Diabetes mellitus is a chronic disease which is increasing, cannot be cured and so must be suffered for whole life. In recent years, research on herbal medicines for the treatment of diabetes has been increasing. Terminalia species have been used as traditional medicines to treat several diseases including diabetic diseases for a great many years. The aim of this study is to evaluate the anti-oxidant and antidiabetic activities of methanol extracts of the trunk-bark of three Terminalia species, T. alata, T. belirica and T. corticosa Pierre ex Laness. The anti-oxidant activity was determined by DPPH radical scavenging and the antidiabetic activity was determined by digestive enzymes inhibition and lowering fasting blood glucose in diabetic rats. The flavonoids and polyphenol contents were also determined by spectroscopic methods. The results indicated that the three trunk-bark extracts of the investigated plants possessed relatively high anti-oxidant activity with IC50 values of 0.24 mg/ml for T. alata, 1.02 mg/ml for T. belirica and 0.25 mg/ml for T. corticosa and 0.24 mg/ml for the positive control of L-ascorbic acid. In addition, these extracts also exhibited inhibitory activity on α-amylase and α-glucosidase and lowered fasting blood glucose levels in streptozotocin-induced diabetic rats but without inducing body weight loss comparing to acarbose. Amongst the extracts, the highest effect on lowering in diabetic rats was found in the extract of T. belirica followed by T. corticosa and T. alata. However, the extracts did not produce any hypoglycemic effect in normal rats at a dose up to 200 mg/kg body weight. The results suggest that the methanol extracts of the investigated plants may prove to be useful in treating type 2 diabetes.
Research on Chemical Intermediates 42(6), p.5859–5871