红芪多糖HPS4-1A的化学结构特征研究及分子构象初步分析

Chemical structural features and primary molecular conformation of polysaccharide HPS4-1A from Hedysarum polybotrys

目的研究红芪多糖HPS4-1A的化学结构特征,并初步分析其构象。方法红芪经水提醇沉法提取、Sevage法脱蛋白、H2O2脱色素、Sephadex G-200色谱柱分离纯化得到均一的红芪多糖HPS4-1A。以GC法、高效液相凝胶色谱(HPGC)法、凝胶渗透色谱-多角度激光散射仪联用(GPC-MALLS)法、元素分析、苯酚硫酸法、Bradford法研究其理化性质;以GPC-MALLS法对其构象进行初步分析。采用甲基化、部分酸水解、以及NMR研究其连接方式、主链和支链结构及分支点状况。结果 HPS4-1A的绝对分子质量为7.386×104,相对分子质量6.68×105以上;由鼠李糖、阿拉伯糖、葡萄糖、半乳糖组成,其摩尔比为1∶2∶1∶2,主链骨架由1,5、1,3,5连接的α-L-呋喃阿拉伯糖和1,6、1,2,6连接的α-D-吡喃半乳糖组成,侧链分支点位于阿拉伯糖的3位与半乳糖的2位。侧链分支由1,4、1,4,6-α-D-吡喃葡萄糖,1,2、1,2,4-α-L-呋喃鼠李糖组成。主链末端连接主要是阿拉伯糖,并且连接在1,5连接的阿拉伯糖的5位。侧链末端连接主要是葡萄糖,还有少量的阿拉伯糖。结论 HPS4-1A为一种新的中性红芪杂多糖,其构象为无规线团状,并且相对分子质量分布呈单分散性。

Objective To study the chemical structural features and conformation of polysaccharide HPS4-1A from Hedysarum polybotrys. Methods A fraction of water-soluble neutral polysaccharide was obtained from H. polybotrys by aqueous extraction followed by precipitation with ethanol. The homogeneous polysaccharide named HPS4-1A was obtained after treated with Savage method and H2O2, and purified with Sephadex G-200 gel filtration chromatography. Then GC, HPGC, GPC-MALLS, element alanalyser, phenol sulfuric acid method, and Bradford method were used to study the physicochemical property of HPS4-1A; The conformation was primarily analyzed with GPC-MALLS method. The connection, main chain and branched-chain structures, and the condition of branching point were studied by methylation, partial acid hydrolysis, and NMR method. Results The absolute and relative molecular weights of HPS4-1A were 7.386 × 10^4 and above 6.68 × 10^5; HPS4-1A was a heteropolysaccharide and consisted of L-rhamnose, L-arabinose, D-glucose, and D-galactose （1 ： 2 ： 1 ： 2）. HPS4-1A proved to be a neutral sugar, with 1, 6- and 1, 2, 6-α-D-galactopyranosyl and 1, 5- and 1, 3, 5-α-L-arabinofuranosyl residues in backbone, and 1, 4- and 1, 4, 6-α-D-glucopyranosyl and l, 2- and 1, 2, 4-α-L-rhamnofuranosyl residues in branches. Arabinose mainly connected the end of backbone, and glucose and a small quantity of arabinose mainly connected the end of branches. Conclusion HPS4-1A is a new neutral heteropolysaccharide from H. polybotrys. HPS4-1A has a random coil state conformation with monodisperse mass distribution.