Dimeric benzylisoquinoline alkaloids from Thalictrum delavayi and their biological activities

A phytochemical investigation of the whole plants of T. delavayi led to the isolation of five new dimeric benzylisoquinoline alkaloids, thalidelavines A–E (1–5), together with six known congeners (6–11). The structures and absolute configurations of new compounds were established based on analyses of spectroscopic data, ECD calculations, and single crystal X-ray crystallography. Thalidelavines A–E (1–5) were structurally complex bisbenzylisoquinoline alkaloids with various configurations. These isolated alkaloids were evaluated for their cytotoxic and immunosuppressive effects. Among them, both 9 and 10 displayed significant cytotoxicities against T98G cell lines with an IC50 value of 2.1 μM, compared with the positive CPT-11 (IC50 = 3.0 μM). In addition, 5–7 showed remarkable immunosuppressive effects. These findings not only enrich the structural diversity of bisbenzylisoquinoline alkaloids, but also provide potential candidates for the further development of the antitumor and immunosuppressive agents.