RESUMEN
O 1,8-cineol, o α-pineno e β-pineno são monoterpenos constituintes do óleo essencial de plantas encontradas no Nordeste do Brasil como a "malva-santa" e o "eucalipto" (Óleo Essencial do Eucalyptus tereticornis - OEET) que, na medicina popular, são usadas no tratamento de distúrbios intestinais e respiratórios. As ações miorrelaxantes desses óleos essenciais são atribuídas à presença desses monoterpenos. Nosso objetivo foi estudar mais detalhadamente os efeitos desses constituintes, assim como o do OEET, sobre a contratilidade do músculo liso gastrintestinal e sobre o efeito procinético em ratos. No presente estudo, foram usados ratos Wistar machos (180-250g) sacrificados por deslocamento cervical. Tiras de duodeno, íleo e fundo de estômago foram cortados e mantidos em solução de Tyrode normal. As contrações isométricas foram registradas através de transdutores de força conectados a sistema computadorizado. Soluções contendo o 1,8-cineol, o α-pineno ou β-pineno foram preparadas em Tween 80 (concentração final <= 0,2% v/v). Usados isoladamente, o OEET, o 1,8-cineol, o α-pineno e β-pineno diminuíram o tônus basal em tiras de duodeno. Em tônus basal de tiras isoladas de fundo gástrico, o OEET e o 1,8-cineol possuíram efeito miorrelaxante, enquanto o α-pineno e o β-pineno possuíram efeito contrátil...
Asunto(s)
Humanos , Eucalyptus , Músculo Liso , Aceites VolátilesRESUMEN
The essential oil of Eucalyptus tereticornis (EOET) has pharmacological activities but their effects on the gastrointestinal tract are yet unknown. It possesses α- and ß-pinene as minor constituents, isomers largely used as food or drink additives. In this work, we studied their actions on gut motility. After feeding with a liquid test meal, conscious rats received perorally EOET, α-, or ß-pinene, and the fractional dye retention was determined. EOET and its constituents decreased the gastric retention. In anesthetized rats, pinenes increased gastric tonus, while enhancing the meal progression in the small intestine of conscious rats. Both α- and ß-pinene contracted gastric strips IN VITRO but relaxed the duodenum. Conversely, EOET relaxed both the gastric and duodenal strips. In conclusion, EOET accelerates the gastric emptying of liquid, and part of its action is attributed to the contrasting effects induced by α- and ß-pinene on the gut.
Asunto(s)
Compuestos Bicíclicos con Puentes/farmacología , Eucalyptus/química , Fármacos Gastrointestinales/farmacología , Motilidad Gastrointestinal/efectos de los fármacos , Monoterpenos/farmacología , Aceites Volátiles/farmacología , Aceites de Plantas/farmacología , Animales , Monoterpenos Bicíclicos , Fármacos Gastrointestinales/química , Fármacos Gastrointestinales/aislamiento & purificación , Masculino , Monoterpenos/química , Monoterpenos/aislamiento & purificación , Aceites Volátiles/química , Aceites Volátiles/aislamiento & purificación , Aceites de Plantas/química , Aceites de Plantas/aislamiento & purificación , Ratas , Ratas WistarRESUMEN
Previously, we reported that essential oil of Croton nepetaefolius (EOCN) decreases blood pressure in normotensive rats, an effect that seems resulting from its vasodilatory action directly upon vascular smooth muscle. In the present study, we aimed to study the role of endothelium-nitric oxide pathway in the mediation of vasodilatory effects of EOCN and two of its constituents, methyleugenol and alpha-terpineol, using rat isolated thoracic aorta and mesenteric vascular bed preparations. EOCN (1-300 microg/mL), in a concentration-dependent manner, relaxed isolated endothelium-intact aortic rings precontracted with KCl 60 mM, with an IC(50) value of 26.7 (14.7-48.2) microg/mL. Either pretreatment of the tissue with L-NAME, a nitric oxide synthase inhibitor, or mechanical endothelium removal increased significantly the IC(50) value to 66.6 (52.7-84.1) or 105.6 (91.3-122.2) microg/mL, respectively. In endothelium-intact aortic rings precontracted with norepinephrine, EOCN (10-200 microg/mL) produced a vasorelaxant action which was decreased by the pretreatment of the aortic rings with methylene blue, a guanylate cyclase inhibitor. In mesenteric bed preparations perfused under constant pressure, EOCN reverted the reduction of mesenteric flow caused by KCl (60 mM), an effect that was attenuated by L-NAME. Vasodilator responses to EOCN in mesenteric bed preparations were mimicked by methyleugenol and alpha-terpineol, and were also significantly reduced in the presence of L-NAME. In conclusion, EOCN has vasorelaxant effects in both a resistance vascular bed and in a conduit artery. They seem attributed, at least in part, to the actions of its main constituents methyleugenol and alpha-terpineol and appear partially dependent upon the integrity of a functional vascular endothelium. Inhibition of other transduction pathways may be involved in the mediation of these effects.
Asunto(s)
Aorta Torácica/efectos de los fármacos , Endotelio Vascular/fisiología , Euphorbiaceae/química , Aceites Volátiles/farmacología , Vasodilatadores/farmacología , Análisis de Varianza , Animales , Aorta Torácica/fisiología , Monoterpenos Ciclohexánicos , Ciclohexenos/farmacología , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/farmacología , Eugenol/análogos & derivados , Eugenol/farmacología , Técnicas In Vitro , Masculino , Arterias Mesentéricas/efectos de los fármacos , Monoterpenos/farmacología , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/fisiología , NG-Nitroarginina Metil Éster/farmacología , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa/antagonistas & inhibidores , Óxido Nítrico Sintasa/metabolismo , Ratas , Ratas Wistar , Vasodilatación/efectos de los fármacosRESUMEN
Intravenous (i.v.) treatment of conscious DOCA-salt hypertensive rats with the essential oil of Ocimum gratissimum L. (Labiatae) (EOOG) induced a hypotensive effect that seems related to an active vascular relaxation rather than withdrawal of sympathetic tone. To corroborate this hypothesis, the present study examined the vascular effects of EOOG and its main constituent, eugenol (EUG) and the putative mechanisms underlying these effects. Additionally, the role of the vascular beta(2)-adrenergic mechanism in the mediation of EOOG-induced hypotension has also been investigated. In conscious DOCA-salt hypertensive rats, the EOOG-induced hypotension was reversible and remained unchanged by i.v. pretreatment with propranolol (2 mg/kg). In isolated aorta preparations with intact endothelium from DOCA-salt hypertensive rats, EOOG (1-1000 microg/mL) and EUG (0.006-6 mM) relaxed the phenylephrine-induced contraction similarly with IC(50) [geometric mean (95% confidence interval)] values of 226.9 (147.8-348.3) microg/mL and 1.2 (0.6-2.1) mm, respectively. Vasorelaxant effects of EOOG were significantly altered by removal of the vascular endothelium [IC(50) = 417.2 (349.5-497.8) microg/mL]. In a calcium-free medium, the CaCl(2)-induced contractions were significantly reduced and even abolished by EOOG at 300 and 1000 microg/mL, respectively, whereas EOOG (1000 microg/mL) did not have any significant effect on caffeine-induced contractions. Similar results were obtained with EUG (1.8 and 6 mM) on both CaCl(2)- and caffeine-induced contractions, respectively. The data suggest that hypotensive responses to EOOG in DOCA-salt hypertensive rats are due to an active vascular relaxation, which is partly dependent upon the integrity of the vascular endothelium and seems predominantly mediated through an inhibition of plasmalemmal Ca(2+) influx rather than Ca(2+)-induced Ca(2+) release from the sarcoplasmic reticulum.