Isolation, Purification, Structural Elucidatuion And Biological Activity Of Polysaccharides From The Fruting Bodies Of Pleurotus Citrinopileatus

Yuhuangmo(Pleurotus citrinopileatus), also called "golden oyster mushroom", belongs to the family Basidiomycotina, Agaricales, Tricholomataceae, Pleurotus. This mushroom has recently become a popular delicacy in Asia, including China, Japan. Yuhuangmo not only taste good but also have become an important source of bioactive compounds beneficial to the treatment of various diseases, including hypolipidemic, antioxidant, hypoglycemic, immunostimulant,antitumor activities.In this study, the fruiting bodies of P. citrinopileatus were first degreased by95%ethanol, and then extracted with hot water to get the crude polysaccharide fraction, which was graded by ethanol precipitation into three groups, PCP30, PCP60and PCP80.Thjeir antioxidant activities were investigated in vitro systems including hydroxyl assay, superoxide radical assay, DPPH radical assay and reducing power. Among these three polysaccharides, PCP60showed highest reducing power and superoxide radical scavenging activity, and was significant in inhibitory effects on hydroxyl radical and DPPH radical. Based on this finding, PCP60was selected for further separation and purification.One water-soluble polysaccharide (PCP60W) was purified from the crude polysaccharide PCP60by chromatography on DEAE Sepharose Fast Flow and Sephadex G-300column. PCP60W (Mw=2.74×104Da), was further characterized using UV absorption at wavelengths of280nm and260nm, indicating no evidence of protein and nucleic acid presence in the PCP60W, and IR spectra showed PCP60W was a neutral polysaccharide. The structure of PCP60W after acetylation and methylation was investigated by both GC and GC-MS analyses, also combined with NMR spectroscopic methods (1HNMR,13C NMR;1H-1HCOSY, HMQC,TOCSY, NOESY and HMBC spectra). The results showed that PCP60W was predominantly composed of mannose and galactose, and3(4)-O-methyl-hexose. The methylated GC-MS analysis revealed the substituted positions were the end groups of the galactose,6-substituted mannose, and6-substituted galactose. Using NMR spectra analysis, the repeating unit of the polysaccharide was established as:â†'6)-[α-D-Galp]m-(1â†'6)-[α-3-O-Me-D-Galp]n-(1â†'...