Juliette Koube

We previously reported that stem bark of Alstonia boonei De Wild. (Apocynaceae) aqueous extract significantly prevented the rise in blood glucose in the Oral Glucose Tolerance Test (OGTT). This result suggest that Alstonia boonei aqueous extract possesses antihyperglycemic properties. In the present study, we will examine whether or not Alstonia boonei stem bark aqueous extract inhibits intestinal glucose uptake or/and inhibits the intestinal alpha-glucosidases by using everted jejunum sacs from normal rats. We will also examine if the aqueous extract increases the uptake of glucose by the isolated diaphragm glucose uptake from normal and diabetic rats. The extract was tested at the concentrations of 2 mg/mL and 5 mg/mL, sodium fluoride (2 mol/dL) and insulin (10 UI/mL) were used as a positive control. Glucose and maltose were used respectively to evaluate inhibition of glucose absorption and alpha-glucosidase inhibition. The results showed that the extract at concentrations of 2 and 5 mg/mL caused a reduction of intestinal glucose uptake (respectively 26.01 ± 3.00 and 42.99 ± 0.91 %) and inhibited alpha-glucosidase (respectively 33.19 ± 1.25 and 49.88 ± 1.21 %) in a dose response manner. The results also showed that the aqueous extract of Alstonia boonei favors the entry and storage of glucose in the cell, this by activating the glucose transporters namely GLUT4. This study suggests that the aqueous extract of stem bark of Alstonia boonei inhibits the intestinal glucose uptake as well as digestive enzymes including alpha-glucosidases and favors the entry and storage of glucose in the cell.