Tea is a typical processed beverage from the fresh leaves of Camellia sinensis [Camellia sinensis (L.) O. Kuntze] or Camellia assamica [Camellia sinensis var. assamica (Mast.) Kitamura] through different manufacturing techniques. The secondary metabolites of fresh tea leaves are mainly flavan‐3‐ols, phenolic acids, purine alkaloids, condensed tannins, hydrolysable tannins, saponins, flavonols, and their glycoside forms. During the processing, tea leaves go through several steps, such as withering, rolling, fermentation, postfermentation, and roasting (drying) to produce different types of tea. After processing, theaflavins, thearubigins, and flavan‐3‐ols derivatives emerge as the newly formed compounds with a corresponding decrease in concentrations of catechins. Each type of tea has its own critical process and presents unique chemical composition and flavor. The components among different teas also cause significant changes in their biological activities both in vitro and in vivo. In the present review, the progress of tea chemistry and the effects of individual unit operation on components were comprehensively described. The health benefits of tea were also reviewed based on the human epidemiological and clinical studies. Although there have been multiple studies about the tea chemistry and biological activities, most of existing results are related to tea polyphenols, especially (‐)‐epigallocatechin gallate. Other compounds, including the novel compounds, as well as isomers of amino acids and catechins, have not been explored in depth.

中文翻译：

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加工茶油茶的化学和生物活性：综述。

茶是从新鲜叶的典型处理的饮料茶树[茶树（L.）O. Kuntze]或山茶阿萨姆[茶树变种。阿萨米卡（（北村））通过不同的制造技术。新鲜茶叶的次生代谢产物主要是黄烷-3-醇，酚酸，嘌呤生物碱，缩合单宁，可水解单宁，皂角苷，黄酮醇及其糖苷形式。在加工过程中，茶叶经过多个步骤，例如枯萎，滚动，发酵，后发酵和烘焙（干燥），以生产不同类型的茶。加工后，茶黄素，茶红素和黄烷-3-醇衍生物以新形成的化合物形式出现，儿茶素的浓度相应降低。每种茶都有其自身的关键过程，并呈现出独特的化学成分和风味。不同茶中的成分在体外均会引起其生物学活性的显着变化和体内。在本综述中，全面描述了茶化学的进展以及各个单元操作对成分的影响。还根据人体流行病学和临床研究对茶的健康益处进行了评估。尽管对茶的化学和生物活性进行了多项研究，但大多数现有结果与茶多酚有关，尤其是（-）-表没食子儿茶素没食子酸酯。其他化合物，包括新型化合物，以及氨基酸和儿茶素的异构体，尚未得到深入研究。