Production of culmorin compounds and other secondary metabolites by Fusarium culmorum and F. graminearum strains isolated from Norwegian cereals.

Twenty-three Fusarium culmorum and 21 F. graminearum isolates were studied for their ability to produce mycotoxins and other secondary metabolites. The strains were cultivated on rice, and the extracts analysed by gas chromatography mass spectrometry (GC-MS) after derivatization with pentafluoropropionic (PFP) reagent. Two F. culmorum strains formed nivalenol and its acetylated derivatives (chemotype II), while all F. graminearum and the other F. culmorum isolates produced deoxynivalenol (DON) via 3-acetyldeoxynivalenol (3-acetyl-DON) (chemotype IA). 15-hydroxy-culmorin, followed by 5-hydroxy-culmorin were the main other metabolites produced F. culmorum, while 5-, 12- and an unidentified hydroxy-culmorin, suggested to be 14-hydroxy-culmorin, were the main metabolites of F. graminearum. The hydroxy-culmorin profile was found to be significantly different for the two Fusarium species. Minor amounts of about ten other hydroxy-culmorins, four hydroxy-culmorones and 3,13-dihydroxy- epiapotrichothecene were also detected in most cultures. Traces of sambucinol seemed to be present in some of the isolates, but were not detected in any significant amounts. The precursors in the biosynthetic sequence to 3-acetyldeoxynivalenol, 7,8-dihydroxycalonectrin and 15-deacetyl-7,8-dihydroxycalonectrin, were detected in most cultures. We also report the assignment of both the 1H and 13C NMR data of 15-deacetyl-7,8-dihydroxycalonectrin, which has only been reported incorrectly before.