Metabolism of dietary polyphenols and possible interactions with drugs.

Polyphenolic compounds are abundant in the human diet and gram quantities are ingested daily. The consumption of polyphenols is expected to rise due to the use of dietary supplements and public health initiatives promoting the consumption of more fruits and vegetables. It is known that these dietary polyphenols are extensively metabolized. Many of these compounds are therefore are expected to compete with other substrates of Phases I, II, III enzymes and transporters. In addition, some dietary polyphenols may induce certain drug metabolizing enzymes and affect the metabolism of important therapeutic agents. This review will discuss 1) the metabolism of dietary polyphenols using green tea polyphenols (catechins) as an example, 2) inhibition of drug metabolism by polyphenols, and 3) induction of drug metabolizing enzymes by dietary polyphenols. The potential consequences of these effects on drug metabolism will also be discussed.