Canavalia polysaccharide, extraction method and application thereof

Abstract

The application belongs to the technical field of biological medicine, and particularly relates to a canavalia gladiata polysaccharide and an extraction method and application thereof. The canavalia gladiata polysaccharide is extracted by using an alkali method, a eutectic solvent and a traditional water extraction method, chemical components, molecular mass, monosaccharide composition, infrared spectrum and appearance form and other structural characteristics of the three kinds of polysaccharides are determined, and in-vitro antioxidant, hypoglycemic and hypolipidemic activities of the three kinds of canavalia gladiata polysaccharides are compared. The results show that the three kinds of canavalia gladiata polysaccharides all have certain antioxidant, hypoglycemic and hypolipidemic activities, and the antioxidant, hypoglycemic and hypolipidemic activities of the canavalia gladiata polysaccharide extracted by the alkali method are obviously better than those of the canavalia gladiata polysaccharides extracted by the eutectic solvent and the traditional water extraction method.

Description

Technical Field

[0001] This invention belongs to the field of biomedical technology, specifically relating to a canavalia polysaccharide, its extraction method, and its application. Background Technology

[0002] Sword bean (Canavalia gladiata (Jacq.) DC.) is the dried, mature seed of the legume Canavalia gladiata. It is sweet, neutral in nature, and non-toxic, possessing high medicinal value in traditional Chinese medicine. It exhibits good antioxidant, hypoglycemic, lipid-lowering, anti-tumor, and immunomodulatory effects. Previous phytochemical studies have shown that sword beans contain flavonoids, terpenes, steroids, organic acids, nitrogenous compounds, amino acids, and proteins. However, many components of sword beans remain under investigation, offering the potential for discovering new substances and expanding its applications. Therefore, in-depth research into the chemical composition of sword beans is necessary. Secondly, although the secondary metabolites of sword beans have been studied to some extent, the stability and reproducibility of their chemical components remain questionable. Crude extracts of sword beans exhibit various biological activities, including antioxidant, antitumor, antibacterial, anti-inflammatory, anti-allergic, immunomodulatory, anti-obesity, hepatoprotective, anti-diabetic, and other biological activities. However, the active components exhibiting these biological activities have not yet been identified, and the underlying mechanisms of these effects remain unclear. Although many secondary metabolites have been isolated, their activities have not yet been thoroughly evaluated. Therefore, further research should focus on revealing the bioactivity of crude extracts and isolated components through in vivo and in vitro experiments.

[0003] Plant polysaccharides, a widely distributed class of complex carbohydrates derived from various plant organs and tissues, are structurally composed of ten or more monosaccharide molecules linked by glycosidic bonds. They exhibit multiple pharmacological effects, including antioxidant and immunomodulatory activities, lipid-lowering effects, and antibacterial and antitumor activities. Studies have shown that extraction methods have varying degrees of influence on the chemical composition, extraction rate, and biological activity of polysaccharides. Currently, research on the active components of sword bean mainly focuses on sword bean protein; no sword bean polysaccharides have been reported in existing patents and literature. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention utilizes alkaline extraction of canavalia gladiate alkaline polysaccharide (CGAP), eutectic solvent extraction of canavalia gladiate DES polysaccharide (CGDP), and conventional water extraction of canavalia gladiate water polysaccharide (CGWP). The chemical composition, molecular weight, monosaccharide composition, infrared spectrum, and morphological characteristics of the three polysaccharides were determined. Furthermore, the in vitro antioxidant, hypoglycemic, and hypolipidemic activities of the three canavalia gladiate polysaccharides were compared, demonstrating their excellent antioxidant, hypoglycemic, and hypolipidemic activities.

[0005] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0006] A canavalia polysaccharide, wherein the canavalia polysaccharide is composed of rhamnose, galacturonic acid, glucose, galactose and arabinose; or wherein the canavalia polysaccharide is composed of galacturonic acid, glucose and galactose, named CGWP.

[0007] Furthermore, the canavalia polysaccharide composed of rhamnose, galacturonic acid, glucose, galactose, and arabinose, with a monosaccharide molar ratio of 0.097:0.421:84.076:6.528:8.879, is named CGAP; or the canavalia polysaccharide composed of rhamnose, galacturonic acid, glucose, galactose, and arabinose, with a monosaccharide molar ratio of 2.290:1.053:88.751:2.033:5.873, is named CGDP;

[0008] The canavalia polysaccharide, composed of galacturonic acid, glucose, and galactose, has a monosaccharide molar ratio of 0.245:99.570:0.185.

[0009] A method for extracting the above-mentioned canavalia polysaccharide, comprising the following steps:

[0010] (1) Select dried sword bean seeds, crush them, sieve them, add defatting solvent to remove fat-soluble impurities, centrifuge them, collect the precipitate, dry them, preferably add ethanol, petroleum ether or n-hexane, and remove fat-soluble impurities in a shaker at room temperature (180 rpm, 6 h).

[0011] (2) Select any of the following methods to extract the solid obtained in (1) to obtain canavalia polysaccharide:

[0012] (2-1) Water extraction: Add distilled water (preferably solid-liquid ratio 1g:20mL) and extract completely (preferably at 95℃ for 6h), centrifuge to collect the supernatant, add trichloroacetic acid (preferably add an equal volume concentration of 3w / v% trichloroacetic acid), let stand overnight, centrifuge to collect the supernatant, add ethanol, let stand overnight, and freeze-dry the precipitate after centrifugation to obtain polysaccharide CGWP;

[0013] (2-2) Eutectic solvent extraction: After complete extraction with eutectic solvent (preferably solid-liquid ratio 1g:20mL) (preferably at 95℃ for 2h), centrifuge to collect the supernatant, add trichloroacetic acid (preferably add an equal volume concentration of 3w / v% trichloroacetic acid), let stand overnight, centrifuge to collect the supernatant, add ethanol, let stand overnight, and freeze-dry the precipitate after centrifugation to obtain polysaccharide CGDP;

[0014] (2-3) Alkaline extraction: After complete extraction with alkaline solution (preferably solid-liquid ratio 1g:20mL) (preferably at 95℃ for 2h), centrifuge to collect the supernatant, adjust the pH to neutral, add trichloroacetic acid (preferably add an equal volume concentration of 3w / v% trichloroacetic acid), let stand overnight, centrifuge to collect the supernatant, add ethanol, let stand overnight, freeze-dry the precipitate after centrifugation to obtain polysaccharide CGAP;

[0015] Furthermore, the composition of the eutectic solvent in (2-2) is: choline chloride and urea in a molar ratio of 1:4 and deionized water, wherein the amount of deionized water accounts for 40% of the total mass of the eutectic solvent.

[0016] Furthermore, the alkaline solution is a NaOH solution, preferably with a concentration of 0.5M.

[0017] This invention also provides the application of the canavalia polysaccharide obtained by the above extraction method in the preparation of antioxidant, hypoglycemic and / or hypolipidemic drugs.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] (1) Plant polysaccharides are natural macromolecules that play an important role in their life activities. In recent years, polysaccharides have become a research hotspot due to their non-toxicity and good biological activity, and are widely used in food, biomedicine and other fields. Previous studies on the active components of sword bean did not involve polysaccharides. This study has enriched the isolation and identification of active components of sword bean, and provided a theoretical basis for further research and development of functional products made from sword bean polysaccharides.

[0020] (2) The different compositions and glycosidic bonds of polysaccharides result in differences in their spatial structure and biological activity. Changes in extraction methods and extraction process conditions of sword bean active ingredients will directly affect the composition of the effective components, and thus affect the biological activity of the extract. Polysaccharides extracted with different solvents have different structures and biological activities. This may be because polysaccharides in plants often coexist with other components, and polysaccharides exist in different forms under different solvent conditions.

[0021] (3) To obtain better bioactive polysaccharides, this invention utilized alkaline extraction of canavalia gladiate alkaline polysaccharide (CGAP), eutectic solvent extraction of canavalia gladiate DES polysaccharide (CGDP), and conventional water extraction of canavalia gladiate water polysaccharide (CGWP). The chemical composition, molecular weight, monosaccharide composition, infrared spectrum, and morphological characteristics of the three polysaccharides were determined. The in vitro antioxidant, hypoglycemic, and hypolipidemic activities of the three canavalia gladiate polysaccharides were compared. The results showed that all three canavalia gladiate polysaccharides possessed certain antioxidant, hypoglycemic, and hypolipidemic activities. When the polysaccharide concentration was 1.5 mg / mL, the DPPH free radical scavenging rate of alkaline-extracted canavalia gladiate CGAP was (86.38±0.81)%. When the polysaccharide concentration was 4 mg / mL, the alkaline-extracted canavalia gladiate CGAP showed a significant effect against ABTS. + The free radical scavenging rate, hydroxyl radical reduction capacity, and iron ion reducing capacity were (84.97±0.46)%, (62.59±0.80)%, and (283.80±2.64) μmol / L, respectively. The inhibition rate against α-amylase and the binding capacity of sodium glycocholate and sodium taurocholate were (59.07±0.58)%, (67.59±1.19)%, and (63.45±1.39)%, respectively. The antioxidant, hypoglycemic, and hypolipidemic activities of CGAP extracted by the alkaline method were significantly superior to those of CGDP extracted by the eutectic solvent and CGWP extracted by conventional water extraction.

[0022] Alkaline extraction can extract intracellular and cell wall-bound polysaccharides, as well as polysaccharides bound to polyphenols or other small molecules. Therefore, canavalia polysaccharides extracted using the alkaline method are low-cost, widely applicable, and exhibit enhanced bioactivity, making them valuable for development and commercial use. Furthermore, it provides a scientific basis for the extraction and utilization of canavalia polysaccharides. Attached Figure Description

[0023] Figure 1 The examples show a comparison of the structures of three polysaccharides, where A. molecular weight distribution map; B. high-performance liquid chromatography (HPLC) chromatogram of monosaccharide composition; and C. infrared spectrum.

[0024] Figure 2 The images shown are scanning electron microscope (SEM) images of three types of canavalia polysaccharides in the examples: A. CGAP; B. CGDP; C. CGWP. From left to right, the SEM images are 200×, 500×, 1000×, 2000×, and 5000×.

[0025] Figure 3 The water-holding capacity, water solubility, and fat-binding capacity of the three polysaccharides in the examples are shown. Different lowercase letters indicate significant differences in the same index among different polysaccharides (P<0.05).

[0026] Figure 4 To illustrate the in vitro antioxidant activity of the three polysaccharides in the examples, we consider: A. DPPH free radical scavenging ability; B. ABTS+ free radical scavenging ability; C. hydroxyl free radical scavenging ability; and D. ferric ion reducing ability. Different lowercase letters indicate significant differences between samples of the same concentration (P<0.05).

[0027] Figure 5 The figure shows the α-amylase activity inhibition rate of the three polysaccharides in the examples. Different lowercase letters indicate significant differences between samples of the same concentration (P<0.05).

[0028] Figure 6 The bile salt binding capacity of the three polysaccharides in the examples is: A. binding capacity of sodium glycocholate; B. binding capacity of sodium taurocholate. Different lowercase letters indicate significant differences between samples of the same concentration (P<0.05).

[0029] Figure 7 The photo shows the sword bean seeds used in the example, purchased from Jilin Mengmengda Trading Co., Ltd., product batch number YC8716. Detailed Implementation

[0030] To make the purpose and content of this invention clearer, the applicant will now provide a clear and complete description of the technical solution of this invention in conjunction with specific embodiments.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0032] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0033] Example 1: A method for extracting polysaccharides from sword bean, the specific steps of which are as follows:

[0034] (1) Water extraction process flow

[0035] Select dry, smooth-skinned sword bean seeds that are free of wormholes and mold (e.g.) Figure 7(As shown), crush, pass through a 60-mesh sieve, take 20g of the sieved soybean powder, add 95% ethanol at a ratio of 1g:10mL (95% is a volume fraction, the same below, not repeated), shake on a shaker at room temperature (25℃, the same below) (180rpm, 6h); centrifuge the sample (6000rpm, 10min), collect the precipitate, and dry at 70℃; add distilled water at a ratio of 1g:20mL, extract at 95℃ for 6h, cool and centrifuge (6000rpm, 10min), collect the supernatant; add an equal volume of trichloroacetic acid (3w / v%, where w / v=g / mL, the same below, not repeated), mix well, let stand overnight at 4℃ (the overnight time in this application refers to 12h), centrifuge (8000rpm, 10min), collect the supernatant; add an equal volume of anhydrous ethanol, let stand overnight at 4℃, centrifuge (8000rpm, 10min), collect the precipitate, and freeze-dry to obtain the polysaccharide CGWP.

[0036] (2) Extraction process of eutectic solvent

[0037] (2-1) Preparation of eutectic solvent

[0038] Weigh choline chloride and urea separately at a molar ratio of 1:4 and add them to a blue-capped reagent bottle. Add deionized water to the bottle (the water content of the mixture after addition is 40 wt%). Then place the reagent bottle on a magnetic stirrer and heat and stir until the solution becomes a homogeneous and transparent liquid, and no crystals precipitate after cooling. The desired eutectic solvent is obtained and stored at 4°C for later use.

[0039] (2-2) Extraction of polysaccharides

[0040] Select dry, smooth-skinned sword bean seeds that are free of wormholes and mold (e.g.) Figure 7 (As shown), grind, pass through a 60-mesh sieve, take 20g of the sieved soybean flour, add 95% ethanol at a ratio of 1g:10mL, shake on a shaker at room temperature (180rpm, 6h); centrifuge the sample (6000rpm, 10min), collect the precipitate, and dry at 70℃; add a eutectic solvent at a ratio of 1g:20mL, extract at 95℃ for 2h, cool and centrifuge (8000rpm, 10min), collect the supernatant; add an equal volume of trichloroacetic acid (3w / v%), mix well, let stand overnight at 4℃, centrifuge (8000rpm, 10min), collect the supernatant; add an equal volume of anhydrous ethanol, let stand overnight at 4℃, centrifuge (8000rpm, 10min), collect the precipitate, and freeze-dry to obtain the polysaccharide CGDP.

[0041] (3) Alkali extraction process flow

[0042] Select dry, smooth-skinned sword bean seeds that are free of wormholes and mold (e.g.) Figure 7(As shown), pulverize, pass through a 60-mesh sieve, take 20g of the sieved soybean flour, add 95% ethanol at a ratio of 1g:10mL, shake on a shaker at room temperature (180rpm, 6h); centrifuge the sample (6000rpm, 10min), collect the precipitate, and dry at 70℃; add 0.5M NaOH solution at a ratio of 1g:20mL, extract at 95℃ for 2h, cool and centrifuge (8000rpm, 10min), collect the supernatant; adjust the pH of the collected supernatant to neutral (pH=7) with dilute hydrochloric acid, add an equal volume of trichloroacetic acid (3w / v%), mix well, let stand overnight at 4℃, centrifuge (8000rpm, 10min), collect the supernatant; add an equal volume of anhydrous ethanol, let stand overnight at 4℃, centrifuge (8000rpm, 10min), collect the precipitate, and freeze-dry to obtain the polysaccharide CGAP.

[0043] Experimental results:

[0044] 1. Yield and composition of three polysaccharides

[0045] Table 1 shows that the yields of the three polysaccharides were (3.76±0.36)%, (8.78±0.44)%, and (10.59±0.41)%, respectively. The total sugar content of CGAP was (39.28±2.70)%, significantly higher than that of CGDP and CGWP (P<0.05). The uronic acid content of the three polysaccharides differed significantly (P<0.05), with CGDP containing the highest uronic acid content. Meanwhile, the protein content was low in all three polysaccharides, indicating that the trichloroacetic acid method for protein removal was more effective in the polysaccharide extraction process.

[0046] Table 1. Yield and chemical composition of three polysaccharides

[0047]

[0048] Note: a represents the same indicator as b and c, and the differences between different polysaccharides are significant (P<0.05).

[0049] Note: In this invention, the polysaccharide yield refers to the percentage of polysaccharide mass to the mass of sieved sword bean seeds.

[0050] 2. Comparison of the three polysaccharide structures

[0051] Depend on Figure 1 As shown in A, the molecular weight distribution of the three canavalia polysaccharides is uneven and spans a wide range. CGAP is predominantly composed of a 1.689 kDa component, CGDP is predominantly composed of a 16.661 kDa component, and CGWP is predominantly composed of a 588.387 kDa component. The monosaccharide composition of the three canavalia polysaccharides is as follows: Figure 1As shown in Figure B, CGAP is composed of rhamnose, galacturonic acid, glucose, galactose, and arabinose, with a molar ratio of 0.097:0.421:84.076:6.528:8.879 for each monosaccharide; CGDP is composed of rhamnose, galacturonic acid, glucose, galactose, and arabinose, with a molar ratio of 2.290:1.053:88.751:2.033:5.873 for each monosaccharide; and CGWP is composed of galacturonic acid, glucose, and galactose, with a molar ratio of 0.245:99.570:0.185 for each monosaccharide. The results indicate that both the alkaline-extracted and eutectic solvent-extracted canavaliabe polysaccharides contain monosaccharide components not found in traditional water-extracted polysaccharides: rhamnose and arabinose.

[0052] Infrared spectra of three types of sword bean polysaccharides, such as Figure 1 As shown in C, the three types of sword bean polysaccharides were at 3405.19 cm⁻¹. -1 3435.08cm -1 3429.78cm -1 There is an absorption peak at 2931.27 cm⁻¹, which is the stretching vibration absorption peak of -OH and is a characteristic peak of carbohydrates. -1 2931.75cm -1 2935.61cm -1 There is an absorption peak at [cm⁻¹], which is likely due to the -CH stretching vibration. Most carbonyl absorption is concentrated in the 1900–1650 cm⁻¹ range. -1 This characteristic peak, usually the strongest or second strongest peak in the spectrum, is caused by the stretching vibration of the C=O functional group. All three types of canavalia polysaccharides contain this characteristic peak. It is found in the 1200–1000 cm⁻¹ range. -1 The absorption peak at 900–800 cm⁻¹ is likely due to the OH- angular vibration. -1 The absorption peak at 576.13 cm⁻¹ may be due to the CH-trans-angle vibration of the differential isomerization at the β-end of the pyran ring and the CH-trans-angle vibration at the α-end of the pyran ring. -1 583.12cm -1 577.58cm -1 The area near the peaks shows characteristic absorption peaks of α-glycosidic bonds, indicating that the three canavalia polysaccharides are acidic polysaccharides with both α- and β-configurations. Infrared spectral analysis shows that the three polysaccharides conform to the characteristics of polysaccharide molecular structures.

[0053] Figure 2 At magnifications of 200×, 500×, 1000×, 2000×, and 5000×, SEM images clearly showed changes in the surface microstructure of polysaccharides. Among these, CGAP extracted by the alkaline method and CGWP extracted by traditional water extraction had relatively loose surfaces, appearing as irregular lumps. In contrast, CGDP obtained by eutectic solvent extraction was generally stacked and aggregated, with a relatively compact surface and irregular protrusions.

[0054] 3. Applications of the three polysaccharides

[0055] like Figure 3 As shown, the water-holding capacity of CGAP was (63.33±7.64)%, that of CGDP was (28.00±33.46)%, and that of CGWP was (77.33±1.15)%, with significant differences among the three (P<0.05). The water solubility of CGAP was (58.33±2.89)%, that of CGDP was (21.33±1.15)%, and that of CGWP was (28.67±4.16)%, with significant differences among the three (P<0.05). The fat-binding capacity of CGAP was (210.73±7.27)%, that of CGDP was (121.60±12.48)%, and that of CGWP was (321.47±1.75)%, with significant differences among the three (P<0.05).

[0056] The DPPH free radical scavenging capacity of three polysaccharides, ABTS + The results of the determination of free radical scavenging ability, hydroxyl radical scavenging ability, and iron ion reducing ability are shown in the figure. Figure 4 All three polysaccharides possess certain antioxidant activity, exhibiting a concentration-dependent effect within a specific concentration range. The DPPH free radical scavenging rates of the three polysaccharides are as follows: Figure 4 As shown in Figure A, when the polysaccharide concentration was 1.5 mg / mL, the DPPH free radical scavenging rate of CGAP was (86.38±0.81)%, which was significantly better than that of CGDP (82.16±0.81)% and CGWP (73.71±0.81)% (P<0.05), but lower than that of VC (99.10±1.56)%.

[0057] Three polysaccharides on ABTS + Free radical scavenging rate, such as Figure 4 As shown in Figure B, when the polysaccharide concentration is 4.0 mg / mL, the ABTS of CGAP + The free radical scavenging rate was (84.97±0.46)%, which was significantly better than CGDP (47.05±0.44)% and CGWP (36.98±0.22)% (P<0.05), but lower than the scavenging rate of VC (99.64±0.33)%.

[0058] The scavenging rates of three polysaccharides on hydroxyl radicals are as follows: Figure 4 As shown in C, when the polysaccharide concentration was 4.0 mg / mL, the hydroxyl radical scavenging rate of CGAP was (62.59±0.80)%, which was significantly better than that of CGDP (31.11±1.39)% and CGWP (14.63±0.85)% (P<0.05), but lower than that of VC (100.65±0.64)%.

[0059] The iron-reducing capacity of the three polysaccharides are as follows Figure 4 As shown in D, when the polysaccharide concentration was 4.0 mg / mL, the iron ion reducing power of CGAP was (283.80±2.64) μmol / L, which was significantly better than that of CGDP (100.63±3.81) μmol / L and CGWP (107.83±5.13) μmol / L (P<0.05).

[0060] In conclusion, the antioxidant capacity of CGAP extracted by alkaline method is significantly better than that of CGDP extracted by eutectic solvent and CGWP extracted by conventional water method.

[0061] Determination of the inhibition rate of three polysaccharides against α-amylase, as follows: Figure 5 As shown, all three polysaccharides exhibited some inhibitory activity against α-amylase, but their inhibitory capacity was weaker than that of acarbose. Within a concentration range of 0.5–4.0 mg / mL, the inhibition rate of α-amylase activity gradually increased. When the polysaccharide concentration was 4.0 mg / mL, the inhibition rate of α-amylase by CGAP was (59.07 ± 0.58)%, significantly better than that of CGDP (42.49 ± 0.15)% and CGWP (24.37 ± 1.32)% (P < 0.05), but lower than that of acarbose (70.22 ± 0.45)%.

[0062] The determination of the binding capacity of three polysaccharides to sodium glycoside deoxycholate and sodium tauroside deoxycholate is shown in [reference needed]. Figure 6 The bile salt binding capacity of the three canavalia polysaccharides showed a dose-dependent effect. The binding capacity of the three polysaccharides to sodium glycocholate was as follows: Figure 6 As shown in Figure A, when the polysaccharide concentration was 4 mg / mL, the sodium glycocholate binding capacity of CGAP was (67.59±1.19)%, which was significantly better than that of CGDP (60.72±1.19)% and CGWP (57.29±1.19)% (P<0.05).

[0063] The binding capacity of the three polysaccharides to sodium taurocholate is as follows: Figure 6 As shown in B, when the polysaccharide concentration was 4 mg / mL, the sodium taurocholate binding capacity of CGAP was (63.45±1.39)%, which was significantly better than that of CGDP (37.74±1.39)% and CGWP (44.97±2.78)% (P<0.05).

[0064] In conclusion, the in vitro hypoglycemic and hypolipidemic effects of CGAP extracted by alkaline method are superior to those of CGDP extracted by eutectic solvent and CGWP extracted by conventional water method.

[0065] The above tests are all conventional testing methods in this field. In this embodiment, except for the test of fat binding capacity, all other tests are performed in accordance with the methods listed in the embodiment of CN 118834303B.

[0066] The method for detecting fat-binding capacity is as follows:

[0067] Weigh 50 mg of CGAP, CGDP, and CGWP respectively, add 1 mL of vegetable oil (soybean oil in this example), vortex for 30 seconds every 5 minutes, repeat 6 times, centrifuge at 1600×g for 20 minutes, discard the supernatant, drain on filter paper for 30 minutes to ensure dryness, and then weigh the precipitate. The formula for calculating the fat binding capacity is:

[0068]

Claims

1. The application of a canavalia polysaccharide in the preparation of antioxidant, hypoglycemic and hypolipidemic drugs, wherein the canavalia polysaccharide is composed of rhamnose, galacturonic acid, glucose, galactose and arabinose, and the molar ratio of each monosaccharide is 0.097:0.421:84.076:6.528:8.879, and is named CGAP; The extraction method of the canavalia polysaccharide is as follows: (1) Select dried sword bean seeds, crush them, sieve them, add defatting solvent to remove impurities, centrifuge, collect the precipitate, and dry it; (2) The solid obtained in (1) was extracted by alkaline extraction to obtain canavalia polysaccharide: Add 0.5 M NaOH solution at a solid-liquid ratio of 1 g: 20 mL, extract at 95°C for 2 h, centrifuge to collect the supernatant, adjust the pH to neutral, add an equal volume of 3 w / % trichloroacetic acid, let stand overnight, centrifuge to collect the supernatant, add ethanol, let stand overnight, and freeze-dry the precipitate after centrifugation to obtain polysaccharide CGAP.

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