title: Flavonols and flavan-3-ols as modulators of xanthine oxidase and manganese superoxide dismutase activity.
abstract: Experiments were performed to assess the dose-dependent effects of quercetin, kaempferol, (+) catechin, and (-) 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 µM to 100 µM. This investigation highlighted that flavonols induced opposite effects on superoxide radical production at different doses, i.e. pro-oxidant at the highest concentration (100 µM) and anti-oxidant at the lowest concentration (1 µM). 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.
authors: Unit of Physiology and Pharmacology, Department DIGISPO, University of Palermo , Italy and.
authors: Danila
authors: D
authors: Di Majo
authors: Maurizio
authors: M
authors: La Guardia
authors: Gaetano
authors: G
authors: Leto
authors: Marilena
authors: M
authors: Crescimanno
authors: Carla
authors: C
authors: Flandina
authors: Marco
authors: M
authors: Giammanco
mesh_terms: D005419:Flavonoids / Q000737:chemistry*; D044948:Flavonols / Q000737:chemistry*; D015394:Molecular Structure; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors* / Q000378:metabolism*
chemical_list: D005419:Flavonoids; D044948:Flavonols; C404987:flavan-3-ol; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase
keywords: Antioxidant; dose response; functional food; inhibitor; pro-oxidant; structure-activity relationship