导　　师： 戚向阳

学科专业： 083201

授予学位： 硕士

作　　者： ;

机构地区： 华中农业大学

摘　　要： 目前国内外对茶多酚及其各儿茶素单体的化学及生物活性的研究已十分系统深入，而对儿茶素氧化产物的研究却起步较晚。有关儿茶素的转化及形成的氧化产物的化学结构与生物活性的关系也很少有详细的研究报道。以往的观点认为，氧化会破坏儿茶素氧化产物的生物活性，但近年有研究表明，儿茶素氧化产物可能有比儿茶素更强的生物活性。为进一步深入研究酚类氧化产物，本文以儿茶素中活性最强的表没食子儿茶素没食子酸酯/(EGCG/)为代表，确定了其体外最佳氧化条件、氧化动力学模型，并对EGCG氧化产物的分离、纯化、鉴定及活性等进行了系列研究，主要结果如下： 1 EGCG体外最佳氧化条件的确定 通过单因素实验及响应面分析，考察了反应温度、氧化时间、反应体系pH值、氧化剂与EGCG质量比对EGCG氧化反应液抗·OH活性的影响，并以·OH抑制率为指标，确定EGCG体外最佳氧化条件为：温度25℃，氧化时间15min，反应体系pH 7.0，氧化剂与EGCG的质量比1.5∶1。在此条件下，氧化反应液的·OH抑制率最高，可达53.40％，且超过了EGCG对·OH的抑制率41.50％。即适度氧化时，EGCG氧化反应液的活性最强。 2 EGCG体外氧化动力学的研究 HPLC／MS分析表明，EGCG氧化反应液中主要存在3种氧化低聚物/(EOP/)，且均属于EGCG氧化二聚体。动力学的研究表明，在反应前期/(0-10min/)，EGCG氧化及EOP生成为二级动力学的反应机理。二者反应速率均随温度的升高及氧化剂所占质量比的增大而加快；在碱性条件下，二者反应速率较快。 从有利于EOP的形成及保持其稳定看来，EOP生成的最适条件为：温度25℃，pH 7.5，氧化剂与底物的质量比为1.5∶1，氧化时间15min，与以·OH抑制率为指标所确定的EGCG体外最佳氧化条件基本一致，说明EOP可能为EGCG氧化反应液中抗·OH的 Researches about the chemical and biological activities of tea polyphenol and tea catechins have been done systematically and deeply. But studies on tea catechins oxypolymers have been just carried out. Very few studies on the transformation of tea catechins to tea catechins oxypolymers and relations between the structure and functions of tea catechins oxypolymers have been found reported. Oxidation was regarded to have negative effect on the biological activities of tea catechins in the past, but some recent researches illustrated that tea catechins oxypolymers may have more significant activities than tea catechins. In order to further research the oxidation products of polyphenol, in this paper, /(-/)-epigallocatechin-3-O-gallate /(EGCG/) which is the most powerful catechin was oxidized chemically in vitro and we studied its optimum oxidation condition in vitro, dynamic model and discussed the seperation, purification, structure identification as well as biological activities of EGCG oxidation products. The main results were shown as follows: 1 Determination of the optimum oxidation conditon of EGCG in vitro Through the single-factor experiments and the analysis of response surface method, the influences of reaction temperature, time, pH value, the mass ratio of oxidant to EGCG on inhibiting·OH of EGCG oxidation mixture have been discussed. According to the inhibiting·OH activities, the optimum oxidation condition of EGCG in vitro was determined as follows: temperature 25℃, reaction time 15min, pH 7.0, the mass ratio of oxidant to EGCG 1.5: 1.·OH inhibiting activity could reach the highest /(53.40/%/) under this condition, which higher than that of EGCG /(41.50/%/). Those indicated that EGCG oxidation mixture could possess strong activity when EGCG was oxidized properly. 2 Research of the reaction dynamic of EGCG oxidation in vitro HPLC//MS analysis showed that it existed three EGCG oligomeric products /(EOP/) in EGCG oxidation mixture and EOP belonged to EGCG dimers. The research of react

关 键 词： 表没食子儿茶素没食子酸酯 化学氧化 反应动力学 分离 制备 结构鉴定 抗氧化活性 抑菌活性

领　　域： [化学工程]