Inhibitory effects of flavonoids on molybdenum hydroxylases activity

Molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase, are metalloflavoproteins that catalyze both oxidation and reduction of a broad range of drugs and other xenobiotics indicating the importance of these enzymes in drug oxidation, detoxification and activation. Both enzymes are also involved in some physiological processes and also the metabolism of some endogenous compounds which may indicate their important roles in in vivo conditions. Superoxide radical and hydrogen peroxide produced during molybdenum hydroxylases-catalyzed reactions may be relevant in various disease conditions. Therefore, the interference with the function of molybdenum hydroxylases could be of great importance. Flavonoids are a large group of polyphenolic compounds that are able to interfere with xanthine oxidase and aldehyde oxidase function. As flavonoids are consumed in high content in our daily life, their potential to interfere with molybdenum hydroxylases could be a serious concern for consumer safety. However, the subject has not received enough attention and has usually been overshadowed by that of cytochrome P450 as the most important drug metabolizing enzyme system. The present review focuses on the different aspects of flavonoids interaction with molybdenum hydroxylases considering literature published mainly in the last 2 decades. The review also provides insight into some research areas that may offer a great potential for future studies.