Background: 
Diabetes mellitus is a metabolic disorder characterized by hyperglycemia with impaired metabolism of carbohydrate, proteins and fat due to defects in insulin secretion and/or insulin action. This may lead to complications such as atherosclerosis, retinopathy, nephropathy, neuropathy and cardiac dysfunction. In developing countries, herbal drugs are traditionally used for the treatment of diabetes mellitus as resources are limited and access to modern treatment is a problem. The use of herbal drugs are frequently considered to be less costly, less toxic and also free from side effects, than synthetic ones. Asystasia gangentica (A. gangetica) under the family Acanthaceae, has been employed basically by the traditional healers in the treatment of hypertension in South Africa, rheumatism in India, asthma in Cameroun and diabetes mellitus in Nigeria. Furthermore, it is also used as an anthelmintic in Kenya. However, there is no scientific proves associated with its dose-dependent for its use. 
Aims: 
In this study, the acute toxicity and dose-dependent hypoglycemic activity of Asystesia gangetica leaf extract were evaluated on albino mice and alloxan induced diabetic rats, respectively. 
Methods:
Acute toxicity study of the extract was carried out using thirty albino mice randomly assigned into six groups of five mice each, with each group having a particular dose level of the extract. The rats were observed for toxicity signs and mortality within a period of twenty four hours. For the acute hypoglycemic study, fifty rats randomly divided into five groups of ten rats each, were used. The first group of rats served as the normal control while groups two to five rats were made diabetic with a single intraperitoneal dose of alloxan monohydrate (160mg/kg). Group two served as the diabetic control, while groups three and four were administered 400 and 800mg/kg of the extract. However, group five was administered a standard hypoglycemic agent (glybenclamide, 3mg/kg). Blood glucose concentrations of the rats were determined every two hours for six hours. These were used to assess the acute hypoglycemic effect of the extract. 
Results:
Results obtained for the acute toxicity study indicated no death, even at 5000mg/kg body weight and showed no signs of toxicity in all the groups. However, results obtained from the hypoglycemic study showed significant rise in the plasma glucose level in all the test groups administered with  alloxan monohydrate after 4 days as compared to the normal control group (P<0.05). Treatment with 400mg/kg of the extract, significantly lowered glucose concentrations in the diabetic rats from 427.60±22.53 mg/dl to 178.60±8.31 mg/dl. However, 800mg/kg of the extract, brought down glucose level from 370.40±35.68 mg/dl to 144.60±7.47 mg/dl at the end of 6 hours following administration as compared to the diabetic control group (P<0.05). Interestingly, the effect of the extract also compared favorably to that of glybenclamide which lowered glucose concentration in diabetic rats from 377.40±42.99 mg/dl to 174.00±31.12 mg/dl. 
Discussion:
The record of no death and signs of toxicity implies that, the extract is safe for consumption even at high dosage. The significant increase in the plasma glucose level above 200mg/dl as compared to normal rats during the study is an indication that the study animals were diabetic. This could have led to the destruction of their pancreatic insulin secreting β cells. The significant reduction (p<0.05)  in the plasma glucose level of the treated rats as compared to the control is an indication of blood glucose lowering potential of the extract at two different doses. Furthermore, the significant reduction was evident from 4 hours, 2 hours and 2 hours for 400mg/kg, 800mg/kg of extract and 3mg/kg Glibenclamide, respectively. This implies that the extract rate of lowering potentials is dose- dependent. Interestingly, it was observed that comparing the extract dose of 800mg/kg recorded to that of 3mg/kg glibenclamide had significant reduction effect at 2 hours. This means that the extract could replace the drug in the management of diabetes mellitus since it is safe. Asystesia gangetica leaf extract therefore may be safe and effective for use in the management of diabetes mellitus.
Keywords
Asystasia gangetica ethanolic extract, diabetes mellitus , alloxan- induced rats, acute toxicity and hypoglycaemia.

References 
Hsieh, P. C., Huang, H. J., Ho, Y. L., Lin, Y. H., Huang, S. S. and  Chiang, Y. C. (2010). Activities of antioxidants, α-Glucosidase inhibitors and aldose reductase inhibitors of the aqueous extracts of four Flemingia species in Taiwan. Bot Stud;51:293-302.
Patil, S. B., Ghadyale, V. A., Taklikar, S. S., Kulkarni, C. R. and Arvindekar, A. U. (2011). Insulin secretagogue, alpha-glucosidase and antioxidant activity of some selected spices in streptozotocin-induced diabetic rats. Plant Foods Hum Nutr;66:85-90.

Acute toxicity and hypoglycemic effect of ethanolic extract of Asystesia gangetica leaf