7-(substituted-phenyl)amino-5,8-quinazolinediones: Potent inhibitors of endothelium-dependent vasorelaxation

7-(Substituted-phenyl)amino-5,8-quinazolinediones (4) were synthesized by t he substitution of 7-methoxy-5,8-quinazolinedione (5) with arylamines. All synthesized 5,8-quinazolinediones 4 showed a potent and efficacious inhibit ory effect on the acetylcholine (ACh)-induced vasorelaxation of rat aorta w ith the endothelium. The quinones, at a low concentration of 0.1 muM, reduc ed the maximal response with an increase of EC50 values for ACh. The result s indicate that quinones 4 are potent inhibitors of endothelium-dependent v asorelaxation.