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

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 NG-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.