Vasorelaxing Activity of Stilbenoid and Phenanthrene Derivatives from Brasiliorchis porphyrostele: Involvement of Smooth Muscle CaV1.2 Channels

Abstract

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 CaV1.2 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 CaV1.2 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.

Vietnamese Dalbergia tonkinensis: A Promising Source of Mono- and Bifunctional Vasodilators

“…Dalbergia isolates were assessed for their effects on I KCa1.1 . Under the conditions used in the present experiments, the outward current mostly consisted of iberiotoxin-sensitive I KCa1.1 [ 48 ]. Figure 6 A shows the traces of I KCa1.1 elicited with clamp pulses to 70 mV from a V h of −40 mV, under control conditions and after the cumulative addition of 30 and 100 µM biochanin A.…”

Renal Sympathetic Hyperactivity in Diabetes Is Modulated by 5-HT1D Receptor Activation via NO Pathway

“…Endothelial dysfunction contributes to the pathogenesis of microvascular diabetic complications. Thus, considering that (a) endothelial relaxation depends on several agents such as NO [ 44 ], prostacyclin [ 45 ], and/or endothelium-derived hyperpolarizing factor (EDHF) [ 46 ], (b) endothelial-dependent vasorelaxation is altered in diabetes [ 47 ], and (c) the NO synthesis was involved in 5-HT 1D renal sympatho-inhibitory effect in normoglycaemic rats [ 18 ], we determined the possible role of these vasodilator agents in the serotonergic inhibitory action in diabetic rats using ODQ (a guanylyl cyclase inhibitor), indomethacin (a COX 1/2 inhibitor), or glibenclamide (an ATP-sensitive K + channels blocker) [ 48 , 49 , 50 ]. As was observed in normoglycaemic animals, only the NO pathway is involved in the 5-HT 1D renal sympatholytic action in diabetes, which is also in agreement with previous results by us in the diabetic pithed rat model [ 22 , 51 ].…”

Floral attractants in the black orchid Brasiliorchis schunkeana (Orchidaceae, Maxillariinae): clues for presumed sapromyophily and potential antimicrobial activity

“…It is not a secret that orchids are widely used in traditional medicine for the treatment of different health conditions such as for instance hypertension, tuberculosis, paralysis, stomach disorders, or arthritis [ 83 ]. Some of them are used as emetics, aphrodisiacs, vermifuges, bronchodilators, or sex stimulators, or to treat scorpion stings and snake bites [ 84 ].…”

“…Representatives of Maxillaria sensu lato are not an exception and are also widely used in traditional medicine for their antispasmodic and anti-inflammatory activities [ 85 , 86 ]. Waratchareeyakul et al [ 83 ] have for example reported vasorelaxant activity of stilbenoid and phenanthrene derivatives from Brasiliorchis porphyrostele (Rchb.f). The major compounds identified in dichloromethane extract from B. schunkeana were 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione (77.06%) and 2,5-di-tert-butyl-1,4-benzoquinone (16.65%).…”