Studies on the presence of spasmogenic and spasmolytic constituents in Hibiscus rosasinensis aerial parts

The aqueous-ethanolic extract of the Hibiscus rosasinensis aerial parts (Hr.Cr) was studied for the possible presence of spasmogenic and spasmolytic constituents to rationalize some of its traditional uses in gastrointestinal disorders. Segments of isolated rabbit jejunum and guinea-pig ileum, 2-3 cm long were mounted seprately in Tyrode’s solution and aerated with 95% oxygen in carbon dioxide. Isotonic responses were measured on Bioscience oscillograph. The Hr.Cr at the dose of 1-10 mg/ml caused a moderate degree of atropine sensitive spasmogenic effect in guinea-pig ileum. In rabbit jejunum, Hr.Cr caused a dose-dependent (0.03-0.3 mg/mL) weak stimulatory effect on spontaneous contractions, followed by relaxation at the higher doses (1-3 mg/ml). In the presence of atropine (0.03 µM), the spasmogenic effect was abolished and the relaxant effect was obtained at lower doses (0.1-1.0 mg/ml) shifting the dose response curves to the left. The spasmolytic effect on the spontaneous and K+-induced contractions in atropinized preparations was mediated at the similar doses (0.03-1.0 mg/ml) suggestive of the involvement of calcium channel blocking (CCB) effect. The CCB effect was confirmed when pretreatment of the tissue with the Hr.Cr produced a dose-dependent shift in the Ca++ dose-response curves to the right, similar to that of verapamil, a standard calcium channel blocker. Activity-directed fractionation revealed that the spasmolytic effect is separated in ethyl acetate and dichloromethane fractions, while spasmogenic activity in the petroleum ether fraction. These data indicate that the crude extract of Hibiscus rosasinensis aerial parts contains spasmogenic and spasmolytic constituents mediating their effect through cholinergic and CCB actions respectively, which explains the traditional use of plant in the gastrointestinal disorders like constipation and diarrhea.