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.

Caesalpinia ferrea is a plant very used in the folk medicine for treatment of several diseases, such as diabetes. This study investigated the cardiovascular effects of the aqueous extract from stem bark of C. ferrea (AECF). In non-anesthetized rats, AECF (10, 20, 40, 60 and 80 mg/kg; i.v.) induced hypotension (-9+/-1;-12+/-1;-14+/-1; -20+/-3 and -51+/-6%; respectively) and tachycardia (6+/-1; 8+/-1; 12+/-2; 14+/-2 and 26+/-3%; respectively). Hypotension was not affected after atropine or L-NAME. Furthermore, AECF (40 mg/kg) induced atrioventricular block and extrasystoles, which was not affected after atropine. In intact rings of the rat mesenteric artery, AECF (0.001-30 mg/ml, n=6) induced relaxations of phenylephrine tonus (Emax=110+/-4%), which was not changed after the removal of endothelium (Emax=113+/-9%). In rings without endothelium pre-contracted with KCl 80 mM, phenylephrine plus KCl 20 mM or phenylephrine plus glibenclamide, the curve to AECF was significantly attenuated (Emax=24+/-4%, 70+/-5% and 62+/-7%, respectively, n=6), but was not affected in the presence of tetraethylammonium or 4-aminopyridine (Emax=125+/-15% and 114+/-7%, respectively, n=6). These results demonstrate that AECF induces hypotension associated to tachycardia; however, in dose of 40 mg/kg, AECF induces transient bradyarrhythmias. Furthermore, AECF induces vasodilatation in rat mesenteric artery which appears to be mediated by ATP-sensitive K+ channel openings.

These results demonstrated that EOCW induced hypotension and vasorelaxation. These effects appeared to be mainly mediated by Ca(+2)-channel blocking. Furthermore, the higher dose of EOCW induced transient bradycardia and arrhythmias due to a cardiac muscarinic activation secondary to a vagal discharge.

This work aimed to characterize and evaluate the antihypertensive effect of the (-)-β-pinene/β-cyclodextrin (βP/β-CD) complex. The complex was prepared through physical mixture and slurry complexation methods and was analyzed through differential scanning calorimetry, thermogravimetry/derivative thermogravimetry, fourier transform infrared spectroscopy, diffraction X-ray, docking and scanning electron microscopy. Normotensive or L-NAME-induced hypertensive rats were used in pharmacological experiments. Mean arterial pressure (MAP) was determined with direct blood pressure measurements from the abdominal aorta. The drugs were orally administrated and their effects were recorded during 48 hours. Vascular effects of βP were evaluated in isolated ring of mesenteric artery. The physicochemical characterization showed βP/β-CD complex formation. In hypertensive rats (MAP = 156±16 mmHg), the complex, but not βP alone, promoted hypotension at 36 and 48 hours after administration (MAP = 124±3 and 110±5 mmHg, respectively). In arterial rings, βP vasorelaxed rings precontracted with phenylephrine (Emax = 105±6%), which was not changed after the removal of the vascular endothelium (Emax = 108±4%), after the pre-contraction with KCl 80 mM (Emax = 107±8%) or S(-)-BayK8644 (Emax = 107±5%), or after incubation with TEA (Emax = 113±4%). Finally, βP inhibited CaCl2- and sodium-orthovanadate-induced contractions. In conclusion, the slurry complexation method was the best among them. Pharmacological results demonstrated that the complex promoted antihypertensive effect. Furthermore, βP induced endothelium- independent vasorelaxation possibly caused by the inhibition of the Ca2+ influx through L-type Ca2+ channel associated to a decrease in calcium sensitivity.

RESUMO: "Efeito vasorelaxante do extrato diclorometano de Hyptis fruticosa Salzm. ex Benth., Lamiaceae, em artéria mesentérica de ratos". O efeito vasorelaxante do extrato diclorometano de Hyptis fruticosa Salzm. ex Benth., Lamiaceae (HFDE), em anéis isolados de artéria mesentérica de ratos foi avaliado nesse estudo. Em anéis intactos, pré-contraídos com fenilefrina (10 µM), HFDE (0,1-3000 µg/mL) induziu vasorelaxamento de maneira dependente de concentração (E max = 119±14%; n = 6), o qual não foi afetado após remoção do endotélio (E max = 116±6%; n = 6), após KCl 20 mM (E max = 135±9%; n = 6) ou em anéis pré-contraídos com KCl 80 mM (E max = 125±4%; n = 6). Em anéis sem endotélio, HFDE (300 ou 1000 µg/mL) inibiu as contrações induzidas por CaCl 2 (inibição máxima = 25±7% e 95±1%, respectivamente). Além disso, HFDE promoveu um vasorelaxamento adicional (15±3%; n = 7) sobre o relaxamento máximo de 10 µM de nifedipina (78±3%, n = 7). Em conclusão, HFDE induz efeito vasorelaxante através de uma via independente de endotélio, possivelmente devido à inibição do influxo de Ca 2+ através de canais de Ca 2+ operados por voltagem. Unitermos:Hyptis fruticosa, extrato diclorometano, efeito vasorelaxante, artéria mesentérica, ratos.ABSTRACT: Vasorelaxant effect of Hyptis fruticosa dichloromethane extract (HFDE) on isolated rings of rat mesenteric artery was evaluated in this study. In intact rings, HFDE (0.1-3000 µg/ mL) induced concentration-dependent vasorelaxations (E max = 119±14%; n = 6) of phenylephrine tonus that were not modified after endothelium removal (E max = 116±6%; n = 6), after KCl 20 mM (E max = 135±9%; n = 6) or in rings pre-contracted with KCl 80 mM (E max = 125±4%; n = 6). In endothelium denuded rings, HFDE (300 or 1000 µg/mL) inhibited contractions induced by CaCl 2 (maximal inhibition = 25±7% and 95±1%; respectively). Furthermore, HFDE promoted an additional vasorelaxation (15±3%; n = 7) after maximal response of 10 µM nifedipine (78±3%; n = 7). In conclusion, HFDE induces vasorelaxant effect through an endothelium-independent pathway, which mostly seems to occur due inhibition of the Ca 2+ influx through voltage-operated Ca 2+ channels.