Identification of Unknown Isomers of Fumonisin B5mycotoxin in Afusarium Verticillioidesculture by High-Performance Liquid Chromatography/Electrospray Ionization Time-of-Flight and Ion Trap Mass Spectrometry

Several new fumonisin B5 mycotoxin isomers (iso-FB5) present in a rice culture inoculated with Fusarium verticillioides were separated on a RP-HPLC column recommended for the separation of structural isomers, and subsequently detected by time-of-flight and ion trap mass spectrometry. The exact masses of the eluted compounds were determined by using time-of-flight mass spectrometry. The m/z values of the 20 characteristic product ions including the hydrocarbon backbone and the characteristic neutral mass losses from the molecular and product ions of the compounds obtained by ion trap mass spectrometry, unambiguously indicated of the unknown iso-FB5 compounds. The total amount of FB5 toxin and its isomers was 0.9% of the quantity of the main compound (FB1 toxin), which is a noteworthy quantity considering their potential toxicity. Based on the semi-quantitative measurement data it can be assumed that, in addition to the FB5 of unknown structure, isomers designated 1, 2, and 20 can also be isolated among the iso-FB5 compounds.