Extracts ofCoreopsis tinctoriaNutt. Flower Exhibit Antidiabetic Effects via the Inhibition ofα-Glucosidase Activity

Abstract

The aim of this study was to assay the effects ofCoreopsis tinctoriaNutt. flower extracts on hyperglycemia of diet-induced obese mice and the underlying mechanisms.Coreopsis tinctoriaflower was extracted with ethanol and water, respectively. The total phenol, flavonoid levels, and the constituents of the extracts were measured. For the animal experiments, C57BL/6 mice were fed with a chow diet, high-fat diet, or high-fat diet mixed with 0.4% (w/w) water and ethanol extracts ofCoreopsis tinctoriaflower for 8 weeks. The inhibitory effects of the extracts onα-glucosidase activity and the antioxidant properties were assayedin vitro. We found that the extracts blocked the increase of fasting blood glucose, serum triglyceride (TG), insulin, leptin, and liver lipid levels and prevented the development of glucose tolerance impairment and insulin resistance in the C57BL/6 mice induced by a high-fat diet. The extracts inhibitedα-glycosidase activity and increased oxidant activityin vitro. In conclusion,Coreopsis tinctoriaflower extracts may ameliorate high-fat diet-induced hyperglycemia and insulin resistance. The underling mechanism may be via the inhibition ofα-glucosidase activity. Our data indicate thatCoreopsis tinctoriaflower could be used as a beverage supplement and a potential source of drugs for treatment of diabetics.