硫酸酯化茶多糖的制备及清除羟自由基活性的研究

Preparation and Hydroxyl Radical-Scavenging Activity of Sulfated Derivatives of Tea Polysaccharides

粗老绿茶用醇提、水提、醇沉,经弱碱性的大孔阴离子交换树脂D315柱层析分级,得到以中性糖为主的多糖样品NTPS和以酸性糖为主的多糖样品ATPS。采用吡啶磺酸法将NTPS和ATPS分别进行硫酸酯化修饰,合成相应的硫酸酯化多糖NTPS-S和ATPS-S,并用氯化钡-明胶比浊法测定硫酸基的含量,发现ATPS-S的取代度比NTPS-S低很多,表明以中性糖为主的茶多糖容易发生硫酸酯化。红外光谱扫描发现硫酸酯化茶多糖在1258cm-1、1146cm-1、832cm-1和617cm-1处有强的特征吸收峰。通过邻菲罗啉化学发光体系产生羟自由基(·OH)模型,对比研究茶多糖化学修饰前后体外清除羟自由基(·OH)的能力。实验表明,ATPS清除羟自由基能力明显强于NTPS,表明茶多糖的清除羟自由基活性可能与其含有的带负电荷的糖醛酸有关;茶多糖经硫酸酯化后,NTPS-S清除羟自由基能力比酯化前多糖NTPS明显增强,ATPS-S清除羟自由基能力比酯化前多糖ATPS稍减弱,表明茶多糖的清除羟自由基活性可能与多糖的糖基所带的负电荷的多少有关,而与所带负电荷的官能团种类关系不大。

Two kinds of tea polysaccharides NTPS which was mainly neutral polysaccharides and ATPS which was mainly acid polysaccharides were gotten by fractionation with anion exchange resin D315. NTPS-S and ATPS-S were gotten by the method of piperidine and chlorosulfonic acid and sulfuric group content was determined by BaC12-glutin turbimetry. Results showed that substitution degree of ATPS-S is much less than that of NTPS-S. Some strong characteristic absorption peaks of sulfated polysaccharides were 1258 cm^-1,1146 cm^-1, 832 cm^-1 and 617 cm^-1 by FTIR. 1,10-phenanthroline chemical radiation systems was used as a producing hydroxyl radical model and capacities of different fractions of sulfated polysaccharides for scavenging .OH were compared with those of the unsulfated. Results showed that hydroxyl radical-scavenging activity of ATPS was higher than that of NTPS, which was suggested that hydroxyl radical-scavenging activity of TPS might be related with its uronic acids content. After sulfonic esterification, radical-scavenging activity of NTPS improved greatly, but that of ATPS reduced. It was showed that hydroxyl radical-scavenging activity of polysaccharide was probably related with negatively-charged functional groups linked with polysaccharide, but it seemed that there was not a great relationship between the activity and kinds of those negatively-charged groups.