Effect of the insulin plant (Costus igneus) leaves on dexamethasone-induced hyperglycemia

Costus igneus, commonly known as insulin plant in India, belongs to the family Costaceae. Consumption of the leaves are believed to lower blood glucose levels, and diabetics who consumed the leaves of this plant did report a fall in their blood glucose levels. Objectives: The present study was planned to evaluate the effect of the leaves of Costus igeus on dexamethasone-induced hyperglycemia in male Wistar rats. Four groups of male Wistar rats (n= 6) were treated with 10 mg/kg/day of dexamethasone subcutaneously for 20 days. From day 11 to day 20, different groups received 100, 250 or 500 mg/kg/day of powdered leaves of Costus igeus in distilled water orally or Glibenclamide 500 µg/kg orally. On the 20th day, after overnight fasting, a retro-orbital puncture was performed for obtaining blood samples to estimate the fasting blood glucose level, and the same procedure was followed on the other eye 1 hour after a glucose load of 2.5 g/kg orally for estimation of post-glucose load blood glucose levels. Fasting blood sugar and postglucose load blood sugar levels were raised in the group that received dexamethasone when compared to normal controls (P < 0.001), whereas 250 and 500 mg/kg powdered leaf of Costus igeus and Glibenclamide 500 µg/kg decreased the dexamethasone-induced hyperglycemia (P < 0.01). The leaves of Costus igeus reduced the fasting and postprandial blood sugar levels, bringing them towards normal, in dexamethasone-induced hyperglycemia in rats.