Assessing the anti-hyperglycemic and anti-hyperlipidemic effects of an aqueous extract of lannea edulis in alloxan-induced diabetic rats

Abstract

Lannea edulis is a perennial dwarf shrub found in Eastern and Southern African countries such as Tanzania, Uganda, Zambia and South Africa, whose leaves are traditionally used for the treatment of sore eyes, boils and abscesses whilst its roots are used to treat diabetes mellitus, diarrhea, gonorrhea and bilharzia. The objectives of this research were to carry out phytochemical screening, and determine the antihyperglycemic and anti-hyperlipidemic effect of an aqueous extract of L. edulis in alloxan induced diabetic rats. L. edulis was collected in December 2016 from different parts of Zambia and an aqueous extract obtained by using the hot infusion and evaporation method. Phytochemical screening tests were carried out and subsequently toxicity studies were performed to establish the Lethal Dose 50 (LD50) in rats. Alloxan monohydrate was used to induce diabetes in rats. The normal and diabetic rats were placed into 6 groups, 6 animals per group. Group 1 (Normal Control) and Group 2 (Diabetic Control) were administered with distilled water. Group 3 was the Positive Control group and was administered with 5 mg/kg glibenclamide, Groups 4, 5 and 6 were administered 100 mg/kg, 300 mg/kg and 500 mg/kg L. edulis doses respectively. All doses were given for 14 days. Blood was drawn from the retro-orbital plexus on days 0 and 14 for determination of lipids and on days 0, 1, 3, 5, 7 and 14 from the rat tail vein for blood glucose. Analysis was carried out using one-way ANOVA followed by Dunnett’s multiple comparisons test. Phytochemical screening revealed the presence of flavonoids, saponins, tannins, cardiac glycosides, alkaloids and steroids. The Positive Control, 300 mg/kg and 500 mg/kg L. edulis treatment groups showed statistically significant difference (P<0.0001) in blood glucose levels compared to the diabetic control group by day 3. In addition, when day 0 mean blood glucose levels were compared to day 3 mean blood glucose levels of their respective groups, the positive control group showed a 15.5 percent drop, the 300 mg/kg L. edulis group showed a 23.3 percent drop and the 500 mg/kg L. edulis group showed a 52.6 percent drop. The 100 mg/kg treatment group showed statistically significant difference (P<0.0001) compared to diabetic control group on day 5; when its day 0 mean blood glucose levels were compared to its day 5 mean blood glucose levels, the 100 mg/kg group showed a 25.1 percent drop. In addition, administration of aqueous extract of L. edulis to diabetic rats for 14 days significantly decreased (P<0.0001) the levels of serum total cholesterol, triglycerides, Low Density Lipoprotein (LDL) and Very Low Density Lipoprotein (VLDL) whilst increasing the levels of High Density Lipoprotein (HDL), when compared to the diabetic control group. Therefore, the aqueous extract of L. edulis showed dose dependent reductions in blood glucose and serum lipid levels in Alloxan induced diabetic rats.