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KEYNOTE LECTURE SESSION 2: SECONDARY METABOLITES –
BIOCHEMISTRY, BIOSYNTHESIS, FEED AND FOOD SAFETY
Metabolisation of deoxynivalenol in planta: Old and
new compounds and their role in food safety
F. Berthiller 1 , V. Nagl 1 , B. Kluger 1 , E. Varga 1 , A. Malachova 1 , C. Büschl 1 , H.
Schwartz 1 , M. Lemmens 2 , R. Schuhmacher 1 , G. Adam 3 , R. Krska 1
University of Natural Resources and Life Sciences, Vienna, Austria (BOKU); 1 Department IFA-Tulln,
Christian Doppler Laboratory for Mycotoxin Metabolism and Center for Analytical Chemistry, 3430
Tulln, Austria; 2 Department IFA-Tulln, Biotechnology in Plant Production, 3430 Tulln, Austria;
3 Department of Applied Genetics and Cell Biology, 1190 Vienna, Austria
E-mail: franz.berthiller@boku.ac.at
Fusarium mycotoxins are prone to be metabolised by growing plants on the field. The
toxins can be chemically altered as part of the plants´ defense against fungal invasion
and harmful xenobiotics, such as deoxynivalenol (DON), are more or less efficiently
detoxified by various crops. The occurring metabolites, sometimes referred to as
“masked mycotoxins”, can partly explain the mode of action of plant resistance.
Furthermore, masked mycotoxins are also transferred into food. The possible
hydrolysis of these metabolites back to their toxic parents during mammalian digestion
raises concerns, as the total mycotoxin load of consumers might be underestimated.
We employed a metabolomics LC-HR-MS based approach using in vivo stable
isotopic labelling combined with a newly developed sophisticated software tool
(MetExtract) to extract biological features originating from true metabolites. Flowering
ears were inoculated with a mixture of non-labelled and 13 C labelled DON.
Subsequent sample preparation, LC-HRMS measurements and data processing
revealed a total of 57 corresponding peak pairs, which originated from ten
metabolites. Besides DON and the known DON-3-glucoside (D3G), eight further DONbiotransformation
products were found by the untargeted screening approach. These
metabolites include two DON-glutathione forms and their processing products DON-Scysteine
and DON-S-cysteinyl-glycine.
In a recent survey, 374 beer samples from 38 countries were analysed for the
presence of DON and D3G. In total, 77% of all beers contained DON, while even 93%
contained D3G above the limit of detection. Average concentrations of all beers were
8.4 µg DON/L and 6.9 µg D3G/L. The highest contamination was detected in a pale
beer from an Austrian microbrewery with 89 µg DON/L and 81 µg D3G/L. While the
average contamination of beer is not of toxicological concern for moderate beer
drinkers, heavy beer consumption considerably contributes to the overall DON intake.
We have been able to describe the fate of DON-3-glucoside during digestion with in
vitro and in vivo models. These results suggest that DON-3-glucoside is little
bioavailable and readily hydrolysed to DON during digestion. In rats the liberated DON
is partially converted to DOM-1 and excreted in faeces. DON is also taken up in the
blood stream and metabolised to DON-glucuronide prior to excretion by urine. As the
majority of D3G is excreted in faeces after hydrolisation, D3G in food and feed seems
to have a significantly lower toxic equivalency compared to DON. Due to the
differences regarding the anatomy and gut microbiota, the bioavailability and more
importantly the metabolisation may be species dependent. Further studies, including
other animal models are warranted.
Keywords: masked mycotoxins, deoxynivalenol, deoxynivalenol-3-glucoside, digestion
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