Avaliação dos efeitos cardiovasculares induzidos pelo extrato hidroalcoólico dos frutos de Syzygium cumini (L.) Skeels

Abstract

The cardiovascular effects of hydroalcoholic extract of the Syzygium cumini (L.) Skeels fruits (Myrtaceae) (EHSCF) were study in rats using a combination of in vivo and in vitro. After administration of single oral dose (200 mg/kg) we observed a significant decrease in blood pressure from four hours after administration in spontaneously hypertensive rats (SHR) Moreover EHFSC (0.5; 1; 5; 10; 20 and 30 mg/kg; i.v.) produced hypotension ( -15.1 ± 1.4%; - 13.8 ± 1.1%; -14.9 ± 1.5%; -13 ± 0.9%; -11.2 ± 1.5 and -13 ± 1.7%, respectively) associated with bradycardia (-5.7 ± 1%; -5.3 ± 1.3%; -5.6 ± 0.5%; -14 ± 1.5%; -8.3 ± 1% and -9.6 ± 1.7%, respectively) in normotensive rats, as well as SHR, hypotension (-7.4 ± 0.5%; -11 ± 2%; -8 ± 1%;-5.9 ± 0.7%; -9 ± 0.7% and -9.9 ±1.6%, respectively) followed by bradycardic effect (-0.8 ± 0.8%; -3.5 ± 2%; -3.3 ± 0.5%; -0.4 ± 0.3%; -4.0 ± 0.3% e -6.9 ± 1.5%, respectively).The bradycardia was reversed in tachycardia (2.3 ± 0.5%; 1.3 ± 0.9%; 2.4 ± 1.3%; 2.5 ± 1.2%; 0.1 ± 1.1% and 5 ± 0.6%, respectively) after L-NAME (20 mg/kg), after indomethacin (2 mg/kg) both hypotension (-4.8 ± 0.9%; -3.8 ± 0.4%; -8.6 ± 0.9%; -6.1 ± 0.9%; -3.8 ± 0.5% and -4.6 ± 1.1%, respectively) and bradycardia (1.6 ± 1.2%; 2.1 ± 0.4;% -0.9 ± 0.5%; -2.0 ± 1.6% and -1.7 ± 0.8%, respectively) were reduced and after pretreatment with atropine the bradycardic effect was attenuate jus in higher doses (-2.4 ± 1%; -4.1 ± 0.9%; -5.2 ± 1% and -5.2 ± 0.4%, respectively). The hypotension just doses 0.5; 5 and 10 mg/kg (-6.8 ± 0.7; -5.8 ± 1 % and -7.9 ± 1.9%, respectively) and bradycardia in all doses (-0.1 ± 0.5%; -1.5 ± 0.9%; -2.3 ± 0.7%; 1.5 ± 1.5% and 3.7 ± 0.8%, respectively) were significantly reduced after hexamethonium. Moreover, EHFSC (1 - 1000 μg/mL) induced a concentration-dependent vasodilator effect in endothelium-dependent in mesenteric artery rings pre-contracted by Phe (10-4 M) and KCl (80 mM) (pD2 = 2.74 0.1 e 2.16 0.06 μg/mL, respectively). L-NAME (100 μM) pretreatment not inhibited the vasorelaxation inibido (pD2= 2.92 0.12 μg/mL), however in KCl (20 mM) preparations vasorelaxant response was attenuated (pD2= 1.73 0.1 μg/mL). These results so far show that extract induced antihypertensive effect and hypotension due the probably release of prostanoids and bradycardia which could be due to both indirect cardiac muscarinic activation. The vasorelaxant effect is probably mediated by potassium channel activated in endothelium.