Effect of ascorbic acid and curcumin on quercetin-induced nuclear DNA damage, lipid peroxidation and protein degradation.

The effects of ascorbic acid and curcumin on quercetin-induced DNA damage, lipid peroxidation protein degradation were investigated in a model system of isolated rat-liver nuclei under aerobic conditions and in the presence of equimolar concentrations of iron or copper. Neither ascorbic acid nor curcumin inhibited quercetin-induced nuclear DNA damage, lipid peroxidation, or protein degradation. In fact, both antioxidants stimulated the oxidative damage to nuclear macromolecules. Ascorbic acid significantly increased the quercetin-induced nuclear DNA damage in the presence of either iron or copper. The increases in quercetin-induced nuclear lipid peroxidation and protein degradation by ascorbic acid were statistically significant only in the presence of iron or copper, respectively. Similarly, stimulation of quercetin-induced DNA damage and lipid peroxidation by curcumin was statistically significant only in the presence of copper or iron, respectively. Curcumin had no significant effect on nuclear protein degradation. These results demonstrate the pro-oxidant properties of ascorbic acid and curcumin, compounds that also demonstrate antioxidant and anticarcinogenic properties. Ascorbic acid and curcumin may therefore each have a dual role in carcinogenesis.