Antidiabetic, Toxicity Studies and Phytochemical Profile of <i>Hedranthera barteri</i> (Hook. f.) Pichon

Objective: This work investigated the antihyperglycaemic activities, safety and chemical composition of Hedranthera barteri (Hook. f.) Pichon (Apocynaceae) methanol leaf extract aimed at establishing its antidiabetic folkloric usage. Methods: Acute and sub acute toxicity tests of the plant extract were assessed with a modified OECD test guidelines. The effects of the extract on glucose, haematological and biochemical parameters were evaluated using standard procedures. Its antidiabetic activities were assayed in α-amylase, α-glucosidase, glucose and streptozotocin-induced diabetic rats’ models at various doses with acarbose and glibenclamide (5 mg/kg) as positive controls. Histopathological examination of the pancreas, liver and kidney of rats administered with the extract at 250, 500 and 1000 mg/kg was also carried out. The phytochemical components of the extract were analysed with GC-MS. The results obtained from these studies were subjected to statistical analysis using Analysis of Variance (ANOVA), followed by the Student Newman Keul's test, and p< 0.05 was taken as significant. Results: The median lethal dose, LD₅₀ of the extract was above 5000 mg/kg in rats without adverse effects on blood glucose levels and biochemical components of normal rats especially at 250 and 500 mg/kg while it significantly potentiated PCV, RBC and haemoglobin levels of the rats. The extract caused an inhibition of α-amylase and α-glucosidase enzymes in concentration dependent manner, reduced hyperglycaemia in glucose loaded rats with 200 mg/kg as the most effective dose and elicited hyperglycaemia lowering activity that was comparable to glibenclamide in drug-induced diabetic rats. The extract had no adverse effect on the histology of the pancreas, liver and kidney at 250 mg/kg while 500 and 1000 mg/kg caused moderate and severe effects on these organs, respectively. Tannins, flavonoids, saponins, alkaloids, terpenoids, deoxy-sugars were observed in the extract by preliminary phytochemical screening while some GC-MS identified possible antidiabetic constituents of the plant include 9, 12-Octadecadinoic acid, phytol and catechol. Conclusion: The study validated the folkloric use of the leaves of Hedranthera barteri in the management of diabetes mellitus and confirmed its non toxic effect on different blood components of animals and their organs at low doses.