Vasodilatory and hypoglycaemic effects of two pyrano-isoflavone extractives from Eriosema kraussianum N. E. Br. [Fabaceae] rootstock in experimental rat models

Zulu traditional health practitioners have claimed that the roots of Eriosema kraussianum N. E. Br. (Fabaceae) and other Eriosema species (Zulu indigenous umbrella name of "uBangalala") are effective remedies for the treatment of erectile dysfunction (ED) and/or impotence. In order to scientifically appraise the significance and contribution of Eriosema kraussianum to its ethnomedical use as "uBangalala" and "VIAGRA substitute", the present study was undertaken to investigate the vasodilatory and hypoglycaemic properties of the two main bioactive chemical compounds [Kraussianone-1 (K1), and Kraussianone-2 (K2), Drewes, S.E., Horn, M.M., Munro, O.Q., Dhlamini, J.T.B., Meyer, J.J.M., Rakuambo, N.C., 2002. Pyrano-isoflavones with erectile-dysfunction activity from Eriosema kraussianum. Phytochemistry 59 739-747.] obtained from E. kraussianum, in experimental rat models, using sildenafil citrate (VIAGRA) as the reference drug for comparison. The two E. kraussianum rootstock constituents (K1 and K2, 20-80 mg/kg p.o.) caused dose-dependent and significant (P < 0.05-0.001) hypoglycaemia in rats. Relatively low to high concentrations of the plant's extracts (K1 and K2, 100-2000 μg/ml) always produced biphasic effects on rat isolated portal veins. K1- and K2-provoked responses of the isolated portal veins always consisted of concentration-related initial transient, but significant (P < 0.05), contractions of the venous muscle preparations, followed by secondary, longer-lasting, highly significant (P < 0.01-0.001) relaxations of the venous muscle strips. Sildenafil citrate (VIAGRA, 5-100 μg/ml) always produced concentration-related and highly significant relaxations of the rat isolated portal veins. Unlike K1 and K2 (20-80 mg/kg p.o.), however, sildenafil citrate (VIAGRA, 100 mg/kg p. o.) only caused slight and insignificant (P > 0.05) reductions in the blood glucose levels of the experimental animals used. On the other hand, glibenclamide (10 mg/kg p.o.) induced highly significant (P < 0.05-0.001), marked reductions in the blood glucose concentrations of the rats. The findings of this laboratory animal study indicate that the two hydro-ethanol extractives of E. kraussianum (K1 and K2) possess hypoglycaemic and secondary, vasorelaxant effects in the experimental paradigms used.