Dias, CatarinaPaulo, AlexandraNascimento, JoséHoughton, PeterHawkes, Jane E.Gonçalves, Maria Lurdes2011-08-092011-08-092003Planta Med 2003; 69(11): 1060-10620032-0943http://dx.doi.org/10.1055/s-2003-45158http://hdl.handle.net/10451/3888A new natural pyrimidine derivative, 2-(4´-aminobenzenamine)-pyrimidine (1), was isolated from the bulbs of Autonoë madeirensis, a Hyacinthaceae of Madeira Archipelago (Portugal) and the structure determined on the basis of spectroscopic data. As some pyrimidine compounds are important alfa-1-adrenergic antagonists, we investigated the effect of 1 in the rat vas deferens contractility induced by the alfa-1-agonist phenylephrine. In concentrations virtually devoid of effect on the rat vas deferens contractility, 1 shifted to the right the concentration-response curves of phenylephrine without changing the maximal effect. These results provide evidence that 1 acts as an alfa-1-adrenoceptor antagonist and suggest a competitive mechanism of action.engjournal article