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.
Highlights
Hypertension is the most common risk factor of cardiovascular diseases
Some characteristic peaks hidden in the original IR spectrum can be clearly seen in its second derivative infrared (SD-IR) spectrum, such as those at 1780, 1746, 1706, 1470, 1605, 1518, 1497, and 989 cmÀ1, whereas the synchronous 2D-correlation IR spectra of VA ethanol extract (VAE) in the range of 1200–1800 cmÀ1 had showed its auto peaks at 1237, 1382, 1493, 1619, and 1735 cmÀ1
The results show that the contraction elicited by CaCl2 dramatically dropped to 0.16 ± 0.01 g (87% inhibition), 0.13 ± 0.01 g (90% inhibition), and 0.07 ± 0.01 g (94% inhibition) in the presence of 0.1 mM, 0.3 mM, and 1.0 mM (n 1⁄4 8, p < 0.001) nifedipine compared to the control group that had a maximum contraction of 1.24 ± 0.04 g, whereas, in Figure 6, accounting for the differences in VAE concentrations (0.01, 0.04, 0.16, and 0.64 mg/mL), there was an attenuated contraction effect compared to the control group
Summary
Hypertension is the most common risk factor of cardiovascular diseases. It is an important public health problem worldwide due to its high prevalence and its detrimental effects such as stroke, chronic kidney disease, and cardiac restructuring and damage (Rampal et al 2008). There is an imminent need to decrease the prevalence of hypertension. Lowering blood pressure by relaxing arteries can greatly reduce hypertension complication such as cerebrovascular, cardiovascular, and renal disease (Wang et al 2014), the common antihypertensive drugs present in the market nowadays have low effectiveness and undesired chronic side effects. Seeking new effective antihypertensive drugs with minimal side effects is urgent for human populations. Efforts are concentrated on investigating the therapeutic efficacy of locally available medicinal herbs because they are more readily available and are perceived to be safer (Taiwo et al 2010)
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