A method for extracting total flavonoids from Morus alba bark

Abstract

The present invention provides a method for extracting total flavonoids from white mulberry bark. First, white mulberry bark is dispersed in a specific ionic liquid solution, then dispersed in an alcohol solution, and finally subjected to pulse electric field treatment under specific conditions. The present invention pre-treats white mulberry bark with a specific ionic liquid solution, which can not only better dissolve lignocellulose and expose the cell membrane protoplasm layer, but also avoid excessive cell fragmentation, greatly reduce the exudation of cell contents, eliminate or almost eliminate the loss of flavonoids at this stage, and significantly improve the extraction rate, purity and antioxidant properties of total flavonoids from white mulberry bark; then, cell membrane electroporation is achieved through specific control of the pulse electric field treatment method and conditions, which facilitates the rapid infiltration of the alcohol solution into the cell, and realizes the directional extraction of total flavonoids from white mulberry bark. Therefore, the present invention adopts a method of ionic liquid solution in coordination with pulse electric field-assisted solvent extraction, which significantly improves the extraction rate, purity and antioxidant properties of total flavonoids from white mulberry bark.

Description

Technical Field

[0001] The invention belongs to the technical field of plant extraction, and more specifically, relates to a method for extracting total flavonoids from Morus alba bark. Background Art

[0002] Morus alba bark is the root bark of the plant Morus alba L., which mainly contains flavonoids, alkaloids, polysaccharides and other effective ingredients. As a commonly used Chinese herbal medicine, it has the effects of lowering blood pressure, diuresis, relieving asthma and purging the lungs, sedation and analgesia. It is mainly used for cough and asthma caused by lung heat, facial and skin edema, acute bronchitis, etc. Modern pharmacological studies have shown that its main active ingredients are flavonoids, including flavonoids (alcohols), isoflavones, dihydroflavonoids (alcohols), chalcones, dihydrochalcones, etc., which have strong antioxidant activity, especially against hydroxyl radicals and superoxide anions, which are stronger than V C Therefore, how to efficiently extract total flavonoids from Morus alba bark has become a research hotspot today.

[0003] At present, in addition to the traditional solvent extraction method, various other methods are often used to assist solvent extraction for the efficient extraction of bioactive ingredients in plants, including enzyme-assisted extraction, ultrasound-assisted extraction, microwave-assisted extraction, supercritical CO2 extraction-assisted extraction, pulsed electric field-assisted extraction, etc. Among them, pulsed electric field, as an emerging non-thermal food processing technology, has been widely used in recent years to break plant cell walls and assist in the extraction of functional active ingredients in cells. The principle is: under the action of high-intensity electric pulses, the induced charges are distributed in a directional manner on the cell membrane, polarizing the cell membrane and forming an electric potential difference inside and outside. When the electric potential difference reaches the voltage repair limit of the cell membrane, an irreversible permanent aperture channel will be formed, thereby achieving the effect of efficiently enhancing the extraction of functional active ingredients in plant cells.

[0004] However, as a traditional Chinese medicinal material, the functional active ingredients of mulberry bark are mainly flavonoids located in the root cells, and the cells are wrapped by lignocellulose (lignin, cellulose and hemicellulose). The direct use of pulsed electric field wall breaking treatment assisted by ethanol solution will lead to unsatisfactory extraction effect. Therefore, the first key point to achieve efficient extraction of flavonoids in mulberry bark cells is to remove the lignocellulose wrapped outside the cells.

[0005] In order to remove the wood cellulose wrapped outside the plant cells, scholars have come up with many methods, such as: combining pulsed electric field with ultrasonic pretreatment to extract bitter-free rutin and polyphenols from sweet tea leaves, but this method will cause excessive cell fragmentation, complete exudation of the contents, and mixed impurities in the extracted product, resulting in low purity and difficulty in purification of the final target product; another example: ultrafine grinding, compound enzyme hydrolysis combined with pulsed electric field wall breaking and low-temperature supercritical carbon dioxide extraction to achieve gingerol extraction from ginger, but this method uses compound fiber enzyme to assist wall breaking, which has the disadvantages of slow reaction speed and low enzymatic hydrolysis efficiency, and the enzyme is easily inactivated and has a low reuse rate, resulting in high production costs. In addition, these methods all involve the combination of multiple physical fields, resulting in large equipment investment and high energy consumption.

[0006] Therefore, there is an urgent need to find a method for extracting total flavonoids from Morus alba bark that can both improve the extraction efficiency and ensure the purity of the product. Summary of the invention

[0007] The present invention aims to provide a method for extracting total flavonoids from Morus alba bark, so as to simultaneously improve the extraction efficiency and purity of total flavonoids from Morus alba bark.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The invention provides a method for efficiently extracting total flavonoids from Morus alba, which comprises the following steps: firstly dispersing the Morus alba in an ionic liquid solution, then dispersing it in an alcohol solution, and finally performing a pulse electric field treatment;

[0010] The ionic liquid solution is obtained by dissolving one or more of 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-butyl-3-methylimidazolium bromide ([Bmim]Br), 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) or 1-ethyl-3-methylimidazolium bromide ([Emim]Br) in a polar solvent, and the field intensity of the pulse electric field treatment is 15 to 30 kV / cm.

[0011] Due to the presence of lignocellulose outside and between cells of the mulberry bark, the single pulse electric field wall breaking assisted solvent extraction of intracellular flavonoids is not effective. Therefore, the present invention first conducts targeted research on the mulberry bark through a large number of experiments, determines that the method of pretreatment with an ionic liquid solution is the best means to remove the lignocellulose of the mulberry bark, and uses a specific type of ionic liquid solution to pretreat the mulberry bark, which can not only utilize the high ionic strength of the ionic liquid solution to interrupt the interaction between cellulose molecules and intramolecular hydrogen bonds in the mulberry bark root cells, but also better dissolve the lignocellulose that is difficult to dissolve in water and ordinary solvents, so that the cells are dispersed and the cell membrane protoplasm layer is exposed, but also avoid excessive cell fragmentation, greatly reduce the exudation of cell contents, and eliminate or almost eliminate the loss of flavonoids at this stage, thereby significantly improving the extraction rate, purity and antioxidant activity of total flavonoids in the mulberry bark; then, through the pulse electric field treatment method and specific control of its conditions, cell membrane electroporation is achieved, which facilitates the rapid penetration of the alcohol solution into the cells, thereby achieving efficient and directional extraction of flavonoids in the mulberry bark cells. In addition, the present invention adopts a combination of ionic liquid solution pretreatment and pulsed electric field treatment to assist alcohol solution in extracting total flavonoids from the white mulberry bark. This not only avoids the problems of low product purity caused by excessive cell fragmentation, high production costs caused by the combination of multiple physical fields or enzymatic hydrolysis that are not conducive to industrial applications, but also significantly improves the extraction efficiency, purity and antioxidant properties of total flavonoids from the white mulberry bark.

[0012] Ionic liquid is a liquid composed entirely of ions, with the advantages of low vapor pressure, non-flammable, stable composition, etc., and can be reused at low cost. The present invention found in the research and development process that the type of ionic liquid solution is crucial for the extraction purity and extraction rate of total flavonoids in Morus alba. Compared with other conventional ionic liquid solutions, the present invention adopts a specific ionic liquid solution to avoid excessive cell fragmentation, greatly reduce the exudation of cell contents, eliminate or almost eliminate the loss of flavonoids at this stage, significantly improve the extraction rate and purity of total flavonoids in Morus alba, and then significantly improve the extraction rate and purity of total flavonoids in Morus alba. In addition, the optimization of the pulsed electric field intensity in the pulsed electric field treatment is also crucial for the extraction efficiency of total flavonoids in Morus alba. The low pulsed field intensity will lead to poor effect of cell membrane electroporation, which is not conducive to the rapid infiltration of alcohol solution and will seriously affect the extraction efficiency of total flavonoids in Morus alba.

[0013] In summary, the present invention has conducted targeted research on the characteristics of Morus alba bark, and customized a method for extracting flavonoids in Morus alba bark by ionic liquid solution synergistically with pulsed electric field-assisted solvent, which not only improves the extraction rate of total flavonoids in Morus alba bark, but also further improves the purity and antioxidant properties of total flavonoids in Morus alba bark.

[0014] Preferably, the mass volume ratio of the mulberry bark to the ionic liquid solution is 1-3 g:4-6 mL.

[0015] Preferably, the polar solvent is water.

[0016] Preferably, the Morus alba bark is crushed before being dispersed in the ionic liquid solution.

[0017] More preferably, the pulverizing is to pulverize the mulberry bark into 40-80 meshes.

[0018] Preferably, in the ionic liquid solution, the concentration of the ionic liquid is 20-40% (w / v).

[0019] Preferably, the time for dispersing the Morus alba bark in the ionic liquid solution is 0.5 to 2 hours.

[0020] Preferably, the mulberry bark is dispersed in the ionic liquid solution and heated at the same time, and the heating temperature is 40-70°C.

[0021] More preferably, the heating is accompanied by stirring, such as stirring at a speed of 100 to 250 rpm / min.

[0022] More preferably, after the heating, the supernatant is removed by centrifugation, and the precipitate is dispersed in water, and the precipitate is washed after centrifugation again.

[0023] More preferably, the centrifugation to remove the supernatant is performed at a speed of 3000 to 6000 rpm / min for 10 to 20 min.

[0024] More preferably, the ratio of the precipitate to water is 2-5 g:10-20 mL.

[0025] More preferably, the second centrifugation is performed at a rotation speed of 4000-6000 rpm / min for 10-15 min, and most preferably at a rotation speed of 5000 rpm / min for 10 min.

[0026] More preferably, the washing of the precipitate is washing with water.

[0027] Preferably, the alcohol solution is an ethanol solution, such as an ethanol solution with a concentration of 40% to 80% (v / v).

[0028] Further preferably, the mass volume ratio of the mulberry bark to the ethanol solution is 1-3 g: 2-8 mL.

[0029] Preferably, during the pulse electric field treatment, the flow rate of the liquid pumped into the pulse electric field treatment chamber is 50-100 mL / min.

[0030] Preferably, the number of pulses in the pulsed electric field treatment is 100 to 300.

[0031] Preferably, the pulse frequency of the pulse electric field treatment is 1 to 5 kHz.

[0032] Preferably, the pulse electric field treatment time is 2 to 5 minutes.

[0033] Preferably, the temperature of the pulse electric field treatment is 30-45°C.

[0034] Preferably, after the pulse electric field treatment, post-treatment is further performed, such as centrifugation, rotary evaporation, and freeze-drying in sequence.

[0035] More preferably, the centrifugation is performed at a speed of 7000 to 9000 rpm / min for 10 to 20 min, and most preferably at a speed of 9000 rpm / min for 20 min.

[0036] More preferably, the rotary evaporation is carried out at 45-65° C. for 30-60 min.

[0037] Further preferably, before freeze-drying, the rotary evaporation product is pre-frozen, such as at -35 to -25°C.

[0038] The present invention has the following beneficial effects:

[0039] 1. The present invention first pre-treats the mulberry bark by using a specific ionic liquid solution, which can not only better dissolve lignocellulose and expose the cell membrane protoplasm layer, but also avoid excessive cell fragmentation, greatly reduce the exudation of cell contents, and eliminate or almost eliminate the loss of flavonoids at this stage, significantly improving the extraction rate, purity and antioxidant properties of the total flavonoids of the mulberry bark; then, the cell membrane is electroporated by the pulsed electric field treatment method and the specific control of its conditions, which facilitates the rapid infiltration of the alcohol solution into the cell, and realizes the efficient directional extraction of the total flavonoids of the mulberry bark. Therefore, the present invention adopts the method of ionic liquid solution coordinated with pulsed electric field assisted solvent extraction, which significantly improves the extraction efficiency, purity and antioxidant properties of the total flavonoids of the mulberry bark.

[0040] 2. The method of the present invention has simple equipment and low energy consumption, and meets the requirements of low carbon and green. DETAILED DESCRIPTION

[0041] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0042] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0043] Example 1 A method for efficiently extracting total flavonoids from Morus alba

[0044] 100g of mulberry bark powder crushed to 60 mesh was dispersed in 200mL of 1-butyl-3-methylimidazolium chloride ionic liquid solution with a concentration of 20% (w / v), reacted at 60℃ and 150rpm / min for 1h, centrifuged at 5000rpm / min for 15min, and the precipitate was dispersed with deionized water (so that the ratio of precipitate to deionized water was 1g:5mL), then centrifuged at 5000rpm / min for 10min to obtain the precipitate, and the precipitate was washed twice, and then the washed precipitate was dispersed in 200mL of 60% (v / v) ethanol solution. The ethanol solution dispersion of the precipitate was pumped into the pulse electric field treatment chamber by a peristaltic pump for treatment, the flow rate of the liquid was 50mL / min, and the pulse electric field treatment parameters were: field strength 25kV / cm, number of pulses 300, pulse frequency 1kHz, pulse time 2min, pulse temperature 45℃. After the pulse electric field treatment, the solution was centrifuged at 9000 rpm / min for 20 min to obtain a supernatant, and the supernatant was rotary evaporated at 60° C. for 50 min. The liquid after rotary evaporation was pre-frozen at -30° C. and freeze-dried to obtain total flavonoids from Morus alba bark.

[0045] Example 2 A method for efficiently extracting total flavonoids from Morus alba

[0046] 150g of mulberry bark powder crushed to 40 mesh was dispersed in 300mL of 1-butyl-3-methylimidazolium chloride ionic liquid solution with a concentration of 40% (w / v), reacted at 70℃ and 200rpm / min for 1.5h, centrifuged at 6000rpm / min for 10min, and the precipitate was dispersed with deionized water (so that the ratio of precipitate to deionized water was 1g:2mL), then centrifuged at 6000rpm / min for 10min to obtain the precipitate, washed the precipitate 3 times, and then dispersed the washed precipitate in 100mL of 40% (v / v) ethanol solution. The ethanol solution dispersion of the precipitate was pumped into the pulse electric field treatment chamber by a peristaltic pump for treatment, the flow rate of the liquid was 100mL / min, and the pulse electric field treatment parameters were: field strength 30kV / cm, number of pulses 200, pulse frequency 2kHz, pulse time 2min, pulse temperature 45℃. After the pulse electric field treatment, the solution was centrifuged at 8000 rpm / min for 15 min to obtain a supernatant, and the supernatant was rotary evaporated at 65°C for 40 min. The liquid after rotary evaporation was pre-frozen at -30°C and freeze-dried to obtain total flavonoids from Morus alba bark.

[0047] Example 3 A method for efficiently extracting total flavonoids from Morus alba

[0048] 50g of mulberry bark powder crushed to 80 mesh was dispersed in 200mL of 1-butyl-3-methylimidazolium chloride ionic liquid solution with a concentration of 30% (w / v), reacted at 50℃ and 250rpm / min for 2h, centrifuged at 5000rpm / min for 20min, and the precipitate was dispersed with deionized water (so that the ratio of precipitate to deionized water was 1g:10mL), then centrifuged at 4000rpm / min for 15min to obtain the precipitate, and the precipitate was washed twice, and then the washed precipitate was dispersed in 400mL of 50% (v / v) ethanol solution. The ethanol solution dispersion of the precipitate was pumped into the pulse electric field treatment chamber by a peristaltic pump for treatment, the flow rate of the liquid was 75mL / min, and the pulse electric field treatment parameters were: field strength 15kV / cm, number of pulses 100, pulse frequency 5kHz, pulse time 3min, pulse temperature 30℃. After the pulse electric field treatment, the solution was centrifuged at 7000 rpm / min for 10 min to obtain a supernatant, and the supernatant was rotary evaporated at 50°C for 40 min. The liquid after rotary evaporation was pre-frozen at -30°C and freeze-dried to obtain total flavonoids from Morus alba bark.

[0049] Example 4 A method for efficiently extracting total flavonoids from Morus alba

[0050] Same as Example 2, except that 1-butyl-3-methylimidazolium chloride is replaced by 1-ethyl-3-methylimidazolium bromide.

[0051] Example 5 A method for efficiently extracting total flavonoids from Morus alba

[0052] Same as Example 2, except that 1-butyl-3-methylimidazolium chloride is replaced by 1-butyl-3-methylimidazolium bromide.

[0053] Example 6 A method for efficiently extracting total flavonoids from Morus alba

[0054] Same as Example 2, except that 1-butyl-3-methylimidazolium chloride is replaced by 1-ethyl-3-methylimidazolium chloride.

[0055] Comparative Example 1

[0056] Same as Example 2, except that 1-butyl-3-methylimidazolium chloride is replaced by N-butylpyridinium bistrifluoromethanesulfonimide.

[0057] Comparative Example 2

[0058] Same as Example 2, except that 1-butyl-3-methylimidazolium chloride is replaced by 1-dodecyl-3-methylimidazolium methanesulfonate.

[0059] Comparative Example 3

[0060] Same as Example 2, except that 1-butyl-3-methylimidazolium chloride is replaced by 2-hydroxy-N,N,N,-trimethylethylamine hexafluorophosphate.

[0061] Comparative Example 4

[0062] Same as Example 2, except that the field intensity of the pulse electric field treatment is adjusted to 10 kV / cm.

[0063] Comparative Example 5

[0064] The same as Example 2, except that the ionic liquid solution pretreatment is replaced by ultrasonic pretreatment, as follows:

[0065] 150g of mulberry bark powder crushed to 40 mesh was added to 750mL of 0.125mol / L sodium hydroxide solution, and after ultrasonic treatment at 25℃ and 120W for 40min, it was centrifuged at 6000rpm / min for 10min, and the precipitate was dispersed with deionized water (so that the ratio of precipitate to deionized water was 1g:2mL), and then centrifuged at 6000rpm / min for 10min to obtain the precipitate, which was washed three times, and then the washed precipitate was dispersed in 100mL of 40% (v / v) ethanol solution. The ethanol solution dispersion of the precipitate was pumped into the pulse electric field treatment chamber by a peristaltic pump for treatment, the flow rate of the liquid was 100mL / min, and the pulse electric field treatment parameters were: field strength 30kV / cm, number of pulses 200, pulse frequency 2kHz, pulse time 2min, pulse temperature 45℃. After the pulse electric field treatment, the solution was centrifuged at 8000 rpm / min for 15 min to obtain a supernatant, and the supernatant was rotary evaporated at 65°C for 40 min. The liquid after rotary evaporation was pre-frozen at -30°C and freeze-dried to obtain total flavonoids from Morus alba bark.

[0066] Comparative Example 6

[0067] The same as Example 2, except that the ionic liquid solution pretreatment is replaced by an organic solvent pretreatment, as follows:

[0068] 150g of mulberry bark powder crushed to 40 mesh was added to 1000mL of 65% (v / v) ethanol solution, heated at 190℃ for 2h, centrifuged at 6000rpm / min for 10min, the precipitate was dispersed with deionized water (the ratio of precipitate to deionized water was 1g:2mL), then centrifuged at 6000rpm / min for 10min to obtain the precipitate, washed the precipitate 3 times, and then dispersed the washed precipitate in 100mL of 40% (v / v) ethanol solution. The ethanol solution dispersion of the precipitate was pumped into the pulse electric field treatment chamber by a peristaltic pump for treatment, the flow rate of the liquid was 100mL / min, and the pulse electric field treatment parameters were: field strength 30kV / cm, number of pulses 200, pulse frequency 2kHz, pulse time 2min, pulse temperature 45℃. After the pulse electric field treatment, the solution was centrifuged at 8000 rpm / min for 15 min to obtain a supernatant, and the supernatant was rotary evaporated at 65°C for 40 min. The liquid after rotary evaporation was pre-frozen at -30°C and freeze-dried to obtain total flavonoids from Morus alba bark.

[0069] Test Example 1 Determination of the extraction rate of the product

[0070] The total flavonoids of the mulberry bark obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were weighed, and the extraction rate of the total flavonoids of the mulberry bark was calculated according to the formula "extraction rate of total flavonoids of the mulberry bark = mass of total flavonoids of the mulberry bark / mass of mulberry bark powder × 100%". The results are shown in Table 1.

[0071] Table 1 Extraction rate of total flavonoids from Morus alba

[0072]

[0073]

[0074] It can be seen that the extraction rates of total flavonoids from the white mulberry bark in Examples 1 to 6 are all above 3.5%, and the highest in Example 2 is even close to 4%. However, in Comparative Examples 1 to 6, which replaced the type of ionic liquid solution, changed the pulsed electric field treatment conditions, or adopted other means of removing lignocellulose, the highest extraction rate of total flavonoids from the white mulberry bark was only 2.35%, indicating that the selection of specific means of removing lignocellulose, the type of ionic liquid solution, and the conditions of pulsed electric field treatment are crucial to the extraction rate of total flavonoids from the white mulberry bark. It is precisely because this application specifically selected the pretreatment with ionic liquid solution as the means of removing the white mulberry bark lignocellulose, and specifically controlled the type of ionic liquid solution and the field strength of the pulsed electric field, that the extraction rate of total flavonoids from the white mulberry bark can be significantly improved. Test Example 2 Purity and Antioxidant Test of Products

[0075] 0.5 mg of the total flavonoids of Morus alba obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were weighed and dissolved in 10 mL of 50% ethanol solution, i.e., the final concentration of the total flavonoids of Morus alba was 0.05 mg / mL, as sample groups 1 to 12 (among which, sample groups 1 to 6 used the total flavonoids of Morus alba obtained in Examples 1 to 6, and sample groups 7 to 12 used the total flavonoids of Morus alba obtained in Comparative Examples 1 to 6). c The ethanol solution was used as the positive control group, the ethanol solution without sample was used as the blank control group, and mulberry flavonoids (CAS62949-79-5, HPLC≥98%) was used as the standard group. Then 4 mL of 0.05 mg / mL DPPH free radical solution was added to 1.0 mL of the solution of all groups, and the solution was kept in the dark for 50 minutes, and the absorbance was measured at 517 nm. The DPPH free radical scavenging rate was calculated as follows: DPPH free radical scavenging rate (%) = (A i -A j ) / A i × 100%, where A i is the absorbance value of the blank control group, A j is the absorbance value of the test group.

[0076] The results are shown in Table 2.

[0077] Table 2 Antioxidant test results of total flavonoids of Morus alba

[0078]

[0079]

[0080] As shown in Table 2, the DPPH radical scavenging rates of sample groups 1 to 6 are all above 80%, and sample groups 2, 4, and 6 are all above 85%, which are closer to the standard group, while the DPPH radical scavenging rates of sample groups 7 to 12 and the positive control group, which have changed the type of ionic liquid solution, changed the pulsed electric field treatment conditions, or adopted other means of removing lignocellulose, are significantly lower than those of sample groups 1 to 6. It can be seen that the antioxidant activity of the total flavonoids of Morus alba obtained in Examples 1 to 6 is closer to the standard of the total flavonoids of Morus alba than that of Comparative Examples 1 to 6, and the antioxidant activity of the total flavonoids of Morus alba is closely related to the purity, which means that the purity of the total flavonoids of Morus alba obtained in Examples 1 to 6 is higher; and the DPPH radical scavenging rates of the total flavonoids of Morus alba obtained in Examples 1 to 6 are significantly higher than those of Comparative Examples 1 to 6 and the use of the common antioxidant V cThe positive control group has better antioxidant performance. This shows that the selection of specific means for removing lignocellulose, the type of ionic liquid solution and the conditions of pulsed electric field treatment are crucial to the purity and antioxidant properties of total flavonoids in Morus alba. It is precisely because this application specifically selects ionic liquid solution pretreatment as a means of removing lignocellulose from Morus alba, and specifically controls the type of ionic liquid solution and the field strength of the pulsed electric field, that the purity and antioxidant properties of total flavonoids in Morus alba can be significantly improved.

[0081] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for extracting total flavonoids from Morus alba bark, characterized in that: First, the mulberry bark is crushed and dispersed in an ionic liquid solution, the supernatant is removed by centrifugation, and the precipitate is dispersed in water, centrifuged again and washed, and dispersed in an ethanol solution with a concentration of 40% to 80% v / v, and then subjected to a pulse electric field treatment at a field strength of 15 to 30 kV / cm, and finally centrifuged, rotary evaporated, and freeze-dried in sequence to obtain the product; The ionic liquid solution is obtained by dissolving one of 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium chloride or 1-ethyl-3-methylimidazolium bromide in water; the concentration of the ionic liquid in the ionic liquid solution is 20% to 40% w / v; and the mulberry bark is dispersed in the ionic liquid solution while being heated at 40 to 70°C.

2. The method according to claim 1, characterized in that The mass volume ratio of the mulberry bark to the ionic liquid solution is 1-3 g:4-6 mL.

3. The method according to claim 1, characterized in that The time for dispersing the Morus alba bark in the ionic liquid solution is 0.5 to 2 h.

4. According to the method of claim 1, the mass volume ratio of the mulberry bark to the ethanol solution is 1-3 g: 2-8 mL.

5. The method according to claim 1, characterized in that During the pulse electric field treatment, the flow rate of the liquid pumped into the pulse electric field treatment chamber is 50-100 mL / min.

6. The method according to claim 1, characterized in that: The number of pulses in the pulse electric field treatment is 100 to 300; the pulse frequency of the pulse electric field treatment is 1 to 5 kHz.

7. The method according to claim 1, characterized in that: The pulse electric field treatment time is 2 to 5 minutes; the pulse electric field treatment temperature is 30 to 45°C.

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