表没食子儿茶素没食子酸酯(EGCG)自然氧化产物的分析

Analysis of Epigallocatechin Gallate Normal Oxidation Products

【目的】茶多酚是茶叶中最重要的活性物质,而儿茶素含量占茶多酚总量70%以上。EGCG是儿茶素中最主要的活性物质,具有多种生物学活性,但其稳定性较差,在自然条件下容易发生氧化。目前,对其氧化产物的化学结构没有详细的报道。【方法】本研究使用ESI-MS、NMR等方法,鉴定EGCG的自然氧化产物,并检测不同反应条件(如时间、温度、pH值)下,EGCG主要自然氧化产物的变化规律。【结果】鉴定得到了2个主要的EGCG自然氧化产物:C-4位与C-8″连接的EGCG二聚化合物1;B-B″环间氧化的化合物2。【结论】确定了当自然氧化条件分别为氧化时间2 h、反应温度20℃、反应pH值8.0时,化合物2的生成占主导,且产率最高,可达到27~30μg/mL。

[ Objective ] The most important active substances in tea were tea polyphenols, more than 70 % of them were composed by cate-chins. EGCG was the majorbioactive compound in the catechins and had many biological activities. But its stability was poor and it wasprone to oxidation under the normal conditions. At present,there was no detailed reports about the EGCG oxidation products＇ chemical struc-tures. [ Method] We used ESI-MS, NMR methods to identify the EGCG natural oxidation products and study the changes of EGCG major nor-mal oxidation products＇ productivity in different reaction conditions （ such as time, temperature, pH value）. [ Result ] Two major EGCG nor-mal oxidative products were identified, EGCG dimerization compoundl that connected with C-4 and C-8 . Compound 2 which was oxidatedbetween B-B＂ ring. [ Conclusion ] We confirmed that the natural oxidation conditions were oxidation time 2 h, reaction temperature 20 %, pHvalue 8.0. The production of compound 2 was dominant, and had the highest yield, could reach 27 - 30 μg/mL.