Abstract
The effects of the volatile oil of Rosmarinus officinalis leaves on the vascular smooth muscle of rabbit were tested in vitro using isolated aortic segments (rings). The volatile oil of R. officinalis leaves inhibited the contractions of rabbit aortic rings induced by norepinephrine (NE) stimulation in Ca2+-containing solution. Also, the volatile oil inhibited the contractions of rabbit aortic rings induced by high potassium (K+) solutions. This inhibition was dose-dependent and reversible. Furthermore, the volatile oil inhibited the contractions of rabbit aortic rings induced by NE stimulation in Ca2+-free solution. These data suggest that the volatile oil of R. officinalis leaves has a direct vascular smooth muscle relaxant effect.