Hypoglycemic and antihyperglycemic effects of diethyl ether fraction isolated from the aqueous extract of the leaves of Cogniauxia podoleana Baillon in normal and alloxan-induced diabetic rats

Abstract

Cogniauxia podoleana Baillon (Cucurbitaceae family) leaves are used in Congolese traditional medicine for the treatment of diabetes mellitus. Based on an increasing number of reports on blood glucose level reduction associated with some saponins and flavonoids isolated from medicinal plants, the hypoglycemic and antihyperglycemic effects of flavonoid and saponin fractions were investigated. Saponin fractions were obtained by the fractionation of aqueous extract of leaves using benzene and ethyl acetate. Flavonoid fraction was isolated from the aqueous phase obtained after the settling of benzene–aqueous extract mixture by means of diethyl ether. The diethyl ether fraction (100 mg/kg) reduced the blood glucose levels in 40.0% 3 h after oral administration to normal rats. In contrast, the oral administration of benzene and ethyl acetate fractions at a dose of 100 mg/kg to normal rats did not decrease the blood glucose levels. The diethyl ether fraction at a dose of 50 mg/kg was found to reduce the increase of blood glucose levels in 29.4 and 44.5%, respectively, 3 and 4 h after oral administration to alloxan-induced diabetic rats, whereas at a dose of 100 mg/kg, it decreased the levels of hyperglycemia in 41.4 and 70.4%, recpectively, after 3 and 4 h. These data confirm the antidiabetic activity of the leaves of Cogniauxia podoleana Baillon in Congolese traditional medicine for diabetes mellitus treatment. However, it was important to note that the antihyperglycemic action could not be attributed to the presence of flavonoids; contamination is detected (amino acids, carbohydrates and other compounds) in the diethyl ether fraction containing flavonoids.