Hypotensive and Vasorelaxant Effects of Citronellol, a Monoterpene Alcohol, in Rats

Citronellol is an essential oil constituent from the medicinal plants Cymbopogon citratus, Cymbopogon winterianus and Lippia alba which are thought to possess antihypertensive properties. Citronellol-induced cardiovascular effects were eval- uated in this study. In rats, citronellol (1-20 mg ⁄ kg, i.v.) induced hypotension, which was not affected by pre-treatment with atropine, hexamethonium, N x -nitro-L-arginine methyl ester hydrochloride or indomethacin, and tachycardia, which was only attenuated by pre-treatment with atropine and hexamethonium. These responses were less than those obtained for nifedipine, a reference drug. In intact rings of rat mesenteric artery pre-contracted with 10 lM phenylephrine, citronellol induced relax- ations (pD2 = 0.71 € 0.11; Emax = 102 € 5%; n = 6) that were not affected by endothelium removal, after tetraethylamonium in rings without endothelium pre-contracted with KCl 80 mM. Citronellol strongly antagonized (maximal inhibi- tion = 97 € 4%; n = 6) the contractions induced by CaCl2 (10 )6 to 3 · 10 )3 M) and did not induce additional effects on the maximal response of nifedipine (10 lM). Finally, citronellol inhibited the contractions induced by 10 lM phenylephrine or 20 mM caffeine. The present results suggest that citronellol lowers blood pressure by a direct effect on the vascular smooth muscle leading to vasodilation.