Vasorelaxant properties of Vernonia amygdalina ethanol extract and its possible mechanism

Abstract

Context:Vernonia amygdalina Del. (VA) (Asteraceae) is commonly used to treat hypertension in Malaysia.Objective: This study investigates the vasorelaxant mechanism of VA ethanol extract (VAE) and analyzes its tri-step FTIR spectroscopy fingerprint.Materials and methods: Dried VA leaves were extracted with ethanol through maceration and concentrated using rotary evaporator before freeze-dried. The vasorelaxant activity and the underlying mechanisms of VAE using the cumulative concentration (0.01–2.55 mg/mL at 20-min intervals) were evaluated on aortic rings isolated from Sprague Dawley rats in the presence of antagonists.Results: The tri-step FTIR spectroscopy showed that VAE contains alkaloids, flavonoids, and saponins. VAE caused the relaxation of pre-contracted aortic rings in the presence and absence of endothelium with EC50 of 0.057 ± 0.006 and 0.430 ± 0.196 mg/mL, respectively. In the presence of Nω-nitro-l-arginine methyl ester (EC50 0.971 ± 0.459 mg/mL), methylene blue (EC50 1.203 ± 0.426 mg/mL), indomethacin (EC50 2.128 ± 1.218 mg/mL), atropine (EC50 0.470 ± 0.325 mg/mL), and propranolol (EC50 0.314 ± 0.032 mg/mL), relaxation stimulated by VAE was significantly reduced. VAE acted on potassium channels, with its vasorelaxation effects significantly reduced by tetraethylammonium, 4-aminopyridine, barium chloride, and glibenclamide (EC50 0.548 ± 0.184, 0.158 ± 0.012, 0.847 ± 0.342, and 0.304 ± 0.075 mg/mL, respectively). VAE was also found to be active in reducing Ca2+ released from the sarcoplasmic reticulum and blocking calcium channels.Conclusions: The vasorelaxation effect of VAE involves upregulation of NO/cGMP and PGI2 signalling pathways, and modulation of calcium/potassium channels, and muscarinic and β2-adrenergic receptor levels.

Review of Natural Resources With Vasodilation: Traditional Medicinal Plants, Natural Products, and Their Mechanism and Clinical Efficacy

“…β 2 -adrenoreceptor, a GPCR, only exists on the membrane of VSMCs. This receptor passes through the GPCR/AC pathway, which catalyses the breakdown of ATP into cAMP and subsequently causes vasodilation ( Ch'ng et al, 2017 ). Propranolol, a nonselective β 2-adrenergic receptor inhibitor, eventually causes vasoconstriction through inhibiting this channel.…”

“…However, its effects were significantly reduced by endothelial removal, TEA, 4-AP, BaCl 2 , glibenclamide, L-NAME (eNOS blocker), methylene blue (cGMP inhibitor), indomethacin (COX inhibitor), atropine (muscarinic receptor inhibitor) and propranolol (β 2 -adrenoreceptor inhibitor). Hence, the effect of VAE was related with the NO/cGMP/PGI2 pathways, Ca 2+ /K + channels or β 2 -adrenergic receptor ( Ch’ng et al, 2017 ). Additionally, VA (i.v.…”

Orthogonal Stimulus-Response as a Tool to Formulate Traditional Chinese Medicinal Herbal Combination

“…Generally, there are three key information that could be speculated from the findings presented above, the results of these research clearly presented the competency of combined drugs over single drugs in terms of exhibiting vasodilatory effects, the orthogonal stimulus-response compatibility study approach could be used to formulate TCM formula in terms of treating complex diseases, and the crude extracts of the herbs could provide promising therapeutic effects rather than single compounds due to holistic mechanisms of actions whilst providing cost-effective beneficial from the commercial viewpoint as compared to pure compound [ 21 – 24 ].…”

Overview of the Microenvironment of Vasculature in Vascular Tone Regulation

“…The production of these second messengers are strictly dependent on the activation of various types of the receptors that are located on the vasculature including EDRFs, enzyme-linked, G-protein-coupled, and channel-linked receptors. According to literatures, the vasodilative receptors are more frequently being included in the experimental study on mechanisms of actions of test compounds rather than vasoconstrictive receptors [ 86 , 87 , 88 , 89 , 90 , 91 ]. Therefore, following the current trend of pharmacological research, all the vasodilation-mediated receptors pathways that should be investigated during the mechanisms of actions study of test compounds were suggested at this section.…”

“…The activation of IP 3 R is strictly dependent on the activation of G q α-protein-coupled receptors, which allows the Ca 2+ ions released from the store of sacroplasmic reticulum into the cytosol. Therefore, all these channel-linked pathways should be investigated during the mechanisms of actions study on vasodilatory effects of test compounds [ 5 , 86 , 87 , 88 , 89 , 90 , 91 ].…”