Browning of Epicatechin (EC) and Epigallocatechin (EGC) by Auto-Oxidation

文献类型： 外文期刊

第一作者： Tan, Junfeng

作者： Tan, Junfeng;Lin, Zhi;Tan, Junfeng;de Bruijn, Wouter J. C.;van Zadelhoff, Annemiek;Vincken, Jean-Paul

作者机构：

关键词： tea; catechins; nonenzymatic; oxidation; discoloration

期刊名称：JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY （ 影响因子：5.279； 五年影响因子：5.269 ）

ISSN： 0021-8561

年卷期： 2020 年 68 卷 47 期

页码：

收录情况： SCI

摘要： Green tea catechins are well known for their health benefits. However, these compounds can easily be oxidized, resulting in brown color formation, even in the absence of active oxidative enzymes. Browning of catechin-rich beverages, such as green tea, during their shelf life is undesired. The mechanisms of auto-oxidation of catechins and the brown products formed are still largely unknown. Therefore, we studied auto-oxidative browning of epicatechin (EC) and epigallocatechin (EGC) in model systems. Products of EC and EGC auto-oxidation were analyzed by reversed-phase ultra-high-performance liquid chromatography with photodiode array detection coupled to mass spectrometry (RP-UHPLC-PDA-MS). In the EC model system, 11 delta-type dehydrodicatechins (DhC(2)s) and 18 delta-type dehydrotricatechins (DhC(3)s) that were related to browning could be tentatively identified by their MS2 signature fragments. In the EGC model system, auto-oxidation led to the formation of 13 dihydro-indenecarboxylic acid derivatives and 2 theaflagallins that were related to browning. Based on the products formed, we propose mechanisms for the auto-oxidative browning of EC and EGC. Furthermore, our results indicate that dimers and oligomers that possess a combination of an extended conjugated system, fused rings, and carbonyl groups are responsible for the brown color formation in the absence of oxidative enzymes.

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