EGCG与EC酶促氧化产物及其形成途径分析  

Enzymatic Oxidation Products of EGCG and EC and Their Formation Routes

作　　者：施莉婷 江和源[1] 张建勇[1] 王伟伟[1] 苏威[1,2] SHI Liting;JIANG Heyuan;ZHANG Jianyong;WANG Weiwei;SU Wei(Tea Research Institute,Key Laboratory of Tea Plants Biology and Resources Utilization,Ministry of Agriculture,Key Laboratory of Tea Processing Engineering of Zhejiang Province,Chinese Academy of Agricultural Sciences,Hangzhou 310008,China;Graduate School of Chinese Academy of Agricultural Sciences,Beijing 100081,China)

机构地区：[1]中国农业科学院茶叶研究所,农业部茶树生物学与资源利用重点实验室,浙江省茶叶加工工程重点实验室,浙江杭州310008 [2]中国农业科学院研究生院,北京100081

出　　处：《食品科学》2018年第22期1-7,共7页Food Science

基　　金：国家自然科学基金面上项目(31670692);公益性行业(农业)科研专项(201503142-11);中国农业科学院科技创新工程项目(CAAS-ASTIP-2017-TRICAAS)。

摘　　要：选择不同的表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)和表儿茶素(epicatechin,EC)底物组合反应,通过酶促氧化过程得到脱氢聚酯型儿茶素A(dehydrotheasinensin A,DTSA)和茶黄素-3-没食子酸酯(theaflavin-3-gallate,TF-3-G),探究EGCG的多条主要氧化反应途径,并探讨歧化途径与苯骈化途径的竞争机制。结果表明:EGCG溶液加入多酚氧化酶液催化反应后会形成DTSA、没食子酸等产物;在反应液中添加EC后,会形成TF-3-G。添加EC后,EGCG的总消耗率最终提高了3.86%～4.95%;反应前期DTSA的形成率差异不显著,后期DTSA含量在EGCG+EC体系中较单一体系有所降低,差异最大时可达10.84%;添加5 mmol/L EC体系中,TF-3-G的形成量显著高于添加2.5 mmol/L EC体系,其最大值增加了11.16%。EGCG+EC的酶促氧化反应过程,大致可分为4个阶段:反应初始阶段、二聚产物增长阶段、主要途径变更阶段以及二聚产物消耗阶段。初始阶段,体系中以歧化途径和苯骈化途径为主,两条途径所占比例高于85%;在二聚产物增长阶段,随EC的加入,苯骈化途径所占比例增加,而转化形成DTSA的EGCG所占比例明显降低,歧化途径逐渐减弱。随反应进行,体系中逐步出现多条氧化聚合途径,其他物质所占的比例逐渐增大。产物形成主要途径变更阶段,DTSA出现消耗,TF-3-G缓慢增加。整个过程,歧化途径一直是EGCG酶促氧化的主要反应途径。The aim of this study was to explore several major oxidation pathways of epigallocatechin gallate(EGCG)and the competition mechanism between the disproportionation pathway and the benzene pathway.Dehydrotheasinensin A(DTSA)and theaflavin-3-gallate(TF)were obtained by enzymatic oxidation of mixtures of different proportions of EGCG and epicatechin(EC).The results showed that several products including DTSA and GA were formed from the hydrolysis of EGCG by polyphenol oxidase(POD),while theaflavin-3-gallate(TF-3-G)was formed and the consumption rate of EGCG was increased by 3.86%–4.95%when epicatechin(EC)was added to the reaction solution.The formation rate of DTSA was not significantly changed during the early reaction stage but it was lower in EGCG+EC systems than in the single system during the later stage with a maximum difference of up to 10.84%.The formation of TF-3-G was significantly higher(up to 11.16%)at 5 mmol/L EC than at 2.5 mmol/L EC concentration.The enzymatic oxidation process of EGCG+EC could be divided into four stages:initial stage,dimer formation,change of the main pathways and dimer consumption.At the initial stage,the disproportionation and the benzene pathways were both dominant and their proportions were higher than 85%.At the second stage,the proportion of the benzene pathway was increased with the addition of EC while the proportion of EGCG transformed into DTSA was significantly reduced and the disproportionation pathway was weakened.As the reaction processed,a number of oxidation polymerization pathways gradually appeared in the system and the proportions of other substances were increased.At the third stage,DTSA began to be consumed and TF-3-G was slowly increased.The disproportionation pathway was dominant during the whole process of EGCG enzymatic oxidation.

关 键 词：脱氢聚酯型儿茶素A 茶黄素-3-没食子酸酯 歧化途径 苯骈化途径 

分 类 号：S571.1[农业科学—茶叶生产加工]