Vasodilator profile of flavonoid and phenylbutanoid compounds isolated from Croton schiedeanus Schlecht

Background. Croton schiedeanus Schlecht (Euphorbiaceae), specie is used in Colombian folk medicine in hypertension treatment. Objective. To assess the vasorelaxant effect of the flavonoid compounds: 3-O-methyl-quercetin, 3,7-di-O-methylquercetin, and 3,3',4',7-tetra-O-methylquercetin, and the phenylbutanoids compounds: (2S)-7,9-dimethoxyrhododendrol, (2S)-2-acetoxy-7,9-dimetho-xyrho-dodendrol, (2S)-2,8-diacetatoxy-7,9-dimethoxyrho-dodendrol in isolated aortic rings of Wistar rats. Materials and methods. These compounds were evaluated in phenylephrine (PE, 1 µM) and KCl (80 mM) precontracted aortic rings. In order to examine possible interactions related with: endothelium, nitric oxide (NO), guanylyl ciclasa, prostanoid or ATP dependent potassium (K+ATP) channels, the compounds with greater relaxant effect: 3-O-methylquercetin, and 3,7-di-O-methylquer-cetin, were assessed in phenylephrine precontracted rings in presence or absence of: endothelium, L-NAME (G -nitro-L-Arginine-Methyl Ester, 100 µM), ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, 1 µM), sodium meclofenamate (10 µM) or glibenclamide (1 µM). Results. Whereas phenylbutanoid compounds did not shown significant relaxant properties, 3-O-methylquercetin and 3,7-di-O-methyl-quercetin displayed important vasodilator responses with IC50 of 2.5 and 4.9 µM against phenylephrine respectively. ODQ and L-NAME effectively displaced to the right the dose-response curves of these compounds, especially in the case of 3-O-methylquercetin (IC50 ratio: 7.4 and 3.8) whereas glibenclamide did not and meclofenamate only slightly. Conclusion. 3-O-methylquercetin and 3,7-di-O-methylquercetin, flavonoid compounds isolated from Croton schiedeanus play important vasorelaxant effects related to the NO/cyclic GMP pathway. These results support the etnobotanical use of Croton schiedeanus.