Calcium antagonistic activity of Bacopa monniera on vascular and intestinal smooth muscles of rabbit and guinea-pig

The present study demonstrates the calcium antagonistic activity in ethanol extract of Bacopa monniera. The plant extract inhibited the spontaneous mo vements of both guinea-pig ileum (IC50 = 24 +/- 4 mu g/ml) and rabbit jejun um (IC50 = 136 +/- 9 mu g/ml). A marked reduction in acetylcholine- and his tamine-induced responses (0.0001-10 mu M) in the ileum was evident in the p resence of extract (260 mu g/ml). The acetylcholine (1 mu M)-induced contra ction in the ileum was also inhibited by the extract (100-700 mu g/ml) in a concentration dependent way (IC50 = 285 +/- 56 mu g/ml). All these results indicate a direct action of the extract on smooth muscles. Calcium chlorid e-induced responses in the rabbit blood vessels and jejunum were attenuated in the presence of plant extract (10-700 mu g/ml) implying a direct interf erence of plant extract with influx of calcium ions in the cells. However: the lack of modification of either noradrenaline- or caffeine-induced contr actions in the presence of extract suggests tl;at extract has no detectable effect on mobilization of intracellular calcium. These results indicate th at spasmolytic effect of the B. monniera extract in smooth muscles is predo minantly due to inhibition of calcium influx via both voltage and receptor operated calcium channels of the cell membrane. (C) 1999 Elsevier Science I reland Ltd. All rights reserved.