Phytochemical Studies and Blood Glucose Lowering Effect of Zambian Cultivars of Piliostigma thonningii in Alloxan - Induced Diabetic Rats

Abstract

Background: There is anecdotal evidence among some Zambian traditional medicine practitioners that Piliostigma thonningii possesses antidiabetic effects. This study assessed the in-vivo antidiabetic effects of ethanol extract of the plant in alloxaninduced diabetic wistar rats.
Study design: A laboratory-based experimental study involving 24 rats divided into 4 groups of 6 and administered the extract,  glibenclamide and placebo.
Methods: Diabetes was induced by a single intraperitoneal injection of 150mg/kg alloxan monohydrate. The in-vivo glucose lowering  effect of ethanol extract of stem bark of Piliostigma thonningii was evaluated in comparison to normal saline as negative control and glibenclamide as positive control. Standard methods for identification of alkaloids, flavonoids, saponins, tannins, glycosides, terpenoids and anthraquinones were employed in the phytochemical analysis of the extract.
Results: Piliostigma thonningii ethanol stem bark extract showed presence of alkaloids, flavonoids, saponins, tannins, glycosides and terpenoids. The extract caused a 55.3% (P=0.002) reduction in blood glucose of the experimental animals over the treatment period from the initial 19.7±7.0 mmol/l to 8.8±2.5 mmol/l, compared with glibenclamide which caused 68.3 % (P=0.001) lowering blood glucose levels from 24.0±4.5 mmol/l to 7.6±5.9 mmol/l.
Conclusions: Stem bark extract of Piliostigma thonningii showed a significant glucose lowering effect in diabetic rats. The study also demonstrated presence of secondary plant metabolites which could be responsible for some of the medicinal properties of the plant. Further studies are required to purify the plant and identify active fractions responsible for the anti-diabetic effect observed.