Seven new isoquinoline alkaloids, 9-(2'-formyl-5', 6 '-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy dehydroaporphine (1), 9-(2'-formyl-5, 6'-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy oxoaporphine (2), 3-methoxy-2'-formyl oxohemandalin (3), (-)-9-(2'-methoxycarbonyl-5', 6 '-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy aporphine (4), (-)-2'-methoxycarbonyl thaliadin (5), (-)-9-(2'-methoxyethy1-5', 6'-dimethoxyphenoxy)-1, 2, 3, 10-tetramethoxy aporphine (6), (-)-3-methoxy hydroxyhemandalinol (7), together with six known isoquinoline alkaloids (8-13) were isolated from the roots of Thalictrum foetidum. Their structures were elucidated by extensive spectroscopic measurements. Compounds 1 and 2 showed significant selective cytotoxicity against glioma stem cells (GSC-3(#) and GSC-18(#) ) with IC50 values ranging from 2.36 to 5.37 mu g.mL(-1).