Immune-inhibitive phenyl-C1 substituent aporphine alkaloids from Thalictrum cirrhosum

Five new phenyl-C1 substituent aporphine alkaloids, 6aR-2′-methoxycarbonyl-thaliadin (1), 6aR-2′-carboxyl-thaliadin (2), 6aR-3-methoxy-hernandalinol (3), 6aS-1,3,10-trimethoxy-natalamine (4), and 3-methoxy-2′-methoxycarbonyl-oxohernandalincin (5), together with sixteen known isoquinoline alkaloids (6–21) were isolated from the whole herb of Thalictrum cirrhosum (Levl.). Their structures were elucidated by extensive spectroscopic measurements, and six isoquinoline alkaloids showed significant inhibitory activity on concanavalin A-stimulated splenocytes proliferation with IC50 values 36–44 μM by the immunosuppressive bioassay.