Evaluation of the protective effects of quercetin and gallic acid against oxidative toxicity in rat's kidney and HEK-293 cells

Quercetin and gallic acid are phytochemicals with interesting pharmacological properties. We herein investigated the protective effect of quercetin (QUE) in comparison with gallic acid (GAL) against exogenouslyinduced oxidative damage in rats' kidney and human embryonic kidney (HEK-293) cell lines. Adult Wistar rats were treated with QUE and GAL (50 mg/kg) separately or in combination with di-n-butylphthalate (DnBP) for 14 days; and HEK-293 cells were treated with different concentrations of GAL (25-294 mu M) or QUE (2-17 mu M or 28-165.43 mu M) singly or in combination with H2O2 (200 mu M). After treatment, the kidney and cell extracts were processed for biochemical analysis and histopathology. We found that GAL but not QUE prevented DnBP-induced increase in lipid peroxidation (2.603 +/- 0.25 vs. 3.65 +/- 0.21 mu mol/mL). Treatment with QUE but not GAL was associated with increased plasma creatinine (729.09 +/- 55.68 vs. 344.25 +/- 50.78 mu mol/l) and tissue malondialdehyde (3.72 +/- 0.62 vs. 1.67 +/- 0.47 mu mol/mL) concentrations, along with histo-pathological changes such as glomerular and tubular degenerations. However, QUE exhibited wider therapeutic concentration ranges than GAL at which it inhibits lipid peroxidation in HEK-293 cells, and was found to inhibit H2O2-induced lipid peroxidation even at the lowest concentration (2 mu M) that was tested (0.607 +/- 0.074 vs. 0.927 +/- 0.106 mu mol/l). These suggest that the in vivo dosages required for the antioxidant protective effects of QUE in renal tissues are low.