Vasorelaxant effects of the edible flowers Tagetes erecta L. and its possible mechanism of action.

Abstract

Context: Tagetes erecta is widely cultivated for its ornamental flowers and has traditionally been used as a diuretic and antihypertensive. However, its effects on blood pressure have not yet been studied.

Objective: To evaluate the vasorelaxant potential of ethanolic extract of T. erecta from two cultivars of edible flowers, yellow and orange.

Materials and methods: The pharmacological effects of T. erecta extracts as vasorelaxant agents were evaluated using isolated rat aorta rings in an organ bath and by measuring the pharyngeal pumping rate in the Caenorhabditis elegans model.

Results: The extracts induced relaxation in endothelium-intact aortic rings pre-contracted with different agents. Vasorelaxant effect was attenuated by endothelial removal and by pretreatment with L-NAME or ODQ, but not by indomethacin. Statistically significant effects were observed only at low concentrations. Atropine and H-89 reduced the extract-induced response, whereas okadaic acid had no effect. In a calcium-free medium, the extracts reduced contractions induced by CaCl₂ and phenylephrine. Relaxation was significantly attenuated by iberiotoxin, glibenclamide, BaCl₂, and 4-aminopyridine, while apamin and TRAM-34 had mild effect. The extracts also significantly decreased the pharyngeal pumping rate in C. elegans.

Discussion and conclusion: The extracts induced concentration-dependent vasorelaxation though both endothelium-dependent and -independent mechanisms. At low concentrations, relaxation was mediated by nitric oxide, while at higher concentrations it involved inhibition of intracellular Ca²⁺, opening of K⁺ channels, and activation of protein kinase A. In C. elegans, the extracts significantly reduced pharyngeal pumping. This study is the first to suggest that T. erecta could be beneficial in treating pathologies associated with endothelial dysfunction, such as hypertension.