Two new C-18 norwithanolides based on a C(27) skeleton, subtrifloralactones K (1) and L (2), a new C-18 oxygenated withanolide, 13 beta-hydroxymethylsubtrifloralactone E (3), and a new alpha-ionone derivative, (+)-7 alpha,8 alpha-epoxyblumenol B (4), along with five known compounds, philadelphicalactone A (5), (2S,3S,4R)-2-[(2R)-2'-hydroxytetracosanoylamino]-1,3,4-octadecanetriol (6), trans-N-feruloyltyramine, cis-N-feruloyltyramine, and (S)-coriolic acid, were isolated from additional active fractions of the chloroform-soluble extract of Deprea subtriflora, using a quinone reductase (QR) induction assay as a monitor. The structures of compounds 1-4 were characterized by spectroscopic data interpretation. The potential cancer chemopreventive activities of all isolates in terms of their ability to induce QR activity with cultured Hepa 1c1c7 mouse hepatoma cells were evaluated.