Cardiodepressive effect elicited by the essential oil of Alpinia speciosa is related to L-type Ca2+ current blockade

This study was undertaken to elucidate the effect of the essential oil from Alpinia speciosa (EOAs) on cardiac contractility and the underlying mechanisms. The essential oil was obtained from Alpinia speciosa leaves and flowers and the oil was analyzed by GC-MS method. Chemical analysis revealed the presence of at least 18 components. Terpinen-4-ol and 1,8-cineole corresponded to 38% and 18% of the crude oil, respectively. The experiments were conducted on spontaneously-beating right atria and on electrically stimulated left atria isolated from adult rats. The effect of EOAs on the isometric contractions and cardiac frequency in vitro was examined. EOAs decreased rat left atrial force of contraction with an EC50 of 292.2 ± 75.7 μg/ml. Nifedipine, a well known L-type Ca2+ blocker, inhibited in a concentration-dependent manner left atrial force of contraction with an EC50 of 12.1 ± 3.5 μg/ml. Sinus rhythm was diminished by EOAs with an EC50 of 595.4 ± 56.2 μg/ml. Whole-cell L-type Ca2+ currents were recorded by using the patch-clamp technique. EOAs at 25 μg/ml decreased ICa,L by 32.6 ± 9.2% and at 250 μg/ml it decreased by 89.3 ± 7.4%. Thus, inhibition of L-type Ca2+ channels is involved in the cardiodepressive effect elicited by the essential oil of Alpinia speciosa in rat heart.