The leaves of Aquilaria spp. promote "physiological balance", and are "cardiotonic and provide blood nourishment". In Asia, these leaves are increasingly consumed as tea and claimed to provide benefits to cardiovascular function, albeit without any scientific proof. Therefore, this study sought to evaluate the action of Aquilaria crassna leaf aqueous extract (AE) on vascular function and vascular smooth muscle cytotoxicity. AE and a main constituent, mangiferin were investigated for their vasorelaxation of rat mesenteric arteries and aortae in vitro. Acute cytotoxicity of AE (0.1-1000 μg/ml) and mangiferin (0.1-100 μM) on rat enzymatically isolated vascular smooth muscle cells was assayed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. AE dilated rat mesenteric arteries (EC50∼107 μg/ml, Emax∼95%) more than aorta (EC50∼265 μg/ml, Emax∼76%, p < 0.05). AE-induced vasodilation in mesenteric artery was reduced by endothelial removal (EC50∼202 μg/ml, p < 0.05), incubation with endothelial nitric oxide synthase (eNOS) (100 μM, L-NAME) (EC50∼309 μg/ml, p < 0.05), and partly reduced by L-type Ca2+ channel blockade at higher concentrations. Likewise, mangiferin (1-100 μM) dilated the mesenteric artery more potently than the aorta. However, its maximum relaxation was less than with AE (41% in the mesenteric artery and <10% in the aorta). Isolated vascular smooth muscle cells incubated in AE or mangiferin for 1 h showed no cytotoxicity. Thus, AE is a vasorelaxant while being free of acute cytotoxicity towards vascular smooth muscle, thus potentially ameliorating human vascular dysfunction.
Keywords: Aquilaria crassna; Cytotoxicity; Mangiferin; Vascular smooth muscle cells; Vasodilation.