A novel black tea pigment and two new oxidation products of epigallocatechin-3-O-gallate
A novel black tea pigment and two new oxidation products of epigallocatechin-3-O-gallate
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DOI：
10.1021/jf0512656
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发表时间：
2005-09-21
影响因子：
6.1
通讯作者：
Kouno, I
中科院分区：
文献类型：
--
作者：
Tanaka, T;Matsuo, Y;Kouno, I
茶叶发酵过程中，儿茶素醌类代谢产物发生氧化还原歧化反应，产生大量的副产物，给红茶多酚的分离纯化带来困难。在这项研究中，表没食子儿茶素-3-O-没食子酸酯的酶促氧化，然后在氧化混合物中的不稳定的醌代谢产物与2-巯基乙醇氢化，以减少不可分离的小歧化产物的生产。结果，分离出三种新的氧化产物，其中包括一种新的红茶色素，并根据化学和光谱数据确定了它们的结构。脱氢茶氨酸AQ是一种新的具有1，2-二酮结构的红橙色色素，已被证实存在于商品红茶中。此外，一个新的醌二聚体与一个复杂的笼状结构和一个三聚体的表没食子儿茶素-3-O-没食子酸酯也被分离和他们的生产机制提出。这种三聚体的存在表明没食子酰醌参与红茶中微量多酚的产生。
During tea fermentation, oxidation-reduction dismutation of a number of quinone metabolites of tea catechins yields numerous minor products, which make it difficult to separate and purify black tea polyphenols. In this study, epigallocatechin-3-O-gallate was enzymatically oxidized and then the unstable quinone metabolites in the oxidation mixture were hydrogenated with 2-mercaptoethanol to reduce production of inseparable minor dismutation products. As a result, three new oxidation products including a new black tea pigment were isolated, and their structures were determined based on chemical and spectroscopic data. Dehydrotheasinensin AQ is a new reddish-orange pigment with a 1,2-diketone structure, and its presence in commercial black tea was confirmed. In addition, a new quinone dimer with a complex caged structure and a trimer of epigallocatechin-3-O-gallate were also isolated and their production mechanisms are proposed. The presence of this trimer suggested participation of galloyl quinones in production of minor polyphenols in black tea.