Structural elucidation and analysis of thermal degradation products of the Fusarium mycotoxin nivalenol.
The major class of mycotoxins produced by Fusarium moulds are trichothecenes, a large group of sesquiterpenes sharing the same basic chemical structure, a 12,13-epoxytrichothec-9-ene ring system. Their toxic effects range from causing diarrhoea, vomiting and gastro-intestinal inflammation to noncompetitive inhibition of the biosynthesis of proteins in eukaryotic cells. Trichothecenes in general are relatively stable compounds, their degradation is observed only at high temperatures and prolonged heating time. In order to investigate the stability of the trichothecene nivalenol (NIV) under food processing conditions such as cooking or baking, we performed model heating experiments and screened the residue for degradation products using gas chromatography-mass spectrometry (GC-MS). Heating of nivalenol, especially under mild alkaline conditions, gave a mixture of four compounds (norNIV A, norNIV B, norNIV C, and NIV lactone), which where isolated and identified by nuclear magnetic resonance (NMR) and MS experiments. Although their formation was also demonstrated in heating experiments with spiked flour samples, only norNIV B was detectable in a screening of several commercially available samples, possibly due to the very low contamination with nivalenol. Furthermore, cell culture experiments using immortalized human kidney epithelial (IHKE) cells showed that the four compounds are less cytotoxic (formazan dye cytotoxicity assay) compared to nivalenol. Whereas nivalenol revealed an EC50 at 0.9 micromol, all other compounds did not show any significant effect up to 100 micromol.
Bretz
Michael
M
Institut für Lebensmittelchemie, Westfälische Wilhelms-Universität Münster, Münster, Germany.
Knecht
Anja
A
Göckler
Simon
S
Humpf
Hans-Ulrich
HU
D002461:Cell Line, Transformed; D002851:Chromatography, High Pressure Liquid; D004622:Embryo, Mammalian; D004847:Epithelial Cells; D005670:Fusarium / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D006801:Humans; D007668:Kidney; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009183:Mycotoxins / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D014255:Trichothecenes / Q000737:chemistry* / Q000633:toxicity
D009183:Mycotoxins; D014255:Trichothecenes; C038405:nivalenol