| Plant polysaccharides,a group of natural macromolecular polysaccharides,are widely found in plants and has extremely important biological activities.Astragalus membranaceus is a popular medicinal material in China,and Astragalus polysaccharide is one of the main active ingredients of Astragalus.Among the different sources of medicinal materials of Astragalus membranaceus,Astragalus membranaceus(Fisch.)Bge.var.monghulicus(Bge.)Hsiao(Astragali radix),which is produced from the northern part of Shanxi Province to the south-central part of Inner Mongolia Autonomous Region,has the highest polysaccharide content and the best curative effect,so it is highly praised.Numerous studies have shown that Astragalus polysaccharide can improve pathological changes such as intestinal mucosal damage and membrane permeability changes caused by ulcerative colitis,and effectively treat ulcerative colitis.In this study,Astragali radix was used as raw material,and the Astragali radix polysaccharides were extracted by ultrasonic assisted-water extraction method.The extraction process was optimized by response surface methodology and the optimal process parameters were obtained.After the separation and purification,the pure polysaccharide was obtained.Through a series of physical and chemical experiments and feature analysis,the physicochemical properties and structural characteristics of the Astragali radix polysaccharide were discussed.The partial activity of Astragali radix polysaccharide was studied by comparing experimental indicators of animals.The main results are as follows:(1)Ultrasonic time,water bath time,ultrasonic power and ratio of material to liquid were selected.On the basis of single factor test,the extraction process was optimized by response surface method.The optimal process parameters were obtained by response surface methodology:ultrasonic time 46 min,ultrasonic power 414 W,water bath time 41 min,and solid-liquid ratio 1:23(g/mL).Under this condition,the crude polysaccharides extraction rate was(20.77±0.12)%.(2)After obtaining the crude Astragali radix polysaccharides by the optimal conditions,the protein was removed by papain-Sevage and then separated by a DEAE-52 cellulose column to collect the fraction of the largest eluting peak area.Further purification was carried out using a Sephadex G-100 column,and the elution curve showed a single symmetrical peak.The eluted peak fractions were collected,concentrated and lyophilized to get a relatively pure polysaccharide.(3)The physicochemical properties of the purified Astragali radix polysaccharide was determined.The results showed that Astragali radix polysaccharide was light yellow flocculent solid,soluble in water,and insoluble in organic solvents such as methanol,ethanol,acetone,chloroform and n-butanol.Purified Astragali radix polysaccharide,free of reducing sugar,starch and protein.High performance liquid chromatography analysis shows that the monosaccharide composition of Astragali radix polysaccharide is mannose,rhamnose,glucuronic acid,glucose,arabinose,the amount ratio of each monosaccharide substance is 5.97:1.05:1:8.41:24.15.The results of Fourier transform infrared spectroscopy indicated that the purified polysaccharides of Astragali radix met the typical structure of polysaccharides.(4)Mice with ulcerative colitis were induced with 5%Dextran Sulfute Sodium(DSS)aqueous solution and treated with different doses of Astragali radix polysaccharide.Experiments have shown that high-dose Astragali radix polysaccharide(0.7 mg/mL)can significantly reduce Disease Activity Index(DAI)score,restore colon length,improve and repair colon tissue damage in diseased mice;reduce Myeloperoxidase(MPO),Nitric Oxide Synthase(NOS)activity in colon tissue,Nitric Oxide(NO)and Malondialdehyde(MDA)levels,increase Superoxide Dismutase(SOD)activity in colon tissue of diseased mice;reduce the concentration of Interleukin 6(IL-6),Interleukin 1β(IL-1β),Tumor Necrosis Factor-a(TNF-a)and Diamine Oxidase(DAO),D-lactic acid(D-LA)levels in diseased mice serum.This proves that daily consumption of 0.7 mg/mL of Astragali radix polysaccharide solution for 7 consecutive days can effectively treat DSS-induced ulcerative colitis in mice. |
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