Drug From The Woods

A city scientist discovers a herbal 
extract that lowers blood sugars, reports Biplab Das 

To witness how herbal medicines have regained their lost glory, pay a visit to the biometry research unit of the Indian Statistical Institute (ISI), Calcutta. 

Here, a research team led by Sanjib Kumar Gupta, physiologist at ISI, has discovered that the leaf extract of meshasringee, a woody vine, effectively combats diabetes in rats. This plant is scientifically known as Gymnema sylvestre and its leaves and roots are medicinally useful. 

Gupta and team-mates' work has been published in a recent issue of the Indian Journal of Physiology and Allied Science. Besides Gupta, the research team comprised Bithin Kumar Maji and Sampa Roy. They took the help of Prof. G. Poddar of the School of Tropical Medicine, Calcutta, to identify the leaves of G. sylvestre. The research team studied the glucose lowering effects of G. sylvestre's leaf extract in a phased manner. 

Before the main research, Gupta's team ran pharmacological test on the rats to determine the so-called lethal dose, the amount of the chemical that can kill experimental subjects. All research teams have to perform this study. This was achieved by administering leaf extract to normal rats. The lethal dose of G. sylvestre for rats was found to be 500 mg/Kg of body weight. One-fifth of the lethal dose was to be the working dose. 

Now, Gupta's team administered the leaf extract to glucose-fed rats. They found that in glucose-fed rats, the extract started lowering blood glucose levels within half an hour after glucose feeding. The extract reduced glucose levels by 39 per cent. On the other hand, a synthetic drug called tolbutamide reduced blood glucose levels by 42 per cent. 

In the next phase, Gupta and his teammates injected adrenalin into rats to increase their blood glucose levels, and then administered the leaf extract to them. In these rats, it was found to have diminished blood glucose levels by 50 per cent. In the same rats, tolbutamide lowered blood glucose levels by 45 per cent. 

In diabetes mellitus, some cells of the pancreas go haywire and stop releasing the amount of insulin that is needed to maintain normal blood glucose level. 

Gupta's work revealed that leaf extract initiated a marked decrease in blood glucose levels in normal, glucose-fed and adrenalin-induced rats with high glucose levels. Several other Indian research works, too, corroborate the findings of Gupta and his team-mates. 

The glucose lowering effect of the leaf extract reached its optimum level 6 hours after the extract administration. "A drug made of this extract will not only be cost-effective but also devoid of harmful side effects," said Gupta. 

Repeated experiments showed that the extract has almost the same glucose lowering activity as the synthetic drug. "Since the degree of difference in lowering of blood glucose levels showed by the extract and tolbutamide appears insignificant, it can be safely concluded that the potency of the extract and the drug is almost similar. So, the extract might have therapeutic value in other diseases too, which raise blood glucose levels, like diabetes mellitus," wrote Gupta in the report in the Indian Journal of Physiology and Allied Science. 

Gupta's team has just completed another study, which bears out the findings of this one. This will also be published in a forthcoming issue of the same journal. In that study, the research team from ISI induced diabetes in rats with a synthetic drug known as streptozotocin. Three days after a single administration of streptozotocin, the blood glucose level increased significantly. 

Next, the team injected leaf extract of G. sylvestre into one group of diabetic rats. Another group received tolbutamide. The diabetic rats that received the leaf extract showed 9 per cent, 33 per cent and 37 per cent reduction of blood glucose levels at 2 hours, 4 hours and 6 hours respectively. But, tolbutamide caused 49 per cent, 54 per cent, and 60 per cent reduction at the same intervals. 

This study also reveals the glucose lowering effect of G. sylvestre leaf extract in streptozotocin-induced diabetic rats. "Our experimental data, so far, reveal that G. sylvestre definitely lowers blood glucose levels.  

Now, the question arises, whether it increases the secretion of beta cells [those cells that stop releasing insulin among diabetics] of the pancreas, thereby releasing insulin, or whether it increases carbohydrate utilisation without taking into consideration the increase or decrease of the beta cell activity," explains Gupta. Further research is required to clarify this.