Four new corynanthe-type alkaloids from the roots of Alstonia scholaris

Four new corynanthe-type alkaloids, meloslines C-F ( 1-4 ), together with four known ones ( 5-8 ) were isolated from the roots of Alstonia scholaris. Their structures including absolute configurations were elucidated by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation. Compounds 1 and 2 exhibited potent vasorelaxant activity on endothelium-intact renal arteries precontracted with KCl.