Effects of constituents of Beli (Aegle marmelos) on spontaneous beating and calcium-paradox of myocardial cells

Effects of methanolic extract of root bark of Beli (Aegle marmelos Corr.), an Ayurvedic crude drug used for heart diseases, and constituents isolated from the extract on spontaneous beating of cultured mouse myocardial cells were examined. The extract at a concentration of 100 micrograms/ml inhibited the beating rate by approximately 50%. Among the isolated constituents, aurapten was the most potent inhibitor; the IC50 of aurapten is 0.6 microgram/ml, which is comparable with that of verapamil, a calcium antagonist. Addition of aurapten at concentrations higher than 1 microgram/ml significantly reduced the ratio of morphologically changed myocardial cells which originated from calcium overload caused by successive treatment with calcium-free and calcium-containing solutions.