| Yam is the dried root of Dioscorea opposite Thunb., which belongs to Dioscorea, recorded in the previous books of the Chinese materia medica. It is recognized as one of top grade in the books of "Shen Nong’s herbal classic". There is many fuctions of Yam, such as tonifies the spleen, nourishes the stomach, promotes the secretion of saliva or body fluids, benefits the lung, and tonifies kidney and seminal fluids. Yam is widely used in clinical treatment and health care, which being used as food and drug. Overseas and domestic research show that Yam could reduce blood glucose, ad juste and decrease blood lipid, regulate immune system, intestines and stomach, tonify kidney. And it is also anti-aging, anti-oxidativet, anti-tumor and anti-mutation. The main active ingredient in it is the Yam polysaccharide. In this thesis, water soluble polysaccharide from Dioscorea opposita Foshou is to obtained by water extraction and of which a high proportion of neutral polysaccharide composition and structure as well as the in vitro antioxidant effects were studied.This thesis takes Fo Shou yam from Wuxue city of Hubei province as raw material. Firstly, the yam powder is degreased with the petroleum ether, the fat soluble components are removed. The oligosaccharides and ethanol soluble components are removed with reflux by ethanol, whose concentration is 80%. The ratio of material to water is 1 to 20. The extraction temperature is 60℃. The materials are extracted two times, and each extraction duration is 3 hours. The solution is combined and concentrated. The starch and protein of the concentrated solution are discarded and the color is removed. Precipitated with ethanol whose concentration is 80% for 10 hours, the fine yam polysaccharide is obtained after centrifugation, washing and drying.One neutral polysaccharide (named as YPn) and two kinds of acidic polysaccharide (named as YPa-I and YPa-II) are obtained by DEAE-Cellulose 52 column chromatography from refined Yam polysaccharide. One polysaccharide is isolated on Sephadex G-100 gel chromatography from neutral polysaccharides. The composition of monosaccharide are Mannose,Glucose,Galactose and Arabinose by derivatization and liquid chromatography, which the mole ratio is 1:22.94:0.47:0.38. The average molecular weight of neutral polysaccharide in Dioscorea opposita Foshou is 8.850×103 Dal, determined by multi angle laser light scattering detector (MALLS), refractive index detector (RI) and gel permeation chromatography. The scanning electron microscope shows that Dioscorea opposita Foshou has microstructure characteristics of neutral polysaccharides. The Congo red experiment shows that there are three strands of the helix structure in the neutral polysaccharide of Dioscorea opposita Foshou.Finally, the in vitro antioxidant activity of neutral polysaccharide in Dioscorea opposita Foshou is studied. The indexes are the reducing power of polysaccharide, DPPH radical scavenging, superoxide anion radical scavenging rate and hydroxyl radical scavenging rate. Different concentrations of neutral polysaccharide in Dioscorea opposita Foshou are compared by antioxidant activities. The results show that, there is antioxidant effect in the neutral polysaccharide of Dioscorea opposita Foshou. The clearance rates to the free radical are 35.6%,31.9% and 38.3%, respectively, at the concentration of 2 mg/ml. |
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