Flavonoids inhibiting drug metabolism

The antiulcer effect of some flavonoids might be related to their ability to increase the mucosal levels of these prostanoids. This is the case of solon, which inhibits the metabolizing enzyme 15-OH-PG-DH 15-hydroxy-pro staglandindehydrogenase [83]. The cytoprotective mechanism would be similar to the one of carbenoxolone, a drug frequently used in experimental models because of its ability to stimulate the mucosal defenses. 

In view of their reduction potential, flavonoids have also been shown to interact with enzymes either unspecifically or specifically and modify their activity through reduction of metals in the active center. Of particular interest, because of their role in inflammatory conditions, is the reductive inactivation of lipoxygenases, cyclo-oxygenases, myeloperoxidase, and xanthine oxidase. In view of prooxidant activity of the enzymes, their inhibition by polyphenols may be regarded as an indirect antioxidation action. The list of enzymatic activities inhibited by flavonoids and other polyphenols also include phospholipase A2, protein kinases, metalloproteinases, drug metabolism enzymes, and telomerase, as reviewed elsewhere (Frade et al, 2005). 

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