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 evaluated 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 relaxations (pD 2 = 0.71 € 0.11; E max = 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 inhibition = 97 € 4%; n = 6) the contractions induced by CaCl 2 (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.
RESUMO: "Composição química e efeitos cardiovasculares do óleo essencial de Cymbopogon citratus DC. Stapf, Poaceae, em ratos". C. citratus é utilizada na medicina popular para tratar hipertensão. Este trabalho investigou a composição química e os efeitos cardiovasculares do óleo essencial do C. citratus (OECC). Foram identificados oito constituintes no OECC, sendo geranial o majoritário (43,08%). Em ratos, o OECC (1, 5, 10 e 20 mg/kg, i.v.) induziu hipotensão e bradicardia que foram atenuadas pela atropina e tiopental sódico, mas não por L-NAME ou indometacina. Em anéis de artéria mesentérica de ratos pré-contraídos com fenilefrina, o OECC (1 a 3000 µg/mL) induziu relaxamento que não foi afetado após remoção do endotélio, após TEA ou em anéis pré-contraídos com KCl (80 mM). Além disso, o OECC (1000 µg/mL) não induziu efeito adicional sobre o relaxamento máximo da nifedipina (10 µM). Em conclusão, o OECC induz hipotensão possivelmente devido à redução da resistência vascular que pode ser causada por inibição do influxo de Ca 2+ , e bradicardia provavelmente devido à ativação de receptores muscarínicos cardíacos.Unitermos: Cymbopogon citratus, óleo essencial, efeitos cardiovasculares, ratos. ABSTRACT:Cymbopogon citratus DC. Stapf, Poaceae, is used in the folk medicine for hypertension treatment. This work investigated the chemical composition and cardiovascular effects in rats of C. citratus essential oil (EOCC). A phytochemical screening demonstrated the presence of eight constituents, being geranial the major compound (43.08%). In rats, EOCC (1, 5, 10, and 20 mg/kg, i.v.) induced transient hypotension and bradycardia that were attenuated by atropine and sodium thiopental, but not by L-NAME or indomethacin. In rings of rat superior mesenteric artery pre-contracted with phenylephrine, EOCC (1 to 3000 µg/mL) induced relaxation that was not affected after removal of the endothelium, after TEA or in rings pre-contracted with KCl (80 mM). Furthermore, EOCC (1000 µg/mL) was not able to induce additional effect on maximal relaxation of nifedipine (10 µM). In conclusions, EOCC induces hypotension, possibly by reduction in vascular resistance caused by inhibition of the Ca 2+ influx, and bradycardia probably due to an activation of cardiac muscarinic receptors.
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