IDENTIFICATION OF UNKNOWN ISOMERS OF FUMONISIN B₅ MYCOTOXIN IN A FUSARIUM VERTICILLIOIDES CULTURE BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY/ELECTROSPRAY IONIZATION TIME-OF-FLIGHT AND ION TRAP MASS SPECTROMETRY

Abstract

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.

Keywords:

• LC-MS
• Fusarium verticillioides
• FB₅
• fumonisin B₅ isomers
• LC-MS/MS
• mycotoxin

ACKNOWLEDGMENT

This work was supported by EC (KBBE-2007-22269-2 MYCORED) and Hungarian State Research (OTKA 77612) grants.

Notes

TCA = tricarballylic acid; propane-1,2,3-tricarboxylic acid.

^a The configuration of C-3 in the 3-epi isomers is R,^{[ 18 ]} whereas in FB₃ and FB₄ is S.^{[ 17 ]}

^b Structure not confirmed.

^c The fumonisin denoted as FB₆ in a recent article^{[ 20 ]}presumably corresponds to one of the several FB₁ isomers (compound 28) reported in our former publication.^{[ 14 ]}