Abstract
The aim of this study was to apply RP-HPLC/ESI-ITMS and RP-HPLC/ESI-TOFMS to investigate and characterise six new higher molecular weight fumonisins (three pairs of isomers) extracted from a Fusarium verticillioides-infected solid rice culture. The ITMS and ITMS2 spectra clearly indicated the m/z values (960, 984 and 986) of the protonated molecules and the FB1 toxin-like structures of these compounds, respectively. Moreover, the data evaluation software of the TOFMS equipment unambiguously demonstrated the exact masses of the protonated molecules and the suggested empirical formulae (C50H89NO16, C52H89NO16 and C52H91NO16) of the new fumonisins, with mass accuracy in the range between 0.1 and −1.1 ppm. Subtraction of the empirical formula of FB1 toxin (C34H59NO15) from these formulae and correction for the mass of water split-off from the fumonisin molecule during ester formation resulted in the empirical formulae of the fumonisin backbone esterifying agents (fatty acids): C16H32O2 (palmitic acid, PA), C18H32O2 (linoleic acid, LA) and C18H34O2 (oleic acid, OA). We denoted the new compounds as esterified FB1 (EFB1) toxins, with the suggested names EFB1 PA, iso-EFB1 PA, EFB1 LA, iso-EFB1 LA, EFB1 OA and iso-EFB1 OA. The total amount of these new compounds comprised 0.1% of the FB1 concentration, which may be rated as significant when it is considered that these new components are significantly more apolar than earlier-described fumonisins, and their uptake into and toxicity elicited in the various tissues of living organisms may therefore also be significantly different from those of other fumonisins.
Acknowledgements
Financial support was provided by EC (KBBE-2007-22269-2 MYCORED) and Hungarian State Research (OTKA 77612) grants.