Endothelium-independent relaxation of aorta rings by two stilbenoids from the orchids Scaphyglottis livida

Abstract

Gigantol ( 1) and 3,7-dihydroxy-2,4-dimethoxyphenanthrene ( 2) from the orchid Scaphyglottis livida induced a significant concentration-dependent relaxation of the contractions evoked by noradrenaline (NA) in endothelium-intact and denuded rat aorta rings. Incubation with N G-nitro- l-arginine methyl ester ( l-NAME, 1 × 10 − 5 M) or methylene blue (MB, 1 × 10 − 7 M) significantly reduced the relaxation induced by the stilbenoids 1 and 2. The results suggested that two or more mechanisms are involved in the vasorelaxant effects of both compounds.