Effects of flavonoids on the metabolism of xenobiotics.

Flavonoids represent a large class of naturally occurring plant constituents that are consumed in substantial amounts by experimental animals and by human beings. The ability of flavonoids to activate or inhibit the principal enzyme system involved in the metabolism of lipophilic xenobiotics, including drugs, carcinogens, insecticides and other environmental pollutants, or to induce the synthesis of this enzyme system may have significant pharmacological and toxicological importance. The significant body of literature which illustrates that flavonoids can modulate the tumorigenic activity of polycyclic hydrocarbons and other chemical carcinogens has been reviewed recently (Slaga, Di Giovanni 1984; Wiebel 1980), but further elucidation of mechanisms of action are needed. Possible effects of flavonoids on the metabolism of lipophilic normal body constituents such as steroids and bile acids should be considered, and additional research is needed to determine the extent to which dietary flavonoids can influence the in vivo metabolism of xenobiotics.