Vasorelaxant effect of isoquinoline derivatives from two species of Popowia perakensis and Phaeanthus crassipetalus on rat aortic artery

Five bisbenzyl isoquinolines (1–5), three benzyl isoquinolines (6–8), four isoquinoline alkaloids (9–12), and two unclassified compounds (13 and 14) from Popowia perakensis and Phaeanthus crassipetalus were evaluated for their vasorelaxant effect on rat aortic arteries. In aortic rings pre-contracted with phenylephrine (PE, 0.3 μM), some of the bisbenzyl isoquinoline alkaloids, benzyl isoquinoline alkaloids, and isoquinoline alkaloids showed clearly vasorelaxant effects at 30 μM. The action of (−)-limacine (4) was deduced to be mediated through the increased release of NO from endothelial cells, and that of pecrassipine A (7) and backebergine (12) partly mediated by NO release. Further, the action of pecrassipine A (7) and backebergine (12) may be attributed to their inhibition of the voltage-dependent Ca2+ channel and receptor-operated Ca2+ channel.