Novel bioactive isoquinoline alkaloids from Carduus crispus

Four novel isoquinoline alkaloids crispine B–E (), along with a new natural isoquinoline alkaloid, crispine A (), were isolated from Carduus crispus, and the structures were elucidated on the basis of spectroscopic data. Crispine A and B are alkaloids with pyrrolo-[2,1-a]isoquinoline skeleton and crispine C–E are isoquinoline alkaloids with guanidinyl group. All compounds were evaluated for their cytotoxic activity ad compound showed certain cytotoxic activity against some human-cancer lines in vitro.