Cytotoxic Limonoids from the Twigs and Leaves of Toona ciliata

Eight new limonoids, toononoids A–H (1–8), eight new B-seco-29-norlimonoids, toonanoronoids A–H (9–16), and seven known analogues were obtained from the EtOAc extract of the twigs and leaves of Toona ciliata. Compounds 2, 4, 8, and 16 are rare lactam-bearing limonoids. Compounds 1, 14, and 15 possess an unusual γ-methoxybutenolide moiety at C-17, while compounds 9, 10, and 15 have a rare 3β-hydroxy group. Their 2D structure and relative configurations were identified using spectroscopic data. The absolute configurations of 1, 9, 14, and 15 were established via X-ray diffraction crystallography or comparison of experimental and calculated ECD data. The cytotoxicity of the compounds was assessed toward five human tumor cell lines, and their anti-inflammatory activity was assessed based on NO production using LPS-stimulated RAW264.7 macrophages. Compounds 11 and 12 exerted inhibition toward two tumor cell lines (MCF-7, SW-480) with IC₅₀ values between 2.1 and 3.7 μM, while 18–22 inhibited the proliferation of HL-60, MCF-7, and SW-480 cells (IC₅₀ 0.6–4.0 μM). Only compound 4 exhibited weak anti-inflammatory activity with an IC₅₀ value of 28.3 μM.