Bioavailability of coffee chlorogenic acids and green tea flavan-3-ols

This paper reviews recent human studies on the bioavailability of chlorogenic acids in coffee and green tea flavan-3-ols in which the identification of metabolites, catabolites and parent compounds in plasma, urine and ileal fluid was based on mass spectrometric methodology. Both the chlorogenic acids and the flavan-3-ols are absorbed in the small intestine and appear in the circulatory system predominantly as glucuronide, sulfate and methylated metabolites. Even when absorption occurs in the small intestine, feeding studies with ileostomists reveal that substantial amounts of the parent compounds and some of their metabolites appear in ileal fluid indicating that in volunteers with a functioning colon these compounds will pass to the large intestine where they are subjected to the action of the colonic microflora. A diversity of colonic-derived catabolites are absorbed into the bloodstream and pass through the body prior to excretion in urine. There is growing evidence that these compounds, which were little investigated until recently, are produced in quantity in the colon and form a key part of the bioavailability equation of flavonoids and related compounds that occur in fruits, vegetables and beverages. Recent evidence indicates that some colon-derived phenolic acids have in vitro anti-inflammatory activity.