木枣多糖ZJP2的初步结构特征及抗氧化活性研究

本文经水提、醇沉、脱蛋白和脱色等工艺提取木枣粗多糖(CP),经DEAE-52离子交换层析和Sephadex G-100柱层析纯化得到单一木枣多糖组分(ZJP2),并对CP和ZJP2进行初级结构分析及抗氧化活性测定。结果表明:CP和ZJP2的酯化度分别为38.40%和47.10%,糖含量分别为71.95和91.29%,糖醛酸含量分别为51.05%和58.27%,分子量分别为59.1 ku和13.7 ku;化学衍生化结合GC分析表明ZJP2由鼠李糖、阿拉伯糖、木糖、半乳糖和半乳糖醛酸5种单糖组成,其相对摩尔比为4.5:26.1:1.4:11.9:18.1;碘-碘化钾试验和红外光谱分析证明ZJP2具有典型的多糖类结构特征,并且可能有较多的侧链和分支;体外抗氧化分析表明ZJP2的DPPH自由基和羟自由基清除力均强于CP,在样品浓度为6.0 mg/m L时,ZJP2的DPPH自由基清除率为71.34%,羟自由基清除率为75.45%,清除力与样品浓度呈明显的量效关系。

Primary Structural Characteristics and Antioxidant Activity of the Polysaccharide ZJP2 from Zizyphus jujuba cv. Muzao

Crude polysaccharides (CPs) were extracted from Zizyphus jujuba cv. Muzao by water extraction, ethanol precipitation, deproteinization, and discoloration, and a purified polysaccharide fraction (ZJP2) was obtained by DEAE-52 ion-exchange chromatography and Sephadex G-100 column chromatography. The primary structure and antioxidant activity of both the CP and ZJP2 were analyzed and measured. The degree of esterification, total sugar content, uronic acid content, and molecular mass for CP were 38.40%, 71.95, 51.05%, and 59.1 kDa, respectively, and the corresponding values for ZJP2 were 47.10%, 91.29%, 58.27%, and 13.7 kDa, respectively. Chemical derivatization combined with gas chromatography analysis revealed that ZJP2 was composed of five monosaccharides; namely, rhamnose, arabinose, xylose, galactose, and galacturonic acid, with a molar ratio of 4.5:26.1:1.4:11.9:18.1. The iodine-potassium iodide experiment and infrared analysis verified that ZJP2 possessed a typical polysaccharide structure and probably had a large number of side-chains and branches. In the in vitro antioxidant study, the 2,2-diphenyl-1-picrylhydrazyl (DPPH?) and hydroxyl free-radical-scavenging rates of ZJP2 were 71.34% and 75.45%, respectively, at a sample concentration of 6.0 mg/mL, and were stronger than the rates of CP. Moreover, the scavenging abilities showed an apparent dose-response relationship with the sample concentration.