Positive inotropic effect of the leaf extracts of parent and tissue culture plants of Coleus amboinicus on an isolated perfused frog heart preparation

The leaves of the indigenous plant Coleus amboinicus Lour (Lamiaceae) possess a characteristic aroma and are used in many food preparations to enhance the flavour. Apart from this, they also exhibit medicinal properties. Aqueous extracts of fresh leaves of C. amboinicus Lour. parent (CAP), as well as tissue culture-raised plants (CAT), showed a dose-dependent positive inotropic effect on isolated frog heart. The extracts of CAT showed higher activity. The responses to CAP and CAT (50–800 μg) were not affected in either way by propranolol, atropine, verapamil or imidazole. The responses to both CAP and CAT were inhibited after lowering sodium chloride concentration (from 111 to 55.6 mM) and potentiated after increasing sodium chloride concentration (from 111 to 222 mM). Lignocaine was found to inhibit the responses significantly. Thus, C. amboinicus induces a positive inotropic effect, possibly by increasing sodium influx, leading to greater intracellular availability of calcium.