Recent studies on the bioavailability of dietary (poly)phenolics

Abstract

HPLC-tandem mass spectrometry is now is now used widely as an the analytical tool in studies on the bioavailability of dietary (poly)phenolics. Recent information on the absorption, disposition, metabolism and excretion of hydroxycinnamates, ellagitannins and various flavonoids that has been obtained in acute human feeding studies with teas, coffee, berries and fruit juices will be summarised. Typically, aglycones released by the action of cytosolic b-glucosidases or lactase phlorizen hydrolase in the small intestine appear in the circulatory system as glucuronide, sulfate and methyl metabolites 1–2h after ingestion. Studies with ileostomists in which ileal fluid collected after ingestion was analysed indicate that substantial amounts of dietary (poly)phenols pass from the small to the large intestine where as a result of the action of the colonic microflora, a diversity of phenolic catabolites are produced. Evidence indicates that these catabolites are absorbed into the circulatory system and can be subjected to some degree of phase II metabolism before excretion in urine in substantial amounts. Of particular interest in this context are valerolactones, derived from flavan-3-ol monomers found in especially high concentrations in green tea and cocoa-based products, and urolithins which are produced in the colon from ellagitannins found in pomegranates and several berries. The potential bioactivity of colonic catabolites will be discussed.