Oxidative coupling of the pyrogallol B-ring with a galloyl group during enzymatic oxidation of epigallocatechin 3-O-gallate
Oxidative coupling of the pyrogallol B-ring with a galloyl group during enzymatic oxidation of epigallocatechin 3-O-gallate
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DOI：
10.1016/j.phytochem.2007.01.005
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发表时间：
2007-04-01
期刊：
影响因子：
3.8
通讯作者：
Kouno, Isao
中科院分区：
文献类型：
--
作者：
Li, Yan;Tanaka, Takashi;Kouno, Isao
为了阐明红茶发酵过程中儿茶素低聚物的形成机理，采用酶促氧化法将新鲜茶叶中含量最高的茶黄烷醇-表没食子儿茶素-3-O-没食子酸酯（epigallocatechin-3-O-gallate）氧化，并将其不稳定的醌类代谢产物用邻苯二胺转化为吩嗪衍生物。除了形成单体和二聚体衍生物，分离出四种三聚体衍生物，其结构通过应用光谱方法确定。这些衍生物在吩嗪部分的位置和联苯键的阻转异构性方面彼此不同。结果表明，没食子酰基基团与B-环的氧化偶联通过类似于用于生产茶氨酸的醌二聚化机制进行。(C)2007爱思唯尔有限公司保留所有权利。
In order to clarify the mechanism for formation of catechin oligomers during the fermentation stage of black tea manufacture, epigallocatechin-3-O-gallate, the most abundant tea flavanol in fresh tea leaves, was enzymatically oxidized and the resulting unstable quinone metabolites were converted to phenazine derivatives by treatment with o-phenylenediamine. In addition to formation of monomeric and dimeric derivatives, four trimeric derivatives were isolated whose structures were determined by application of spectroscopic methods. The derivatives differed from each other in the location of the phenazine moieties and in the atropisomerism of the biphenyl bond. The results suggested that oxidative coupling of the galloyl group with the B-ring proceeds by a quinone dimerization mechanism similar to that for production of theasinensins. (C) 2007 Elsevier Ltd. All rights reserved.