Gymnema Sylvestre from India

Gymnema sylvestre

Gymnema sylvestre a plant used in the Ayurvedic medicine of India for the treatment of Diabetes mellitus has been known from antiquity also to have an antisaccharin taste effect. The active principles are glycosides (several Gymnemic acid) which shows selective anaesthetic effect1. In a study conducted on rats the feeding of powdered leaves of Gymnema sylvestris in the diet for 10 days prior and 15 days after the treatment of beryllium nitrate significantly protected the animals from the full fall of blood glucose seen in rats receiving beryllium nitrate alone. The feeding of the leaves for 25 days to normal rats did not alter blood glucose significantly. The exact mode of protective action against beryllium toxicity was not established.

Experimental studies were conducted on rats fed on high carbohydrate diet for 15 days and later rendered hyperglycaemic by injecting anterior pituitary extract 100mg/kg subcutaneously daily for ten days. These animals were treated with ethanol extract of Gymnema sylvestre at a dosage of 100mg/kg orally.
Results indicated insignificant reduction in blood sugar in normal rats, whereas significant reduction in anterior pituitary treated hyperglycaemic rats. Effect of the drug was comparable to that of tolbutamide (50mg/kg) in the hyperglycaemic rats. The drug influenced the disturbed carbohydrate metabolism in hyperglycaemic animals by limiting the carbohydrate turnover and thus inhibiting the vicious cycle of hyperglycaemia. Further studies were conducted on albino rats to establish the antidiabetic activity of Gymnemasylvestre, which was compared with other conventional indigenous oral antidiabetic drugs like Coccinia indica, Pterocarpus marsupium, Momordia charantia.

The animals were subcutaneouly injected with 100mg/kg dose of the anterior pituitary extract, these animals were then fed with alcoholic extract of Gymnema sylvestre and Coccinia indica (100mg/kg each), aqueous infusion of Pterocarpus marsupium (20ml/kg), extract of Momordia charantia (5ml/kg) and tolbutamide (50mg/kg) orally. Inhibition of the hyperglycaemic response of the anterior pituitary extract at 6, 12 and 24 hours was most marked in tolbutamide & Gymnema sylvestre.

The inhibitory effect was highly significant in Gymnema sylvestre when compared with Pterocarpus marsupium and Momordia charantia The usefulness of Gymnema sylvestre therapy in alloxan induced diabetic rabbits in correcting the abnormal accumulation of lipids, glycogen and protein depletion in the liver, kidney and muscle were investigated by feeding crude leaf powder at a dosage of 250mg/kg body weight once a day. Gymnema sylvestre therapy not only produced blood glucose homeostasis but also increased the activities of the enzymes affording the utilization of glucose by insulin dependent pathways, it controlled phosphorylase levels, gluconeogenic enzymes and sorbitol dehydrogenase.

The uptake and incorporation of glucose into the glycogen and protein are increased in the liver, kidney and muscle in Gymnema sylvestre administered diabetic animal when compared to the untreated diabetic animals.The inhibitory effects of an extract of Gymnema sylvestre and purified gymnemic acid on Gastic Inhibitory Peptide (GIP) release was studied in rats. The GIP release into the portal vein in response to duodenal infusion of D-glucose in presence of leaf extract of Gymnema sylvestre at a dosage of 0.5ml/kg. The results suggested that a glucose receptor which interacted with the leaf extracts of Gymnema sylvestre and purified Gymnemic acid. The inhibition of GIP release by Gymnemic acid observed was attributed to the interaction with the glucose receptor for GIP release which was similar in specificity to the active glucose transport system.Two water soluble extracts GS3 and GS4 obtained from the leaves of Gymnema sylvestre, were tested in streptozotocin treated rats for their effects on blood glucose homeostasis and pancreatic endocrine tissue. In the diabetic rats, fasting blood glucose levels returned to normal after 60 days of GS3 and after 20 days of GS4 oral administration. In diabetic rat pancreas, both therapy led to a rise in serum insulin to levels close to normal testing levels. In diabetic rats pancreas both GS3 and GS4 doubled the islet number and beta cell number. This herbal therapy appeared to bring about blood glucose homeostasis through increased serum insulin levels provided by repair/regeneration of the endocrine pancreas.