A medicinal plant is any plant containing substances that are effective therapeutically or are precursors for drug manufacture in one or more of its organs. This work was a comparative study of the hypoglycaemic and hyperglycaemia-lowering activities of the methanol extracts of the leaf, stem, and root barks of Xylopia aethiopica used folklorically in the management of type 2 diabetes mellitus with the view of determining its most active morphological part. The pulverized leaves, stem and root barks of the plant were separately subjected to cold extraction using methanol to obtain leaf, stem and root barks extracts respectively. The hypoglycaemic and antihyperglycaemic effects of the extracts were carried out on normoglycaemic and glucose-induced hyperglycaemic rats, respectively at 100, 200 and 400 mg/kg using glibenclamide (5 mg/kg) as positive control. The most effective antihyperglycaemic doses of the extracts were used to determine its anti-diabetic activity on streptozotocin-induced diabetic rats. The results obtained from the study were subjected to analysis of variance (ANOVA), followed by Student–Newman-Keuls post hoc tests and p< 0.05 was considered significant. The results of the study showed that the root bark extract of X. aethiopica did not cause hypoglycaemia in rats at all the tested doses while hypoglycaemia was obtained at 400 mg/kg of the leaf and stem bark extracts. In the hyperglycaemia-lowering experiment using glucose loaded rats’ model, the leaf, stem and root bark extracts gave 10, 13, 10, 29; 35, 36, 38, 41 and 25, 27, 33, 44 % blood glucose levels reduction at 0.5, 1, 2 and 4 h, respectively which showed the stem bark as the most active plant part especially at 0.5-2 h. In the streptozotocin-induced hyperglycaemic rats experiment, the order of antihyperglycaemic effect of the morphological parts of X. aethiopica is, stem bark extract > leaf extract > root bark extract. It was concluded from the results obtained from the study that the stem bark extract of Xylopia aethiopica was the most active plant part both in glucose and streptozotocin-induced hyperglycaemia and it does not cause hypoglycaemia at low doses.
