Abstract
Fumonisin A-series (FAs) in a reference material of corn sample that was naturally contaminated with fumonisins was characterized using high-resolution liquid chromatography-Orbitrap mass spectrometry (LC-Orbitap MS). Peaks for fumonisin B1 (FB1), fumonisin B2 (FB2), and fumonisin B3 (FB3), in addition to three peaks corresponding to unknown compounds I, II, and III, were detected in the chromatogram for the corn sample. Fragment ion analysis for FB1, FB2, and FB3 showed that while the ions formed at m/z values of 200–800 were similar to those formed by the cleavage of the tricarballylic acids and the hydroxyl groups, the fragmentation patterns at m/z values of 50–200 varied depending on the hydroxyl group locations in the compounds. Fragment ion analysis of compounds I–III revealed structural similarities to FBs, only differing by an additional C2H2O in the unknown compounds. Using these results and by comparing the product ion mass spectra of compound I with fumonisin A1 (FA1) synthesized from FB1 standards, compounds I–III were hypothesized to be N-acetyl analogs of FBs: fumonisins A1 (FA1), A2 (FA2), and A3 (FA3). The method for determining concentrations was validated with FA1, FB1, FB2, and FB3 standards and applied to analyze the reference material. The FB1, FB2, and FB3 analytical levels were within acceptance limits and the amount of FA1 in the material was ~15% of FB1 amount at 4.2 mg/kg.
Highlights
There is significant worldwide concern over the health risks posed by the presence of fumonisins, which are one of the key mycotoxin contaminants in corn
ID 2 was present in all of three product ion spectra, and the calculated formula is C6H7O5, possibly representing tricarballylic acids (TCAs). These results indicate that the fragmentation of fumonisin B1 (FB1), fumonisin B2 (FB2), and fumonisin B3 (FB3) exhibits characteristic patterns, such as the formation of fragment ions by the cleavage of TCAs and the hydroxyl groups from the precursor ion, the formation of different fragment ions depending on the position of the hydroxyl group, and the formation of TCA present in the each compound
The analytical levels of FB1, FB2, and FB3 in MTC-9999E were within the acceptance limits, which reconfirmed the validity of the method
Summary
There is significant worldwide concern over the health risks posed by the presence of fumonisins (chemical structure shown in Figure 1), which are one of the key mycotoxin contaminants in corn. In addition to FBs, several analogs of this group including fumonisin A-series (N-acetyl analogs, FAs), the fumonisin C-series (demethyl analogs, FCs), and the fumonisin P-series (N-3-hydroxypiridinium analogs, FPs) have been discovered in the culture media of genus Fusarium. In order to comprehensively analyze the mycotoxins, the LC-Orbitrap mass spectrometer (MS) has been introduced for the simultaneous screening [15,16] and characterization of mycotoxins [17,18,19], which enables comprehensive analysis with high selectivity by providing high resolution and enables exact mass measurements for a full mass scan This technique allows the estimation of the formulae of fragment ions by incorporating a quadrupole mass filter and collision cell in the Orbitrap. A technique to determine the amount of FB1, FB2, FB3, and fumonisin A1 (FA1) has been developed and applied for the quantification of FA1 in MTC-9999E
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