Efeito hipotensor e anti-hipertensivo do extrato hexânico das folhas de Anacardium Occidentale linn em ratos

Abstract

Hypertension is a chronic disease difficult to control characterized low rate adherence to medication, wherefore, the use of alternative therapies, herbs occurs at a very high rate among patients with cardiovascular disease including hypertension. Anacardium occidentale Linn. (Anacardiaceae) popularly known as cashew, is present on the national list of plants of interest to the SUS. It is used in folk medicine as anti-inflammatory against arthritis, diabetes. The literature reports cardiovascular studies with extracts of this plant with potent antihypertensive effect induced by bark extract. Anacardium occidentale L leaves extracts exhibited relaxing effect on isolated rat aortic ring preparations. Hence, present study was designed to study the acute cardiovascular effects of the Anacardium occidentale L. leaves hexane extract (AOHE) in rats, by in vivo and in vitro approach. AOHE (0.5; 1; 5; 10; 20 and 30 mg/kg, i.v.) induced hypotensive (-12.9 ± 1.1, -10.8 ± 1, 1, -15.5 ± 1.6, -19.7 ± 3.0, -20.9 ± 2.8 and -17.7 ± 0.9%, respectively) and bradycardic (-7.5 ± 0.7, -4.5 ± 1, 0, -9.3 ± 2.5, -16.8 ± 0.8, -31.0 ± 1.3 and -19.9 ± 0.9%, respectively). This response was changed after preinjection L-NAME, no selective Nitric Oxide (NO) synthase inhibitor, the hypontensive effect was attenuated, as well as, the bradycardia was blocked or reversed. Similary, a inhibitor of cyclooxygenase (indomethacin, 3 mg/kg, i.v.) produced attenuation of hypotensive action induced by AOHE and abolished or reversed the bradycardia response. Pretreatment with muscarinic antagonist, atropine, reduced the hypotensor effect. Moreover, the depressor effects of extract on heart rates were abolished or reversed (only, 30 mg/kg, i.v.). On the other hand, the administration of ganglionic blocker, hexamethoniun, produced significantly change the pressor response AOHE-induced, except in the second, fifth and sixth dose. However, the bradycardic effect was abolished. In the superior mesenteric artery rings isolated from rats pre-contracted with FEN (100 μM), EHAO (1 to 1000 μg / mL) induced vasorelaxation, concentration dependent manner and dependent on the presence of functional endothelium (Emax = 52.56 ± 3.4 %). Similarly EHAO induced vasorelaxation in rings precontracted with 80 mM KCl concentration dependent manner and dependent on the presence of functional endothelium (Emax = 33.30 ± 3.20 %). The administration of a single intragastric dose of 300 mg/kg of AOHE produced antihypertensive activity after the 2h. Our results suggest wich hypotensive, bradycardiac and antihypertensive responses could be mediated by the endothelial and cardiac muscarinic receptors or EDRFs.