Method for extracting flavonoid substances from white mulberry root-bark and application of flavonoid substances

Abstract

The invention discloses a method for extracting flavonoid substances from white mulberry root-bark and application of the flavonoid substances, and belongs to the technical field of natural medicine extraction. The method comprises the following steps: 1, weighing white mulberry root-bark, and carrying out pretreatment to obtain white mulberry root-bark powder; 2, weighing the white mulberry root-bark powder, adding an ethanol water solution, stirring and extracting at constant temperature, and carrying out solid-liquid separation to obtain a first filtrate and a first filter residue; 3, adding a mixed solution of ethyl acetate and acetone into the first filter residue, carrying out ultrasonic treatment assisted extraction, and carrying out solid-liquid separation to obtain a second filtrate and a second filter residue; and 4, mixing the first filtrate and the second filtrate, carrying out reduced pressure distillation concentration, and drying to obtain the white mulberry root-bark flavonoid extract. Through step-by-step extraction and optimization of extraction conditions and process sequence, the extraction rate and purity of the flavonoid substances are remarkably improved, operation is performed under mild conditions, the structure and activity of the flavonoid substances are protected, and the method is easy and convenient to operate, efficient, environmentally friendly and good in application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural medicine extraction, and specifically relates to a method for efficiently extracting flavonoids from mulberry bark. Background Art

[0002] Flavonoids are a class of natural organic compounds widely present in plants, with various biological activities such as antioxidant, anti-inflammatory, antibacterial, antiviral, antitumor, and cardiovascular protection. Mulberry bark is the dried root bark of the mulberry plant (Morus alba L.), a traditional Chinese medicine with a long history in clinical applications of traditional Chinese medicine. Mulberry bark contains rich flavonoids, such as mulberroside and sanggenone, and these flavonoids are important active ingredients for mulberry bark to exert its pharmacological effects.

[0003] However, there are many deficiencies in the current methods for extracting flavonoids from mulberry bark. Traditional extraction methods such as solvent extraction often have problems such as low extraction rate, low purity of flavonoids in the extract, long extraction time, large amount of solvent used and difficult recovery. In addition, some extraction methods may cause the destruction of the structure of flavonoids due to improper extraction conditions, affecting their biological activities.

[0004] With the continuous in-depth research on flavonoids in mulberry bark and the increasing application demands in the fields of medicine, health products, cosmetics, etc., there is an urgent need for an extraction method that is efficient, environmentally friendly, mild and can ensure the activity of flavonoids. Summary of the Invention

[0005] Aiming at the defects existing in the above-mentioned prior art, the purpose of the present invention is to design and provide a method for extracting flavonoids from mulberry bark. By stepwise extraction, optimizing the extraction conditions and process sequence, the present invention significantly improves the extraction rate and purity of flavonoids, and operates under mild conditions to protect the structure and activity of flavonoids. It is simple, efficient, environmentally friendly and has good application prospects.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a method for extracting flavonoids from mulberry bark, comprising the following steps:

[0008] (1) Weigh mulberry bark, perform pretreatment to obtain mulberry bark powder;

[0009] (2) Weigh the above-mentioned mulberry bark powder, add an ethanol aqueous solution, perform constant-temperature stirring extraction, and carry out solid-liquid separation to obtain a first filtrate and a first filter residue;

[0010] (3) Add a mixed solution of ethyl acetate and acetone to the first filter residue, perform ultrasonic treatment to assist extraction, carry out solid-liquid separation, and obtain a second filtrate and a second filter residue;

[0011] (4) Mix the above-mentioned first filtrate and second filtrate, carry out vacuum distillation and concentration until the volume is reduced to 1 / 5 - 1 / 3 of the original volume, and dry to obtain an extract of flavonoid substances from mulberry bark.

[0012] For the method for extracting flavonoid substances from mulberry bark, the specific method of the pretreatment is: select mulberry bark, remove impurities, wash it, cut it into small pieces or filaments, carry out drying treatment until the water content of the mulberry bark is lower than 10%, carry out pulverization, and sieve to obtain mulberry bark powder.

[0013] For the method for extracting flavonoid substances from mulberry bark, the conditions for drying are: temperature 40 - 60 °C, time 8 - 12 hours.

[0014] For the method for extracting flavonoid substances from mulberry bark, the particle size of the mulberry bark powder is 0.2 - 0.6 mm;

[0015] The mass-volume ratio of the mulberry bark powder to the ethanol aqueous solution is 1:100 - 250 g / mL;

[0016] The volume fraction of the ethanol aqueous solution is 30% - 50%.

[0017] For the method for extracting flavonoid substances from mulberry bark, the conditions for constant-temperature stirring extraction are: temperature 30 - 40 °C, time 2 - 4 hours, stirring speed 100 - 300 r / min.

[0018] For the method for extracting flavonoid substances from mulberry bark, the method of solid-liquid separation is suction filtration or centrifugation.

[0019] For the method for extracting flavonoid substances from mulberry bark, the volume ratio of ethyl acetate to acetone is 1:2 - 2:1;

[0020] For the method for extracting flavonoid substances from mulberry bark, the mass-volume ratio of the first filter residue to the mixed solution is 1:100 - 300 g / mL;

[0021] For the method for extracting flavonoid substances from mulberry bark, the conditions for ultrasonic treatment-assisted extraction are: temperature 25 - 35 °C, ultrasonic frequency 20 - 50 kHz, ultrasonic power 300 - 500 W, extraction time 0.5 - 1.5 hours;

[0022] The conditions for vacuum distillation and concentration are: temperature 50 - 70 °C, pressure 0.05 - 0.1 MPa.

[0023] The drying in step (4) is freeze drying, wherein the freeze drying conditions are: temperature -40 to -20°C, vacuum degree 0.01 to 0.1 Pa, and drying time 12 to 24 hours.

[0024] In a second aspect, the present invention provides the use of any of the methods described above in extracting flavonoids from Morus alba bark.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Synergistic extraction improves extraction rate

[0027] The invention adopts a step-by-step extraction method, firstly using an ethanol aqueous solution for a single extraction, the ethanol molecular structure has both hydrophilic hydroxyl groups and lipophilic ethyl groups, which makes it have good solubility and can interact with polar flavonoids in the mulberry bark through hydrogen bonds and the like, thereby promoting these substances to dissolve from the mulberry bark into the ethanol aqueous solution.

[0028] Then, a secondary extraction is performed using a mixed solution of ethyl acetate and acetone. The mixed solvent of ethyl acetate and acetone has strong lipophilicity and low polarity, and can effectively extract lipophilic or medium-polar flavonoids, such as some flavonoid compounds with a benzene ring structure and not easily soluble in water. This process can dissolve substances that were not completely extracted in the first extraction, especially fat-soluble or non-polar flavonoids.

[0029] The two extraction methods work synergistically. First, ethanol-water solution is used to extract flavonoids with strong polarity, and then ethyl acetate-acetone mixed solution is used to extract fat-soluble or weakly polar flavonoids. The synergistic effect of this solvent system effectively avoids excessive extraction of a single solvent and ensures the efficiency and selectivity of the extraction process. Ethanol-water solution can extract hydrophilic and highly polar flavonoids, while ethyl acetate-acetone mixed solution focuses on extracting fat-soluble or medium-polar flavonoid compounds, which can more comprehensively extract various flavonoids in Morus alba bark, thereby significantly improving the extraction rate of flavonoids.

[0030] 2. Protect flavonoid structure and activity under mild conditions

[0031] During the entire extraction process, the extraction temperature is controlled in a relatively low range (mainly below 40°C) to avoid the damage of high temperature to the structure of flavonoids. At the same time, the ultrasonic-assisted extraction is carried out at a mild temperature. The cavitation effect and mechanical vibration generated by ultrasound can accelerate the contact and mass transfer process between the solvent molecules and the flavonoids in the mulberry bark powder, improve the extraction efficiency, and at the same time will not adversely affect the activity of the flavonoids, thus ensuring the biological activity of the flavonoids in the extract.

[0032] 3. Optimize Process Parameters to Improve Purity and Efficiency

[0033] By optimizing process parameters such as the ratio of material to liquid, extraction time, and ultrasonic power, the extraction process becomes more efficient and precise. A reasonable ratio of material to liquid ensures sufficient contact between the solvent and the mulberry bark powder. Appropriate extraction time and ultrasonic power not only increase the extraction rate but also reduce the dissolution of impurities, thereby improving the purity of flavonoids in the extract. In addition, methods such as vacuum distillation concentration and freeze-drying help remove solvent residues, further improving product quality and also contributing to maintaining the stability of flavonoids. Detailed Implementation Modes

[0034] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following will describe in detail the specific implementation modes of the present invention with reference to specific embodiments. However, the protection scope of the present invention is not limited thereto. In the following specific implementation modes, for parts where specific experimental steps or conditions are not specified, the standard experimental steps or conditions described in conventional literature in the field can be referred to for operation.

[0035] Example 1:

[0036] (1) Take 50 g of fresh mulberry bark, remove impurities, rinse it thoroughly with clean water, cut it into small pieces, and dry it at 50 °C for 10 hours to make its water content less than 10%. Then pulverize it with a pulverizer and sieve it to obtain mulberry bark powder with a particle size of 0.2 - 0.6 mm.

[0037] (2) Weigh 2.5 g of mulberry bark powder and place it in a 500 mL three-necked flask. Add 400 mL of an ethanol aqueous solution with a volume fraction of 40%, and stir and extract at 35 °C at a stirring speed of 200 r / min for 3 hours. After the extraction is completed, filter it with a suction filtration device to obtain the first filtrate and the first filter residue.

[0038] (3) Weigh the first filter residue, which is 1.25 g, transfer it to a 250 mL conical flask, add 200 mL of a mixed solution with a volume ratio of ethyl acetate to acetone of 1:1, and perform ultrasonic-assisted extraction at 30 °C with an ultrasonic frequency of 30 kHz and an ultrasonic power of 400 W for 1 hour. After the extraction is completed, centrifuge to obtain the second filtrate and the second filter residue.

[0039] (4) Combine the first filtrate and the second filtrate. The combined volume is 600 mL. Distill and concentrate it under reduced pressure at 60 °C and 0.08 MPa until the solution volume is about 160 mL. Then freeze-dry the concentrated solution at -30 °C and a vacuum degree of 0.05 Pa for 18 hours to obtain the mulberry bark flavonoid extract.

[0040] Example 2:

[0041] (1) Take 50 g of dry mulberry bark, and process it according to the method of Example 1 to obtain mulberry bark powder.

[0042] (2) Weigh 2.5 g of mulberry bark powder and place it in a 1000 mL three-necked flask. Add 500 mL of an ethanol aqueous solution with a volume fraction of 30%, and stir and extract at 30 °C with a stirring speed of 150 r / min for 4 hours. After the extraction is completed, perform suction filtration to obtain the first filtrate and the first filter residue.

[0043] (3) Weigh the first filter residue, which is 1.2 g, transfer it to a 300 mL conical flask, add 240 mL of a mixed solution with a volume ratio of ethyl acetate to acetone of 2:1, and perform ultrasonic-assisted extraction at 25 °C with an ultrasonic frequency of 25 kHz and an ultrasonic power of 350 W for 1.5 hours. After the extraction is completed, perform centrifugal separation to obtain the second filtrate and the second filter residue.

[0044] (4) Combine the first filtrate and the second filtrate. The combined volume is 740 mL. Distill and concentrate it under reduced pressure at 55 °C and 0.06 MPa until the solution volume is about 160 mL. Then freeze-dry the concentrated solution at -35 °C and a vacuum degree of 0.03 Pa for 20 hours to obtain the mulberry bark flavonoid extract.

[0045] Example 3:

[0046] (1) Take 50 g of dry mulberry bark, and process it according to the method of Example 1 to obtain mulberry bark powder.

[0047] (2) Weigh 2.5 g of mulberry bark powder and place it in an 800 mL three-necked flask. Add 600 mL of an ethanol aqueous solution with a volume fraction of 50%, and stir and extract at 40 °C with a stirring speed of 250 r / min for 2 hours. After the extraction is completed, perform centrifugal separation to obtain the first filtrate and the first filter residue.

[0048] (3) Weigh the first filter residue, which is 0.6 g, transfer it to a 200 mL conical flask, add 160 mL of a mixed solution with a volume ratio of ethyl acetate to acetone of 1:2, and perform ultrasonic-assisted extraction at 35 °C with an ultrasonic frequency of 40 kHz and an ultrasonic power of 450 W for 0.5 hours. After the extraction is completed, perform centrifugal separation to obtain the second filtrate and the second filter residue.

[0049] (4) Combine the first filtrate and the second filtrate. The combined volume is 760 mL. Distill and concentrate it under reduced pressure at 65 °C and 0.09 MPa until the solution volume is about 160 mL. Then freeze-dry the concentrated solution at -25 °C and a vacuum degree of 0.08 Pa for 15 hours to obtain the mulberry bark flavonoid extract.

[0050] Comparative Example 1:

[0051] The difference from Example 1 is only that the volume fraction of the ethanol aqueous solution in step (2) is changed to 60%, and the remaining steps are the same, obtaining the mulberry bark flavonoid extract.

[0052] Comparative Example 2:

[0053] The difference from Example 1 is only that in step (3), "adding 200 mL of a mixed solution with a volume ratio of ethyl acetate to acetone of 1:1" is changed to: adding 200 mL of ethyl acetate, and the remaining steps are the same, obtaining the mulberry bark flavonoid extract.

[0054] Comparative Example 3:

[0055] The difference from Example 1 is only that in step (3), "under 30 °C, performing ultrasonic-assisted extraction for 1 hour with an ultrasonic frequency of 30 kHz and an ultrasonic power of 400 W" is changed to: performing conventional stirring extraction for 2 hours, and the remaining steps are the same, obtaining the mulberry bark flavonoid extract.

[0056] Comparative Example 4:

[0057] The difference from Example 1 is only that step (3) is omitted and only one extraction is performed, and the remaining steps are the same, obtaining the mulberry bark flavonoid extract.

[0058] Comparative Example 5:

[0059] The difference from Example 1 is only that the order of steps (2) and (3) is interchanged, and the remaining steps are the same, obtaining the mulberry bark flavonoid extract.

[0060] Effect evaluation

[0061] 1. Determination of extraction rate

[0062] Accurately weigh the masses of the mulberry bark flavonoid extracts obtained in Examples 1 to 3 and Comparative Examples 1 to 5 respectively, and calculate the extraction rate of the flavonoid according to the following formula (Ⅰ):

[0063] Extraction rate = m / (M × n) × 100% (Ⅰ)

[0064] Wherein, m is the mass (g) of the flavonoid in the extract, M is the mass (g) of the mulberry bark raw material, and n is the theoretical content of the flavonoid in the mulberry bark (according to relevant literature reports, the flavonoid content in the mulberry bark is about 1.5% - 3.5%, and the average value of 2.5% is taken for calculation here).

[0065] The determination of the flavonoid mass is carried out by high performance liquid chromatography (HPLC), and a standard curve is made with quercetin as the standard product to determine the content of the flavonoid in the extract. The specific operation is as follows:

[0066] (1) Standard curve drawing: Weigh an appropriate amount of quercetin reference substance accurately, dissolve it with methanol and make up the volume to prepare a series of standard solutions with different concentrations: 1, 5, 10, 20, 50 μg / mL. Inject the standard solutions into the high-performance liquid chromatograph for analysis and record the chromatographic peak areas. Taking the quercetin concentration (μg / mL) as the abscissa and the peak area as the ordinate, draw the standard curve. According to the experimental data, the regression equation obtained is:

[0067] y = 851x + 100

[0068] where y is the chromatographic peak area and x is the quercetin concentration (μg / mL). The correlation coefficient R of the regression equation 2 = 0.9998 indicates a good linear relationship.

[0069] (2) Sample determination: Take an appropriate amount of the flavonoid extract from Morus alba L. root bark, dissolve it with methanol and make up the volume, filter it, and inject the filtrate into the high-performance liquid chromatograph. Calculate the content of flavonoids in the extract according to the regression equation of the standard curve, and then calculate the extraction rate. The HPLC peak areas with quercetin as the reference substance are shown in Table 1 below.

[0070] The chromatographic conditions are as follows:

[0071] Chromatographic column: C18 column (such as 250 mm × 4.6 mm, 5 μm).

[0072] Mobile phase: Methanol - 0.4% phosphoric acid aqueous solution (gradient elution, such as 0 - 10 min, 30% methanol - 70% phosphoric acid aqueous solution; 10 - 30 min, 30% - 60% methanol - 40% - 70% phosphoric acid aqueous solution; 30 - 45 min, 60% - 80% methanol - 20% - 40% phosphoric acid aqueous solution; 45 - 60 min, 80% methanol - 20% phosphoric acid aqueous solution).

[0073] Flow rate: 1.0 mL / min.

[0074] Detection wavelength: 360 nm.

[0075] Column temperature: 30 °C.

[0076] Table 1 HPLC peak areas with quercetin as the reference substance

[0077]

[0078] 2. Determination of flavonoid purity

[0079] The HPLC method was used to determine the purity of the flavonoids in the flavonoid extracts from Morus alba L. root bark obtained in Examples 1 - 3 and Comparative Examples 1 - 5, that is, the percentage of the flavonoid peak area in the total peak area.

[0080] The chromatographic conditions are as follows:

[0081] Chromatographic column: C18 column (such as 250 mm × 4.6 mm, 5 μm).

[0082] Mobile phase: methanol - 0.4% phosphoric acid aqueous solution (gradient elution, such as 0 - 10 min, 30% methanol - 70% phosphoric acid aqueous solution; 10 - 30 min, 30% - 60% methanol - 40% - 70% phosphoric acid aqueous solution; 30 - 45 min, 60% - 80% methanol - 20% - 40% phosphoric acid aqueous solution; 45 - 60 min, 80% methanol - 20% phosphoric acid aqueous solution).

[0083] Flow rate: 1.0 mL / min.

[0084] Detection wavelength: 360 nm.

[0085] Column temperature: 30 °C.

[0086] Take 2 g of the flavonoid extract from Morus alba L. root bark, dissolve it with the mobile phase of 40% methanol - 60% phosphoric acid aqueous solution, make up the volume to 100 mL with a volumetric flask and filter. Inject the filtrate into the high - performance liquid chromatograph, with a flow rate of 1.0 mL / min, a detection wavelength of 360 nm, and a column temperature of 30 °C, and record the chromatogram. Calculate the purity of the flavonoids according to the chromatographic peak area. The measurement results are shown in Table 2 below:

[0087] Table 2 Evaluation results of the flavonoid extracts from Morus alba L. root bark obtained in Examples 1 - 3 and Comparative Examples 1 - 5

[0088]

[0089] It can be seen from the data in Table 2 that compared with the extraction methods of Comparative Examples 1 - 5, the extraction methods of Examples 1 - 3 significantly improve the extraction rate and purity of flavonoids in Morus alba L. root bark.

[0090] In Comparative Example 1, a relatively high - concentration ethanol aqueous solution was used for single - extraction, and both the extraction rate and purity were lower than those of Example 1, indicating that the volume fraction of the ethanol aqueous solution for single - extraction in the present invention is more suitable at 30% - 50%. A relatively high - concentration ethanol may cause excessive dissolution of impurities, affecting the extraction and subsequent purification of flavonoids, and may also have a certain impact on the structure of flavonoids, reducing their extraction rate and purity.

[0091] In Comparative Example 2, only ethyl acetate was used as the secondary extraction solution, and the extraction rate and purity of flavonoids decreased, indicating that the mixed solution of ethyl acetate and acetone was a better secondary extraction solution. Due to the structural differences of flavonoids with different polarities, their solubility in a single solvent has limitations. The mixture of ethyl acetate and acetone can provide a more suitable polar environment. The presence of acetone increases the overall polarity of the mixed solvent, enabling the mixed solvent to have a better dissolution ability for some medium-polar flavonoids that were poorly soluble in pure ethyl acetate. At the same time, the lipophilicity of ethyl acetate can adjust the polarity of the mixed solvent, preventing the decrease in solubility of some highly lipophilic flavonoids due to the excessive polarity of acetone. Therefore, the mixed solution is beneficial to the dissolution of flavonoids with different polarities and improves the extraction effect.

[0092] In Comparative Example 3, ultrasonic assistance was not used in the secondary extraction, and the extraction rate and purity were lower than those in Example 1, proving that ultrasonic-assisted extraction plays an important role in improving the extraction efficiency and purity. The cavitation effect and mechanical vibration generated by ultrasound can break the plant cell wall, accelerate the entry of solvent molecules into the cell to contact flavonoids, promote their dissolution and diffusion, thereby improving the extraction efficiency, and reducing the dissolution of impurities in a short time, which is beneficial to improving the purity.

[0093] In Comparative Example 4, the secondary extraction step was omitted, and the extraction rate and purity decreased significantly, indicating that the secondary extraction is crucial for improving the extraction rate and purity of flavonoids. A single extraction cannot fully extract various flavonoids in mulberry bark, especially some highly lipophilic flavonoid components, resulting in low extraction rate and purity.

[0094] In Comparative Example 5, the order of the first extraction and the secondary extraction steps was reversed, and the extraction rate and purity were both inferior to those in Example 1, indicating that the order of first performing the first extraction and then the secondary extraction is necessary for improving the extraction effect. First, use an ethanol aqueous solution to preliminarily extract highly polar flavonoids, and then use a mixed solution of ethyl acetate - acetone to further extract lipophilic flavonoids. This order is beneficial to improving the extraction selectivity and efficiency, ensuring the full extraction and high purity of flavonoids. From a mechanistic perspective, if the extraction is first carried out using a mixed solution of ethyl acetate and acetone, since it has a certain solubility for both polar and lipophilic substances, it may extract more non-flavonoid lipophilic impurities and some other components with slightly lower polarity, resulting in increased difficulty in subsequent separation and purification and affecting the purity and extraction efficiency of flavonoids; while first using an ethanol aqueous solution to preliminarily extract highly polar flavonoids can initially separate most polar impurities and polar flavonoids from lipophilic components, and then using a mixed solution of ethyl acetate and acetone to extract lipophilic flavonoids can reduce the generation of co-extracts and improve the extraction selectivity and purity.

[0095] In summary, the method for extracting flavonoids from mulberry bark of the present invention significantly improves the extraction rate and purity of flavonoids by optimizing the extraction solvent, extraction method, process sequence, etc., and has good application prospects.

Claims

1. A method for extracting flavonoids from Morus alba bark, characterized in that: The following steps are involved: (1) weighing mulberry bark and pretreating it to obtain mulberry bark powder; (2) weighing the mulberry bark powder, adding ethanol aqueous solution, stirring and leaching at a constant temperature, and performing solid-liquid separation to obtain a first filtrate and a first filter residue; (3) adding a mixed solution of ethyl acetate and acetone to the first filter residue, performing ultrasonic treatment to assist leaching, and performing solid-liquid separation to obtain a second filtrate and a second filter residue; (4) The first filtrate and the second filtrate are mixed, concentrated by vacuum distillation until the volume is reduced to 1 / 5 to 1 / 3 of the original volume, and dried to obtain a Morus alba flavonoid extract.

2. The method for extracting flavonoids from Morus alba bark as claimed in claim 1, characterized in that: The specific method of the pretreatment is: select mulberry bark, remove impurities, wash, cut into small pieces or filaments, dry until the water content of the mulberry bark is less than 10%, crush, sieve, and obtain mulberry bark powder.

3. The method for extracting flavonoids from Morus alba bark as claimed in claim 2, characterized in that: The drying conditions are: temperature 40-60° C., time 8-12 hours.

4. The method for extracting flavonoids from Morus alba bark as claimed in claim 1, characterized in that: The particle size of the mulberry bark powder is 0.2 to 0.6 mm; The mass volume ratio of the mulberry bark powder to the ethanol aqueous solution is 1:100-250 g / mL; The volume fraction of the ethanol aqueous solution is 30% to 50%.

5. The method for extracting flavonoids from Morus alba bark as claimed in claim 1, characterized in that: The conditions for the constant temperature stirring leaching are: temperature 30-40° C., time 2-4 hours, and stirring speed 100-300 r / min.

6. The method for extracting flavonoids from Morus alba bark as claimed in claim 1, characterized in that: The solid-liquid separation method is suction filtration or centrifugation.

7. The method for extracting flavonoids from Morus alba bark as claimed in claim 1, characterized in that: The volume ratio of ethyl acetate to acetone is 1:2 to 2:

1.

8. The method for extracting flavonoids from Morus alba bark as claimed in claim 1, characterized in that: The mass volume ratio of the first filter residue to the mixed solution is 1:100-300 g / mL.

9. The method for extracting flavonoids from Morus alba bark as claimed in claim 1, characterized in that: The conditions for the ultrasonic treatment-assisted extraction are: temperature 25-35°C, ultrasonic frequency 20-50kHz, ultrasonic power 300-500W, and extraction time 0.5-1.5 hours; The conditions for the reduced pressure distillation concentration are: temperature 50-70° C., pressure 0.05-0.1 MPa.

10. Use of the method according to any one of claims 1 to 9 in extracting flavonoids from Morus alba bark.

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