Quercetin inhibits hydrogen peroxide-induced oxidation of the rat lens

Cataract results from oxidative damage to the lens. The mechanism involves disruption of the redox system, membrane damage, proteolysis, protein aggregation and a loss of lens transparency. Diet has a significant impact on cataract development, but the individual dietary components responsible for this effect are not known. We show that low micromolar concentrations of the naturally-occurring flavonoid, quercetin, inhibit cataractogenesis in a rat lens organ cultured model exposed to the endogenous oxidant hydrogen peroxide. Other phenolic antioxidants, (+)epicatechin and chlorogenic acid, are much less effective. Quercetin was active both when incubated in the culture medium together with hydrogen peroxide, and was also active when the lenses were pre-treated with quercetin prior to oxidative insult. Quercetin protected the lens from calcium and sodium influx, which are early events leading to lens opacity, and this implies that the non- selective cation channel is protected by this phenolic. It did not, however, protect against formation of oxidized glutathione resulting from H₂O₂ treatment. The results demonstrate that quercetin helps to maintain lens transparency after an oxidative insult. The lens organ culture/hydrogen peroxide (LOCH) model is also suitable for examining the effect of other dietary antioxidants.