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 exogenously-induced 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 μM) or QUE (2-17 μM or 28-165.43 μM) singly or in combination with H₂O₂ (200 μM). 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 μmol/mL). Treatment with QUE but not GAL was associated with increased plasma creatinine (729.09 ± 55.68 vs. 344.25 ± 50.78 μmol/l) and tissue malondialdehyde (3.72 ± 0.62 vs. 1.67 ± 0.47 μmol/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 μM) that was tested (0.607 ± 0.074 vs. 0.927 ± 0.106 μmol/l). These suggest that the in vivo dosages required for the antioxidant protective effects of QUE in renal tissues are low.

Keywords: Antioxidant; Gallic acid; HEK- 293 cells; Kidney; Oxidative stress; Quercetin.