A phenalenone-type phytoalexin has been isolated from infected roots of banana plants (Musa acuminata AA ‘Pisang Jari Buaya’ group cultivar Pisang sipulu). This product was produced de novo by the plants upon infection with the nematode species Radopholus similis. The structure of this phytoalexin was elucidated using spectroscopic evidence and chemical correlation using reverse phase HPLC and 1HNMR analysis. This compound has previously been described as a natural product, anigorufone from Anigozanthos rufus (Haemodoraceae) and has recently been described as a phytoalexin-like compound from Musa acuminata (AAA) Grand Nain. This compound is new to diploid species of Musa and is the first compound known to be produced in response to nematode invasion in the banana.