Biotransformation of tea polyphenols by gut microbiota

Tea is one of the most widely consumed beverages worldwide and has received increasing attention from researchers and food industries for various reasons mainly related to its health benefits. Polyphenols, such as catechins for green tea and theaflavins and thearubigins for black tea, are considered to be the main active components of tea. Recently, there is increasing awareness that the beneficial health effects of tea could be partly contributed by breakdown products of its polyphenols formed in the gut. Different studies have been carried out to understand the formation of microbially derived metabolites of tea components and their bioactivities. In general, tea catechins are typically transformed to specific hydroxyphenyl-γ-valerolactones, which could be further metabolized to smaller phenolic acids by gut flora. This review summarizes the current knowledge on the metabolism of major tea components by gut microbiota and the bioactivities of their metabolites.