[Norstephalagine and atherospermidine: two smooth muscle relaxant aporphines from Artabotrys maingayi].

Nine isoquinoline alkaloids have been isolated from the bark of Artabotrys maingayi: four noraporphines (norstephalagine, 3-hydroxynornuciferine, anonaine, and nornuciferine), one 7-hydroxyaporphine (ushinsunine), three oxoaporphines (atherospermidine, liriodenine, and lysicamine), and one protoberberine (discretamine). The effects of the main alkaloids, norstephalagine and atherospermidine, have been studied on the Ca-dependent contractile activity of smooth muscle (uterus). Both norstephalagine and atherospermidine show relaxing activity on rat uterine contractions induced by KCl or rhythmic contractions induced by oxytocin in the presence of Ca, but only atherospermidine can relax oxytocin- or vanadate-induced contractions in a Ca-free medium.