Four novel isoquinoline alkaloids crispine B-E (2-5), along with a new natural isoquinoline alkaloid, crispine A (1), 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 2 showed certain cytotoxic activity against some human-cancer lines in vitro. (C) 2002 Elsevier Science Ltd. All rights reserved.