Bioavailability and biotransformation of tea polyphenols

• Published in: Health Benefits of Green Tea pp. 52 - 64
• Main Authors: Yang, C. S, Lee MaoJung
• Format: Book Chapter
• Language: English
• Published: Wallingford, UK CABI 2017; CAB International
• Subjects: angiosperms; Camellia; Camellia sinensis; chemical composition; chemical constituents of plants; epicatechin; Ericales; eudicots; eukaryotes; gut flora; intestinal micro-organisms; intestinal microorganisms; micro-organisms; microorganisms; plant composition; plants; polyphenols; Spermatophyta; tea; Theaceae; theaflavine
• ISBN: 9781786392398; 1786392399
• DOI: 10.1079/9781786392398.0052

Tea, a popular beverage worldwide, has been reported to have many beneficial health effects. Most of these biological effects have been attributed to the tea polyphenols: (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin-3-gallate (ECG), and (-)-epicatechin (EC). Of these, EGCG is the most abundant and most biologically active constituent. Its biological activity is limited by its relatively low systemic bioavailability because of efflux mechanisms. In comparison to gallated catechins (EGCG and ECG), the bioavailability of EGC and EC are much higher. These catechins are mainly methylated, glucuronidated, and sulfated before elimination. The rather large molecular weight black tea polyphenols, theaflavins, and theasubigim, appear to have very low or no bioavailability, but this topic remains to be further investigated. On the other hand, the low molecular weight microbial metabolites in "dark tea" are expected to have good bioavailabilities. The unabsorbed green and black tea polyphenols can be degraded by microbes in the intestine and may affect health through modifying the intestinal microbiota. These subjects remain to be further studied.