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Dihydrogoniothalamin is a styrylpyrone isolated from the leaves of Aniba panurensis. The present work aimed at investigating the vasorelaxant activity of dihydrogoniothalamin and its underlying mechanism of action in the rat aorta. Dihydrogoniothalamin (0.01-100 μM) induced a concentration- dependent vasodilatation of aortas precontracted with phenylephrine. Endothelium removal or pretreatment of the preparation with NG nitro- L-arginine-methyl-ester abolished the vasodilator response for dihydrogoniothalamin. Pretreatment with calmidazolium did not affect the vasodilator response of dihydrogoniothalamin. On the other hand, wortmannin, a nonselective inhibitor of phosphatidylinositol 3-kinases, and protein kinase B inhibitor IV significantly shifted the concentration-response curve of dihydrogoniothalamin to the right and reduced its maximal effect. A nonselective antagonist of estrogen receptors, ICI 182,780, and a selective antagonist of estrogen receptor α, methyl-piperidino-pyrazole, were able to reduce the relaxation induced by dihydrogoniothalamin, but no effect was observed in the presence of the selective antagonists of estrogen receptor β and G protein-coupled receptor 30, 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo [1,5-a]pyrimidin-3-yl]phenol (PHTPP), and G-15, respectively. Dihydrogoniothalamin also increased the phosphorylation of the activation sites of endothelial nitric oxide synthase and protein kinase B. The present results led us to conclude that dihydrogoniothalamin is a vasodilator drug acting in an endothelium- and nitric oxidedependent manner through a mechanism involving the activation of nitric oxide synthase via the phosphatidylinositol 3-kinase/protein kinase B pathway, partially by stimulation of estrogen receptor α. [ABSTRACT FROM AUTHOR]

Hypertension is a leading cause of death and disability globally, and its prevalence continues to accelerate. The cardiovascular effects of the flavonoid tiliroside have never been reported. In this work, using complementary in vivo and in vitro approaches, we describe the antihypertensive effect of tiliroside and the underlying mechanisms involved in the reduction of blood pressure. Tiliroside (1, 5 or 10mg/kg) induced a dose-dependent long-lasting decrease in blood pressure in conscious DOCA-salt hypertensive rats that was accompanied by an increased heart rate. Tiliroside also induced a concentration-dependent vasodilation of mesenteric resistance arteries precontracted with phenylephrine. Removal of the endothelium or pretreatment of the preparation with L-NAME or indomethacin did not modify the vasodilator response for tiliroside. When vessels were precontracted with a high K+ (50 mM) solution, tiliroside exhibited a vasodilator effect similar to that observed in vessels precontracted with phenylephrine. Experiments carried out in nominally Ca2+-free solution showed that tiliroside antagonized CaCl2-induced contractions. Moreover, tiliroside reduced the rise in intracellular Ca2+ concentration induced by membrane depolarization in vascular smooth muscle cells. Finally, tiliroside decreased the voltage-activated peak amplitude of the L-type Ca2+ channel current in freshly dissociated vascular smooth muscle cells from mesenteric arteries. Altogether, our results point to an antihypertensive effect of tiliroside due to a reduction in peripheral resistance through blockage of voltage-activated peak amplitude of the L-type Ca2+ channel in smooth muscle cells. [ABSTRACT FROM AUTHOR]