Exploration of pro-oxidant and antioxidant activities of the flavonoid myricetin

Abstract

Objectives: Flavonoids are ubiquitous phenolic plant metabolites. Many of them are well known for their proand antioxidant properties. Myricetin has been reported to be either a potent antioxidant or a pro-oxidant depending on the conditions. The reaction conditions for the pro- and antioxidant activities were therefore investigated using variations of the deoxyribose degradation assay systems. Methods: The deoxyribose degradation assay systems were conducted as follows; H 2O 2/Fe III/ascorbic acid, H 2O 2/Fe III, Fe III/ascorbic acid, and Fe III. Each system was carried out in two variants, FeCl 3 (iron ions added as FeCl 3) and FeEDTA (iron added in complex with ethylenediaminetetraacetic acid). Results: When ascorbic acid was present, myricetin showed antioxidant properties, especially when it occurred in complex with iron. In ascorbic acid-free systems, pro-oxidant activities prevailed, which where enhanced if iron was in complex with EDTA. Discussion: Myricetin's antioxidant activity depends on both the reactive oxygen species (ROS) scavenging and iron ions chelation properties. The pro-oxidative properties are caused by reduction of molecular oxygen to ROS and iron(III) to iron(II). Myricetin is able to substitute for ascorbic acid albeit less efficiently. © W.S. Maney & Son Ltd 2011.