Abstract
Background: Ethnopharmacological studies demonstrated the potential for Eulophia species to treat inflammation, cancer, and cardio-metabolic diseases. The aim of the study was to investigate the vasorelaxant effect of ethanolic Eulophia macrobulbon (EM) extract and its main phenanthrene on rat isolated mesenteric artery and to investigate the hypotensive effect of EM.Methods: The vasorelaxant effects of EM extract or phenanthrene and the underlying mechanisms were evaluated on second-order mesenteric arteries from Sprague Dawley rats. In addition, the acute hypotensive effect was evaluated in anesthetized rats infused with cumulative concentrations of the EM extract.Results: Both EM extract (10-4–1 mg/ml) and phenanthrene (10-7–10-4 M) relaxed endothelium-intact arteries, an effect that was partly reduced by endothelium removal (p < 0.001). A significant decrease in the relaxant effect of the extract and the phenanthrene was observed with L-NAME and apamin/charybdotoxin in endothelium-intact vessels, and with iberiotoxin in denuded vessels. SNP (sodium nitroprusside)-induced relaxation was significantly enhanced by EM extract and phenanthrene. By contrast, ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one), 4-aminopyridine and glibenclamide (endothelium-denuded vessels) and indomethacin (endothelium-intact vessels) had no effect. In calcium-free solution, both the EM extract and phenanthrene inhibited extracellular Ca2+-induced contraction in high KCl and phenylephrine (PE) pre-contracted rings. They also inhibited the intracellular Ca2+ release sensitive to PE. The acute infusion of EM extract (20 and 70 mg/kg) induced an immediate and transient dose-dependent hypotensive effect.Conclusion: The ethanolic extract of EM tubers and its main active compound, 1-(4′-hydroxybenzyl)-4,8-dimethoxyphenanthrene-2,7-diol (phenanthrene) induced vasorelaxant effects on rat resistance vessels, through pleiotropic effects including endothelium-dependent effects (NOS activation, enhanced EDH production) and endothelium-independent effects (opening of KCa channels, inhibition of Ca2+ channels, inhibition of intracellular Ca2+ release and PDE inhibition).
Highlights
Orchids belong to the plant family Orchidaceae, one of the most diverse group among the angiosperm with near 25,000 species (Behera et al, 2013)
As PDE enzymes are widely expressed in smooth muscle cells including vascular smooth muscle cells (VSMC) (Komas et al, 1991), the aim of the present study was to investigate the vasorelaxant effect of an ethanolic extract of Eulophia macrobulbon (EM) and its main constituent, 1-(4 -hydroxybenzyl)-4,8-dimethoxyphenanthrene2,7-diol, and to unravel the mechanisms involved on isolated rat mesenteric artery
As regards endothelium-dependent pathways, the data showed that increased production of endothelium-derived hyperpolarizing factor (EDH) and to a lesser extent activation of NOS is involved in the effect of EM extract, whereas both production of EDH and activation of NOS contribute to the effect of phenanthrene
Summary
Orchids belong to the plant family Orchidaceae, one of the most diverse group among the angiosperm with near 25,000 species (Behera et al, 2013). Aside from their ornamental value, orchids are acknowledged for their use in traditional medicines (Bulpitt, 2005; Behera et al, 2013; Pant, 2013; Patil and Mahajan, 2013; Narkhede et al, 2016). Other pharmacopeias from India and many countries from SouthAsia such as Taiwan, Singapore, Vietnam, Sri Lanka, Thailand, Myanmar, use orchids in traditional medicine since the ancient time (Suresh Kumar et al, 2000; Hernández-Romero et al, 2005; Luo et al, 2007). The aim of the study was to investigate the vasorelaxant effect of ethanolic Eulophia macrobulbon (EM) extract and its main phenanthrene on rat isolated mesenteric artery and to investigate the hypotensive effect of EM
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
