A new alkaloid, isothalisopavine, was isolated from Thalictrum minus and shown to be 2,3,8-trimethoxy-7-hydroxyisopavine from spectral evidence. The known thalisopavine, from T. dasycarpum, is 2,3,8-trimethoxy-9-hydroxyisopavine. Isothalisopavine is the first of its class to be substituted unsymmetrically. in the two aromatic rings. (C) 1998 Elsevier Science Ltd. All rights reserved.