Antihyperglycemic activity of ethanolic extract of leaves of Dioscorea japonica in STZ-induced diabetic rats

To evaluate the antihyperglycemic activity of ethanolic extract of leaves of Dioscorea japonica in STZ induced diabetic rats. STZ-induced (60 mg/kg, i.p.) diabetic mice given ethanolic leaf extract (200, 300, 350 and 400 mg/kg, p.o.,n=6) of D. japonica and in vehicle (distilled water, 10 ml/kg.,p.o.) and in standard drug metformin (500 mg/kg.,p.o.) respectively for 14 days. The dose of 350 mg/kg body weight (bw) reduced the fasting blood glucose (FBG) level by 6.0% within 1 hr, whereas, the peak blood glucose at 1 hr during glucose tolerance test (GTT) was reduced by 17.1% in normal rats. The same dose of ethanolic extract reduced FBG by 13.0% and improved glucose tolerance by 37.2 and 60.6% at 1and2 h, respectively, during GTT in STZ-diabetic rats. The dose of 350 mg/kg body weight of ethanolic extract in 14-day treatment of a group of STZ-diabetic rats produced 73.3% fall in FBG level and no sugar was observed in fasting urine. It brought about fall in the level of total cholesterol (TC) by 49.3% with increase of 30.3% in high-density lipoprotein (HDL) and decrease of 71.9 and 28.7% in low-density lipoprotein (LDL) and triglycerides (TG) levels, respectively. The ethanolic leaf extract of D. japonica (200, 300, 350 and 400 mg/kg, p.o) showed significant (P<0.01) reduction of serum glucose level in STZ-induced diabetic mice at 14thday. It is concluded that D. japonica has significant antihypergycemic activity as it lowers serum level of glucose in diabetic mice and significantly increase glucose tolerance.