Quercetin allievates oxidative stress in streptozotocin-induced diabetic rats

Diabetes mellitus is found in almost all populations and is emerging as a growing problem in developing countries. A large number of studies are in progress to fi nd natural sources, which are effective in reducing the intensity of diabetes. Quercetin, a constituent present in fruits and vegetables, was studied in two different doses (50 and 80 mg/kg body weight) for 45 days to assess its effect on streptozotocin induced diabetes. The blood glucose level was elevated in diabetic rats. Circulatory lipid peroxidation, vitamin C, vitamin E and enzymic antioxidants such as superoxide dismutase and catalase were analyzed. Alterations in the antioxidant defense were observed in diabetic animals compared to normal. Oral administration of quercetin to diabetic rats resulted in a decrease in the levels of blood glucose, plasma thiobarbituric acid reactive substances and hydroperoxides. Quercetin also resulted in the activities of superoxide dismutase, catalase coming to near normal, along with the levels of vitamin C and vitamin E. Quercetin at lower doses was found to be more effective. These result indicate that quercetin ameliorated the diabetes-induced changes in oxidative stress. Copyright 2004 John Wiley & Sons, Ltd.