Extraction, Purification And Composition Analysis Of The Polysaccharides From Dioscorea Bulbifera L.

A water-soluble polysaccharide has been extracted from Dioscorea bulbifera L. After precipitation with ethanol, a crude polysaccharide DB was obtained. The fraction of DB1 has been isolated from DB after centrifugation to remove the impurity. The fraction DB2 has been obtained after treatment of DB1 with Sevage reagent to remove proteins. DB2 was further studied for its contents of total carbohydrate, uronic acid, protein and starch. The content of total carbohydrate was 86.3% as determined by phenol-sulfuric acid assay and 77.2% by anthrone method. The content of uronic acid was 33.9% as determinded by the m-hydroxydiphenyl assay. The content of proteins was 1.3% as determined by Bradford method and 14.4% by Folin's reaction. The content of starch was 46.5% as determined by iodine coloration method.The fraction DB2 was chromatographed on Sepharose CL-6B. The eluate was analysed by phenol-sulfuric acid assay and m-hydroxydiphenyl assay. Data showed that DB2 had a broad molecular weight distribution . Its main component was between 100-300 kDa. Suger comprositional analysis showed that DB2 contained 2.8% Man, 3.4% Rha, 1.4% GlcA, 36.3% GalA, 36.9% Glc, 18.4% Gal and 0.8% Ara.