Isolation and Identification of Novel Terpenoid Phytoalexins in Maize

Inducible chemical defense mechanisms are used by plants in response to insect attack and pathogen infection. The benzoxazinoid class of phytoanticipans is a well documented defense in Zea mays; however, some fungal pathogens and insects are capable of detoxifying these molecules. Recently, two acidic terpenoid phytoalexin families based on the carbon skeletons of ent-kaurane (1) and β-macrocarpene (2), termed kauralexins and zealexins, respectively, were discovered in maize. Continued efforts to identify the diversity of these phytoalexin classes have led to the discovery of surprisingly complex and unstable mixtures. We report the biological interaction between kauralexin A2 (3), and the newly characterized zealexins B3 (4), A4 (5) and A6 (6) with the toxigenic fungus Aspergillus flavus.