Dietary hydroxycinnamic acids, phase I and Phase II metabolism

grantor: University of TorontoPlant phenolics have been found to exert many beneficial health effects. Much is known about their beneficial health effects, but very little is known about their metabolism. The largest group of plant phenolics in the diet are the hydroxycinnamic acids (e.g., chlorogenic acid, caffeic acid, ferulic acid). Mass and UV spectral analyses have been used to show that caffeic, chlorogenic, and dihydrocaffeic acids were metabolized by phase I enzymes to form a reactive 'ortho'-quinone, which in turn formed various conjugates with glutathione. The 'ortho'-quinone formed also underwent further oxidation in the presence of H2O 2/O2 to form a hydroxylated product and possibly its ' para'-quinone oxidation product. The phase II conjugating enzyme catechol ' O'-methyltransferase also catalyzed the 3-'O'-methylation of caffeic, chlorogenic and dihydrocaffeic acids, while CYP 1A1/2 catalyzed an 'O'-demethylation of ferulic acid and dihydroferulic acid. Hepatocytes also catalyzed the reduction of caffeic acid to dihydrocaffeic acid.M.Sc