Free radical scavenging and antidiabetic activities of Euonymus laxiflorus Champ. extract

In recent years, due to the undesirable side-effects of synthetic drugs used to treat diabetes, research into herbal medicines for treatment of this disease has increased. Euonymus laxiflorus Champ. belongs to the Celastraceae family, long used in traditional Vietnamese medicine by ethnic people living in Dak Lak Province of Vietnam. The aim of this study is to evaluate the antioxidant and antidiabetic activities of methanol extract of Euonymus laxiflorus Champ. trunk bark. The antioxidant activity was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, and the antidiabetic activity was determined by inhibition of digestive enzymes and lowering of fasting blood glucose in diabetic rats. The contents of flavonoids and polyphenols were also determined spectroscopically. The results indicated that trunk bark extract of Euonymus laxiflorus Champ. possessed relatively high antioxidant activity with 50% inhibition concentration (IC50) of 0.60 mg/ml, compared with 0.24 mg/ml for l-ascorbic acid as positive control. Furthermore, the extract also exhibited relatively higher α-glucosidase inhibitory and moderately lower α-amylase inhibitory effects compared with acarbose. Moreover, the extract could lower fasting blood glucose levels in rats with streptozotocin-induced diabetes but without inducing body weight loss, compared with acarbose. However, the extract did not produce any hypoglycemic effect in normal rats at dose up to 300 mg/kg body weight. These results suggest that methanol extract of Euonymus laxiflorus Champ. may prove to be useful in treating type 2 diabetes.