Vasorelaxant activity of phthalazinones and related compounds

Several series of dihydrostilbenamide, imidazo[2,1-a]isoindole, pyrimido[2,1-a]isoindole and phthalazinone derivatives were obtained and their vasorelaxant activity was measured on isolated rat aorta rings pre-contracted with phenylephrine (10−5 M). Some phthalazinones attained, practically, the total relaxation of the organ at micromolar concentrations. For the most potent compound 9h (EC50 = 0.43 μM) the affinities for α1A, α1B and α1D adrenergic sub-receptors were determined.