Isolation, Purification And Structural Features Of Polysaccharides From Rheum Palmatum L.

In this paper, Rheum polysaccharide, as traditional Chinese effective medicine, was qualitative studied. Firstly, the crude polysaccharide was obtained by traditional extraction technology, and three polysaccharides RP-1, RP-2, RP-3 were isolated by cellulose anion-exchange chromatography (DEAE-52) and purified on gel-filtration chromatography (Sephacryl S-200).The structures of RP-1, RP-2 and RP-3 were identified by chemical methods of composition analysis, methylation analysis, GC-MS, IR,1HNMR,13CNMR and IR. The information such as monasaccharide composition and molar ratio, the linking form between adjacent glycosyls and the position of branches and the configuration of glycosidic bond was obtained. The results showed that the molecular weight of RP-1, RP-2, RP-3 were 1.1×104, 2.0×104,6.9×104 respectively.The backbone of RP-1 was composed of (1,4)-linked glucose (Glc) with side chains attached to O-6 position. RP-2 and RP-3 were both acidic heteropolysaccharides. RP-2 contained rhamnose (Rha), arabinose (Ara), xylose (Xyl), mannose (Man), Glc and galactose (Gal) with a molar ratio of 0.5:1.0:1.3:1.4:12.4:3.8, mainly including (1,4)-linked Glc and other residues, such as terminated and (1,5)-linked Ara; (1,2)-linked Rha;(1,5)-linked Xyl; (1,4,6)-linked Man; (1,4)-linked Gal and (1,6)-linked Gal. RP-3 consisted of Rha, Ara, Xyl, Man, Glc with a molar ratio of 0.9:3.9:4.7:1.0:2.6, and the linkages of residues were as follows, terminated and (1,2)-linked Rha; terminated and (1,5)-linked Ara; terminated and (1,2,4)-linked Xyl;terminated and (1,4)-linked Man; (1,6)-and (1,4,6)-linked Glc. (1,5)-linked pentose and (1,6)-linked hexose were the main connection mode.