In this study five new limonoids, toosendone [24,25,26,27-tetra-nor-6alpha-acetoxy-21,22-epoxy-7alpha-tigloyl-1alpha,3alpha,28-trihydroxyapotirucalla-(apoeupha)-14,20,22-trien-12-one, 1] and 12-ethoxynimbolinins A-D (2-5), together with five known limonoids, 1-acetyltrichilinin (6), 1-cinnamoyltrichilinin (7), trichilinin B (8), 1,7-di-O-acetyl-14,15-deoxyhavanensin (9) and 12-O-methylnimbolinin B (10),were isolated from the fruits of Melia toosendan. Their structures and relative configurations were established based on spectroscopic analysis. Compound 4 exhibited significant antibacterial activity against the oral pathogen, Porphyromonas gingivalis ATCC 33 277, with an MIC value of 15.6 microg/mL. Compounds 7 and 8 were also active against P. gingivalis ATCC 33 277, with MIC values of 31.3 and 31.5 microg/mL respectively.