Estudo farmacológico do óleo essencial de Ocimum basilicum L. e seu componente majoritário (estragol) em músculo liso aórtico de ratos

Abstract

Ocimum basilicum L., popularly known as basil, has several biological activities related to the essential oil present in its leaves, such as: antifungal, insect repellent, anti-giardia, antioxidant capacity, anxiolytic and sedative. Some studies indicate that the plant has antihypertensive and vasodilatory activity. The present study aims to characterize the pharmacological effects of the essential oil of Ocimum basilicum L. (EOOB) and its major component, estragole, on the vascular smooth muscle of rats through isometric voltage recordings in a data acquisition system. In rat aortic ring preparations, EOOB (1 – 1000 µg/mL) and estragole (1 - 1000 µg / ml) relaxed in a concentration-dependent manner contractions induced by Phe (1 µM), KCl (60 mM) and U-46619 (0.3 µM) (p <0.001, ANOVA). The potency of EOOB to induce vasodilator effect was significantly higher in the presence of the thromboxane analog, U-46619 (0.3 µM). However, only in experiments with EOOB in the presence of Phe (1 µM) was observed a significant difference between the EC50 values of rings with and without intact endothelium (494,7 [425,7 – 569,2] µg/ml e 203,6 [142,9 – 281,0] µg/ml, respectively) (p < 0,05, Mann-Whitney), where it was observed that rings with intact endothelium had a greater difficulty in presenting the relaxing effect of OEOB. In order to evaluate the possible effect of endothelium participation on stimulation with the adrenergic agonist, protocols of concentration-effect curves were performed in the presence of acetylcholine (ACh), sodium nitroprusside (SNP), L-NAME and ruthenium red (20 µM), a TRPV4 channel inhibitor, and it was observed that the endothelium may be involved in promoting difficulty in smooth muscle relaxation through the action of OEOB on TRPV4 receptors present in the endothelium. We also evaluated the ability of EOOB to act on IP3 receptors located in RS through experiments on a calcium-free medium, where it was observed that the transient contraction induced by Phe (10 µM) was not abolished in the presence of EOOB (500 µg / mL). NaVO3, an inhibitory agent of the phosphatases enzymes, was used in increasing concentrations to evaluate the action of EOOB and estragole on enzymes phosphatases and kinases, being verified that they were not able to inhibit the contraction induced by NaVO3. The present study demonstrates that OEOB and its major component (estragol) have vasorelaxant activity in a concentration dependent-manner in aortic rings isolated from rats, with OEOB being more potent and that vascular endothelium is involved when contraction of was induced through the adrenergic pathway.