Li Yan, Tanaka Takashi, Kouno Isao
Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Phytochemistry. 2007 Apr;68(7):1081-8. doi: 10.1016/j.phytochem.2007.01.005. Epub 2007 Feb 22.
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.
为了阐明红茶制造发酵阶段儿茶素低聚物的形成机制，对鲜茶叶中含量最丰富的茶黄烷醇表没食子儿茶素 -3-O-没食子酸酯进行酶促氧化，并用邻苯二胺处理所得不稳定的醌类代谢产物，将其转化为吩嗪衍生物。除了形成单体和二聚体衍生物外，还分离出四种三聚体衍生物，其结构通过光谱方法确定。这些衍生物在吩嗪部分的位置和联苯键的阻转异构方面彼此不同。结果表明，没食子酰基与B环的氧化偶联通过类似于茶黄素生成的醌二聚化机制进行。
