Vasorelaxing effect and possible chemical markers of the flowers of the Mexican <i>Crataegus gracilior</i>

The vasorelaxing effect of the methanol extract of the flowers of Crataegus gracilior, a Mexican medicinal plant used to treat some cardiovascular diseases, was assessed, and its possible chemical markers identified. The extract produced a potent vasodilator effect on isolated rat aortic rings (EC50 = 1.83 ± 1.39 µg/mL; Emax = 100 ± 3.4%). Vitexin, the most commonly identified flavonoid in the flowers and used to standardise some Crataegus species, was not found at all in this plant sample. Instead, daucosterol, and corosolic and euscapic acids were purified. The two triterpene acids have been reported to possess beneficial effects on cardiovascular diseases. These results indicate that the vasodilator effect might induce the hypotensive effect claimed by users, and that euscapic and corosolic acids may be the main vasodilator compounds, and can then be employed as the chemical markers towards the future standardisation of the extract.