The spasmolytic activity of extracts and some isolated compounds from the leaves of Morinda morindoides (Baker) Milne-Redh. (Rubiaceae)

Abstract

Aim The study was aimed to evaluate the in vitro antispasmodic activity of Morinda morindoides leaves aqueous extract, its soluble fractions and isolated compounds to provide the pharmacological basis for its use for the treatment of constipation and diarrhoea in traditional medicine. Methods The antispasmodic activity of each sample was evaluated on acetylcholine (ACh) and the depolarized KCl solution induced contractions on guinea-pig isolated ileum suspended in Tyrode's solution. Results At a test concentration of 40 μg/ml in organ bath, the aqueous extract and its petroleum ether soluble fraction showed a spasmogenic effect on both agonists. The diethylether, ethyl acetate, n-butanol and residual aqueous phase soluble fractions from the partition of the aqueous extract exhibited spasmolytic activity producing 47–100% inhibition of contractions induced by both agonists with IC 50 values ranged from 6 to 15 μg/ml according to the case. In addition, the n-butanol and residual aqueous phase soluble fractions showed an inhibitory effect of 75 and 66% respectively on low high [K +] (25 mM) and 65 and 60% respectively on high [K+] (80 mM). Crude flavonoids showed spasmolytic on both agonists while crude saponins only showed spasmolytic activity on ACh and displayed spasmogenic effect on KCl. Quercetin, quercitrin and rutin exhibited significant antispasmodic effect with IC 50 values <0.1 μg/ml. Epoxygaertneroside and gaertneroside showed good antispasmodic activity on both agonists (4 < IC 50 < 7 μg/ml). Conclusion Morinda morindoides leaves possess spasmogenic and spasmolytic properties that can at least explain and support its traditional use against constipation and diarrhoea respectively.