Abstract
Hypertension is associated with endothelial dysfunction characterized by decreased vasorelaxation. Our research group recently demonstrated that hydroalcoholic extract of Syzygium cumini leaves (HESc) reduces the blood pressure in spontaneously hypertensive rats (SHR). This study evaluated the ability of HESc and chloroform fraction (CF) in promoting vasorelaxation on resistance arteries rings. Endothelium-deprived superior mesenteric artery rings were suspended in organ baths containing warm perfusion medium that was continuously bubbled with carbogen and then the vasorelaxant ability of HESc and CF were assayed. The cumulative additions of HESc (0.1 to 10 mg/mL) caused a concentration-dependent relaxant response, in precontracted preparations by NE or KCl. CF (0.1 to 1.0 mg/mL) exhibited remarkable vasorelaxant activity in preparations endothelium-denuded pre-contracted with NE, in a concentration-dependent manner. The pretreatment of TEA did not decrease significantly in relaxation. The incubation of CF (0.25 and 0.5 mg/ml) reduced in a concentration-dependent way, the Emax induced by NE in mesenteric artery, however, did not altered the pD2 of the NE. Additionally, CF promoted concentration-dependent manner, maximal effect inhibition and also led to a significant rightward shift in the concentration-response curve for Ca2+ in endothelium-denuded rings. This finding indicates that S. cumini acts as a vasorelaxant agent and interfere with the responsiveness of vascular smooth muscle cell, probably acting on the regulation of intracellular Ca2+ levels through voltage-operated calcium channels. Key words: S. cumini, calcium channels, vasorelaxant, medicinal plant, antihypertensive.
Highlights
Cardiovascular disease accounts for approximately 17 million deaths a year
Endothelium-deprived superior mesenteric artery rings were suspended in organ baths containing warm perfusion medium that was continuously bubbled with carbogen and the vasorelaxant ability of hydroalcoholic extract of Syzygium cumini leaves (HESc) and chloroform fraction (CF) were assayed
In endothelium-denuded rings HESc (0.1 to 10 mg/ml) inhibited the sustained tonic contraction induced by NE 10 μM (Figure 1) in a concentration-dependent manner (Emax values= 97.20 ± 2.90%; EC 50 values= 2.82 mg/ml)
Summary
Plant materialLeaves of S. cumini were collected from the campus of the Federal University of Maranhão (2°33'11.7"S 44°18'22.7"W), São Luís, Brazil, in October 2013. Preparation of the hydroalcoholic extract of S. cumini. Leaves were dried at room temperature and pulverized. The crude extract was prepared by maceration of the leaf powder (300 g) in 70% ethanol (1:3 w/v), and concentration in a rotary evaporator under reduced pressure at a temperature below 60°C and lyophilized. The extract obtained was called the hydroalcoholic extract of S. cumini leaves (HESc) with a dry weight of 49.8 g and yield 16.6% (Ribeiro et al, 2014). HESc was partitioned by sequential extraction using hexane, chloroform (CF), ethyl acetate, and nbutanol. Based on previous results demonstrating that the CF was the most potent in inducing vascular relaxation in vitro (Ribeiro, 2007), we evaluated the effects of this fraction. The chloroform (CF) fraction were evaporated, with a yield 5.2% and tested to evaluate the vasorelaxant effect. Phytochemical screening by CF revealed the presence of phenols
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