Isolation, Purification, Structure Analysis And Anti-cancer Activity Of The Polysaccharides From Dioscorea Bulbifera L.

Dioscorea bulbifera L. is dried tuber of Dioscoreaceae Dioscorea plant, It contains many active components, including saponins, terpenoids, flavonoids, phenolic acids and polysacchrides. The activities of antitumor and treatment of thyroid diseases have been studied and applicated in clinical. Polysaccharide is an important component of Dioscorea bulbifera L, but there is little study on it. In this paper, we reported the separation purification of Dioscorea bulbifera polysacchrides, also analyzed their properties, structural features and antitumor activity.The water-soluble polysaccharides of Dioscorea bulbifera (DBP) were extracted with hot water, precipitated by80%ethanol. Sugar composition analysis indicated that DBP contained Man:GalA:Glc:Gal:Ara in a molar ratio of1:8.63:8.74:19.10:1.15. DBP was separated on DEAE-Cellulose column to obtain one neutral fraction (DBPN) and three acidic fractions (DBPA-1, DBPA-2and DBPA-3). DBPN is composed of Glc and Gal, DBPA-1, DBPA-2and DBPA-3are a series of acidic polysaccharides. Among them, the yield of DBPA-2was higher, but the distribution of molecular weight range was very wide. So, DBPA-2was purified with different concentrations of ethanol (40%,60%,80%) to get DBPA-2a, DBPA-2b, DBPA-2c and supernatant DBPA-2s. Among them, DBPA-2b was further fractionated to homogeneous frations DBPA-2b-I and DBPA-2b-II, and DBPA-2s to DBPA-2s-I and DBPA-2s-II by Sepharose CL-6B. DBPA-3was separated on Sepharose CL-6B into two homogeneous frations DBPA-3-I and DBPA-3-II.Sugar composition analysis,FT-IR and13C NMR indicated that the four fractions DBPA-2a, DBPA-2b-II, DBPA-2c and DBPA-2s-II are HG pectin with different lengths of P-1,4glycosidic linkages Galactan side chain.MTT anticancer activity assays found that DBPA-2, DBPA-3and ester-DBPA-2inhibited HCT116tumor cell growth obviously, with a concentration dependence. The activities of DBPA-2a,b,c,s decreased, but the mixture of them recovered the activity again. Blood cells agglutination test found that the activity to inhibit blood cell agglutination related with the lengths and numbers of the side chain, the number of reducing end Gal and so on.