Mulberry leaf extract for reducing body weight based on blood sugar regulation and preparation method thereof

Abstract

The invention discloses a mulberry leaf extract for reducing body weight based on blood sugar regulation and a preparation method thereof, and belongs to the technical field of natural product extraction. The mulberry leaf extract is mulberry leaf DNJ, and the extraction and preparation steps of the mulberry leaf extract comprise pretreatment, composite enzymatic hydrolysis, ultrafiltration purification, resin adsorption and freeze-drying molding. By optimizing enzymolysis conditions and a separation and purification process, the extraction rate (gt; and therefore, a foundation is laid for industrial production. DNJ reduces blood sugar and body weight by promoting secretion of GLP-1, when DNJ is combined with GLP-1RA for use, a remarkable synergistic effect is shown, and the effects of reducing blood sugar and losing weight are further enhanced. The invention provides a natural and safe blood glucose reducing and weight losing active component and a preparation method thereof, provides a novel solution for treating diabetes and obesity, and has important social and economic values.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural product extraction, and particularly relates to a mulberry leaf extract for regulating blood sugar and reducing weight and a preparation method thereof. Background Art

[0002] As a traditional Chinese medicinal material, mulberry leaves have attracted much attention due to their rich active ingredients and significant physiological effects. In recent years, researchers have gradually revealed the biological activities and action mechanisms of various active ingredients in mulberry leaves. Among them, 1-deoxynojirimycin (DNJ), as an important hypoglycemic active ingredient, has received extensive research attention. DNJ reduces the absorption of disaccharides in the small intestine by inhibiting the activity of α-glucosidase, thereby reducing the postprandial blood glucose peak. In addition, DNJ also has the effects of promoting insulin secretion and improving glucose metabolism.

[0003] Although certain progress has been made in the research on mulberry leaves and their active ingredients, there are still some deficiencies in the current preparation methods of mulberry leaf extracts. The traditional water extraction method has a low extraction rate and a complex process, making it difficult to meet the requirements of industrial production. At the same time, with the continuous increase in the incidence of diabetes and obesity, the development of natural and safe hypoglycemic and weight loss products has become a research hotspot. However, existing treatment methods often have problems such as large side effects and limited efficacy, and there is an urgent need to find more effective and safe treatment means.

[0004] In the field of diabetes treatment, glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1RA) have attracted much attention due to their significant hypoglycemic effect and weight loss effect. GLP-1 comprehensively regulates blood glucose metabolism and energy balance through mechanisms such as stimulating insulin secretion, inhibiting glucagon secretion, delaying gastric emptying, and enhancing satiety. However, the long-term use of GLP-1RA may be accompanied by some side effects, such as gastrointestinal discomfort, pancreatitis, etc., which limit its widespread application.

[0005] Currently, the traditional preparation methods of mulberry leaf extracts have problems such as low extraction rate and complex process, making it difficult to meet the requirements of industrial production and clinical application. In addition, the incidence of diabetes and obesity has been increasing year by year, and existing treatment methods (such as chemical drugs) often have problems such as large side effects and limited efficacy. There is an urgent need to develop a natural, safe, and highly effective hypoglycemic and weight loss product. Summary of the Invention

[0006] The present invention aims to solve the problems of low extraction efficiency, complex processes in the extraction technology of natural products, as well as large side effects and limited efficacy of existing hypoglycemic and weight loss products in the field of mulberry leaf active ingredient extraction. It provides a mulberry leaf extract for regulating blood sugar and reducing weight and its preparation method. At the same time, through the combined use of DNJ and GLP-1RA, its synergistic effect in hypoglycemic and weight loss is explored, providing a new natural active ingredient and its application solution for the treatment of diabetes and obesity.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] (I) Preparation steps of the mulberry leaf extract

[0009] a) Pretreatment: Fresh mulberry leaves are broken by liquid nitrogen quick-freezing and thawing cycles to disrupt cells, followed by high-pressure homogenization and then ultrasonic treatment to form a slurry.

[0010] b) Composite enzymatic hydrolysis: Add cellulase, pectinase and amylase to the slurry, and the enzyme activity ratio is (1 - 3):(1 - 2):(1 - 3). Shake and enzymatically hydrolyze at pH 4.5 - 5.5 and temperature 40 - 60 °C for 60 - 120 minutes.

[0011] c) Ultrafiltration purification: Use a 3 - 10 kDa ultrafiltration membrane to concentrate at 4 - 10 °C and a pressure of 0.1 - 0.5 MPa to remove macromolecular impurities.

[0012] d) Resin adsorption: Use AB-8 macroporous resin and elute with a 30% - 80% ethanol gradient, and collect the eluate in the 50% - 80% ethanol fraction.

[0013] e) Freeze-drying and forming: The concentrated solution is pre-frozen and then freeze-dried to obtain a DNJ freeze-dried powder with a purity ≥ 95%.

[0014] Furthermore, in step a), the number of liquid nitrogen quick-freezing and thawing cycles is 2 - 4 times, the high-pressure homogenization pressure is 150 - 250 MPa, and the ultrasonic conditions are 20 - 40 kHz and 200 - 400 W.

[0015] Furthermore, in step b), the activity ratio of cellulase, pectinase and amylase is 2:1:1, the enzymatic hydrolysis temperature is 50 °C, and the time is 60 minutes; 0.05% - 0.2% NaN3 and 0.3% - 0.8% VC are added during the enzymatic hydrolysis step.

[0016] Furthermore, in step c), the molecular weight cut-off of the ultrafiltration membrane is 3 kDa, and the operating pressure is 0.1 - 0.2 MPa.

[0017] Furthermore, in step d), the ethanol elution gradient is 30%, 50%, 80%.

[0018] (II) Application of the mulberry leaf extract

[0019] The mulberry leaf extract (DNJ) of the present invention promotes the secretion of glucagon-like peptide-1 (GLP-1), enhances insulin sensitivity, improves glucose metabolism and energy balance, thereby achieving the effects of regulating blood glucose and reducing body weight. In addition, when DNJ is used in combination with a GLP-1 receptor agonist (GLP-1RA), a significant synergistic effect is shown.

[0020] 1. At the cellular level

[0021] Dose-dependence: 100 μM DNJ increased the GLP-1 secretion of GLUTag cells by 140% (from 50 to 120 pg / mL), and the expression level of Gcg mRNA increased by 150%.

[0022] Synergistic effect: After combining DNJ (50 μM) with GLP-1RA (100 nM), the GLP-1 secretion reached 170 pg / mL (↑240%), indicating the activation of dual pathways (secretion promotion + receptor sensitization).

[0023] 2. Verification in animal models

[0024] Hypoglycemic effect: DNJ (50 mg / kg) reduced the OGTT AUC by 19%, and the reduction rate reached 34% after combining with GLP-1RA.

[0025] Weight loss effect: DNJ alone reduced body weight by 13%, and the combined treatment reduced body weight by 20.2%, with a 30% reduction in food intake.

[0026] Insulin sensitivity: After combined treatment, the HOMA-IR index decreased by 52%, and the fasting blood glucose decreased by 36%.

[0027] Compared with the prior art, the beneficial effects of the present invention mainly lie in:

[0028] The present invention discloses a mulberry leaf extract for regulating blood glucose and reducing body weight and its preparation method. By optimizing the enzymatic hydrolysis conditions and separation and purification processes, the extraction rate of DNJ is significantly increased (>3.0%), which is much higher than that of the traditional water extraction method (0.8% - 1.2%), laying a foundation for industrial production. DNJ promotes GLP-1 secretion, improves insulin resistance, reduces blood glucose and body weight, and has good application prospects. When used in combination with GLP-1RA, a significant synergistic effect is shown, further enhancing the hypoglycemic and weight loss effects. The present invention provides a natural and safe hypoglycemic and weight loss active ingredient and its preparation method, providing a new solution for the treatment of diabetes and obesity, and having important social and economic values. Specific embodiments

[0029] The technical solution of the present invention will be further described below in conjunction with specific embodiments. However, those skilled in the art should understand that the following embodiments are only used to illustrate the present invention and should not be regarded as a limitation to the present invention. The specific conditions not specified in the embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products obtained through commercial channels.

[0030] Example 1

[0031] Fresh mulberry leaf DNJ extraction process

[0032] 1. Raw material pretreatment: Collect fresh mulberry leaves without pests and diseases, rinse them with running water for 5 minutes to remove surface impurities, rinse them 3 times with ultrapure water to thoroughly remove residual ions, and drain the surface moisture. Cut the mulberry leaves into small strips 0.5 cm wide, quickly freeze them in liquid nitrogen for 5 minutes, and then thaw them at room temperature. Repeat this cycle 3 times to fully destroy the cell membrane structure of the mulberry leaves. Add 3 times the volume of distilled water and perform high-pressure homogenization treatment at 200 MPa, supplemented with ultrasonic crushing under ice bath (20 kHz, 300 W, working for 3 seconds / interval of 2 seconds, lasting for 10 minutes) to form a uniform slurry.

[0033] 2. Composite enzymatic hydrolysis optimization: Adjust the pH of the mulberry leaf slurry to 5.0, add the bacteriostatic agent NaN3 and the antioxidant VC to the final concentrations of 0.1% NaN3 and 0.5% VC to maintain the stability of DNJ. Optimize the enzymatic hydrolysis conditions through response surface experiments: Use a composite enzyme system of cellulase, pectinase and amylase, and screen with three ratios (1:1:1, 2:1:1, 1:2:1) combined with different temperatures (40 - 70 °C) and times (40 - 100 minutes). Inactivate the enzyme in a water bath at 80 °C for 10 minutes, and then cool it in an ice bath.

[0034] 3. Separation and purification: Coarsely filter the enzymatic hydrolysis solution with a 200-mesh filter cloth, centrifuge at 8000 rpm for 15 minutes to remove residues, and sterilize the supernatant by passing it through a 0.45-μm filter membrane. Ultrafilter using a 3 kDa ultrafiltration membrane, with an operating pressure of 0.1 - 0.2 MPa, a temperature of 4 - 10 °C, and a flow rate of 300 - 500 mL / min. Stop ultrafiltration when it is detected by the Coomassie brilliant blue method that there is basically no protein in the permeate. Further purify by dynamic adsorption using AB-8 macroporous resin. The resin pretreatment includes: soaking in a water bath at 60 °C for 4 hours, activating it successively with 95%, 50%, and 30% ethanol, and finally rinsing it with pure water until there is no alcohol residue. The sample loading flow rate is 2 - 5 BV / h. First, elute the non-specific adsorbents with 30% ethanol, then elute the target product with 50% ethanol, and finally elute the strongly bound components with 80% ethanol. Collect the eluate in the 50% - 80% ethanol section, and this part is enriched with high-purity DNJ.

[0035] 4. Concentration and freeze-drying: The purified solution was concentrated to 1 / 10 of the original volume by rotary evaporation (40 °C, -0.08 MPa), and then the concentrated solution was pre-frozen in a -40 °C environment for 6 hours. It was transferred to a freeze-dryer and freeze-dried under vacuum conditions of -50 °C and 10 Pa for 48 hours to finally obtain a white freeze-dried powder of DNJ.

[0036] Analysis was performed using a HILIC-Z amino column (4.6×250 mm, 5 μm). The mobile phase was acetonitrile - 0.2% acetic acid (85:15), the flow rate was 1.0 mL / min, the column temperature was 30 °C, and the detection wavelength was 254 nm. The purity of DNJ was measured to be >95%. The yield of DNJ was calculated according to the formula:

[0037]

[0038] Table 1 Extraction conditions and DNJ yield

[0039]

[0040]

[0041] Through the combined technology of complex enzymatic hydrolysis - ultrafiltration purification, the wet basis extraction rate of DNJ was increased to 0.91%. Calculated based on the average moisture content of fresh mulberry leaves being 70%, when the wet basis extraction rate was 0.91%, the dry basis extraction rate reached 3.03% (conversion formula: dry basis extraction rate = wet basis extraction rate / (1 - moisture content)).

[0042] Example 2

[0043] Cell experiment on DNJ promoting GLP-1 secretion

[0044] 1. Cell model construction: The GLUTag cell line (mouse intestinal L cell model, which can specifically secrete GLP-1) was selected for the experiment. The cells were cultured in DMEM medium containing 10% fetal bovine serum and 1% penicillin-streptomycin, inoculated into a 24-well plate at a density of 5×10 5 cells / well, and adherently cultured in a 37 °C, 5% CO2 cell incubator for 24 hours.

[0045] 2. Experimental grouping and treatment: A blank control group (treated with PBS), a low-concentration DNJ group (50 μM DNJ), a high-concentration DNJ group (100 μM DNJ), a positive control group (100 nM GLP-1RA), and a combined treatment group (50 μM DNJ + 50 nM GLP-1RA) were set up. Each group had 3 replicate wells, and the treatment time was 24 hours.

[0046] 3. ELISA detection of GLP-1 secretion: After the treatment, collect the cell culture supernatant, centrifuge at 3000 rpm for 10 minutes to remove cell debris. Take 100 μL of the supernatant and add it to the ELISA kit, and detect the GLP-1 secretion according to the instructions. Use an enzyme-linked immunosorbent assay reader to read the OD value at a wavelength of 450 nm, and calculate the GLP-1 concentration (pg / mL).

[0047] 4. Detection of GLP-1 mRNA level: Collect cells, extract total RNA using the Trizol method, and detect the A260 / A280 ratio to ensure RNA purity. Reverse transcribe the RNA into cDNA, and perform real-time fluorescence quantitative PCR using the SYBR Green method to detect the mRNA expression level of Gcg (GLP-1 precursor gene). Primer sequences:

[0048] Gcg-F: 5'-TGACGCTGACCCCACTAC-3' (SEQ ID NO.1)

[0049] Gcg-R: 5'-CCAGGGTGTGTAGCGGTTA-3' (SEQ ID NO.2)

[0050] PCR cycling conditions: Pre-denature at 95°C for 30 seconds, denature at 95°C for 10 seconds, anneal at 60°C for 30 seconds, for a total of 40 cycles. Calculate the -ΔΔCt value, use β-actin as the internal reference gene, and normalize and analyze the relative expression level. β-actin primer sequences:

[0051] β-actin-F: 5'-GGCTGTATTCCCCTCCATCG-3' (SEQ ID NO.3)

[0052] β-actin-R: 5'-CCAGTTGGTAACAATGCCATGT-3' (SEQ ID NO.4)

[0053] Table 2 GLP-1 secretion and Gcg mRNA level

[0054]

[0055] The results are shown in Table 3. The GLP-1 secretion in the blank control group was 50 ± 5 pg / mL. The GLP-1 secretion in the DNJ treatment group increased in a dose-dependent manner. The 50 μM group was 85 ± 7 pg / mL (↑70%), and the 100 μM group was 120 ± 10 pg / mL (↑140%). The GLP-1 secretion in the positive control group was 150 ± 12 pg / mL (↑200%), and the GLP-1 secretion in the combined treatment group reached 170 ± 12 pg / mL (↑240%), showing a significant synergistic effect.

[0056] The relative expression level of Gcg mRNA in the blank control group was 1.0, and the expression level of Gcg mRNA in the DNJ treatment group also increased in a dose-dependent manner. The 50 μM group was 1.8 ± 0.2 (↑80%), and the 100 μM group was 2.5 ± 0.3 (↑150%). The expression level of Gcg mRNA in the positive control group was 2.9 ± 0.4 (↑190%), and the expression level of Gcg mRNA in the combined treatment group reached 3.5 ± 0.4 (↑250%), further verifying the synergistic effect of DNJ and GLP-1RA.

[0057] The GLP-1 secretion and mRNA expression levels in the combined treatment group were significantly higher than those in the single treatment group, suggesting that DNJ and GLP-1RA have a synergistic effect in promoting GLP-1 secretion. This may be related to the mechanism by which DNJ improves insulin sensitivity and enhances the GLP-1 signaling pathway.

[0058] Example 3

[0059] Hypoglycemic and weight loss effects of DNJ combined with GLP-1RA in animal experiments

[0060] 1. Establishment of animal model: C57BL / 6J mice were selected. Four weeks before the experiment, all mice were fed a high-fat diet (HFD, 60% fat content) to induce obesity and insulin resistance. After 4 weeks of feeding, a single intraperitoneal injection of streptozotocin (STZ, 60 mg / kg) was performed to induce a type 2 diabetes model. The establishment of the diabetes model was verified by fasting plasma glucose (FPG) and oral glucose tolerance test (OGTT).

[0061] 2. Experimental grouping and treatment: The model mice were randomly divided into 6 groups, with 10 mice in each group. Normal control group: Standard diet, treated with PBS. Diabetes model group: HFD + STZ, no intervention. Low-dose DNJ group: HFD + STZ, 50 mg / kg / d DNJ (gavage). High-dose DNJ group: HFD + STZ, 100 mg / kg / d DNJ (gavage). Positive control group: HFD + STZ, liraglutide 0.4 mg / kg / d GLP-1RA (subcutaneous injection). Combined treatment group: HFD + STZ, 50 mg / kg / d DNJ (gavage) + 0.2 mg / kg / d GLP-1RA (subcutaneous injection).

[0062] 3. Oral glucose tolerance test (OGTT): Fast for 12 hours before the end of the experiment, and then gavages with glucose solution (2 g / kg). Collect tail vein blood at 0 min, 15 min, 30 min, 60 min, and 120 min, and measure the blood glucose concentration (mmol / L) using a blood glucose meter. Evaluate glucose tolerance by the area under the blood glucose curve (AUC).

[0063] Table 3 Blood glucose changes after intragastric administration of glucose solution

[0064]

[0065] The results of blood glucose changes are shown in Table 3. The peak blood glucose in the control group was 17.2 ± 0.8 mmol / L (15 min), and it recovered to 10.5 ± 0.5 mmol / L (120 min). The peak blood glucose in the high-dose DNJ group was 15.5 ± 0.6 mmol / L (15 min), and it recovered to 8.3 ± 0.3 mmol / L (120 min). The area under the blood glucose curve (AUC) was 19% lower than that in the control group. The peak blood glucose in the GLP-1RA positive control group was 15.1 ± 0.6 mmol / L (15 min), and it recovered to 8.0 ± 0.4 mmol / L (120 min). The AUC was 21% lower than that in the control group. In the combination treatment group: the peak blood glucose was 13.8 ± 0.5 mmol / L (15 min), and it recovered to 6.8 ± 0.3 mmol / L (120 min). The AUC was 34% lower than that in the control group. Both DNJ and GLP-1RA alone can significantly improve glucose tolerance, and the combination treatment group showed a stronger hypoglycemic effect, suggesting a synergistic effect between the two.

[0066] 4. Detection of fasting blood glucose (FPG) and insulin levels: At the end of the experiment, after fasting for 6 hours, blood was collected from the tail vein to measure fasting blood glucose (FPG, mmol / L). Serum was collected, and an ELISA kit was used to detect insulin concentration (mU / L). Calculation of insulin resistance index (HOMA-IR):

[0067]

[0068] Table 4 Fasting blood glucose and insulin levels

[0069]

[0070] The results are shown in Table 4. The fasting blood glucose of the control group was 9.8 ± 0.5 mmol / L, that of the high-dose DNJ group was 7.9 ± 0.4 mmol / L (↓19%), that of the positive control group of GLP-1RA was 7.1 ± 0.3 mmol / L (↓28%), and that of the combination treatment group was 6.3 ± 0.3 mmol / L (↓36%). The insulin level of the control group was 1.25 ± 0.1 mU / L, that of the high-dose DNJ group was 0.95 ± 0.08 mU / L (↓24%), that of the positive control group was 0.87 ± 0.06 mU / L (↓30%), and that of the combination treatment group was 0.75 ± 0.06 mU / L (↓40%). The HOMA-IR of the control group was 5.44 ± 0.5, that of the high-dose DNJ group was 3.78 ± 0.4 (↓30%), that of the positive control group was 2.74 ± 0.5 (↓50%), and that of the combination treatment group was 2.62 ± 0.3 (↓52%). The combination treatment group significantly reduced the fasting blood glucose and insulin levels and improved insulin resistance, indicating that DNJ and GLP-1RA have a synergistic effect in regulating insulin secretion and sensitivity.

[0071] 5. Detection of GLP-1 secretion: At the end of the experiment, the mice were sacrificed by cervical dislocation, serum was collected, and the concentration of GLP-1 (pmol / L) in the serum was detected using an ELISA kit.

[0072] Table 5 Serum GLP-1 of mice

[0073]

[0074] The results are shown in Table 5. The concentration of serum GLP-1 in the control group was 5.5 ± 0.5 pmol / L, that in the high-dose DNJ group was 9.2 ± 0.8 pmol / L (↑67%), that in the positive control group of GLP-1RA was 11.4 ± 1.2 pmol / L (↑107%), and that in the combination treatment group was 13.6 ± 1.2 pmol / L (↑147%). DNJ significantly promoted GLP-1 secretion, and the combination with GLP-1RA further enhanced the release of GLP-1, providing a mechanism support for blood glucose lowering and weight loss.

[0075] 6. Monitoring of body weight changes and food intake: Weigh once a week and record the body weight change curve. Measure the food intake of mice (g / day) every day and calculate the cumulative energy intake.

[0076] Table 6 Body weight of mice (g)

[0077]

[0078] The body weight changes are shown in Table 6. At the end of the experiment, the body weight of the control group was 41.6 ± 1.6 g, the body weight of the high-dose DNJ group was 36.2 ± 1.4 g (↓13.0%), the body weight of the positive control group was 34.7 ± 1.3 g (↓16.8%), and the body weight of the combination treatment group was 33.2 ± 1.3 g (↓20.2%).

[0079] Table 7 Dietary intake (kcal / day)

[0080]

[0081] The changes in dietary intake are shown in Table 7. The daily food intake of the control group was 16.8 ± 0.7 kcal, the daily food intake of the high-dose DNJ group was 14.2 ± 0.6 kcal (↓15%), the daily food intake of the positive control group was 13.6 ± 0.5 kcal (↓19%), and the daily food intake of the combination treatment group was 11.8 ± 0.5 kcal (↓30%). The combination treatment group significantly reduced body weight and food intake, suggesting that DNJ and GLP-1RA have a synergistic effect in promoting satiety and reducing energy intake.

[0082] The experimental results show that both DNJ and GLP-1RA alone can significantly improve glucose tolerance, reduce blood glucose and body weight. The combination treatment group showed stronger hypoglycemic and weight loss effects, suggesting that DNJ and GLP-1RA have a synergistic effect in promoting GLP-1 secretion, improving insulin resistance and regulating energy metabolism.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. The basic principles and main features of the present invention have been described in the above specific implementation manners. On the basis of the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the present invention claimed.

Claims

1. A preparation method of a mulberry leaf extract with the functions of regulating blood sugar and reducing weight, characterized in that, Comprising the following steps: a) Pretreatment: Fresh mulberry leaves are broken by liquid nitrogen quick-freezing - thawing cycles to disrupt cells, followed by high-pressure homogenization and then ultrasonic treatment to form a slurry; b) Complex enzymatic hydrolysis: Cellulase, pectinase, and amylase are added to the slurry, and the enzyme activity ratio is (1 - 3):(1 - 2):(1 - 3). It is shaken and enzymatically hydrolyzed at pH 4.5 - 5.5 and a temperature of 40 - 60 °C for 60 - 120 minutes; c) Ultrafiltration purification: A 3 - 10 kDa ultrafiltration membrane is used to concentrate at 4 - 10 °C and a pressure of 0.1 - 0.5 MPa to remove macromolecular impurities; d) Resin adsorption: AB - 8 macroporous resin is used, and gradient elution is carried out with 30% - 80% ethanol, and the eluate of the 50% - 80% ethanol fraction is collected; e) Freeze-drying and forming: The concentrated solution is pre-frozen and then freeze-dried to obtain a DNJ freeze-dried powder with a purity of ≥95%; 2. The preparation method according to claim 1, characterized in that, In step a), the number of liquid nitrogen quick-freezing - thawing cycles is 2 - 4 times, the high-pressure homogenization pressure is 150 - 250 MPa, and the ultrasonic conditions are 20 - 40 kHz and 200 - 400 W; 3. The preparation method according to claim 1, characterized in that, In step b), the activity ratio of cellulase, pectinase, and amylase is 2:1:1, the enzymatic hydrolysis temperature is 50 °C, and the time is 60 minutes; 0.05% - 0.2% NaN3 and 0.3% - 0.8% VC are added during the enzymatic hydrolysis step; 4. The preparation method according to claim 1, wherein In step c), the molecular weight cut-off of the ultrafiltration membrane is 3 kDa, and the operating pressure is 0.1 - 0.2 MPa; in step d), the ethanol elution gradient is 30%, 50%, 80%; 5. A mulberry leaf extract having the effects of regulating blood glucose and reducing body weight, characterized in that: Prepared by the method according to claim 1, the purity of DNJ is ≥95%; 6. The mulberry leaf extract according to claim 5, characterized in that, In cell experiments, at a concentration of 100 μM, it can increase the secretion amount of GLP-1 by ≥140% and increase the expression amount of Gcg mRNA by ≥150%; in animal experiments, at a dose of 50 mg / kg, it can reduce OGTT AUC by ≥19% and reduce body weight by ≥13%; 7. A mulberry leaf extract composition with the functions of regulating blood sugar and reducing body weight, characterized in that, Comprising: the mulberry leaf extract according to claim 5, a GLP-1 receptor agonist, and a pharmaceutically or food-acceptable carrier

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