Effect of Extracts of Khat (Catha edulis F.) on Glucose Handling in Normoglycaemic, Diabetic, and Glucose Loaded Rodents
Khat (Catha edulis F., Celastraceae) is widely chewed for its euphoric effects and as recreational drug to improve performance. Although khat is also claimed to be useful in diabetic patients, conflicting results appear in the literature on the benefit of khat in managing diabetes. This study was therefore initiated to investigate the effect of khat on blood glucose homeostasis in rodents. Crude extract as well as flavonoid and alkaloid fractions of khat were used to investigate its effect in normoglycaemic, diabetic, and oral glucose loaded animals. Three doses of crude extract (100, 200, 400 mg/kg), four doses of flavonoid fraction (50, 100, 200, 400 mg/kg), and one dose of alkaloid fraction (200 mg/kg) were employed. Positive and negative controls were treated with 5 mg/kg glibenclamide and 2% Tween-80, respectively. Fractions and doses that provided prominent activity in diabetic mice were selected for oral glucose tolerance test. Blood was then taken from the tail vein at 0, 1, 2, 3 and 4 h to determine blood glucose level using commercial one touch glucometer. The flavonoid fraction at 200 and 400 mg/kg (p < 0.001) as well as the alkaloid fraction (p < 0.05) and glibenclamide (p < 0.05) produced a significant reduction in blood glucose level in normoglycaemic mice compared to the negative control. In diabetic mice, significant decline (p < 0.05) was noted with 400 mg/kg of the crude extract, 50, 100 and 400 mg/kg of the flavonoid fraction, and glibenclamide. In glucose loaded rats, 400 mg/kg of the crude extract was the only group that significantly lowered (p < 0.05) blood glucose level in comparison to vehicle-treated animals. Higher dose of the crude extract was shown to possess antidiabetic activity without producing hypoglycaemia. Antidiabetic effect could be primarily, if not exclusively, linked to the flavonoidal contents. However, since the flavonoid and alkaloid fractions were associated with hypoglycaemia, this effect seems to be counterbalanced by other constituents.
Keywords: Catha edulis, flavonoids, alkaloids, blood glucose, diabetes