Myorelaxant effect of aqueous root bark extract of Carissa edulis (Forssk.) Vahl. is mediated through activation of nitric oxide synthase

Abstract

Many patients in Africa often utilize herbal medicine for the management of hyperactive gut disorders such as diarrhea and abdominal colic. There is therefore a need to scientifically evaluate efficacy of this herbal remedies. This study investigated the myorelaxant effect of Carissa edulis (Forssk.) Vahl and its possible mechanism of action using isolated rabbit jejunum preparations. Pieces of jejunum were isolated from adult New Zealand white rabbits. They were then mounted in an organ bath containing Tyrode's solution. The rate and force of jejunal contraction were recorded and analyzed using a Powerlab that was coupled to Chart5 software for windows. The effects of the extract (0.1-10.0 mg/ml) on spontaneous contraction were investigated. Its effect (3.0 mg/ml) was also studied in the presence of L G-NAME (nitric oxide synthase inhibitor), methylene blue (soluble guanylyl cyclase inhibitor) and propranolol (non-selective β adrenergic receptors antagonist). The extract dose-dependent significantly decreased the force but not the rate of spontaneous rabbit jejunal contraction. Among the blockers used, only L G-NAME significantly blocked the effect of the extract. Aqueous root bark extracts of C. edulis possess significant myorelaxant effect on isolated rabbit jejunum. This appears to be mediated through stimulation of nitric oxide release by nitric oxide synthase.