Calcium Channel Blockade Mediates the Vasorelaxant Activity of Dichloromethane Extract from Roots of Oncidium cebolleta on Isolated Rat Aorta

Abstract

Oncidium cebolleta belongs to the Orchidaceae family, and it is used in preparations in Mexican traditional medicine to treat several diseases. This research aimed to study the vasorelaxant activity of dichloromethane extract from the roots of Oncidium cebolleta (DEROc) on endothelium-intact and -removed rat aorta segments to determine its mode of vasorelaxant action. Several extracts (hexane, dichloromethane, and methanol) obtained from leaves and roots were evaluated on isolated rat aorta rings with and without endothelium to determine their vasorelaxant effect. Except for methanolic extract from leaves, all extracts induced a concentration-dependent vasorelaxant effect on endothelium-intact rat aorta rings pre-contracted with noradrenaline (NA, 0.1 µM). Dichloromethane extract from roots (DEROc) was the most potent and efficient, and the effect was endothelium-independent. Also, DEROc could relax KCl-induced contraction (80 mM) and inhibit the contraction induced by CaCl2-cumulative concentration on endothelium-denuded rings. However, DEROc was less potent than control nifedipine (L-type calcium channel blocker), but its effectiveness was similar. Contractions induced by NA and 5-HT [0.001 µM to 0.1 µM] were significantly reduced by DEROc. However, DEROc vasorelaxation was not reduced by TEA (potassium channel blocker, 10 mM) nor by ODQ (soluble guanylyl cyclase inhibitor, 0.1 µM) in endothelium-denuded aortic rings. Our functional results suggest that DEROc induces its relaxant effect by an endothelium-independent mechanism due to a Ca2+ channels blockade in rat aortic rings.