The present study evaluated the antihyperglycaemic effect and mechanism of action of fractions of the aqueous
seed extract of
Hunteria umbellata
(K. Schum.) Hallier f. (
HU) in normal and alloxan-induced hyperglycaemic rats.
HU was
partitioned in chloroform, acetyl acetate and butan-1-ol to give chloroform fraction (
HUc), ethyl acetate fraction (
HUe), butanol fraction (
HUb) and the “residue” (
HUm), respectively. 200 mg/kg of each of these fraction dissolved in 5% Tween 20 in distilled water was investigated for its acute oral hypoglycaemic effects in normal rats over 6 hours while its repeated dose antihyperglycaemic effect was evaluated in alloxan-induced hyperglycaemic rats over 5 days. In addition, 50 mg/kg of the crude alkaloid fraction (
HUAf) extracted from
HU was evaluated for its possible antihyperglycaemic activity in alloxaninduced hyperglycaemic rats using oral glucose tolerance test (OGTT) over 6 hours. Using the solvent system, distilled
water-butanol-ammonium hydroxide (2:15:1, v/v/v),
HUb was chromatographed and stained with Dragendorff’s reagent for
confirmatory qualitative analysis for alkaloids. Results showed that oral pre-treatment with 200 mg/kg of
HUe,
HUb and
HUm resulted in a significant (
p<0.05,
p<0.001) time dependent hypoglycaemic effect, with the butan-1-ol fraction
HU causing the most significant (
p<0.001) hypoglycaemic effect. In the alloxan-induced hyperglycaemic rats, repeated oral treatment with 200 mg/kg of same
HU fractions for 5 days resulted in significant (
p<0.05) decreases in the fasting blood glucose concentrations with the most significant (
p<0.01) antihyperglycaemic effect also recorded for
HUb. Similarly, oral pretreatment with 50 mg/kg of
HUAf significantly (
p<0.05,
p<0.01 and
p<0.001) attenuated an increase in the post-absorptive glucose concentration at 1
st -6
th h in the alloxan-induced hyperglycaemic OGTT model. In addition, alkaloid was present in most of the separated spots on the TLC plate. In conclusion, results of this study showed that
HU contains a relative high amount of alkaloids which could have accounted for the antihyperglycaemic action of
HU that was mediated via intestinal glucose uptake inhibition.
