Extraction,Purification And Anti-aging Activity Of Astragalus Polysaccharides

Astragalus membranaceus is a traditional Chinese medicine,which is rich in saponins,polysaccharides,flavonoids and other active substances.Polysaccharide is the main nutritional component and important active substance of Astragalus membranaceus.It has the effects of anti-oxidation,anti-inflammatory and enhancing immunity.In this study,Astragalus polysaccharides were isolated and extracted by semi-bionic extraction method,the crude polysaccharide was purified,and the composition,structure and biological activity of the purified polysaccharide were studied;Astragalus nutritional rice paste was developed.The main results are as follows:(1)Isolation,extraction and purification of Astragalus polysaccharides.The best isolation,extraction method and conditions of Astragalus polysaccharides were determined by single factor experiment and orthogonal experiment,and the semi-bionic method was selected to extract Astragalus polysaccharides.The extraction conditions were as follows:Astragalus dry powder and simulated gastric and intestinal fluid 1:10,extraction temperature 100 ℃,extraction time 60 min;Astragalus dry powder was extracted by simulated gastric fluid and intestinal fluid once respectively;and the yield of crude polysaccharide was 18.38 %.The protein of the crude polysaccharide was removed by Sevage method;the polysaccharide was dialyzed using a dialysis membrane of 7000 Da;the pigment was removed by macroporous resin;the polysaccharide was separated by DEAE-52 cellulose column chromatography,and the yield of the purified polysaccharide was 2.41 %.The saccharide content of the purified polysaccharide was 44.81% determined by phenol sulfuric acid method.(2)Structure and composition analysis of Astragalus polysaccharides.The monosaccharide and oligosaccharide composition of crude Astragalus polysaccharide was analyzed by GC-MS,which result showed there were maltose,d-arabinose,D-fructose and glucose,and the sum of the content was 4.22 mg/g.The monosaccharide composition,glycosidic bond type and polysaccharide structure of purified polysaccharide of Astragalus membranaceus were analyzed with UV absorption spectrum,FTIR,scanning electron microscope and HPLC.The results showed that the purified polysaccharide containedα-glycosidic bond and β-glycosidic bond,and there was uronic acid in the polysaccharides,which was the typical structure of polysaccharide.The glucose content of the purified polysaccharide after acid hydrolysis was 66.47 % determined by HPLC.(3)Invitro antioxidant and hypoglycemic activities of the purified polysaccharide.Taking the inhibitory rate of DPPH and iron ion reducing power(FRAP value)as the evaluation system of invitro antioxidant activity,the inhibitory rate of the purified polysaccharide against DPPH free radical was 32.2 % at the concentration of 0.1 mg/m L,which was about one-half that of BHT;The FRAP value was 0.54 at the concentration of0.8 mg/m L,which was about a quarter that of VC.Taking the inhibitory rate ofα-glucosidase as the evaluation system of invitro hypoglycemic activity.When the concentration of the purified polysaccharide was 30 μg/m L,its inhibition rate ofα-glucosidase was 33.23 %,which was about one-third of that of acarbose.(4)Anti-aging effect of the purified polysaccharide on D-galactose induced aging rats.The activities of SOD of model rats increased significantly with the low-dose purified polysaccharide treatment,and the content of MDA decreased significantly.The results of the high-dose treatment were consistent with the low-dose treatment.A total of 48 potential biomarkers with significant differences was found by analyzing the blood metabolites of each group rats.After analyzing the metabolic pathway of different metabolites,it was found that they were related to phenylalanine metabolism;biosynthesis of phenylalanine,tyrosine and tryptophan;nicotinic acid and nicotinamide metabolism;glycerol phospholipid metabolism;alanine,aspartate and glutamate metabolism.(5)Preparation of Astragalus nutritional rice paste.The optimum formula of Astragalus nutritional rice paste was determined by single factor and orthogonal experiment: taking the fried glutinous millet as 100 %,the addition amount of Astragalus was 15 %,Chinese yam 8 %,corn 8 %,xylitol 25 %,hawthorn 2 %,red jujube 2 %,Poria cocos 1 % and pueraria 1 %.The moisture content per 100 g of Astragalus rice paste was3.53 g,ash was 1.39 g,protein was 11.80 g,lipid was 3.68 g,calcium was 0.06 g,reducing sugar was 6.62 g and starch was 56.27 g.