Mechanism of Endothelium-Dependent Vasodilation Induced by a Proanthocyanidin-Rich Fraction from Ouratea semiserrata

Abstract

The vasodilator effects of Ouratea semiserrata stem hydroethanolic extract (OSE) and its ethyl acetate fraction (OSR) were evaluated in endothelium-intact aortic rings. OSR produced a more potent vasodilatation (IC(50) = 3.5 +/- 0.8 microg/ml) than OSE (IC(50) > 30 microg/ml). OSR also presented a higher content of total proanthocyanidins (21.8 +/- 1.5 %) in comparison to OSE (6.5 +/- 0.4 %), suggesting that compounds of this class play a role in the vasorelaxing activity. The vasodilatation mechanism of OSR was further investigated. In endothelium-intact aortic rings, its vasorelaxing effect was completely abolished by L-NAME (300 microM), a nitric oxide (NO) synthase inhibitor, but not by a muscarinic antagonist (atropine, 1 microM) nor by a cyclo-oxygenase inhibitor (indomethacin, 10 microM). The OSR vasodilator effect was completely abolished in endothelium-denuded vessels. Furthermore, OSR did not change the vasodilatation produced by SIN-1, an NO donor, in endothelium-denuded vessels. These findings led us to conclude that OSR, a proanthocyanidin rich fraction of O. semiserrata, induces vasodilatation by a mechanism dependent on endothelium-derived factors, likely NO.

Hypotensive and vasorelaxant effects of the procyanidin fraction from Guazuma ulmifolia bark in normotensive and hypertensive rats

“…Previous in vitro studies have shown that procyanidins produce an endothelium-dependent relaxation in rat thoracic aorta and it is mediated by releasing NO from vascular endothelial cells (Cortes et al, 2002). The in vitro vasorelaxant effects produced by PCF were similar to those described by Cortes; thus, it can be postulated that the hypotensive effect observed in the present study is mediated at least in part, by an endothelial l-arginine/NO pathway.…”

“…pharmacological activity broad spectrum including both antihypertensive and vasorelaxant effects (Cheng et al, 1993;Cortes et al, 2002) which make us consider them remarkably as being responsible for the cardiovascular activity.…”

Biodiversidade flavonoídica e aspectos farmacológicos em espécies dos gêneros Ouratea e Luxemburgia (Ochnaceae)

“…O aumento da atividade dessa enzima está relacionado com a patogênese da maioria das complicações da diabetes, como cataratas, retinopatia, neuropatia 16 . O extrato hidroetanólico e a fração acetato de etila de O. semiserrata apresentaram efeito vasodilatador endotélio-dependente e atividade antiipertensiva in vitro, inibindo a conversão da enzima angiotensina I(ACE) 27 . O extrato aquoso de Ouratea sp., contendo proantocianidina, mostrou atividade antitumoral contra o carcinossarcoma de Walker 256 e sarcoma 180 em ratos 28,29 .…”

Um olhar holístico sobre a química de produtos naturais brasileira

“…Nestes dois estados a associação de grupos de PN e de farmacologia é sólida e vem de longa data. A determinação estrutural acoplada com atividade biológica também está consolidada nos estados do Rio de Janeiro 8 , São Paulo 9 e Minas Gerais 10 . O grupo de farmacologia de produtos naturais mais consolidado está no estado de Santa Catarina 11 .…”