Attenuation of streptozotocin-induced oxidative stress in hepatic and intestinal tissues of wistar rat by methanolic-garlic extract

Diabetes is a major socio-economical burden with serious health consequences. The reactive oxygen species generated in this pathology alters the internal milieu of the cellular systems paving way to metabolic disorders. In the present investigation garlic's dose-dependent protective action against streptozotocin (STZ)-induced oxidative stress in hepatic and intestinal tissues has been studied. Methanolic garlic extract scavenged the DPPH radical with an IC50 of 424 +/- 4.4 mu g/ml proving its efficient antioxidant property. Garlic administration at 250 and 500 mg/kg body wt. significantly normalized the blood glucose in the diabetic rats. Biochemical analysis revealed a pronounced oxidative stress in STZ-rats (G-II) consequent to hyperglycemia as seen by a significant (P < 0.05 and 0.01) rise in malondialdehyde, protein carbonyls; accumulation of glycation products; disintegration of protein integrity (tryptophan fluorescence) followed by a decrease in reduced glutathione, antioxidant (GPx and CAT) enzymes culminating in apoptosis. Garlic administration in a dose-dependent manner has been found to restore and normalize significantly the above changes and thus restoring a normal functional integrity. These beneficial effects are prominent with 500 mg/kg body wt. dosage of garlic in comparison with 250 mg/kg body wt. dosage. But, 500 mg/kg body wt. dosage is not totally free from side effects as the decrease in body weight and increased intestinal tissue apoptosis were also found in control rats administered with garlic extract at 500 mg/kg body wt. along with diabetic rats. Based on these findings it is suggested that consumption of garlic at a lower dose is beneficial in terms of defensive action against oxidative stress.