Cytotoxic isoquinoline alkaloids from the roots of Thalictrum foliolosum.

Phytochemical investigation on the 70% EtOH extract of the roots of Thalictrum foliolosum DC. resulted in the isolation of three new isoquinoline alkaloids, 5,6,7,12-tetramethoxy-2-methyl-13-hydroxy-11-(4'-methoxycarbonylphenoxy)benzylisoquinoline (1), 5,6,7,12-tetramethoxy-2-methyl-13-hydroxy-11-(4'-carbonylphenoxy) benzylisoquinoline (2), and 3-methoxy-10-O-acetylprodensiflorin B (3). The new structures were elucidated by using spectroscopic data (NMR, IR, UV, and MS). The isolated alkaloids were tested in vitro for cytotoxic potentials against six human lung cancer cell lines (H460, H23, HTB-58, A549, H441, and H2170). As a result, alkaloids 1 and 2 exhibited significant cytotoxic activities against all the tested tumor cell lines with IC₅₀ values less than 20 μM.