Method for extracting isopentenyl flavonoid compound from black mulberry

Abstract

The invention discloses a method for extracting isopentenyl flavonoid compounds from black mulberries, which adopts an ultrasonic-assisted ionic liquid extraction method and comprises the following steps: crushing the black mulberries, mixing the crushed black mulberries with ionic liquid, soaking the mixed black mulberries, and carrying out ultrasonic extraction. Compared with a traditional water extraction method, the total content of the extracted isopentenyl flavonoid compounds sanggenone D and sanggenone C is increased by about 3.00 times. Meanwhile, the extraction method is green, efficient and energy-saving, and avoids environmental pollution to a greater extent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plant active ingredient extraction, and particularly relates to a method for extracting isoprenyl flavonoids from black mulberry. BACKGROUND

[0002] Black mulberry (Morus nigra L.) is a rare mulberry variety in the Morus genus. Morus nigra As a characteristic anti-diabetic drug of traditional Uighur medicine, the application of black mulberry is clearly recorded in ancient books such as the Medical Classics, and has the medicinal properties of "cold and dry, dry and heat clearing", which is commonly used in the folk for treating diabetes.

[0003] As a medicinal and edible plant, the chemical components of black mulberry are mainly flavonoids, alkaloids and polysaccharides, among which isoprenyl flavonoids are of particular concern due to their unique structural characteristics and significant biological activity. In the field of anti-diabetes, kuwanon H / G / C and morusin have been found to have significant alpha-glucosidase inhibitory activity, with kuwanon H and kuwanon G being significantly more active than DNJ, with half maximal inhibitory concentrations (IC 50 ) of 2.82 μM and 2.83 μM, respectively, exhibiting strong glucose metabolism regulation ability. More importantly, research has shown that isoprenyl flavonoid compound MnPE-11 promotes adipocyte differentiation by activating the C / EBPbeta-PPARgamma-C / EBPalpha signal, synchronously up-regulating GLUT4 expression levels to promote glucose transport and increase insulin sensitivity. This proves that isoprenyl flavonoids are a new type of effective material for treating diabetes in black mulberry, which is different from traditional alkaloids.

[0004] Currently, the extraction of isoprenyl flavonoids mainly relies on traditional techniques such as multiple extraction, recrystallization, silica gel column chromatography and resin adsorption. However, these methods have the following key problems in application: first, the selectivity of isoprenyl flavonoids is not good, there are many impurities, and it is difficult to target extract high-purity target compounds; second, the multi-stage purification process is complex; third, the traditional process consumes a large amount of organic solvent, which not only increases the cost, but also causes environmental pollution and physical harm. Therefore, for isoprenyl flavonoids in black mulberry leaves, which have low content, small polarity and specific active effect, developing a high selectivity, high efficiency, energy saving and environment-friendly targeted extraction technology has become a core scientific problem restricting its in-depth development.

[0005] Ionic liquid is usually composed of organic cation and organic / inorganic anion, which is liquid at room temperature. It has the advantages of no pollutant emission, wide liquid range, low volatility, non-flammability and high stability. The most important thing is that its structure can be adjusted by controlling the combination of anion and cation, so as to customize the properties such as polarity, hydrophobicity and solubility, thereby adjusting the dissolution and extraction efficiency of target compounds. There is no related report on its application in the extraction of prenyl flavonoids in black mulberry. SUMMARY

[0006] The purpose of the present application is to overcome the shortcomings of the prior art, improve the extraction rate of prenyl flavonoids in black mulberry, and provide a method for ultrasonic-assisted ionic liquid extraction of prenyl flavonoids in black mulberry.

[0007] In order to achieve the purpose of the present application, the following technical solutions are provided.

[0008] In some embodiments, the present application provides a method for extracting prenyl flavonoids from black mulberry, characterized in that: ultrasonic-assisted ionic liquid extraction method is used, which comprises crushing black mulberry medicinal materials, soaking in ionic liquid with a concentration of 0.5-2 mol / L for 2-8 h, and extracting under ultrasonic conditions to efficiently extract prenyl flavonoids.

[0009] In some embodiments, the method of the present application, the liquid-solid ratio of the ionic liquid to black mulberry is 10:1-30:1 mL / g.

[0010] In some embodiments, the method of the present application, the ultrasonic-assisted ionic liquid extraction method has an ultrasonic power of 400-500 W.

[0011] In some embodiments, the method of the present application, the ionic liquid is selected from the group consisting of [C6mim]N(CN)2, [C6mim]HSO4, [C6mim]NO3, [C6mim]BF4, [C6mim]OAC, [C2mim]Br, [C4mim]Br, [C6mim]Br, [C8mim]Br, [C 10 mim]Br and [C 12 mim]Br) ethanol solution, preferably [C6mim]N(CN)2 ethanol solution.

[0012] In some embodiments, the method of the present application, the concentration of the ionic liquid is 0.5-1.5 mol / L, preferably 1-1.3 mol / L.

[0013] In some embodiments, the method of the present application, the liquid-solid ratio of the ionic liquid to black mulberry is 15:1-20:1 mL / g, preferably 16:1-20:1 mL / g.

[0014] In some embodiments, the above method of the present application, the soaking time is 4-8 h, preferably 4-5.1 h.

[0015] In some embodiments, the above method of the present application, the ultrasonic power is 450-500 W.

[0016] In some embodiments, the above method of the present application, the isoprenyl flavonoids are morin D and morin C.

[0017]

[0018] In a specific embodiment, the above method of the present application, preferably, the liquid-solid ratio of the ionic liquid to black mulberry is 16.26 mL / g, the soaking time is 5.07 h, the ultrasonic power is 450 W, the ionic liquid is [C6mim]N(CN)2, and the ionic liquid concentration is 1.30 mol / L.

[0019] The technical effects of the present application have the following advantages compared with the prior art: The present application uses ionic liquids such as [C6mim]N(CN)2 ethanol solution as an extractant, and is assisted by ultrasonic extraction, which on the one hand promotes the dissolution of low-abundance / high-activity isoprenyl flavonoids in black mulberry, improves the extraction efficiency of effective components, especially morin D and morin C. On the other hand, through the selection of ionic liquid types and the optimization of extraction conditions in the extraction process of black mulberry isoprenyl flavonoids, the extraction rate of black mulberry isoprenyl flavonoids is finally improved to 128.79 μg / g. Compared with the extraction rates (32.17 μg / g, 42.99 μg / g and 50.65 μg / g) of the ultrasonic extraction method of the conventional extraction solvent (methanol extraction, water extraction and ethanol extraction), the extraction rate is increased by about 4.00 times, 3.00 times and 2.54 times, respectively. Compared with the extraction rate (60.42 μg / g) of the ionic liquid static extraction method, the extraction rate is increased by about 2.13 times. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The standard curves of morin D and morin C (A is the standard curve of morin D, and B is the standard curve of morin C).

[0021] Figure 2 The chromatograms of the reference substance and the ionic liquid extract (A: reference substance; B: ionic liquid black mulberry extract).

[0022] Figure 3 The effects of five different cations and anions of ionic liquids on the extraction rate of isoprenyl flavonoids in black mulberry (A is the cation, and B is the anion).

[0023] Figure 4 The effects of different ionic liquid concentrations, different ultrasonic powers, different liquid-to-solid ratios, and different soaking times on the extraction rate of isopentenyl flavonoids from black mulberry (A represents different ionic liquid concentrations, B represents different ultrasonic powers, C represents different liquid-to-solid ratios, and D represents different soaking times).

[0024] Figure 5 The surface plot shows the response of the interaction to the extraction rate of isopentenyl flavonoids from black mulberry.

[0025] Figure 6 Glucose uptake capacity of black mulberry extract in different solutions (data are presented as mean ± SD (n=3)). * P <0.05, **P <0.01, ***P <0.001) Bar chart. Detailed Implementation

[0026] The present invention will now be described in detail with reference to embodiments, but this is not intended to limit the scope of the invention.

[0027] Example 1: Determination of the content of isopentenyl flavonoids Chromatographic conditions: Waters XTERRA Phenyl column (5 μm, 4.6 × 250 mm); mobile phase: acetonitrile-0.1% phosphoric acid water (49:51); detection wavelength: 280 nm.

[0028] Construction of standard curves: Morusol D and Morusol C were prepared into standard solutions of 0.316 μg / mL, 1.265 μg / mL, 2.53 μg / mL, 5.06 μg / mL, 10.12 μg / mL, and 40.48 μg / mL, respectively; and Morusol C standard solutions of 0.168 μg / mL, 0.280 μg / mL, 1.402 μg / mL, 7.008 μg / mL, 35.040 μg / mL, 175.200 μg / mL, and 350.400 μg / mL, respectively. The peak areas of the standards at different concentrations were measured, and the peak areas were plotted on the x-axis and y-axis. The regression equations for each component were calculated and are shown in Table 1. The standard curves are shown in Table 2. Figure 1 As shown, the chromatogram is... Figure 2 The results show that isopentenyl flavonoids exhibit good linearity within their respective ranges, with correlation coefficients ≥0.9990.

[0029] Table 1. Linear relationships of isopentenyl flavonoids

[0030] Example 2: Extraction of isopentenyl flavonoids Weigh out black mulberry powder and add 0.5-2 mol / L ionic liquid, such as [C6mim]N(CN)2) ethanol solution. Accurately weigh the solution and soak for 2-8 hours. The liquid-to-solid ratio of black mulberry to ionic liquid should be 15:1-20:1 mL / g. Extract under ultrasonic conditions. If solvent is lost after extraction, replenish to the original weight to ensure consistent volume. Collect the filtrate. Highly efficient extraction of isopentenyl flavonoids mulberry root ketone D and mulberry root ketone C is shown in the chromatogram. Figure 2 .

[0031] Example 3: Selection of Ionic Liquid Type (1) Under the condition that the extraction process conditions and parameters remain unchanged, the ionic liquids with different cations [C2mim]Br, [C4mim]Br, [C6mim]Br, [C8mim]Br, and [C]Br were determined by HPLC. 10 mim]Br、[C 12 Extraction efficiency of isopentenyl flavonoids from black mulberry by [mim]Br (in each data set, the highest average extraction efficiency was defined as 100%, and the relative extraction efficiencies of other groups were obtained by comparing with it, the same below). Results are shown in […]. Figure 3 A, [C6mim] was found. + Cationic ions exhibit the highest extraction efficiency for isopentenyl flavonoids.

[0032] (2) The extraction efficiency of isopentenyl flavonoids from black mulberry was determined by HPLC using ionic liquids with different anions ([C6mim]N(CN)2, [C6mim]HSO4, [C6mim]NO3, [C6mim]BF4, [C6mim]OAC, and [C6mim]Br). The results are shown in [Figure 1]. Figure 3 B, discovered N(CN)2 - It has the highest extraction efficiency for isopentenyl flavonoids.

[0033] Therefore, the optimal ionic liquid is [C6mim]N(CN)2.

[0034] Example 4: Single-factor screening experiment for extraction conditions Four factors were examined: ionic liquid concentration, ultrasonic power, liquid-to-solid ratio, and soaking time. Five levels were selected for each factor, and experiments were conducted with the other three factors fixed to compare the levels of isopentenyl flavonoids and screen out the optimal level for each factor.

[0035] (1) Selection of ionic liquid concentration 0.3 g of dried black mulberry powder was accurately weighed and soaked in ethanol solution of [C6mim]N(CN)2 at concentrations of 0.5 mol / L, 1 mol / L, 2 mol / L, 4 mol / L, and 8 mol / L (liquid-to-solid ratio 10:1 mL / g). The solution was then sonicated for 2 h and ultrasonicated at 400 W for 20 min. If solvent loss occurred after extraction, it was replenished to the original weight to ensure consistent volume. The filtrate was collected as the final product. The content of isopentenyl flavonoids in black mulberry powder at different ionic liquid concentrations was determined by HPLC. Results are shown below. Figure 4 A. The extraction rate is highest when the ionic liquid concentration is 1 mol / L, and decreases as the ion concentration increases.

[0036] (2) Selection of ultrasonic power 0.3 g of dried black mulberry powder was accurately weighed and soaked in 1 mol / L [C6mim]N(CN)2 ethanol solution at a liquid-to-solid ratio of 10:1 mL / g for 2 h. The solution was then sonicated for 20 min at power levels of 200 W, 300 W, 400 W, 450 W, and 500 W. If solvent loss occurred after extraction, it was replenished to the original weight to ensure consistent volume. The filtrate was then collected as the final product. The content of isopentenyl flavonoids in black mulberry powder under different ultrasonic powers was determined by HPLC. The results are shown below. Figure 4 B. With the increase of ultrasonic power, the extraction rate of isopentenyl flavonoids in black mulberry increases, and the extraction rate is the highest when the ultrasonic power is 500W.

[0037] (3) Selection of liquid-solid ratio 0.3 g of dried black mulberry powder was weighed and dissolved in 1 mol / L ethanol solution of [C6mim]N(CN)2 at liquid-to-solid ratios of 10:1 mL / g, 20:1 mL / g, 30:1 mL / g, 40:1 mL / g, and 50:1 mL / g. The solution was accurately weighed, soaked for 2 h, and ultrasonicated for 20 min at 500 W. If solvent loss occurred after extraction, it was replenished to the original weight to ensure consistent volume. The filtrate was then collected as the final product. The content of isopentenyl flavonoids in black mulberry powder under different liquid-to-solid ratios was determined by HPLC. The results are shown below. Figure 4 C. When the liquid-to-solid ratio is 20:1 mL / g, the extraction rate of isopentenyl flavonoids from black mulberry is the highest. As the liquid-to-solid ratio continues to increase, the extraction rate decreases, which may be related to the properties of ionic liquids.

[0038] (4) Selection of soaking time 0.3 g of dried black mulberry powder was accurately weighed and soaked in 1 mol / L [C6mim]N(CN)2 ethanol solution at a liquid-to-solid ratio of 20:1 mL / g for 0 h, 2 h, 4 h, 8 h, and 24 h, respectively, under ultrasonication for 20 min at a power of 500 W. If solvent loss occurred after extraction, it was replenished to the original weight to ensure consistent volume. The filtrate was then collected as the final product. The content of isopentenyl flavonoids in black mulberry powder at different soaking times was determined by HPLC. The results are shown below. Figure 4 D. When the soaking time is 4 h, the extraction rate of isopentenyl flavonoids in black mulberry reaches its peak. However, the extraction rate decreases with the extension of soaking time.

[0039] Example 5: Response surface methodology optimization of optimal extraction conditions Based on the central composite experimental design principle of Box-Behnken, the total extraction efficiency of mulberry root ketone D and mulberry root ketone C from black mulberry was used as the response value (Y). Four factors were selected: ultrasonic power (A), liquid-to-solid ratio (B), ionic liquid concentration (C), and soaking time (D). A four-factor, three-level response surface methodology was employed. The experimental factors and levels are shown in Table 2.

[0040] Table 2. Response Surface Factor Level Design Table

[0041] To examine the impact of each factor and their interactions on the overall extraction efficiency, this invention uses Design-Expert software to perform multiple regression fitting on the four factors and three levels in Table 2. The analysis of variance is shown in Table 3, and the calculation equation for the overall extraction efficiency is as follows: Y=-876.165+3.798A+3.372B+96.049C+10.037D-0.004AB-0.106AC+0.003AD-0.195BC+0.245BD-2.040CD-0.004A 2 -0.074B 2 -13.319C 2 -1.234D 2 .

[0042] Table 3. Results of Analysis of Variance

[0043] Note: * indicates significance (*, P <0.05;**, P <0.01; ***, P <0.001).

[0044] According to Table 3, the model PThe value <0.0001 indicates significance, while the lack-of-fit term =0.6097 indicates no significance. This suggests that the regression equation has a good fit across the entire regression space, indicating that the experimental model can be used to predict response values.

[0045] The R of the model 2 A value of 0.9237 indicates high accuracy and predicts R0. 2 The value is 0.6612 and the adjusted R 2 The value is 0.8474, and the difference between the two is less than 0.2, indicating reasonable consistency. Model density is used to measure the signal-to-noise ratio. The model precision is 13.0958 > 4, indicating that the signal is sufficient and can predict any combination of the four influencing factors with reliability and reasonableness.

[0046] The response surface plot obtained based on the regression equation is as follows: Figure 5 The figure shows the relationship between the effects and interactions of various factors and the extraction efficiency. Analysis revealed the optimal extraction conditions for the two main isopentenyl flavonoids in black mulberry as follows: ultrasonic power 452.15 W; liquid-to-solid ratio 16.26:1 mL / g; ionic liquid concentration 1.30 mol / L; soaking time 5.07 h. Under similar conditions (ultrasonic power 450 W; liquid-to-solid ratio 16.26:1 mL / g; ionic liquid concentration 1.30 mol / L; soaking time 5.07 h), the contents of mulberry root ketone D and mulberry root ketone C in black mulberry were found to be close to the model calculations, indicating that the optimal extraction conditions obtained using the response surface methodology are accurate and reliable, and have practical application value.

[0047] Example 6 Extraction of isopentenyl flavonoids (ultrasound-assisted ionic liquid extraction) Weigh 0.3 g of pulverized black mulberry herb and add it to a 1.30 mol / L ionic liquid ([C6mim]N(CN)2 ethanol solution) at a liquid-to-solid ratio of 16.26:1 mL / g. Accurately weigh the solution, soak for 5.07 h, and extract under ultrasonic conditions at 450 W for 20 min. If solvent is lost after extraction, replenish to the original weight to ensure consistent volume. Collect the filtrate. The contents of mulberry root ketone D and mulberry root ketone C were determined using the aforementioned HPLC method. The contents of mulberry root ketone D and mulberry root ketone C were found to be 58.04 μg / g and 70.75 μg / g, respectively (total content 128.79 μg / g).

[0048] Example 7: Effects of different extracts of black mulberry on glucose uptake activity Sample preparation: Black mulberry samples were extracted with 100 μg / mL ionic liquids (ILs), water, and methanol (MeOH), respectively. Positive reagent preparation: A 100 μmol / L insulin solution was prepared.

[0049] Glucose uptake assay: Glucose uptake levels were detected using a glucose oxidase assay kit. First, cells in good growth condition were subjected to an induction reaction at a concentration of 1×10⁻⁶ cells / mL. 4 –5×10 4 Cells were seeded at a density of 1:1 in 96-well plates and incubated overnight. When the cells reached 80% confluence, the medium was replaced with α-MEM containing 2% fetal bovine serum, and the medium was changed every two days. Once the cells differentiated into spindle-shaped myotube cells, they were ready for drug administration. Differentiated L6 cells were starved for 2 h in serum-free medium, and samples were added with α-MEM, positive control with α-MEM, DMSO with α-MEM, and α-MEM, respectively. After successful drug administration, the cells were incubated for 12 h. Then, following the kit manufacturer's instructions, the residual glucose concentration in the culture medium was measured at 505 nm using a multi-mode microplate reader. Results are shown below. Figure 6 The results showed that ILs black mulberry extract significantly increased cellular glucose uptake. P <0.001), Water and MeOH black mulberry extract had no significant effect on the glucose uptake capacity of cells ( P >0.05). Furthermore, the glucose uptake activity of ILs black mulberry extract was significantly higher than that of Water and MeOH black mulberry extracts ( P <0.05). This indicates that ionic liquids are highly efficient at extracting isopentenyl flavonoids from black mulberry and have the effect of enriching anti-diabetic active ingredients.

[0050] Comparative Example 1: Extraction using methanol as solvent Weigh 0.3 g of dried black mulberry powder, add 4.5 mL of methanol (accurately weighed), soak for 5 h, and sonicate for 20 min at 450 W. If solvent is lost after extraction, replenish to the original weight to ensure consistent volume. Collect the filtrate. The contents of mulberry root ketone D and mulberry root ketone C were determined using pre-HPLC. The contents of mulberry root ketone D and mulberry root ketone C were found to be 10.28 μg / g and 21.89 μg / g, respectively (total content 32.17 μg / g).

[0051] Comparative Example 2: Extraction using water as a solvent Weigh 0.3 g of dried black mulberry powder, add 4.5 mL of water (accurately weighed), soak for 5 h, and sonicate for 20 min at 450 W. If solvent is lost after extraction, replenish to the original weight to ensure consistent volume. Collect the filtrate. The contents of mulberry root ketone D and mulberry root ketone C were determined by pre-HPLC. The contents of mulberry root ketone D and mulberry root ketone C were found to be 32.27 μg / g and 10.72 μg / g, respectively (total content 42.99 μg / g).

[0052] Comparative Example 3: Extraction using ethanol as solvent Weigh 0.3 g of dried black mulberry powder, add 4.5 mL of ethanol (accurately weighed), soak for 5 h, and sonicate for 20 min at 450 W. If solvent is lost after extraction, replenish to the original weight to ensure consistent volume. Collect the filtrate. The contents of mulberry root ketone D and mulberry root ketone C were determined using pre-HPLC. The contents of mulberry root ketone D and mulberry root ketone C were found to be 16.36 μg / g and 34.29 μg / g, respectively (total content 50.65 μg / g).

[0053] Comparative Example 4: Ionic Liquid Static Extraction Weigh 0.3 g of pulverized black mulberry herb and add it to a 1.30 mol / L ionic liquid ([C6mim]N(CN)2 ethanol solution) at a liquid-to-solid ratio of 16.26:1 mL / g. Accurately weigh the solution, soak for 5.07 h, and if solvent is lost after standing, replenish to the original weight to ensure consistent volume. Take the filtrate. The contents of mulberry root ketone D and mulberry root ketone C were determined using the aforementioned HPLC method. The contents of mulberry root ketone D and mulberry root ketone C were found to be 33.51 μg / g and 26.91 μg / g, respectively (total content 60.42 μg / g).

[0054] The content of isopentenyl flavonoids extracted from black mulberry by methanol, ethanol, and water was analyzed by HPLC. It was found that ionic liquids significantly increased the content of isopentenyl flavonoids in black mulberry, achieving 4.00 times the content obtained by methanol extraction, 3.00 times that by water extraction, and 2.54 times that by ethanol extraction using existing techniques. This indicates that ionic liquids played a crucial role in the extraction process. Using ionic liquids as extraction solvents, a comparison of static and ultrasonic extraction methods revealed that ultrasonic-assisted ionic liquid extraction increased the extraction rate of isopentenyl flavonoids, with a content 2.13 times higher than that obtained by static extraction.

[0055] Conclusion: This invention is the first to employ ultrasound-assisted ionic liquid extraction of isopentenyl flavonoids from black mulberry. The optimal ionic liquid and extraction process were selected, demonstrating higher specificity and improved extraction rate of isopentenyl flavonoids compared to traditional methods. Furthermore, this method is simple to operate and environmentally friendly, providing a new approach for the rapid acquisition of isopentenyl flavonoids from black mulberry.

[0056] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details. All equivalent changes and modifications made in accordance with the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for extracting isopentenyl flavonoids from black mulberry, characterized in that: An ultrasound-assisted ionic liquid extraction method was used, which involved pulverizing black mulberry medicinal material, soaking it in an ionic liquid with a concentration of 0.5-2 mol / L for 2-8 h, and extracting it under ultrasonic conditions to efficiently extract isopentenyl flavonoids.

2. The method as described in claim 1, characterized in that: The liquid-to-solid ratio of the ionic liquid to black mulberry is 10:1-30:1 mL / g.

3. The method as described in claim 1, characterized in that: The ultrasonic power is 400-500W.

4. The method as described in claim 1, characterized in that: The ionic liquid is selected from [C6mim]N(CN)2, [C6mim]HSO4, [C6mim]NO3, [C6mim]BF4, [C6mim]OAC, [C2mim]Br, [C4mim]Br, [C6mim]Br, [C8mim]Br, [C 10 mim]Br and [C 12 An ethanolic solution of [mim]Br).

5. The method as described in claim 1, characterized in that: The concentration of the ionic liquid is 0.5-1.5 mol / L, preferably 1.0-1.3 mol / L.

6. The method as described in claim 2, characterized in that: The liquid-to-solid ratio of the ionic liquid to black mulberry is 15:1-20:1 mL / g, preferably 16:1-20:1 mL / g.

7. The method as described in claim 1, characterized in that: The soaking time is 4-8 hours, preferably 4-5.1 hours.

8. The method as described in claim 3, characterized in that: The ultrasonic power is 450-500W.

9. The method as described in claim 1, characterized in that: The isopentenyl flavonoids are morinone D and morinone C.

10. The method as described in claim 1, characterized in that: The ionic liquid is an ethanol solution of [C6mim]N(CN)2, the concentration of the ionic liquid is 1.30 mol / L, the liquid-to-solid ratio is 16.26 mL / g, the soaking time is 5.07 h, and the ultrasonic power is 450 W.

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