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• Twenty-four new limonoids were obtained from Toona ciliata. • Their structures were determined by spectroscopic analysis, quantum chemistry calculations, and X-ray diffraction. • Several compounds showed significant anti-NLRP3 inflammasome activity. Twenty-four new limonoids, toonaolides A−X (1 – 24), characterized with an α , β -unsaturated- γ -lactone A-ring were isolated from the twigs of Toona ciliata. Their structures and absolute configurations were elucidated by spectroscopic data, X-ray diffraction crystallography, and quantum chemistry calculations. Most of the isolated compounds (except 9 , 18 , and 24 which possessed the maleimide ring) featured the rare 21-hydroxybutenolide or 23-hydroxybutenolide moieties. In particular, compound 1 has an unprecedented limonoid architecture with 6/6 cis -fused A/B ring system and 2 has an unusual tetrahydrofuran ring B skeleton, featuring a 7/5/6/5 ring system. The biological evaluation showed that compounds 9 , 11 , 12 , 14 , and 18 exhibited significantly anti-NLRP3 inflammasome activity with IC 50 values ranging from 3.2 to 9.7 μM. Analysis of IL-1 β and caspase-1 expression revealed that compounds 11 and 12 are selective inhibitors of NLRP3 inflammasome, which could ameliorate cell pyroptosis by blocking NLRP3 inflammasome activation. [ABSTRACT FROM AUTHOR]