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Some in vitro and in vivo evidence is consistent with the cardiovascular beneficial activity of propolis. As the single actors responsible for this effect have never been identified, an in-depth investigation of flavonoids isolated from the green propolis of the Caatinga Mimosa tenuiflora was performed and their mechanism of action was described. A comprehensive electrophysiology, functional, and molecular docking approach was applied. Most flavanones and flavones were effective CaV 1.2 channel blockers with a potency order of (2S)-sakuranetin > eriodictyol-7,3′-methyl ether > quercetin 3-methyl ether > 5,4′-dihydroxy-6,7-dimethoxyflavanone > santin > axillarin > penduletin > kumatakenin, ermanin and viscosine being weak or modest stimulators. Except for eriodictyol 5-O-methyl ether, all the flavonoids were also effective spasmolytic agents of vascular rings, kumatakenin and viscosine also showing an endothelium-dependent activity. (2S)-Sakuranetin also stimulated KCa 1.1 channels both in single myocytes and vascular rings. In silico analysis provided interesting insights into the mode of action of (2S)-sakuranetin within both CaV 1.2 and KCa 1.1 channels. The green propolis of the Caatinga Mimosa tenuiflora is a valuable source of multi-target vasoactive flavonoids: this evidence reinforces its nutraceutical value in the cardiovascular disease prevention arena. [ABSTRACT FROM AUTHOR]

Five compounds, 3,4′-dihydroxy-3′,5,5′-trimethoxydihydrostilbene, 1 ; 3,4′-ihydroxy-3′,5′-dimethoxydihydrostilbene, 2 ; 3,4′-dihydroxy-5,5′-dimethoxydihydrostilbene, 3 ; 9,10-dihydro-2,7-dihydroxy-4,6-dimethoxyphenanthrene, 4 ; and the previously unreported 1,2,6,7-tetrahydroxy-4-methoxyphenanthrene, 5 were isolated from the South American orchid, Brasiliorchis porphyrostele. An in-depth analysis of their vascular effects was performed on in vitro rat aorta rings and tail main artery myocytes. Compounds 1 – 4 were shown to possess vasorelaxant activity on rings pre-contracted by the α 1 receptor agonist phenylephrine, the CaV 1.2 stimulator (S)-(−)-Bay K 8644, or depolarized with high K+ concentrations. However, compound 5 was active solely on rings stimulated by 25 mM but not 60 mM K+. The spasmolytic activity of compounds 1 and 4 was significantly affected by the presence of an intact endothelium. The KATP channel blocker glibenclamide and the KV channel blocker 4-aminopyridine significantly antagonized the vasorelaxant activity of compounds 4 and 1 , respectively. In patch-clamp experiments, compounds 1 – 4 inhibited Ba2+ current through CaV 1.2 channels in a concentration-dependent manner, whereas neither compound 4 nor compound 1 affected K+ currents through KATP and KV channels, respectively. The present in vitro , comprehensive study demonstrates that Brasiliorchis porphyrostele may represent a source of vasoactive agents potentially useful for the development of novel antihypertensive agents that has now to be validated in vivo in animal models of hypertension. [ABSTRACT FROM AUTHOR]

Dalbergia species heartwood, widely used in traditional medicine to treat various cardiovascular diseases, might represent a rich source of vasoactive agents. In Vietnam, Dalbergia tonkinensis is an endemic tree. Therefore, the aim of the present work was to investigate the vascular activity of R -(−)-3′-hydroxy-2,4,5-trimethoxydalbergiquinol isolated from the heartwood of D. tonkinensis and to provide circular dichroism features of its R absolute configuration. The vascular effects of R -(−)-3′-hydroxy-2,4,5-trimethoxydalbergiquinol were assessed on the in vitro mechanical activity of rat aorta rings, under isometric conditions, and on whole-cell Ba2+ currents through CaV 1.2 channels (IBa1.2) recorded in single, rat tail main artery myocytes by means of the patch-clamp technique. R -(−)-3′-Hydroxy-2,4,5-trimethoxydalbergiquinol showed concentration-dependent, vasorelaxant activity on both endothelium-deprived and endothelium intact rings precontracted with the α 1 receptor agonist phenylephrine. Neither the NO (nitric oxide) synthase inhibitor Nω-nitro-L-arginine methyl ester nor the cyclooxygenase inhibitor indomethacin affected its spasmolytic activity. R -(−)-3′-Hydroxy-2,4,5-trimethoxydalbergiquinol-induced vasorelaxation was antagonized by (S)-(−)-Bay K 8644 and unaffected by tetraethylammonium plus glibenclamide. In patch-clamp experiments, R -(−)-3′-hydroxy-2,4,5-trimethoxydalbergiquinol inhibited IBa1.2 in a concentration-dependent manner and significantly decreased the time constant of current inactivation. R -(−)-3′-Hydroxy-2,4,5-trimethoxydalbergiquinol likely stabilized the channel in its closed state, as suggested by molecular modelling and docking simulation to the CaV 1.2 channel α 1c subunit. In conclusion, D. tonkinensis species may represent a source of agents potentially useful for the development of novel antihypertensive drugs. [ABSTRACT FROM AUTHOR]

The sesquiterpene zerumbone, isolated from the rhizome of Zingiber zerumbet Sm., besides its widespread use as a food flavouring and appetiser, is also recommended in traditional medicine for the treatment of several ailments. It has attracted great attention recently for its effective chemopreventive and therapeutic effects observed in various models of cancer. To assess the zerumbone safety profile, a pharmacology study designed to flag any potential adverse effect on vasculature was performed. Zerumbone was tested for vasorelaxing activity on rat aorta rings and for L-type Ba2+ current blocking activity on single myocytes isolated from the rat-tail artery. The spasmolytic effect of zerumbone was more marked on rings stimulated with 60 mM than with 30 mM K+ (IC50 values of 16 μM and 102 μM, respectively). In the presence of 60 mM K+, zerumbone concentration-dependently inhibited the contraction induced by the cumulative addi tions of Ca2+, this inhibition being inversely related to the Ca concentration. Phenylephrine-induced contraction was inhibited by the drug, though less efficiently and independently of the presence of an intact endothelium, without affecting Ca2+ release from the intracellular stores. Zerumbone inhibited the L-type Ba2+ current (estimated IC50 value of 458.7 μM) and accelerated the kinetics of current decay. In conclusion, zerumbone showed an overall weak in vitro vasodilating activity, partly attributable to the blocking of the L-type Ca2+ channel, which does not seem to represent, however, a serious threat to its widespread use. [ABSTRACT FROM AUTHOR]

Chronic use of glyceryl trinitrate is limited by serious side effects, inter alia tolerance and endothelial dysfunction of coronary and resistance arteries. The natural flavonoid quercetin has been shown to counteract the development of glyceryl trinitrate tolerance in vitro. Two mitochondriotropic, 4-O-triphenylphosphoniumbutyl derivatives of quercetin (QTA-3BTPI and Q-3BTPI) were compared to quercetin for protection against glyceryl trinitrate- induced tolerance and endothelial dysfunction of isolated rat aorta rings. Both QTA-3BTPI and Q-3BTPI significantly counteracted the reduced vascular responsiveness to both glyceryl trinitrate and acetylcholine caused by prolonged exposure of the vessel to glyceryl trinitrate itself, their potency being much greater than that of quercetin. QTA-3BTPI, however, turned out to cause endothelial dysfunction per se. Since Q-3BTPI antagonized in vitro nitrate tolerance and endothelial dysfunction of vessels, this encourages assessing whether this effect is displayed also in vivo during long-term glyceryl trinitrate treatment [ABSTRACT FROM AUTHOR]