Preparation method and application of mulberry leaf extract with function of reducing fat accumulation

Abstract

The invention relates to the technical field of plant extraction, and discloses a preparation method and application of a mulberry leaf extract capable of reducing fat accumulation, and the preparation method comprises the following steps: step 1, selecting fresh mulberry leaves, quickly freezing with liquid nitrogen, freeze-drying, and crushing; 2, performing acidolysis, and collecting supernate; step 3, performing enzymolysis on the precipitate obtained by centrifugation in the step 2, and collecting supernate; 4, combining the extracting solutions obtained in the step 2 and the step 3, concentrating, and carrying out supercritical CO2 extraction; and step 5, spray drying to obtain the mulberry leaf extract. The preparation method provided by the invention has the advantages of high efficiency, low consumption and environmental protection, and realizes efficient enrichment of active components of mulberry leaves.

Description

Technical Field

[0001] The present application relates to the field of plant extraction technology, and more specifically, to a preparation method and application of a mulberry leaf extract having the effect of reducing fat accumulation. Background Art

[0002] Mulberry leaf is a traditional medicinal plant rich in various bioactive ingredients, such as flavonoids, polysaccharides, and alkaloids. It has significant pharmacological effects, including hypoglycemic and hypolipidemic effects, as well as antioxidant and anti-inflammatory properties. In recent years, with the increasing prevalence of metabolic diseases such as diabetes and obesity, mulberry leaf extract has seen increasing use in functional foods, pharmaceuticals, and health supplements.

[0003] Currently, the extraction of active ingredients from mulberry leaves primarily relies on water extraction and alcohol precipitation, organic solvent extraction, and other techniques, supplemented by ultrasound-assisted or microwave-assisted extraction. Despite the diverse range of mulberry leaf extraction methods, traditional techniques suffer from significant loss of active ingredients, high solvent consumption, and complex processes, making them difficult to meet the demands of industrial production. Therefore, developing novel, efficient, low-cost, and environmentally friendly extraction processes to effectively enrich mulberry leaf active ingredients remains a key research priority. Summary of the Invention

[0004] In order to develop an efficient, low-consumption and environmentally friendly mulberry leaf extraction process, the present invention provides a preparation method of a mulberry leaf extract with the effect of reducing fat accumulation and application thereof.

[0005] In order to achieve the above-mentioned invention objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a method for preparing a mulberry leaf extract having the effect of reducing fat accumulation, comprising the following steps: Step 1: Select fresh mulberry leaves, freeze them in liquid nitrogen for 5-10 seconds, freeze-dry them to a moisture content of ≤5%, and crush them into 200 mesh; Step 2: Mix the chopped mulberry leaves with a citric acid solution, adjust the pH to 2.0-3.0, stir and extract at 4°C, centrifuge, and collect the supernatant; Step 3, adding acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, adding cellulase, shaking enzymolysis, sterilizing, centrifuging, and collecting the supernatant; Step 4, combining the extracts obtained in step 2 and step 3, concentrating, and extracting with supercritical CO2; Step 5: spray drying to obtain mulberry leaf extract.

[0006] Furthermore, the specific steps of step 1 are to select fresh mulberry leaves, immerse them in liquid nitrogen for quick freezing for 5-10s, freeze-dry them to a moisture content of ≤5% under the conditions of temperature ≤-50°C and vacuum degree ≤10Pa, and then crush them to 200 mesh.

[0007] Furthermore, in step 2, the concentration of the citric acid solution is 0.1-0.3 mol / L, and the material-liquid ratio is 1:(10-15).

[0008] Furthermore, the specific steps of step 2 are as follows: mixing the chopped mulberry leaves with 0.1~0.3 mol / L citric acid solution at a solid-liquid ratio of 1:(10~15), adjusting the pH to 2.0~3.0, placing it at 4°C and stirring for extraction for 2~3 hours, centrifuging at 6000~8000 rpm for 10~20 minutes, and collecting the supernatant.

[0009] Furthermore, the specific steps of step 3 are as follows: adding acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, adding 0.3-0.5% cellulase with an enzyme activity of 500-600 U / mg, performing enzymatic hydrolysis at a constant temperature of 37°C and 100-120 rpm for 3-4 hours, heating to 90-95°C and sterilizing for 3-5 minutes, centrifuging at 6000-8000 rpm for 10-20 minutes, and collecting the supernatant.

[0010] Furthermore, the specific steps of step 4 are to combine the extracts obtained in steps 2 and 3, concentrate them to 20-30% of the original volume, and perform supercritical CO2 extraction for 2-3 hours under the conditions of CO2 flow rate 18-20 L / h, pressure 25-30 MPa, and temperature 40-50°C.

[0011] Furthermore, in step 5, 0.03-0.05% L-ascorbic acid and 0.1-0.2% tea polyphenols are added before spray drying.

[0012] Furthermore, the specific steps of step 5 are adding 0.03-0.05% L-ascorbic acid and 0.1-0.2% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0013] In a second aspect, the present application provides a mulberry leaf extract prepared by any of the preparation methods described in the first aspect.

[0014] In a third aspect, the present application provides the use of the mulberry leaf extract described in the second aspect in the preparation of a health product capable of reducing fat accumulation.

[0015] In summary, this application has the following beneficial effects: This application uses liquid nitrogen quick freezing combined with freeze drying to maximize the retention of heat-sensitive active ingredients, and crushing to 200 mesh significantly increases the contact area.

[0016] This application adopts a two-stage extraction system of low-temperature acid extraction and targeted enzymatic hydrolysis, which not only improves the purity of mulberry leaf extract, but also supplemented by supercritical CO2 extraction to replace traditional organic solvents to achieve efficient and green enrichment.

[0017] The present application adds L-ascorbic acid and tea polyphenols to synergistically protect phenolic substances.

[0018] In summary, through collaborative innovation, this application has solved industry problems such as large activity loss, high solvent toxicity, and complex processes in traditional extraction methods, providing a reliable technical path for the high-value utilization of mulberry leaf resources. DETAILED DESCRIPTION

[0019] The technical solutions and effects of the present application are further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the invention, rather than to limit the invention.

[0020] The present invention provides a method for preparing a mulberry leaf extract having the effect of reducing fat accumulation, comprising the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for quick freezing for 5-10 seconds, freeze-dry them at a temperature of ≤-50°C and a vacuum degree of ≤10 Pa to a moisture content of ≤5%, and then grind them into 200 mesh; Step 2: Mix the chopped mulberry leaves with a 0.1-0.3 mol / L citric acid solution at a solid-liquid ratio of 1:(10-15), adjust the pH to 2.0-3.0, stir and extract at 4°C for 2-3 hours, centrifuge at 6000-8000 rpm for 10-20 minutes, and collect the supernatant; Step 3: Add acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, add 0.3-0.5% cellulase with an enzyme activity of 500-600 U / mg, perform enzymatic hydrolysis at 37°C with shaking at 100-120 rpm for 3-4 hours, heat to 90-95°C for sterilization for 3-5 minutes, centrifuge at 6000-8000 rpm for 10-20 minutes, and collect the supernatant; Step 4: combining the extracts obtained in step 2 and step 3, concentrating the extracts to 20-30% of the original volume, and performing supercritical CO2 extraction for 2-3 hours at a CO2 flow rate of 18-20 L / h, a pressure of 25-30 MPa, and a temperature of 40-50°C; Step 5, adding 0.03-0.05% L-ascorbic acid and 0.1-0.2% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0021] Example 1

[0022] A method for preparing a mulberry leaf extract having the effect of reducing fat accumulation comprises the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for 7 seconds, freeze them at a temperature of ≤-50°C and a vacuum of ≤10Pa, freeze-dry them to a moisture content of ≤5%, and then grind them into 200 mesh; Step 2: Mix the chopped mulberry leaves with a 0.2 mol / L citric acid solution at a solid-liquid ratio of 1:12, adjust the pH to 2.0-3.0, stir and extract at 4°C for 2.5 hours, centrifuge at 7000 rpm for 15 minutes, and collect the supernatant; Step 3: Add acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, add 0.4% cellulase with an enzyme activity of 550 U / mg, perform enzymatic hydrolysis at 37°C with shaking at 110 rpm for 3.5 h, heat to 95°C for sterilization for 4 min, centrifuge at 7000 rpm for 15 min, and collect the supernatant; Step 4: Combine the extracts obtained in step 2 and step 3, concentrate to 25% of the original volume, and perform supercritical CO2 extraction for 2.5 hours at a CO2 flow rate of 19 L / h, a pressure of 27 MPa, and a temperature of 45°C; Step 5, adding 0.04% L-ascorbic acid and 0.15% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0023] Example 2

[0024] A method for preparing a mulberry leaf extract having the effect of reducing fat accumulation comprises the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for quick freezing for 5 seconds, freeze-dry them at a temperature of ≤-50°C and a vacuum of ≤10Pa to a moisture content of ≤5%, and then grind them into 200 mesh; Step 2: Mix the chopped mulberry leaves with 0.1 mol / L citric acid solution at a solid-liquid ratio of 1:10, adjust the pH to 2.0-3.0, stir and extract at 4°C for 2 hours, centrifuge at 6000 rpm for 10 minutes, and collect the supernatant; Step 3: Add acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, add 0.3% cellulase with an enzyme activity of 500 U / mg, perform enzymatic hydrolysis at 37°C with shaking at 100 rpm for 3 h, heat to 90°C for sterilization for 3 min, centrifuge at 6000 rpm for 10 min, and collect the supernatant; Step 4: Combine the extracts obtained in step 2 and step 3, concentrate to 20% of the original volume, and perform supercritical CO2 extraction at a CO2 flow rate of 18 L / h, a pressure of 25 MPa, and a temperature of 40°C for 2 hours; Step 5, adding 0.03% L-ascorbic acid and 0.1% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0025] Example 3

[0026] A method for preparing a mulberry leaf extract having the effect of reducing fat accumulation comprises the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for 10 seconds, freeze them at a temperature of ≤-50°C and a vacuum of ≤10Pa, and freeze-dry them to a moisture content of ≤5%, and then crush them into 200 mesh; Step 2: Mix the chopped mulberry leaves with 0.3 mol / L citric acid solution at a solid-liquid ratio of 1:15, adjust the pH to 2.0-3.0, stir and extract at 4°C for 3 hours, centrifuge at 8000 rpm for 20 minutes, and collect the supernatant; Step 3: Add acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, add 0.5% cellulase with an enzyme activity of 600 U / mg, perform enzymatic hydrolysis at 37°C with shaking at 120 rpm for 4 h, heat to 95°C for sterilization for 5 min, centrifuge at 8000 rpm for 20 min, and collect the supernatant; Step 4: Combine the extracts obtained in step 2 and step 3, concentrate to 30% of the original volume, and perform supercritical CO2 extraction at a CO2 flow rate of 20 L / h, a pressure of 30 MPa, and a temperature of 50°C for 3 hours; Step 5, adding 0.05% L-ascorbic acid and 0.2% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0027] Comparative Example 1 A method for preparing mulberry leaf extract comprises the following steps: Step 1: Select fresh mulberry leaves, dry them to a moisture content of ≤5%, and then crush them to 200 mesh; Step 2: Mix the chopped mulberry leaves with a 0.2 mol / L citric acid solution at a solid-liquid ratio of 1:12, adjust the pH to 2.0-3.0, stir and extract at 4°C for 2.5 hours, centrifuge at 7000 rpm for 15 minutes, and collect the supernatant; Step 3: Add acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, add 0.4% cellulase with an enzyme activity of 550 U / mg, perform enzymatic hydrolysis at 37°C with shaking at 110 rpm for 3.5 h, heat to 95°C for sterilization for 4 min, centrifuge at 7000 rpm for 15 min, and collect the supernatant; Step 4: Combine the extracts obtained in step 2 and step 3, concentrate to 25% of the original volume, and perform supercritical CO2 extraction for 2.5 hours at a CO2 flow rate of 19 L / h, a pressure of 27 MPa, and a temperature of 45°C; Step 5, adding 0.04% L-ascorbic acid and 0.15% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0028] Comparative Example 2 A method for preparing mulberry leaf extract comprises the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for 7 seconds, freeze them at a temperature of ≤-50°C and a vacuum of ≤10Pa, freeze-dry them to a moisture content of ≤5%, and then grind them into 200 mesh; Step 2: Mix the chopped mulberry leaves with a 0.2 mol / L citric acid solution at a solid-liquid ratio of 1:12, adjust the pH to 2.0-3.0, stir and extract at 4°C for 2.5 hours, centrifuge at 7000 rpm for 15 minutes, and collect the supernatant; Step 3, concentrating to 25% of the original volume, and performing supercritical CO2 extraction at a CO2 flow rate of 19 L / h, a pressure of 27 MPa, and a temperature of 45°C for 2.5 hours; Step 4, adding 0.04% L-ascorbic acid and 0.15% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0029] Comparative Example 3 A method for preparing mulberry leaf extract comprises the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for 7 seconds, freeze them at a temperature of ≤-50°C and a vacuum of ≤10Pa, freeze-dry them to a moisture content of ≤5%, and then grind them into 200 mesh; Step 2: Add acetic acid-sodium acetate buffer to adjust the pH to 4.5-5.0, add 0.4% cellulase with an enzyme activity of 550 U / mg, and perform enzymatic hydrolysis at 37°C with shaking at 110 rpm for 3.5 h. Then, heat to 95°C for sterilization for 4 min, centrifuge at 7000 rpm for 15 min, and collect the supernatant. Step 3, concentrating to 25% of the original volume, and performing supercritical CO2 extraction at a CO2 flow rate of 19 L / h, a pressure of 27 MPa, and a temperature of 45°C for 2.5 hours; Step 5, adding 0.04% L-ascorbic acid and 0.15% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0030] Comparative Example 4 A method for preparing mulberry leaf extract comprises the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for 7 seconds, freeze them at a temperature of ≤-50°C and a vacuum of ≤10Pa, freeze-dry them to a moisture content of ≤5%, and then grind them into 200 mesh; Step 2: Mix the chopped mulberry leaves with a 0.2 mol / L citric acid solution at a solid-liquid ratio of 1:12, adjust the pH to 2.0-3.0, stir and extract at 4°C for 2.5 hours, centrifuge at 7000 rpm for 15 minutes, and collect the supernatant; Step 3: Add acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, add 0.4% cellulase with an enzyme activity of 550 U / mg, perform enzymatic hydrolysis at 37°C with shaking at 110 rpm for 3.5 h, heat to 95°C for sterilization for 4 min, centrifuge at 7000 rpm for 15 min, and collect the supernatant; Step 4: Combine the extracts obtained in step 2 and step 3, concentrate to 25% of the original volume, and extract with 50% ethanol solution; Step 5, adding 0.04% L-ascorbic acid and 0.15% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

[0031] Comparative Example 5 A method for preparing mulberry leaf extract comprises the following steps: Step 1: Select fresh mulberry leaves, immerse them in liquid nitrogen for 7 seconds, freeze them at a temperature of ≤-50°C and a vacuum of ≤10Pa, freeze-dry them to a moisture content of ≤5%, and then grind them into 200 mesh; Step 2: Mix the chopped mulberry leaves with a 0.2 mol / L citric acid solution at a solid-liquid ratio of 1:12, adjust the pH to 2.0-3.0, stir and extract at 4°C for 2.5 hours, centrifuge at 7000 rpm for 15 minutes, and collect the supernatant; Step 3: Add acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, add 0.4% cellulase with an enzyme activity of 550 U / mg, perform enzymatic hydrolysis at 37°C with shaking at 110 rpm for 3.5 h, heat to 95°C for sterilization for 4 min, centrifuge at 7000 rpm for 15 min, and collect the supernatant; Step 4: Combine the extracts obtained in step 2 and step 3, concentrate to 25% of the original volume, and perform supercritical CO2 extraction for 2.5 hours at a CO2 flow rate of 19 L / h, a pressure of 27 MPa, and a temperature of 45°C; Step 5: spray drying to obtain mulberry leaf extract.

[0032] Performance testing 1. Component Analysis The total flavonoids (calculated as rutin) were determined by ultraviolet spectrophotometry, and the polysaccharide content was determined by phenol-sulfuric acid method. The results are as follows: Group Total flavonoids% Polysaccharide% Example 1 12.0 ± 0.5 8.0 ± 0.3 Example 2 11.5 ± 0.4 7.5 ± 0.4 Example 3 12.5 ± 0.6 8.5 ± 0.5 Comparative Example 1 9.0 ± 0.3 6.0 ± 0.2 Comparative Example 2 10.0 ± 0.4 6.5 ± 0.3 Comparative Example 3 9.5 ± 0.3 7.0 ± 0.4 Comparative Example 4 10.5 ± 0.5 5.5 ± 0.3 Comparative Example 5 11.0 ± 0.4 7.5 ± 0.4 2. Reduce fat accumulation 1. Experimental Design 1.1 Experimental Animals SPF-grade C57BL / 6 male mice (6 weeks old, weighing 20 ± 2 g) were selected; The formal experiment began after 1 week of adaptive feeding; Animal room environment: temperature 23 ± 1 °C, humidity 50 ± 5%, 12 h / 12 ​​h light / dark cycle; 1.2 Feed formula Normal group, standard maintenance diet (20% protein, 10% fat), energy ratio 3.8kcal / g; High-fat model group, high-fat diet (20% protein, 45% fat, 1.2% cholesterol), energy ratio 5.2kcal / g; 1.3 Grouping and Dosage Regimen Grouping (n=12 / group): Normal group (Normal): ordinary feed + 0.5% CMC-Na solution; High-fat model group (HFD): high-fat diet + 0.5% CMC-Na solution; Positive control group (HFD+Orlistat): high-fat diet + orlistat 50 mg / kg; Low-dose group (HFD+LD): high-fat diet + 100 mg / kg mulberry leaf extract of Example 1; High-dose group (HFD+HD): high-fat diet + 300 mg / kg of mulberry leaf extract from Example 1; Dosage: The drug was administered by gavage (10 mL / kg volume) at 9:00 am every day; Orlistat suspension was prepared immediately before use (0.5% CMC-Na was used as solvent); Mulberry leaf extract was dissolved in normal saline; 2. Experimental Procedure 2.1 Modeling and intervention Week 0: All groups except the normal group were switched to a high-fat diet; Week 2: Confirmation of successful model establishment (weight increase of the HFD group ≥15% compared with the normal group); Dosing began in week 3 and continued for 8 weeks; 2.2 Monitoring indicators Weekly Records: body weight (electronic balance, ±0.1 g); Feed intake (remaining feed weighed daily); Fasting blood glucose (blood drawn from tail vein, tested with a blood glucose meter); End point detection: After fasting for 12 hours, the animals were sacrificed by anesthesia; Serum was collected (centrifuged at 3500 rpm for 15 min); The liver and adipose tissue (epididymis / perirenal / inguinal) were separated and weighed; 3. Experimental Results Group Initial body weight (g) Final body weight (g) Fat tissue weight (g) Fat body ratio (%) Normal group 20.1±0.8 25.3±1.2 0.52±0.08 2.06±0.31 High-fat model group 20.3±0.7 32.9±1.6 2.87±0.35 8.72±1.04 Low-dose group 20.2±0.9 28.5±1.3* 1.65±0.21* 5.79±0.73* High-dose group 20.0±1.1 26.8±1.1** 1.02±0.15** 3.81±0.56** 4. Experimental Conclusion The mulberry leaf extract prepared in this example can inhibit cholesterol absorption, and no adverse reactions such as diarrhea occurred in any of the groups (p<0.05 compared with the orlistat group).

[0033] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a mulberry leaf extract having the effect of reducing fat accumulation, characterized in that: The following steps are involved: Step 1: Select fresh mulberry leaves, freeze them in liquid nitrogen for 5-10 seconds, freeze-dry them to a moisture content of ≤5%, and crush them into 200 mesh; Step 2: Mix the chopped mulberry leaves with a citric acid solution, adjust the pH to 2.0-3.0, stir and extract at 4°C, centrifuge, and collect the supernatant; Step 3, adding acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, adding cellulase, shaking enzymolysis, sterilizing, centrifuging, and collecting the supernatant; Step 4, combining the extracts obtained in step 2 and step 3, concentrating, and extracting with supercritical CO2; Step 5: spray drying to obtain mulberry leaf extract.

2. The preparation method according to claim 1, characterized in that The specific steps of step 1 are to select fresh mulberry leaves, immerse them in liquid nitrogen for quick freezing for 5-10 seconds, freeze-dry them to a moisture content of ≤5% under the conditions of temperature ≤-50°C and vacuum degree ≤10Pa, and then crush them to 200 mesh.

3. The preparation method according to claim 1, characterized in that In step 2, the concentration of the citric acid solution is 0.1-0.3 mol / L, and the material-liquid ratio is 1:(10-15).

4. The preparation method according to claim 3, characterized in that The specific steps of step 2 are as follows: mixing the chopped mulberry leaves with 0.1-0.3 mol / L citric acid solution at a solid-liquid ratio of 1:(10-15), adjusting the pH to 2.0-3.0, placing the mixture at 4°C under stirring for 2-3 hours, centrifuging at 6000-8000 rpm for 10-20 minutes, and collecting the supernatant.

5. The preparation method according to claim 1, characterized in that The specific steps of step 3 are as follows: adding acetic acid-sodium acetate buffer to the precipitate obtained by centrifugation in step 2 to adjust the pH to 4.5-5.0, adding 0.3-0.5% cellulase with an enzyme activity of 500-600 U / mg, performing enzymatic hydrolysis at a constant temperature of 37°C and 100-120 rpm for 3-4 hours, heating to 90-95°C for sterilization for 3-5 minutes, centrifuging at 6000-8000 rpm for 10-20 minutes, and collecting the supernatant.

6. The preparation method according to claim 1, characterized in that The specific steps of step 4 are to combine the extracts obtained in step 2 and step 3, concentrate to 20-30% of the original volume, and perform supercritical CO2 extraction for 2-3 hours under the conditions of CO2 flow rate 18-20 L / h, pressure 25-30 MPa, and temperature 40-50°C.

7. The preparation method according to claim 1, characterized in that In step 5, 0.03-0.05% L-ascorbic acid and 0.1-0.2% tea polyphenols are further added before spray drying.

8. The preparation method according to claim 7, characterized in that The specific steps of step 5 are as follows: adding 0.03-0.05% L-ascorbic acid and 0.1-0.2% tea polyphenols to the extract, stirring to dissolve, and spray drying to obtain mulberry leaf extract.

9. A mulberry leaf extract prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the mulberry leaf extract according to claim 9 in the preparation of a health product capable of reducing fat accumulation.