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. Th e strains were cultivated on rice, and the extracts analysed by gas chromat ography mass spectrometry (GC-MS) after derivatization with pentafluoroprop ionic (PFP) reagent. Two F. culmorum strains formed nivalenol and its acety lated 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. Mino r amounts of about ten other hydroxy-culmorins, four hydroxy-culmorones and 3,13-dihydroxy- epiapotrichothecene were also detected in most cultures. T races 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-deacet yl-7,8-dihydroxycalonectrin, were detected in most cultures. We also report the assignment of both the H-1 and C-13 NMR data of 15-deacetyl-7,8-dihydr oxycalonectrin, which has only been reported incorrectly before.