The protective effect of puerarin, an isoflavone purified from Chinese herb radix of Pueraria lobata, on hydrogen peroxide (H(2)O(2))-induced rat pancreatic islets damage was investigated. Exposure of islets to 500 microM H(2)O(2) could cause a significant viability loss and an increase in apoptotic rate. Pretreatment of islets with puerarin for 48 h resulted in a reduction in viability loss and apoptotic rate. 100 microM puerarin significantly inhibited the apoptosis of islets induced by H(2)O(2). In addition, preincubation with puerarin could restore the H(2)O(2)-induced decrease in basal and glucose-stimulated insulin secretion in pancreatic islets. Puerarin was also found to inhibit the free radicals production induced by H(2)O(2) and to increase catalase and superoxide dismutase (SOD) activities in the isolated pancreatic islets. These results suggest that puerarin can protect islets against oxidative stress probably due to stimulating the activities of the antioxidant enzymes. Puerarin may be effective in preventing islet cells from the toxic action of reactive oxygen species in diabetes.