Green tea flavan-3-ols: colonic degradation and urinary excretion of catabolites by humans (original) (raw)

Roowi, S., Stalmach, A., Mullen, W., Lean, M., Edwards, C.A. and Crozier, A.(2010) Green tea flavan-3-ols: colonic degradation and urinary excretion of catabolites by humans.Journal of Agricultural and Food Chemistry, 58(2), pp. 1296-1304. (doi: 10.1021/jf9032975)

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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.

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