Hypoglycemic effect of Catharanthus roseus in normal and streptozotocin-induced diabetic rats

The effects of crude juice (at 0.5 and 1 ml/kg b.w.) and aqueous extract (at 0.30 and 0.45 gm/kg b.w.) of leaves of Catharanthus roseus on serum glucose level in streptozotocin induced diabetic rats were examined at 8 hours, 12 hours and 24 hours following single oral administration. The administration of crude juice at 1 ml/kg b.w. continued for another 9 doses (total 10 single morning doses given) and its effect was examined on the 4th and 11th day. The rats were made diabetic by single intraperitoneal injection of streptozotocin at 45 mg/kg b.w. Glibenclamide was used in the study for comparison. The crude leaf juice at 0.5 and 1 ml/kg b.w. reduced the serum glucose level in streptozotocin induced diabetic rats throughout the 24-hour period significantly (P varies between 0.05 and 0.001 at different times). The aqueous extract at 0.30 and 0.45 gm/kg reduced the serum glucose level in streptozotocin diabetic rats at 8 and 12 hour significantly (P varies between 0.05 to 0.01 at different times) but not at the 24 hour. Glibenclamide, at 500 mug/kg, also reduced the serum glucose level in streptozotocin induced diabetic rats throughout the 24-hour period (P<0.001). The crude leaf juice at 1 ml/kg also significantly reduced the serum glucose level in the streptozotocin induced diabetic rats on the 4th and 11th day (P<0.001 on both occasions). The effect of crude leaf juice at 1 ml/kg b.w administered daily orally over a 10 day period was also examined on a group of normal rats at different times. The study showed significant reduction at 8 hr (P<0.05), 12 hr, 24 hr and on the 4th day (P<0.01 on these 3 occasions) and also on the 11th day (P<0.001).