Prokinetic and laxative effects of the crude methanolic extract of Viola betonicifolia whole plant in rodents

BACKGROUND The present study was aimed to provide ethnopharmacological basis for the medicinal use of Viola betonicifolia whole plant in indigestion and constipation. METHODS Mice were used in in-vivo prokinetic and laxative studies while in-vitro experiments were conducted on isolated tissues of rabbit and guinea-pig gut preparations suspended in a tissue bath to measure isotonic contractions. RESULTS The crude methanolic extract of Viola betonicifolia (VBME) showed partially atropine-sensitive prokinetic (50 and 100 mg/kg) and laxative (30 and 100 mg/kg) activities in mice. When tested in isolated rabbit jejunum and guinea-pig ileum, VBME caused dose-dependent contractions at 0.01-0.3 mg/mL and 0.03-5 mg/mL, respectively. The spasmogenic effect was partially sensitive to atropine, while the presence of pyrilamine, SB203186 or hexamethonium had no effect in both gut preparations. VBME partially inhibited acetylcholinesterase enzyme (19%) in the in-vitro assay. The spasmodic effect of VBME was more efficacious in guinea-pig ileum than rabbit jejunum preparation. The phytochemical analysis of the crude methanolic extract for total alkaloids and saponins revealed that the VBME is a rich source of alkaloids and saponins. CONCLUSIONS This study showed the prokinetic and laxative effects of Viola betonicifolia in mice, partially mediated through cholinergic action. The in-vitro spasmodic effect of the plant extract was also partially sensitive to atropine indicating more than one mechanisms in the gut stimulant effect. This study provides a rationale for the medicinal use of Viola betonicifolia in indigestion and constipation.