榆耳水溶性多糖GIA的结构分析

用6%尿素从榆耳(Gloeostereuminsarnatum)子实体中提取出水溶性粗多糖,经乙醇分级及SeoharoseCL-6B制备柱收集得到组分GIA.经SephadexG-75、DEAE-阴离子交换纤维素和HPLC验证,GIA分子量及极性为均一组分.气相色谱(GC)分析表明,其单糖组成为Xyl,Gal和Glc.HPLC测得平均分子量为18000.经IR、GC、部分酸水解、高碘酸氧化、Smith降解、¹³CNMR、甲基化分析及其产物的GC-MS联机分析表明,GIA为少分支结构,主要由α型糖苷键构成,少部分由β型糖苷键构成;主体结构由Gal和Glc组成,其中主要为Gal1→6,还有Glc1→6;Gal1→6和Glc1→6在3-O处有分支;平均每10个己糖残基有2个分支;GIA的支链部分由Gal1→3和Glc1→3构成;末端残基为Xyl,Gal,Glc.

Structure Analysis of Water Soluable Polysaccharide GIA Obtained from the Fruiting Body of Gloeostereum insarnatum

The water soluble crude polysaccharide was exacted by 6% carbamide from the fruiting body of Gloeostereum insarnatum. After the precipitation in ethanol and the filitration with Sepharose CL-6B gel, the fraction of GIA was obtained.By means of Sephadex G-75, HPLC and DEAE-Sephadex A-25, it was proved to be homogeneous on molecular weight and polar as well. The structure of GIA was determined by several methods. GC analysis results indicate that GIA is composed of the monosaccharide of xylose, galactose and glucose. The molar weight is estimated to be 18 000 by means of HPLC. Through IR, GC, partial hydrolysis with acid, periodate oxidation, Smith degradation, methylation, GC-MS and 13C NMR analysis, the results indicate that GIA has a kind of lowly branched structure.The main chain is mainly made up of major (1→6) galactose and (1→6) glucose, minor (1→3) galactose and (1→3) glucose. Residues are substituted at 6-O.On average, there are 2 branches among (10 main) chain residues. The side chain is composed of (1→3) galactose and (1→3) glucose. The nonreduced end is composed of xylose, galactose and glucose.