A B S T R A C TA phytochemical investigation of the ethanol extract of Toona sinensis (A. Juss.) Roem resulted in the isolation of ten new limonoids, toonasinenines A-J (1-10), together with two known compounds, toonafolin (11) and toonacilianin D (12). Their structures were determined by spectroscopic analyses. The isolated components were evaluated in vitro for radical scavenging potential using ABTS ·+ and DPPH test, anti-inflammatory activities for Cox-1 and Cox-2, and cytotoxicies against nine tumour cell lines (A549, BGC-823, CHG-5, HCT15, HeLa, HepG2, MDA-MB-231, SHG-44 and SGC-7901 cells). As a result, 4, 5 and 7-10 showed potent radical scavenging activities, while limonoids 1-4 and 11 exhibited significant antiinflammatory and cytotoxic potential.