Antidiabetic property of some Nigerian medicinal plants

The antidiabetic properties of extracts of three Nigerian medicinal plants - Ocimum basilicum L. (Lamiaceae, formerly Labiatae), Phyllanthus niruri L. (Euphorbiaceae) and Viscum album L. (Viscaceae or Loranthaceae) parasitic on Psidium guajava L. (Myrtaceae) on normoglycemic and alloxan-induced diabetic rats were studied. The extracts (258.3 g, 6.89% w/w of P. niruri, 189.17 g, 6.76% w/w of V. album and 131.50 g, 6.41% w/w of O. basilicum), obtained by 48 h cold maceration in methanol: methylene chloride (1:1), were evaluated for hypoglycemic and oral glucose tolerance effects in normoglycemic rats and antihyperglycemic effect in alloxan (100 mg/kg i.p) diabetic (blood glucose level ≥ 200 mg/dl) rats. The results showed that acute oral administration of the extracts to normoglycemic rats caused a mild to moderate non-dose-related reduction in blood glucose levels. The extracts significantly (P < 0.05) suppressed the acute postprandial rise in blood glucose to varying extents. Extract of O. basilicum lowered the elevated glucose level to 13.67% at 180 min while P. niruri and V. album reduced the glucose level to 16.87 and 17.33%, respectively. In alloxan diabetic rats, the extracts caused a significant (P < 0.05) non-dose-related reduction in blood glucose with 52.31 (O. basilicum), 44.29 (P. niruri) and 16.71% (V. album) maximum reduction at 6 h.   Key words: Alloxan, diabetes mellitus, Nigerian medicinal plants.