title: Green tea flavan-3-ols: colonic degradation and urinary excretion of catabolites by humans.
abstract: Following the ingestion of green tea, substantial quantities of flavan-3-ols pass from the small to the large intestine (Stalmach et al. Mol. Nutr. Food Res. 2009, 53, S44-S53; Mol. Nutr. Food Res. 2009, doi: 10.1002/mnfr.200900194). To investigate the fate of the flavan-3-ols entering the large intestine, where they are subjected to the action of the colonic microflora, (-)-epicatechin, (-)-epigallocatechin, and (-)-epigallocatechin-3-O-gallate were incubated in vitro with fecal slurries and the production of phenolic acid catabolites was determined by GC-MS. In addition, urinary excretion of phenolic catabolites was investigated over a 24 h period after ingestion of either green tea or water by healthy volunteers with a functioning colon. The green tea was also fed to ileostomists, and 0-24 h urinary excretion of phenolic acid catabolites was monitored. Pathways are proposed for the degradation of green tea flavan-3-ols in the colon and further catabolism of phenolic compounds passing into the circulatory system from the large intestine, prior to urinary excretion in quantities corresponding to ca. 40% of intake compared with ca. 8% absorption of flavan-3-ol methyl, glucuronide, and sulfate metabolites in the small intestine. The data obtained point to the importance of the colonic microflora in the overall bioavailability and potential bioactivity of dietary flavonoids.
authors.affiliation: Plant Products and Human Nutrition Group, Graham Kerr Building, Division of Ecology and Evolutionary Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
authors.forename: Suri
authors.initials: S
authors.lastname: Roowi
authors.forename: Angelique
authors.initials: A
authors.lastname: Stalmach
authors.forename: William
authors.initials: W
authors.lastname: Mullen
authors.forename: Michael E J
authors.initials: ME
authors.lastname: Lean
authors.forename: Christine A
authors.initials: CA
authors.lastname: Edwards
authors.forename: Alan
authors.initials: A
authors.lastname: Crozier
mesh_terms: D000293:Adolescent; D000328:Adult; D002392:Catechin / Q000737:chemistry / Q000378:metabolism; D003106:Colon / Q000737:chemistry / Q000378:metabolism*; D005243:Feces / Q000737:chemistry / Q000382:microbiology; D005260:Female; D005419:Flavonoids / Q000737:chemistry / Q000493:pharmacokinetics* / Q000652:urine; D006801:Humans; D062385:Hydroxybenzoates / Q000032:analysis / Q000378:metabolism; D008297:Male; D013662:Tea / Q000737:chemistry* / Q000378:metabolism; D014551:Urinary Tract / Q000737:chemistry / Q000378:metabolism*; D055815:Young Adult
chemical_list: D005419:Flavonoids; D062385:Hydroxybenzoates; D013662:Tea; C404987:flavan-3-ol; D002392:Catechin; C017616:phenolic acid