摘要
用脉冲辐解技术研究了儿茶素与羟自由基作用的动力学。结果表明：ＥＧＣＧ与ＥＣＧ与羟自由基反应后在３３０ｎｍ与４４０ｎｍ处分别生成羟基加合物与酚氧自由基峰，ＥＧＣ与ＥＣ则在３４０ｎｍ与５００ｎｍ处生成羟基加合物与酚氧自由基峰；羟基加合物在脉冲后０．９～１．５μｓ达峰值，酚氧自由基在脉冲后１０～１５μｓ达峰值；酚氧自由基是羟基加合物的分解产物；４种儿茶素与羟自由基反应的速率常数依次是：ＥＣ为９．０×１０９ｄｍ３ｍｏｌ－１ｓ－１，ＥＧＣ为９．６×１０９ｄｍ３ｍｏｌ－１ｓ－１，ＥＣＧ为１．２×１０９ｄｍ３ｍｏｌ－１ｓ－１，ＥＧＣＧ为１．６×１０９ｄｍ３ｍｏｌ－１ｓ－１，羟基越多，反应速率越大，没食子酰基是稳定酚氧自由基的重要结构因子。
Pulse radiolysis and transient absorption spectroscope were used to investigate the kinetics of the reaction betwen catechins and hydroxyl radicals. Maximum absorption occurred at 330nm,340nm,330nm and 340 nm for the adducts of hydroxyl with EGCG,EGC,ECG and EC,respectively. Maximum absorption occurred at 440nm,500 nm,440nm and 500nm for the phenoxyl radicals,corresponding the order of above catechins,respectively. The absorption of the adduct reached the maximum in 0.9-1.5μs, and that of the phenoxyl radicals in 10-15 μs after pulse radiolysis. Phenoxyl radicals were the products of the degradation of catechins-hydroxyl adducts. The reacting rate constants of the 4 catechins with the hydroxyl radicals were 9.0×10 9dm 3mol -1 s -1 for EC,9.6×10 9 for EGC,1.2×10 9 for ECG and 1.6×10 9 for EGCG. The more the hydroxyl groups the reacting system contained,the greater was the reacting rate constant. The gallate group was very important to the stability of the phenoxyl radicals of these compounds.
出处
《茶叶科学》
CAS
CSCD
1997年第S1期34-39,共6页
Journal of Tea Science
基金
中国科学院辐射化学开放研究实验室资助
浙江省自然科学基金
关键词
儿茶素
羟自由基
反应动力学
脉冲辐解
Catechins Hydroxyl radicals Reacting kinetics Pulse radiolysis
