Endocrine Abstracts

Medical plants believed to be safe and cost effective than synthetic hypoglycaemic agents play important roles in the management of diabetes mellitus in developing countries where resources are meagre. We have isolated triterpenes from Syzygium aromaticum as the bioactive compounds that possesses hypoglycaemic effects in experimental diabetes. However, the poor water solubility of triterpenes observed in oral administration has necessitated the evaluation of alternative methods of administration for effective diabetes management. Accordingly, the aim of this study was to investigate whether transdermal application of Syzygium aromaticum-derived oleanolic acid patch (P-OA) formulations sustain controlled release of oleanolic acid (OA) into the bloodstream of STZ-induced diabetic rats with concomitant alleviation of some of the complications associated with diabetes. Topically applied P-OA patches containing various OA doses (21, 42 and 84 mg/kg) prepared by dissolving pectin/OA in deionised water with subsequent solidification with CaCl₂ were evaluated for oral glucose tolerance responses in groups of STZ-induced diabetic rats. Short-term (5 weeks) effects were assessed in diabetic animals treated thrice daily with P-OA patches 8 hours apart. Animals treated with drug-free pectin and insulin (175 μg/kg, s.c.) acted as untreated and treated positive controls, respectively. Blood and tissue samples were collected for the measurement of selected metabolic parameters. Blood glucose concentrations were significantly reduced following transdermal P-OA treatment thus indicating that OA was transported across the skin. The treatment also restored the reduced glycogen concentrations in muscle and hepatic tissues of diabetic animals to near normalcy. However, there was no change in plasma insulin concentrations of STZ-induced diabetic rats following acute and short-term daily treatment with OA-containing dermal patches. The data indicate successful sustained controlled release of OA into the bloodstream of STZ-induced diabetic rats via P-OA hydrogel matrix patches with a concomitant reduction in plasma glucose concentrations and amelioration of some selected metabolic parameters.