Metabolism of quercitrin by human intestinal bacteria and its relation to some biological activities.

When quercitrin was anaerobically incubated with human intestinal bacteria, quercetin, 3,4-dihydroxyphenylacetic acid and 4-hydroxybenzoic acid were found as metabolites. The main metabolite was quercetin. The bacterium transforming quercitrin to quercetin was Fusobacterium K-60. However, Bacteroides JY-6, which produced alpha-L-rhamnosidase, did not transform quercitrin to quercetin. Among quercitrin and its metabolites, 3,4-dihydroxyphenylacetic acid and 4-hydroxylphenylacetic acid had more potent activity than quercitrin on in vitro anti-platelet aggregation activity, and quercetin and 3,4-dihydroxyphenylacetic acid showed more potent cytotoxicity against tumor cell lines than quercitrin and 4-hydroxylphenylacetic acid.