Acremonium zeae, a protective endophyte of maize produces dihydroresorcylide and 7-hydroxydihydroresorcylides

Acremonium zeae has been characterized as a protective endophyte of maize and displays antifungal activity against other fungi. Pyrrocidines A and B were discovered to be the metabolites accounting for this activity. During a population survey of A. zeae isolates from maize seeds produced in nine states to determine their ability to produce pyrrocidines, another metabolite of A. zeae, unrelated to the pyrrocidines, was found to have widespread occurrence (105 of 154 isolates) and to be produced in amounts comparable to the pyrrocidines. Further chemical studies of fermentation extracts of an A. zeae isolate (NRRL 45893) from maize led to the identification of a new compound, dihydroresorcylide, the saturated analogue of cis-resorcylide. Also identified were the two diastereomers of 7-hydroxydihydroresorcylide. Dihydroresorcylide and pyrrocidines A and B were detected by LC-APCI-MS in symptomatic maize kernels from ears that were wound-inoculated in the milk stage with A. zeae NRRL 34559.