A new cassane diterpene, dipteryxic acid (1), and a new isoflavonolignan, 5-methoxyxanthocercin A (2), as well as four known active compounds, isoliquiritigenin (3), 6,4′-dihydroxy-3′-methoxyaurone (4), sulfuretin (5), and (±)-balanophonin (6), and five known inactive compounds, butin, eriodictyol, 7-hydroxychromone, 7,3′-dihydroxy-8,4′-dimethoxyisoflavone, and (-)-lariciresinol, were isolated from an ethyl acetate-soluble extract of the seeds of Dipteryx odorata, using a bioassay based on the induction of quinone reductase (QR) in cultured Hepa 1c1c7 mouse hepatoma cells to monitor chromatographic fractionation. The structures of compounds 1 and 2 were elucidated by spectroscopic data interpretation. Single-crystal X-ray diffraction analysis was used to confirm the relative stereochemistry of compound 1. Selected compounds (3-5) were evaluated in a mouse mammary organ culture assay, with isoliquiritigenin (3) found to exhibit 76% inhibition at a dose of 10 μg/mL.