Abstract:
Leaf of Vernonia amygdalina has been shown to have hypoglycemic activity. This may be as a result of the presence of secondary metabolites as its constituents. The major secondary metabolites present in the leaf are tannins, carbohydrates, reducing sugars, glycosides, steroids and proteins. This work was designed to identify these secondary metabolites responsible for this activity, test the lethality of the constituents and then determine the best solvent for extraction. A 1 kg crushed leaves of the plant Vernonia amygdalina was extracted with methanol using soxhlet apparatus. The dichloromethane /methanol ratio which showed the best TLC separation was fractionated in a column packed with silica gel GF254 and eluted with dichloromethane/methanol in the ratios of 9:1, 8:2, 7:3, 6:1 and 1:1.
Fractions that showed similar TLC characteristics on monitoring were then pooled. The fractions were then subjected to antidiabetic studies using Wistar albino rats. Alloxan monohydrate was used to induce hyperglycemic condition in the rats. Acute toxicity test was carried out using Lorke’s method. Both the normal rats and alloxan induced diabetic rats were subjected to 24 hours fasting. Five groups of five rats per group were used. Blood samples were collected from the animal tail vein at fixed time intervals of 3, 6, 9 and 12 hours. The blood glucose levels were then determined using One Touch Glucometer. Percentage reduction of mean blood glucose level was calculated at p≤ 0.05. The percentage yield of methanol extract was 20.00 %. The LD50 showed that the drug is safe at the dose of 5000 mg/kg. The administration of alloxan increased significantly (p<0.05) the blood glucose level of rats. Of all the solvents used, the methylene dichloromethane/methanol extract (7:3) gave the best separation of the extract. The visible bands obtained had RF values of 0.140, 0.288.0, 0.153, 0.510 and 0.598. The finding showed that extract of Vernonia amygdalina have hypoglycemic activity. This justifies the use of the plant in traditional medicine practice. Finally, the result of the chromatographic studies can be a reference for the resolution, isolation and characterization of the constituents.
