RESUMO
Carissa opaca (C.O) is a wild shrub, belonging to the family Apocynaceae. The medicinal virtues of this plant have long been known. The present study demonstrates the effects of aqueous-methanolic extract and various fractions (n-butanolic and aqueous) of Carissa opaca on cardiovascular parameters. The perfusion pressure (PP), force of contraction (FC) and heart rate (HR) were assessed on isolated heart of rabbit using Langendroff's technique for crude extract and fractions of C.O, followed by the elucidation of the mechanism of action after estimating toxicity of the plant. Negative ionotropic and positive chronotropic effects, with an increase in PP in isolated perfused rabbit heart were observed the with plant extract and fractions. The aqueous-methanolic extract exhibited maximum response at 1mg/ml while the n-butanolic and aqueous fractions showed a maximum response at 1mg/ml and 10µg/ml respectively. Both fractions produced the same response when treated with atropine (10-5 M), however the actions of adrenaline (10-5 M) and calcium chloride (10-5 M) remained unblocked. Acute toxicity studies indicated that the plant was safe up to 2000 mg/kg and sub-chronic studies demonstrated that no significant change in haematological and biochemical parameters observed. In conclusion, this study supports the folkloric claim of C.O extract.