Flavonols and flavan-3-ols as modulators of xanthine oxidase and manganese superoxide dismutase activity
International Journal of Food Sciences and Nutrition
Experiments were performed to assess the dose-dependent effects of quercetin, kaempferol, (+) catechin, and (À) epicatechin on superoxide radical production through the modulation of manganese superoxide dismutase and xanthine oxidase activities. The experiments were carried out at flavanoid concentrations ranging from 1 mM to 100 mM. This investigation highlighted that flavonols induced opposite effects on superoxide radical production at different doses, i.e. pro-oxidant at the highest
... the highest concentration (100 mM) and anti-oxidant at the lowest concentration (1 mM). Similar behaviors were observed for xanthine oxidase with flavan-3ols. The diastereoisomer (the catechin) acted as a stronger radical scavenger than the epicatechin. However, flavan-3ols were less pro-oxidant than flavonols: in fact, the addition of the superoxide dismutase enzyme was able to cancel the flavan-3ols' pro-oxidant effect. This study also shows that the absence of the 4-carbonyl group conjugated with the 2-3 double bonds in the heterocyclic ring cancelled the pro-oxidant effect of flavan-3ols. The opposite dose-dependent effects of flavonols suggest that they may be used as either a pro-oxidant or antioxidant. Flavonols and flavan-3-ols as modulators of XO and MnSOD 7 Int J Food Sci Nutr Downloaded from informahealthcare.com by Universita Studi Palermo on 07/03/14 For personal use only.