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 Ca channel and receptor-operated Ca channel. [ABSTRACT FROM AUTHOR]