薯蓣多糖的高碘酸氧化Smith降解及甲基化结果分析

Aanlysis of results in periodate oxidation,sequential Smith degradation and methylation of polysaccharide from Dioscorea Opposita Thunb

从薯蓣块茎中分离所得的两种多糖PF-Ⅲ和PF-Ⅳ分别含有15.6％和8.3％的乙酰基团。二者与脱乙酰化的PF-Ⅲ和PF-Ⅳ的高碘酸氧化和Smith降解结果对比,显示乙酰基的存在阻碍了高碘酸对(1→4)键的选择性氧化断裂,表明乙酰基的位置最可能在C-3位。PFⅢ-和PF-Ⅳ经过全甲基化的气相层析结果表明它们是一类以β-(1→4)为主要连接方式、β(1→3)为支链连接方式的甘露聚糖,二者(1→4)键与(1→3)键的比例分别为10:1和7.5:1。

According to the results of periodate oxidation, sequential Smith degrat-ion, PF-Ⅲ and PF-Ⅳ extracted from Dioscorea Opposita Thunb have 1→4 linkages in their main chains with 1—3 linkages in their side chains. Sequential Smith degration of the deaceatylated PF-Ⅲ and PF-Ⅳ suggested O-acetyl groups are attached in such a manner that they block periodate cleavage of the β(1—4) linked D-mannose residues, most probably at the C—3.G.C of the methy-O-acetly-produets from fully methylated mannan revealed the ratio of 1—4 and 1—3 is 10:1 in PF-Ⅲ, 7.5:1 in PF-Ⅳ.