Aqueous Extracts of 'Pterocarpus marsupium', ('Vijayasar'), Increases Glucose Clearance and Stimulates Insulin Responsiveness in Sheep

Abstract

'Vijayasar' is an aqueous extract obtained from the heartwood of the plant 'Pterocarpus marsupium', and is primarily used in the treatment of diabetes mellitus in the Ayurvedic system of medicine. Some of the major active components of 'Pterocarpus marsupium' are thought to be flavones and phenols, 'marsupsin', 'pterosupin', 'pterostilbene' and (-)epicatechin, which have been identified as having hypoglycaemic action on diabetic animal models by increasing the content and secretion of insulin in the islets of Langerhans. The aims of this project were to investigate the effects of 'Vijayasar' on glucose metabolism in non-diabetic and alloxan-induced diabetic sheep. Examination of the hypoglycaemic effects of 'Vijayasar' was accomplished using glucose tolerance tests (GTT) for various doses and routes, on normal and elevated glucose levels, after single and multiple, allopathic and diabetic treatments were administered. Insulin responsiveness and morphological islet studies post-'Vijayasar' were also examined. To accomplish these objectives, a block of 'Pterocarpus marsupium' heartwood was immersed in saline to obtain the 'Vijayasar' extract, which was then administered to Merino sheep (wethers and/or ewes). Animals were randomly divided into specified groups relating to the experimental conditions – treated, diabetic, allopathic and/or non-treated/diabetic controls. Experiments assessed intravenous dose-response (0 – 100.0 mL), kinetics of administration routes (oral, intramuscular 'IM' and intravenous IV) and comparisons of complementary treatments ('Gymnema sylvestre, Red Gum'); the effect of single and multiple doses of 'Vijayasar' administered intravenously on basal glucose, glucose clearance and insulin response for 7-14 day periods; glucose clearance and insulin response post-exposure to 'Vijayasar', tolbutamide and metformin intravenously for 15 days; glucose clearance evaluated in hyperglycaemic states for diabetic (50.0, 25.0 and 12.5 mg/kg – Alloxan) and non-diabetic controls and if discrepancy in glucose clearance exist if these animals were previously exposed to 'Vijayasar'. These findings in sheep suggest that 'Vijayasar' administered intravenously or intramuscularly, is an effective, long-acting agent in the lowering of elevated blood glucose by initiating a rise in plasma insulin concentration. Further study is required to investigate the long term effects with consideration to toxicity and accumulation. Large experiments that effectively assess the induced diabetic states together with the treatment and cause of stimulated glucose clearance and the increased insulin responsiveness. As a final point, the emphasis on the kinetics of administration that is induced by 'Vijayasar' treatment both in ruminant and human models is vital for future therapeutic applications.