Abstract Four new phenalenone-type phytoalexins (2–5) have been isolated from rhizomes of Musa acuminata (AAA) infected with the fungus Fusarium oxysporum. The structures of the new phytoalexins were elucidated using spectroscopic evidence, chemical correlation, synthesis, and X-ray diffraction analysis. The major compound 2, has been previously described as a natural product, named anigorufone, but never as a phytoalexia. The chemical shift for all of the hydrogen and carbon atoms in the substances were unambiguously established by mono- and bidimensional, homo- and heteronuclear NMR experiments (1HNMR, 13CNMR, COSY, HMQC and HMBC). In preliminary in vitro assays, all of the four new phytoalexins have shown inhibitory activity on the growth of the germinative tube of Fusarium oxysporum f. sp. cubense race 4.