Abstract

EVALUATION OF HYPOGLYCEMIC AND ANTIDIABETIC ACTIVITIES OF THE 80% METHANOL EXTRACT FROM THE STEM BARK OF ALSTONIA CONGENSIS ENGL. (APOCYNACEAE) AND ITS FRACTIONS IN NORMAL AND STREPTOZOCIN-INDUCED DIABETIC WISTAR RATS.

Cimanga Kanyanga, R.*, Nsaka Lumpu, S., Tshodi Ehata, M., Kikweta Munduku C., Kambu Kabangua, O., Apers, S., Vlietinck, A.J., Pieters, L.,

ABSTRACT

The effect of the 80% methanol extracts from Alstonia congensis stem bark and its fractions was evaluated for their putative hypoglycemic and antidiabetic properties in normal and in streptozocin-induced diabetic Wistar rats respectively. Results indicated, at administered oral doses of 100, 200 and 400 mg/kg bodyweight, the 80% methanol extract and its fractions induced significant reduction of the concentration levels of glucose in normal and diabetic treated animals in dose-dependent manner. In normal rats, at the highest oral dose of 400 mg/kg, the 80% methanol extract lowered the fasting glucose levels from 5.91 to 7.17% after 1 and 7 h of treatment respectively. The choroform, ethylacetate, n-butanol and residual aqueous soluble fractions reached the reduction of blood glucose from 3.67 to 3.88, 3.55 to 4.57, 1.53 to 2.23 and 2.72 to 3.17% respectivley after the same temps of treatment. In diabetic treated Wistar rats, at the same highest oral dose, the 80% methanol extract and its fractions produced a dosedependent reduction of plasma glucose from 14.16 to 32.25% and 6.60 to 33.29% after 1 and 7h of treatment respectively. But, the concentration level of glucose in treated diabetic rats still remained high and need a special treatment to reach approximately the glucose level near to that of normal rats. In this way, after 21 days of treatment, the 80% methanol extract and its fractions showed significant and marked dose-dependent reduction of glycaemia in treated animals compared to control groups. In both test, insulin used as reference product showed high significant decrease of the glucose concentration levels in normal and treated diabetic rats compared to A. congensis samples. In oral glucose tolerance test, the 80% methanol extract and its fraction lowered in dose-dependent manner the plasma glucose from 121 ±0.5 to 94.0 ± 1.1 mg/dL compared to negative control (139.2 ± 0.3 to 161.3 ± 0.7 mg/dL) from 30 min to 180 min of treatment. Thus, this study shows that A. congensis stem bark extracts have hypoglycemic and antidiabetic properties and are able to ameliorate the diabetic state, and probably can be considered as a new source of hypoglycemic and antidiabetic compounds.

Keywords: Alstonia congensis, stem bark, 80% methanol extract, hypoglycemic and antidiabetic activities.