Endothelium-dependent vasorelaxant effects of the essential oil from aerial parts of Alpinia zerumbet and its main constituent 1,8-cineole in rats

Vasorelaxant effects of essential oil of Alpinia zerumbet (EOAZ) and its main constituent, 1,8-cineole (CIN) were Studied In rat isolated aorta preparations with intact endothelium, EOAZ (0.01-3000 mu g/ml.) induced significant but Incomplete relaxation of the phenylephrine-induced contraction. all effect that wits abolished by removal of vascular endothelium. However, at the same concentrations (0.01-3000 mu g/ml corresponding to 0 0000647-19.5 mM), CIN induced a complete vasorelaxant. effects (IC50 = 663.2 +/- 63 8 mu g/ml) that were significantly reduced in endothelium-denuded rings (IC50 = 1620.6 +/- 35.7 mu g/ml). Neither EOAZ nor CIN affected the basal tonus of isolated aorta. Vasorelaxant effects of both EOAZ and CIN remained unaffected by the addition of tetraethylamonium chloride (500 mu M) or indomethacin (10 mu M) into the bath, but were significantly reduced by N-G-nitro-L-arginine methyl ester (100 mu M) It IS Concluded that EOAZ induces a potent vasorelaxant effect that Could not be fully attributed to the actions of the main constituent CIN, and appears totally dependent oil the integrity of a functional vascular endothelium. The data is novel and corroborate the popular use of A. zerumbet for the treatment of hypertension. (C) 2009 Elsevier GmbH. All rights reserved