อTea is one of the most widely consumed beverages in the world. More than 300 different varieties of tea are produced from the leaves of Camellia sinensis by various manufacturing processes. The three major types of tea, green tea (nonfermented), oolong tea (semifermented), and black tea (fermented), differ in terms of their manufacture and chemical composition. Catechins are the most abundant polyphenols in green tea. The fermentation of tea leaves induces enzymatic oxidation and polymerization of catechins and leads to the formation of theasinensins in oolong tea and theaflavins and thearubigins in black tea