By Ezeani, Chinelo Stella
The mechanisms of antidiabetic activity of extract of aerial part of Ocimum basilicum L. (Lamiaceae) were evaluated. The extract was obtained by cold maceration in a 1:1 mixture of methanol - methylene chloride and subjected to phytochemical analysis for tentative identification of constituents as well as fingerprinting using thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Acute toxicity of the extract was studied in rats using the oral route. The effects of the extract on blood glucose level, oral glucose tolerance, hepatic glucose content, hemoglobin glycosylation and serum biochemistry (lipid profile, total serum protein and liver enzymes) were studied in alloxan diabetic rats. The effects of the extract on glucose metabolizing enzymes- α-amylase and α-glucosidase were assayed in vitro. The results showed that the extraction process afforded 74.12 g (8.1% w/w) of the extract. The extract lowered blood glucose and suppressed rise in blood glucose after a glucose meal in diabetic rats. The extract increased liver glycogen content in diabetic rats, inhibited α- amylase (IC50: 3.86 mg/ml) and α- glucosidase (IC50: 1.62 mg/ml) enzyme activities in vitro and significantly (p< 0.05) reduced hemoglobin glycosylation in non-diabetic rats but not in diabetic rats. The extract caused significant (p< 0.05) reduction in the liver enzymes (especially SGPT and SGOT) and total cholesterol and triglyceride level in both diabetic and non-diabetic rats. It also elevated total serum protein and albumin in diabetic rats. Acute toxicity and lethality test on the extract gave an oral LD50 greater than 5 g/kg in rats. TLC fingerprint of the extract yielded 6 spots (Rf 0.47- 0.97) while the HPLC fingerprint revealed 12 prominent peaks with retention time of 1.547 to 7.814. Phytochemical tests showed that the extract tested positive to tannins, saponins, flavonoids, carbohydrates, terpenes and sterols.