Cytotoxic Quassinoids From the Leaves of Ailanthus altissima

Ten quassinoid‐type compounds, including two previously undescribed ones ( 1 and 2 ), were isolated from the leaves of Ailanthus altissima . Structures of the new quassinoids were unambiguously elucidated through comprehensive spectroscopic analysis, with their absolute configurations further confirmed by single‐crystal x‐ray diffraction, TD‐DFT/ECD calculation, and chemical correlation with known analogues. Preliminary in vitro cell viability assay revealed that compound 1 exhibited significant cytotoxic activity against MDA‐MB‐231, A549, MCF‐7, and 4T1 tumor cell lines, with IC 50 values below 1 µM for all cell types except MCF‐7. Further evaluation indicated that 1 inhibited the proliferation and migration of MDA‐MB‐231 and A549 cells, as well as induced marked apoptosis and cell cycle arrest in both cell lines.