The dual clastogenic and anti-clastogenic properties of quercetin is dose dependent.

Iron is a ubiquitous constituent of cytochromes, oxygen-binding molecules and a variety of enzymes because of its property to transition from ferric (Fe3+) to ferrous (Fe2+) state, leading to change in the redox potential. However, the same property accounts for free radical injury. In order to overcome harmful effects of iron we investigated the possible protective effect of quercetin (QCT), a flavonoid with antioxidant property, against the oxidative DNA damage caused by iron sulfate in vivo. We show that QCT exerts efficient anticlastogenic action in the context of iron sulfate treatment up to a dose of 500 mg/kg while it induces DNA damage at higher doses. These findings show that QCT has a dual effect; at low doses it ameliorates the oxidative damage produced by iron, and it is genotoxic and cytotoxic at a higher dose.