茶叶多糖及钙结合物的抗氧化作用和一级结构初探

【作者】 叶盛；

【导师】 汪东风； 黄继轸；

【作者基本信息】 安徽农业大学 ， 茶学， 2001， 硕士

【摘要】 茶叶多糖（TPS）是茶叶中主要有效化学成分之一。近十年来实验证明，TPS具有多种生理活性作用，如降血糖、降血压、降血脂、抗凝血、抗血栓、抗炎和增强免疫功能等。 本文从粗老茶中提取TPS，制备钙与茶叶多糖络合物（简称钙结合茶叶多糖，Ca-TPS），研究两者对超氧化物歧化酶（SOD）、过氧化物酶（POD）及过氧化氢酶（CAT）活性的影响，以及对超氧阴离子自由基（O₂^-）和羟自由基（OH）的清除作用。本文还对TPS中多糖与蛋白质的结合方式等一级结构进行了初步研究。 结果发现，在一定浓度范围内，TPS、Ca-TPS对三种抗氧化酶的活性均有不同程度的提高。TPS和Ca-TPS对三种抗氧化酶活性的影响趋势几乎一致，即在一定浓度范围内，随着糖浓度的增大，酶活性不断增高，但若糖浓度过大，酶活性反而下降。TPS及Ca-TPS对SOD活性最多提高了40％左右，而对CAT活性甚至最多增加了5倍多和3倍多，对POD活性则分别提高了26％和88％。 TPS及Ca-TPS对自由基的清除试验表明，TPS对自由基有较强的清除作用，TPS与钙结合后不影响对自由基的清除效果。TPS和Ca-TPS对O₂^-的最大清除率分别达到76.69％、83.44％，对OH的最大清除率分别为83.97％、98.08％。 以上实验结果充分说明TPS具有抗氧化活性，而结合钙基本不影响其活性。TPS及Ca-TPS的抗氧化机理表现在两个方面，一是间接作用，即作用于抗氧化酶、提高酶活性；二是直接作用，即TPS和Ca-TPS直接作用于自由基，发挥其对自由基的清除功能。 TPS₂和Ca-TPS₂经温和碱处理后，其光吸收值在240nm处没有明显的增大，初步说明TPS中多糖与蛋白质以N-糖苷键方式结合。根据TPS₂及Ca-TPS₂在碱水解前后氨基酸组成变化，进一步证明TPS中的糖肽键是N-糖苷键。 通过高碘酸氧化，发现TPS糖基中存在以二一2或二一4、l—6 位结合的可氧化方式，其他可氧化方式和不氧化方式（1一3）所占比例较小。 TPS。及Ca－TPS。的紫外及红外图谱表明，TPS结合钙后结构基本维持不变。更多还原

【Abstract】 Tea polysaccharide (TPS) is one of major chemical compositions of tea. In recent ten years, it has been proved that TPS has many biological properties, such as depressing blood-glucose, blood lipid and blood-pressure, anticoagulation, antithrombus, combating inflammation, and enhancing immunological function. In this paper, TPS was isolated from coarse tea, a calcium- polysaccharide complex (Ca-TPS) was prepared, and effect of TPS and Ca-TPS on superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), superoxide anion and hydroxyl radical were studied. The results show that the effect tendency of TPS and Ca-TPS on the antioxidant enzymes is uniform. In a scoop of limited concentration, the activities of antioxidant enzymes were enhanced with the increase of the concentration of TPS and Ca-TPS, and the enzyme activities would decrease if the concentrations of TPS and Ca-TPS were too high. Respectively, TPS could increase the activities of SOD, POD, and CAT by 42%, 25% and 533%, and Ca- TPS could increase by 39%, 88%, 3 39%. The results also show that TPS and Ca-TPS have scavenging effects on free radicals. The effect trend is similar. TPS and Ca- TPS could significantly scavenge superoxide anion (0.7) and hydroxyl radical (OH), while the capacity of scavenging decreased in higher concentration. The highest inhibition percentage of TPS and Ca-TPS on Q respectively were 77% and 83%, and the strongest inhibiton effects of TPS and Ca-TPS on OH were 84% and 98%, respectively. The experimental results proved that TPS had antioxidant activity, which would not be influenced whether TPS bound calcium or not. The antioxidant effects of TPS and Ca-TPS may be by two ways. One is indirect effect by applying to antioxidant enzymes, another is direct effect by scavenging free radicals. The primary structure of TPS2 and Ca-TPS2 were analysed. When TPS and Ca-TPS were treated with dilute alkali, the absorption at 240 nm didn’s increase. When sodium borohydride was added into the above reaction system, alanine and a -amtno-n-butyric acid did not increase, too. It is suggested that the polysaccharide chain is linked to peptide chain in TPS and Ca-TPS through N-glycosidic linkage. The structure of TPS2 was determined by periodate oxidation. The polysaccharide chain may be composed of 1→2,1→3,1→4,1→6 linked glycosyl group, in which the oxidable mode may be 1→2,1→4,1→6 linkage.更多还原