Effects on Blood Glucose of Ethyl Acetate-Butanol Fraction of Dialium guineense Aqueous Leaf Extract (Cesalpiniaceae)

Introduction: The overall objective of the study was to evaluate the effect on blood glucose of the ethyl acetate-butanol fraction (EABF) compounds of the aqueous leaf extract of Dialium guineense (Cesalpiniaceae). 
Materials and Methods: The powder of D. guineense leaves was subjected to decoction. The aqueous solution was respectively fractionated with ethyl acetate and butanol. The sub-fractions were grouped to form the ethyl acetate-butanol fraction (EABF), enriched in flavonoids and tannins. The condensed tannins of EABF were eliminated under the action of casein, resulting in a condensed tannin-free fraction (EAB-TFF). EABF and EAB-TFF were phytochemically characterized and tested in normo-glycemic rats, a glucose tolerance test and type 2 diabetic rats. 
Results, Analysis and Discussion: EABF (300 mg/kg, per os) has no significant effect on blood glucose in normo-glycemic rats (0.80±0.12 vs 0.81±0.01 g/L). Under the same conditions, EABF without tannins (EAB-TFF: 300 mg/kg, per os) is hypoglycemic (0.57±0.05 vs 0.82±0.05 g/L). These results suggest the existence of an antagonism, in the effects on blood glucose, between tannins and probably flavonoid-like compounds. In type 2 diabetic rats, the daily administration of EABF (300 mg/kg/day, per os) varied blood glucose from 2.73±0.39 to 1.14±0.58 g/L (n=5, p<0.05). Similar effects were observed with EAB-TFF (300 mg/kg/day, per os), administered under the same conditions (1.12±0.04 g/L vs 3.01±0.5 g/L) (p<0.05, n=5). EABF has no effect on blood glucose in normo-glycemic rats, whereas under the same conditions, EAB-TFF induces an hypoglycemic effect. These results suggest the existence of compounds acting in opposite directions, in the regulation of blood glucose.