Vasorelaxant Effect of Mexican Medicinal Plants on Isolated Rat Aorta

Abstract

The vasorelaxant effect of methanol extracts (0.86–50 µg/ml) of Iresine calea, Psyttacanthus calyculathus. (DC.) G. Don, Laelia autumnalis. (Lex.) Lindley, Brickellia cavanillesii. (Cass.) Gray, and Lepechinia caulescens. (Ortega) Epling, plant species used in Mexican folk medicine for the treatment of hypertension and related diseases, were evaluated in isolated rat aortic rings. The extracts of I. calea. and P. calyculathus. did not show a vasorelaxant activity on norepinephrine-evoked contraction (NE, 1 × 10−7.5 M) in endothelium-intact (+ E) and endothelium-denuded (− E) rat aorta rings. On the other hand, L. autumnalis. and B. cavanillesii. induced a concentration-dependent and endothelium-independent relaxation on rat aorta. However, the methanol extract of L. caulescens. produced a significant vasodilator effect in a concentration-dependent and endothelium-dependent manner. In order to determine the mode of the vasorelaxant action evoked by L. caulescens., the extract was evaluated in the presence of L-NAME (inhibitor of nitric oxide synthase at 1 × 10−4 M) and indomethacin (inhibitor of cyclooxygenases at 1 × 10−5 M). Relaxation was blocked by L-NAME, indicating the extract vasodilating properties are endothelium mediated due to liberation of nitric oxide.