Updated bioavailability and 48h excretive profile of flavan-3-ols from green tea in humans

Green tea is a popular beverage, prepared with infusion of unfermented dried leaves of Camellia sinensis, and is one of the most relevant sources of polyphenolic compounds in the human diet. This study reports green tea flavan-3-ol absorption, metabolism and complete urinary excretion up to 48h in 20 healthy volunteers. Urinary and tea samples were analysed by HPLC-MS/MS. Green tea contained monomeric flavan-3-ols and proanthocyanidins with a total polyphenol content of 728 µmol. A total of 41 metabolites were identified in urines, all present in conjugated forms. Among these, 6 colonic metabolites of green tea flavan-3-ols were identified for the first time after green tea consumption in humans. The average 48h bioavailability was close to 62%, major contributors being microbial metabolites. Some volunteer showed a 100% absorption/excretion, whereas some others were unable to efficiently absorb/excrete this class of flavonoids. This suggests that colonic ring fission metabolism could be relevant in the putative bioactivity of green tea polyphenols.