefore, separating and extracting phenolic compounds from wolfberry leaves has broad market prospects and application values.

[0003] Currently, phenolic compounds in wolfberry leaves are mainly extracted using organic solvents such as methanol and ethanol, which have problems such as easy volatilization of solvents, low extraction efficiency, and potential environmental pollution. Compared with traditional organic solvents, deep eutectic solvents (DES) have strong dissolution ability, excellent thermal stability, and low melting points, which are convenient for operation at room temperature. In addition, the synthesis process of deep eutectic solvents is simple, the raw material cost is low, and they are biodegradable, which can effectively reduce environmental pollution. In order to further improve the extraction efficiency of deep eutectic solvents, ultrasonic assistance is usually used for extraction. Ultrasonic extraction technology utilizes the cavitation effect, mechanical effect and thermal effect generated when ultrasonic waves propagate in liquids to break the plant cell wall, thereby accelerating the release and dissolution of phenolic compounds in cells. Therefore, the ultrasonic-assisted deep eutectic solvent method is a green and efficient extraction method. However, the high viscosity and low volatility characteristics of deep eutectic solvents themselves make it difficult to separate them from active components, so macroporous resins are needed to enrich and recover target substances from the deep eutectic solvent extracts of plants.

[0004] In summary, in order to solve the problems of low extraction efficiency of phenolic compounds in wolfberry leaves and potential environmental pollution, the present invention intends to use the ultrasonic-assisted deep eutectic solvent method, combined with the macroporous resin separation method to extract and separate phenolic compounds from wolfberry leaves, and evaluate their biological activities to lay a foundation for their application. Summary of the Invention

[0005] The object of the present invention is to provide a method for extracting phenolic compounds from wolfberry leaves and its application.

[0006] To achieve the above object and other related objects, the technical solution provided by the present invention is: A method for extracting phenolic compounds from wolfberry leaves, comprising the following steps:

[0007] Step 1: After drying the wolfberry leaves, they are pulverized to obtain wolfberry leaf powder;

[0008] Step 2: Use the ultrasonic-assisted deep eutectic solvent method to extract the wolfberry leaf powder, centrifuge the extract, collect the supernatant and filter it to obtain a crude extract of wolfberry leaf phenolic compounds;

[0009] Step 3: Use macroporous resin to adsorb the crude extract of wolfberry leaf phenolic compounds, wash and desorb the adsorbed macroporous resin to obtain a desorbed solution;

[0010] Step 4: Concentrate the desorbed solution, and then obtain the freeze-dried product of wolfberry leaf phenolics by vacuum freeze-drying.

[0011] The preferred technical solution is: The deep eutectic solvent used in the ultrasonic-assisted deep eutectic solvent method is choline chloride-lactic acid, and the molar ratio of choline chloride to lactic acid therein is 1:1.5 - 2.5; the water content of the deep eutectic solvent is 10 - 60%. The claims generally should not use parentheses

[0012] The preferred technical solution is: In step 2, the liquid-to-solid ratio of the extraction process is 10 - 60 mL / g; the ultrasonic time is 10 - 60 min, the ultrasonic temperature is 45 - 55 °C, and the ultrasonic power is 800 W.

[0013] The preferred technical solution is: In step 2, the centrifugation speed is 7000 - 10000 r / min, and the centrifugation time is 5 - 15 min.

[0014] The preferred technical solution is: In step 3, deionized water is used to dilute the crude extract of wolfberry leaf phenolics before purification to break the hydrogen bond between the deep eutectic solvent and wolfberry leaf phenolics and enhance the effect of macroporous resin in separating and purifying wolfberry leaf phenolics.

[0015] The preferred technical solution is: In step 3, XAD7HP type macroporous resin is selected to adsorb wolfberry leaf phenolics, and the adsorbed XAD7HP type macroporous resin is washed with distilled water and then desorbed with ethanol with a volume fraction of 75%.

[0016] The preferred technical solution is: In step 4, the temperature of freeze-drying is -80 °C, and the vacuum degree is 18 - 22 Pa.

[0017] To achieve the above object and other related objects, the technical solution provided by the present invention is: the application of the phenolic compound obtained by the above method in the preparation of drugs for treating and preventing alcoholic liver disease.

[0018] To achieve the above object and other related objects, the technical solution provided by the present invention is: the application of the phenolic compound obtained by the above method in the preparation of drugs for treating and preventing hypoglycemic drugs.

[0019] Due to the application of the above technical solution, the advantages of the present invention compared with the prior art are:

[0020] (1) The eutectic solvent selected in the present invention has the characteristics of low melting point, strong solubility, biodegradability, etc., and can extract phenolic compounds from wolfberry leaves greenly and efficiently; (2) The ultrasonic-assisted extraction method is adopted in the present invention, which can improve the release of phenols in wolfberry leaves, thereby improving the extraction efficiency; (3) The present invention studies and optimizes the extraction and purification process of phenolic compounds in wolfberry leaves, and improves the extraction rate of phenolic compounds in wolfberry leaves; (4) The phenolic extract of wolfberry leaves obtained by the present invention has good digestive stability, antioxidant, hypoglycemic and liver protection potential; (5) The present invention has good repeatability, relatively simple operation and high extraction efficiency. Description of the Drawings

[0021] Figure 1 Shows the influence of different types of solvents on the extraction rate of phenols from wolfberry leaves.

[0022] Figure 2 Shows the influence of different liquid-to-solid ratios on the extraction rate of phenols from wolfberry leaves.

[0023] Figure 3 Shows the influence of different ultrasonic times on the extraction rate of phenols from wolfberry leaves.

[0024] Figure 4 Shows the influence of different water contents of DES on the extraction rate of phenols from wolfberry leaves.

[0025] Figure 5 Shows the response surface optimization experiment and results of the extraction process of phenols from wolfberry leaves.

[0026] Figure 6 Shows the response surface diagrams of the influence of various factors on the extraction rate of phenols from wolfberry leaves.

[0027] Figure 7 Shows the adsorption rate and desorption rate of different types of resins to phenols from wolfberry leaves.

[0028] Figure 8 Shows the digestive stability and antioxidant activity results of the phenols from wolfberry leaves prepared by the present invention.

[0029] Figure 9 Shows the hypoglycemic activity results of the phenols from wolfberry leaves prepared by the present invention.

[0030] Figure 10 The liver-protecting activity results of phenolic compounds in wolfberry leaves prepared for this invention. Specific Embodiments

[0031] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in this technology can easily understand other advantages and effects of the present invention from the content disclosed in this embodiment.

[0032] Please refer to Figures 1-10 Note that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the implementation conditions of the present invention. Therefore, they do not have technical essential significance. Any modification of the structure, change of the proportional relationship, or adjustment of the size. The following embodiments are provided to better understand the present invention, rather than to limit the present invention. The experimental materials used in the following embodiments are all obtained from conventional consumables and biochemical reagent stores without special instructions.

[0033] Example 1: Extracting phenolic compounds from wolfberry leaves using a deep eutectic solvent (choline chloride - lactic acid)

[0034] After drying wolfberry leaves to a constant weight, they were crushed and passed through a 60-mesh sieve to obtain a crude sample powder. 0.5 g of wolfberry leaf powder and 10.0 mL of the deep eutectic solvent (choline chloride - lactic acid, molar ratio 1:2) were fully mixed, and the mixture was treated with an ultrasonic cleaner. Under the conditions that the water content of the deep eutectic solvent was 20%, the ultrasonic temperature was 50 °C, and the ultrasonic power was 800 W, ultrasonic treatment was carried out for 30 min. After the extraction was completed, centrifugation was carried out at 8000 r / min for 10 min, and the supernatant was collected and filtered to obtain a crude extract.

[0035] Example 2: Extracting phenolic compounds from wolfberry leaves using a deep eutectic solvent (choline chloride - lactic acid)

[0036] After drying wolfberry leaves to a constant weight, they were crushed and passed through a 60-mesh sieve to obtain a crude sample powder. 0.5 g of wolfberry leaf powder and 15.0 mL of the deep eutectic solvent (choline chloride - lactic acid, molar ratio 1:2) were fully mixed, and the mixture was treated with an ultrasonic cleaner. Under the conditions that the water content of the deep eutectic solvent was 30%, the ultrasonic temperature was 50 °C, and the ultrasonic power was 800 W, ultrasonic treatment was carried out for 50 min. After the extraction was completed, centrifugation was carried out at 8000 r / min for 10 min, and the supernatant was collected and filtered to obtain a crude extract.

[0037] Example 3: Extracting phenolic compounds from wolfberry leaves using a deep eutectic solvent (choline chloride - lactic acid)

[0038] After drying the wolfberry leaves to a constant weight, they were crushed and passed through a 60-mesh sieve to obtain a crude sample powder. 0.5 g of the wolfberry leaf powder was thoroughly mixed with 13.0 mL of the deep eutectic solvent (choline chloride-lactic acid, molar ratio 1:2). The mixture was treated with an ultrasonic cleaner and ultrasonicated for 51 min under the conditions that the water content of the deep eutectic solvent was 29%, the ultrasonic temperature was 50 °C, and the ultrasonic power was 800 W. After the extraction was completed, it was centrifuged at 8000 r / min for 10 min, and the supernatant was collected and filtered to obtain a crude extract. An appropriate amount of pretreated XAD7HP AB-8, D101, HPD100, XAD7HP, NKA resin was weighed and loaded into a glass chromatography column (40 mm × 800 mm). The diluted crude phenolic extract of wolfberry leaves was added to the chromatography column. After it was fully adsorbed, the resin was washed with an appropriate amount of pure water, and a 75% ethanol solution was used as the desorbent to collect the desorbed solution. The desorbed solution was evaporated and concentrated using a rotary evaporator at 45 °C, and the concentrated liquid was freeze-dried under vacuum to obtain the freeze-dried wolfberry leaf phenolics.

[0039] Comparative Example 1: Extracting phenolic compounds from wolfberry leaves using the deep eutectic solvent (choline chloride-D-fructose)

[0040] After drying the wolfberry leaves to a constant weight, they were crushed and passed through a 60-mesh sieve to obtain a crude sample powder. 0.5 g of the wolfberry leaf powder was thoroughly mixed with 10.0 mL of the deep eutectic solvent (choline chloride-D-fructose, molar ratio 1:1). The mixture was treated with an ultrasonic cleaner and ultrasonicated for 30 min under the conditions that the water content of the deep eutectic solvent (choline chloride-D-fructose) was 20%, the ultrasonic temperature was 50 °C, and the ultrasonic power was 800 W. After the extraction was completed, it was centrifuged at 8000 r / min for 10 min, and the supernatant was collected and filtered to obtain a crude extract.

[0041] Comparative Example 2: Extracting phenolic compounds from wolfberry leaves using 70% ethanol

[0042] After drying the wolfberry leaves to a constant weight, they were crushed and passed through a 60-mesh sieve to obtain a crude sample powder. 0.5 g of the wolfberry leaf powder was thoroughly mixed with 10.0 mL of 70% ethanol. The mixture was treated with an ultrasonic cleaner and ultrasonicated for 30 min under the conditions that the ultrasonic temperature was 50 °C and the ultrasonic power was 800 W. After the extraction was completed, it was centrifuged at 8000 r / min for 10 min, and the supernatant was collected and filtered to obtain a crude extract.

[0043] Comparative Example 3: Extracting phenolic compounds from wolfberry leaves using water

[0044] After drying the wolfberry leaves to a constant weight, they were crushed and passed through a 60-mesh sieve to obtain a crude sample powder. 0.5 g of the wolfberry leaf powder was thoroughly mixed with 10.0 mL of deionized water, and the mixture was treated with an ultrasonic cleaner. It was ultrasonicated for 30 min under the conditions of an ultrasonic temperature of 50 °C and an ultrasonic power of 800 W. After the extraction was completed, it was centrifuged at 8000 r / min for 10 min, and the supernatant was collected and filtered to obtain a crude extract.

[0045] Experimental Example 1: Determination of the phenolic content of the wolfberry leaf polyphenol extract

[0046] Total phenolic content detection method: The Folin-Ciocalteu method was used to determine the total phenolic content in wolfberry leaves. 0.2 mL of the first extract was mixed evenly with 1 mL of Folin-Ciocalteu reagent. After standing for 5 min, 0.25 mL of sodium carbonate solution (7.5%, W / V) was added, and after mixing evenly, it was left to stand in the dark for another 40 min. The absorbance value was recorded at a wavelength of 760 nm and compared with the gallic acid standard solution. The total phenolic content was expressed as the amount of gallic acid equivalents per gram of extract (mg GAE / g DW), and the data are shown in Table 1. Gallic acid standard curve: y = 5.7265x + 0.0618, R 2 = 0.9995.

[0047] Determination method of individual phenolic content: HPLC was used to analyze the polyphenol composition of wolfberry leaves. Liquid chromatography conditions: HC-C18 chromatographic column (250×4.6 mm, 5 μm); mobile phase A: 0.1% formic acid-aqueous solution, mobile phase B: 0.1% formic acid-acetonitrile solution; gradient elution conditions: 0 - 10 min, 5% B; 10 - 30 min, 35% B; 30 - 35 min, 100% B; 35 - 45 min, 5% B; injection volume 20 μL. The chromatographic column was operated at 30 °C, the mobile phase was run at a constant flow rate of 1.0 mL / min, and the effluent was monitored at 280 nm.

[0048] Result analysis: In Examples 1, 2, and 3, phenolic compounds were extracted from wolfberry leaves using a deep eutectic solvent (choline chloride-lactic acid) under different extraction conditions. In Comparative Examples 1, 2, and 3, phenolic compounds were extracted using a deep eutectic solvent (choline chloride-D-fructose), 70% ethanol, and water respectively under the extraction conditions of Example 1.

[0049] Table 1 Effects of different extraction conditions on phenolic content

[0050]

[0051]

[0052] As shown in Table 1, the extraction rate of phenols from wolfberry leaves in Example 1 was significantly higher than that in Comparative Examples 1-3, indicating that the extraction efficiency of the deep eutectic solvent (choline chloride-lactic acid) was significantly higher than that of water, ethanol, and other deep eutectic solvents (for the effects of different extraction solvents, see Figure 1 ). The extraction rates of wolfberry leaves in Example 2 and Example 3 increased by 9.22% and 9.95% respectively compared with Example 1, indicating that the extraction process optimization (see Figures 2-6 ) effectively improved the extraction rate of phenolic substances. Therefore, the optimized extraction process of phenols from wolfberry leaves is as follows: the deep eutectic solvent is choline chloride-lactic acid (molar ratio 1:2), the liquid-solid ratio is 31 mL / g, the extraction time is 51 min, and the water content is 33%. Under these conditions, the actual extraction amount of phenols is 18.62 mg / g.

[0053] The results of the static adsorption and desorption of 5 macroporous resins on phenols from wolfberry leaves in Example 3 are shown in Figure 7 . Five different resins (AB-8, D-101, HPD-100, XAD7HP, and NKA) were selected for research. The adsorption and desorption capabilities of the 5 resins for 3 target analytes (chlorogenic acid, rutin, and TPC) were determined through static adsorption and desorption tests. Through comparison, the XAD7HP resin showed better adsorption capabilities for the three target analytes. This is because polar macroporous resins have strong adsorption capabilities for polar and weakly polar substances. There was no significant difference in the adsorption performance of the five macroporous resins for chlorogenic acid during the desorption process (p < 0.05). NKA and XAD7HP had higher desorption capabilities for total phenols and rutin. Finally, the XAD7HP resin was selected as the best resin. Considering the adsorption-desorption results of the XAD7HP resin for phenols, chlorogenic acid, and rutin from wolfberry leaves, the XAD7HP type macroporous resin was finally selected for the purification and separation of phenols from wolfberry leaves.

[0054] Table 2 Determination results of the composition in the wolfberry leaf polyphenol extract prepared by the present invention

[0055]

[0056]

[0057] The component identification results of the wolfberry leaf polyphenols prepared in Example 3 are shown in Table 2. Based on the retention time, precursor ion, and fragment ion peak information, as well as the SciFinder database and relevant literature data, these compounds were preliminarily identified. A total of 68 polyphenol and flavonoid ring compounds were identified in the product. The results showed that the main components in the wolfberry leaf polyphenols prepared by the present invention were rutin, scopolamine, sinapic acid, ferulic acid, quercetin, chlorogenic acid, neochlorogenic acid, p-coumaric acid, O-feruloylquinic acid, etc.

[0058] Test Example 2: Bioactivity determination of wolfberry leaf polyphenol extract before and after digestion

[0059] In vitro digestion experiment: Oral digestion stage: Weigh 5 mg of freeze-dried wolfberry leaf, add it all to 1 mL of distilled water, mix it with 1 mL of simulated saliva containing 10 mM CaCl2 solution and α-amylase (140 U / mL, pH = 6.5), and digest for 5 min. Gastric digestion stage: After adjusting the pH value to 2.0, mix the liquid obtained from oral digestion, add 1 mL of simulated gastric juice (18,000 U / mL), and digest for 2 h. Intestinal digestion stage: Add 2 mg of pancreatic enzyme and 25 mg of porcine bile salt to the gastric digestion sample, adjust the pH to 7.4, and digest for 2 hours. After digestion, use PBS to adjust the final volume of the digestion sample to 10 mL.

[0060] Determination method for antioxidant activity of wolfberry leaf polyphenol extract before and after digestion: (1) Mix 1 mL of the sample with 1 mL of DPPH (0.2 mM), react for 30 minutes under dark conditions, and record the absorbance at 517 nm. Use V C as the positive control to measure the DPPH radical scavenging rate of the sample. (2) Mix 0.2 mL of the sample with 0.8 mL of ABTS working solution, react for 30 minutes in the dark, and record the absorbance at 734 nm to measure the ABTS radical scavenging rate of the sample. (3) Mix 0.2 mL of the sample with FeSO4 (4 mM), 0.2 mL of ethanol-salicylic acid (4.5 mM), and 0.2 mL of H2O2 (8.8 mM) respectively, react for 10 minutes under dark conditions, record the absorbance at 510 nm, and measure the hydroxyl radical scavenging rate of the sample. (4) Mix 0.2 mL of the sample with 3 mL of FRAP reagent, react for 15 minutes in the dark, and record the absorbance at 593 nm. The Trolox equivalent per 1 mL of extract (mg Trolox / mL extract) is used to indicate the ferric ion reducing ability.

[0061] Determination method for the inhibitory ability of wolfberry leaf polyphenol extract on α-glucosidase activity before and after digestion: Mix 100 μL of α-glucosidase solution (0.2 U / mL) and 40 μL of the sample thoroughly, add 560 μL of PBS buffer solution, react at 37 °C for 30 minutes, add 100 μL of pNPG (5 mM), and react for another 20 minutes. Add 400 μL of Na2CO3 (0.2 M) to the solution to terminate the reaction, and measure the absorbance at 405 nm.

[0062] Result analysis: The changes in total phenol and total flavonoid contents and antioxidant activities of wolfberry leaf phenols with different mass concentrations prepared in Example 3 before and after digestion are shown in Figure 8The results showed that the total phenolic and total flavonoid contents and antioxidant activity of phenolic compounds in wolfberry leaves were proportional to the mass concentration, and the changes in the total phenolic and total flavonoid contents of the samples before and after digestion were similar to the change trend of the sample concentration. This indicated that the changes of phenolic compounds in wolfberry leaves were relatively stable during the simulated digestion process. Moreover, the phenolic substances in wolfberry leaves could exhibit a significant hypoglycemic effect through their mechanism of inhibiting α-glucosidase activity before and after digestion. Figure 9 )

[0063] Experimental Example 3: Determination method for the hepatoprotective effect of wolfberry leaf polyphenol extract

[0064] AML-12 cells in the logarithmic growth phase were collected. After enzymatic digestion, they were inoculated into 96-well plates at a concentration of 0.6×10 5 cells / mL. Three groups were established: the wolfberry leaf phenol treatment group, the alcohol model group, and the control group. In the wolfberry leaf phenol treatment group, the original culture medium was discarded after 24 hours of culture, and then the cells were continued to be cultured with phenolic compounds for 24 hours. Subsequently, the culture medium was diluted with 270 mM ethanol and continued to be cultured for 24 hours. After 48 hours of culture in the experimental group, the culture medium was replaced with an ethanol solution and cultured for another 24 hours. The control group cells were cultured for 72 hours. Subsequently, MTT was added to each well and cultured for 4 hours. Then the reaction mixture was removed and DMSO was added, and it was shaken in the dark for 10 minutes, and the absorbance was measured at a wavelength of 490 nm. The percentage of cell viability was calculated using the following formula: Cell viability (%) = (OD test / OD control) × 100%.

[0065] Result analysis: Plant phenolic compounds can regulate the metabolism of intracellular free radicals and play a positive role in alleviating liver injury. The protective effect of the wolfberry leaf phenols prepared in Example 3 on the alcohol-induced damaged hepatocytes AML-12 is shown in Figure 10 。 Figure 10 A The results showed that LLE in the concentration range of 0 - 0.4 mg / mL had no significant toxic effect on the cells. Figure 10 B showed that 270 mM alcohol achieved a 50% inhibition rate on the growth of AML-12 cells; therefore, this concentration was selected for further experiments. Compared with the model group, the cell survival rate of the cells treated with wolfberry leaf phenols (0.05 - 0.3 mg / mL) was significantly increased. In particular, wolfberry leaf phenols at a concentration of 0.1 mg / mL could effectively protect AML-12 cells from alcohol-induced oxidative damage. These results indicated that the wolfberry leaf phenol extract had significant hepatoprotective activity and could be used to develop health foods and drugs with hepatoprotective functions.

[0066] The above are only preferred embodiments for explaining the present invention and are not intended to impose any formal limitations on the present invention. Therefore, any modifications or changes to the present invention made in the same inventive spirit should still be included within the scope intended to be protected by the present invention.

Claims

1. A method for extracting phenolic compounds from wolfberry leaves, characterized in that: It includes the following steps: Step 1: After drying wolfberry leaves, they are crushed to obtain wolfberry leaf powder; Step 2: Use the ultrasonic-assisted deep eutectic solvent method to extract the wolfberry leaf powder. After centrifuging the extract, collect the supernatant and filter it to obtain a crude extract of wolfberry leaf phenolic compounds; Step 3: Use macroporous resin to adsorb the crude extract of wolfberry leaf phenolic compounds. After washing and desorbing the adsorbed macroporous resin, obtain a desorbed solution; Step 4: Concentrate the desorbed solution and then obtain freeze-dried wolfberry leaf phenolic substances through vacuum freeze-drying.

2. The method for extracting phenolic compounds from wolfberry leaves according to claim 1, wherein: The deep eutectic solvent used in the ultrasonic-assisted deep eutectic solvent method is choline chloride-lactic acid, and the molar ratio of choline chloride to lactic acid therein is 1:1.5 - 2.5; the moisture content of the deep eutectic solvent is 10 - 60%.

3. The method for extracting phenolic compounds from wolfberry leaves according to claim 1, characterized in that: In Step 2, the liquid-solid ratio of the extraction process is 10 - 60 mL / g; the ultrasonic time is 10 - 60 min, the ultrasonic temperature is 45 - 55 °C, and the ultrasonic power is 800 W.

4. The method for extracting phenolic compounds from wolfberry leaves according to claim 1, wherein: In Step 2, the centrifugation speed is 7000 - 10000 r / min, and the centrifugation time is 5 - 15 min.

5. The method for extracting phenolic compounds from wolfberry leaves according to claim 1, wherein: In Step 3, before purification, use deionized water to dilute the crude extract of wolfberry leaf phenolics to break the hydrogen bond between the deep eutectic solvent and wolfberry leaf phenolics, and enhance the effect of macroporous resin in separating and purifying wolfberry leaf phenolics.

6. The method for extracting phenolic compounds from wolfberry leaves according to claim 1, characterized in that: In Step 3, select XAD7HP type macroporous resin to adsorb wolfberry leaf phenolics. After adsorption, wash the XAD7HP type macroporous resin with distilled water and then desorb it with ethanol with a volume fraction of 75%.

7. The method for extracting phenolic compounds from wolfberry leaves according to claim 1, characterized in that: In Step 4, the temperature of freeze-drying is -80 °C, and the vacuum degree is 18 - 22 Pa.

8. Use of the phenolic compounds obtained by the method according to any one of claims 1 - 7 in the preparation of drugs for treating and preventing alcoholic liver disease.

9. Use of the phenolic compounds obtained by the method according to any one of claims 1 - 7 in the preparation of drugs for treating and preventing hypoglycemia.

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