Metabolism of the masked mycotoxin deoxynivalenol-3-glucoside in rats

A novel strategy for detoxification of deoxynivalenol via modification of both toxic groups

Deoxynivalenol (DON) is the most abundant mycotoxin in cereal crops and derived foods and is of great concern in agriculture. Bioremediation strategies have long been sought to minimize the impact of mycotoxin contamination, but few direct and effective enzyme-catalyzed detoxification methods are currently available. In this study, we established a multi-enzymatic cascade reaction and successfully achieved detoxification at double sites: glutathionylation for the C-12,13 epoxide group and epimerization for the C-3 hydroxyl group. This yielded novel derivatives of DON, 3-epi-DON-13-glutathione (3-epi-DON-13-GSH) as well as its by-product, 3-keto-DON-13-GSH, for which precise structures were validated via liquid chromatography-high-resolution tandem mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR) spectroscopy. Both cell viability and DNA synthesis assays demonstrated dramatically decreased cytotoxicity of the double-site modified product 3-epi-DON-13-GSH. These findings provide a promising and urgently needed novel method for addressing the problem of DON contamination in agricultural and industrial settings.

Fhb7-GST catalyzed glutathionylation effectively detoxifies the trichothecene family

Trichothecene (TCN) contamination in food and feed is a serious challenge due to the negative health and economic impacts. Here, we confirmed that the glutathione S-transferase (GST) Fhb7-GST could broadly catalyze type A, type B and type D TCNs into glutathione epoxide adducts (TCN-13-GSHs). To evaluate the toxicity of TCN-13-GSH adducts, we performed cell proliferation assays in vitro, which demonstrated decreased cytotoxicity of the adducts. Moreover, in vivo assays (repeated-dose treatment in mice) confirmed that TCN-13-GSH adducts were dramatically less toxic than the corresponding TCNs. To establish whether TCN-13-GSH was metabolized back to free toxin during digestion, single-dose metabolic tests were performed in rats; DON-13-GSH was not hydrolyzed in vivo, but rather was quickly metabolized to another low-toxicity compound, DON-13-N-acetylcysteine. These results demonstrate the promise of Fhb7-GST as a candidate of detoxification enzyme potentially applied in TCN-contaminated agricultural samples, minimizing the detrimental effects of the mycotoxin.

Suspect and nontarget screening of mycotoxins and their modified forms in wheat products based on ultrahigh-performance liquid chromatography-high resolution mass spectrometry

Various forms of mycotoxins commonly exist in food and pose a significant risk to human health. Here a comprehensive suspect and nontarget screening strategy for both parent and modified mycotoxins was developed using ultrahigh-performance liquid chromatography-high resolution mass spectrometry (UHPLCHRMS). We constructed an in-house MS/MS database containing 82 mycotoxins in 8 categories. Then fragmentation characteristics of different classes of mycotoxins were rapidly extracted by a Python program "Fragmentation pattern screener (FPScreener)" and nontarget screening rules were determined by analyzing the frequencies and average intensities of fragmentation characteristics. Using the suspect and nontarget screening strategy, we successfully identified six parent mycotoxins and eight modified mycotoxins with different confidence levels in contaminated wheat and flour samples. This strategy enables screening of unknown parents and modified mycotoxins in food matrices with corresponding fragmentation characteristics.

Modified Mycotoxins and Multitoxin Contamination of Food and Feed as Major Analytical Challenges

Mycotoxins, as natural products of molds, are often unavoidable contaminants of food and feed, to which the increasingly evident climate changes contribute a large part. The consequences are more or less severe and range from economic losses to worrying health problems to a fatal outcome. One of the best preventive approaches is regular monitoring of food and feed for the presence of mycotoxins. However, even under conditions of frequent, comprehensive, and conscientious controls, the desired protection goal may not be achieved. In fact, it often happens that, despite favorable analytical results that do not indicate high mycotoxin contamination, symptoms of their presence occur in practice. The most common reasons for this are the simultaneous presence of several different mycotoxins whose individual content does not exceed the detectable or prescribed values and/or the alteration of the form of the mycotoxin, which renders it impossible to be analytically determined using routine methods. When such contaminated foods enter a living organism, toxic effects occur. This article aims to shed light on the above problems in order to pay more attention to them, work to reduce their impact, and, eventually, overcome them.

Risk Assessment Considering the Bioavailability of 3-β-d-Glucosides of Deoxynivalenol and Nivalenol through Food Intake in Korea

Deoxynivalenol and nivalenol are major type B trichothecenes and the most frequently occurring mycotoxins worldwide. Their 3-β-d-glucoside forms have recently become a safety management issue. These glucoside conjugates are converted back to the parent toxins during human digestion, but studies to confirm their bioavailability are lacking. In this study, a risk assessment was performed considering the bioavailability of glucoside conjugates. A literature review was conducted to compile the existing bioavailability studies of glucoside conjugates, and three exposure scenarios considering bioavailability were established. As a result of a risk assessment using deterministic and probabilistic methods, both the deoxynivalenol and nivalenol groups had safe levels of tolerable daily intake percentage (TDI%), not exceeding 100%. The TDI% for the nivalenol group was approximately 2-3 times higher than that for the deoxynivalenol group. Notably, infants showed higher TDI% than adults for both toxin groups. By food processing type, the overall TDI% was highest for raw material, followed by simple-processed and then fermented-processed. Since glucoside conjugates can be converted into parent toxins during the digestion process, a risk assessment considering bioavailability allows the more accurate evaluation of the risk level of glucoside conjugates and can direct their safety management in the future.

Biocontrol Effect of Clonostachys rosea on Fusarium graminearum Infection and Mycotoxin Detoxification in Oat (Avena sativa)

Oat (Avena sativa) is susceptible to Fusarium head blight (FHB). The quality of oat grain is threatened by the accumulation of mycotoxins, particularly the trichothecene deoxynivalenol (DON), which also acts as a virulence factor for the main pathogen Fusarium graminearum. The plant can defend itself, e.g., by DON detoxification by UGT-glycosyltransferases (UTGs) and accumulation of PR-proteins, even though these mechanisms do not deliver effective levels of resistance. We studied the ability of the fungal biocontrol agent (BCA) Clonostachys rosea to reduce FHB and mycotoxin accumulation. Greenhouse trials showed that C. rosea-inoculation of oat spikelets at anthesis 3 days prior to F. graminearum inoculation reduced both the amount of Fusarium DNA (79%) and DON level (80%) in mature oat kernels substantially. DON applied to C. rosea-treated spikelets resulted in higher conversion of DON to DON-3-Glc than in mock treated plants. Moreover, there was a significant enhancement of expression of two oat UGT-glycosyltransferase genes in C. rosea-treated oat. In addition, C. rosea treatment activated expression of genes encoding four PR-proteins and a WRKY23-like transcription factor, suggesting that C. rosea may induce resistance in oat. Thus, C. rosea IK726 has strong potential to be used as a BCA against FHB in oat as it inhibits F. graminearum infection effectively, whilst detoxifying DON mycotoxin rapidly.

Modified Mycotoxins, a Still Unresolved Issue

Mycotoxins are toxic secondary metabolites produced by filamentous microfungi on almost every agricultural commodity worldwide. After the infection of crop plants, mycotoxins are modified by plant enzymes or other fungi and often conjugated to more polar substances, like sugars. The formed—often less toxic—metabolites are stored in the vacuole in soluble form or bound to macromolecules. As these substances are usually not detected during routine analysis and no maximum limits are in force, they are called modified mycotoxins. While, in most cases, modified mycotoxins have lower intrinsic toxicity, they might be reactivated during mammalian metabolism. In particular, the polar group might be cleaved off (e.g., by intestinal bacteria), releasing the native mycotoxin. This review aims to provide an overview of the critical issues related to modified mycotoxins. The main conclusion is that analytical aspects, toxicological evaluation, and exposure assessment merit more investigation.

Occurrence, transformation, and toxicity of fumonisins and their covert products during food processing

Fumonisins comprise structurally related metabolites mainly produced by Fusarium verticillioides and Fusarium proliferatum. Contamination with fumonisins causes incalculable damage to the economy and poses a great risk to animal and human health. Fumonisins and their covert products are found in cereals and cereal products. Food processing significantly affects the degradation of toxins and the formation of covert toxins. However, studies on fumonisins and their covert mycotoxins remain inadequate. This review aims to summarize changes in fumonisins and the generation of covert fumonisins during processing. It also investigates the toxicity and determination methods of fumonisins and covert fumonisins, and elucidates the factors affecting fumonisins and their covert forms during processing. In addition to the metabolic production by plants and fungi, covert fumonisins are mainly produced by covalent or noncovalent binding, complexation, or physical entrapment of fumonisins with other substances. The toxicity of covert fumonisins is similar to that of free fumonisins and is a non-negligible hazard. Covert fumonisins are commonly found in food matrices, and methods to analyze them have yet to be improved. Food processing significantly affects the conversion of fumonisins to their covert toxins.

Toxicokinetics and metabolism of deoxynivalenol in animals and humans

Deoxynivalenol (DON) is the most widespread mycotoxin in food and feedstuffs, posing a persistent health threat to humans and farm animals. The susceptibilities of DON vary significantly among animals, following the order of pigs, mice/rats and poultry from the most to least susceptible. However, no study comprehensively disentangles factors shaping species-specific sensitivity. In this review, the toxicokinetics and metabolism of DON are summarized in animals and humans. Generally, DON is fast-absorbed and widely distributed in multiple organs. DON is first enriched in the plasma, liver and kidney and subsequently accumulates in the intestine. There are also key variations among animals. Pigs and humans are highly sensitive to DON, and they have similar absorption rates (1 h < t_max < 4 h), high bioavailability (> 55%) and long clearance time (2 h < t_1/2 < 4 h). Also, both species lack detoxification microorganisms and mainly depend on liver glucuronidation and urine excretion. Mice and rats have similar toxicokinetics (t_max < 0.5 h, t_1/2 < 1 h). However, a higher proportion of DON is excreted by feces as DOM-1 in rats than in mice, suggesting an important role of gut microbiota in rats. Poultry is least sensitive to DON due to their fast absorption rate (t_max < 1 h), low oral bioavailability (5-30%), broadly available detoxification gut microorganisms and short clearance time (t_1/2 < 1 h). Aquatic animals have significantly slower plasma clearance of DON than land animals. Overall, studies on toxicokinetics provide valuable information for risk assessment, prevention and control of DON contamination.

Exploration of Mycotoxin Accumulation and Transcriptomes of Different Wheat Cultivars during Fusarium graminearum Infection

Fusarium graminearum is one of the most devastating diseases of wheat worldwide, and can cause Fusarium head blight (FHB). F. graminearum infection and mycotoxin production mainly present in wheat and can be influenced by environmental factors and wheat cultivars. The objectives of this study were to examine the effect of wheat cultivars and interacting conditions of temperature and water activity (aw) on mycotoxin production by two strains of F. graminearum and investigate the response mechanisms of different wheat cultivars to F. graminearum infection. In this regard, six cultivars of wheat spikes under field conditions and three cultivars of post-harvest wheat grains under three different temperature conditions combined with five water activity (aw) conditions were used for F. graminearum infection in our studies. Liquid chromatography tandem mass spectrometry (LC–MS/MS) analysis showed significant differences in the concentration of Fusarium mycotoxins deoxynivalenol (DON) and its derivative deoxynivalenol-3-glucoside (D3G) resulting from wheat cultivars and environmental factors. Transcriptome profiles of wheat infected with F. graminearum revealed the lower expression of disease defense-factor-related genes, such as mitogen-activated protein kinases (MAPK)-encoding genes and hypersensitivity response (HR)-related genes of infected Annong 0711 grains compared with infected Sumai 3 grains. These findings demonstrated the optimal temperature and air humidity resulting in mycotoxin accumulation, which will be beneficial in determining the conditions of the relative level of risk of contamination with FHB and mycotoxins. More importantly, our transcriptome profiling illustrated differences at the molecular level between wheat cultivars with different FHB resistances, which will lay the foundation for further research on mycotoxin biosynthesis of F. graminearum and regulatory mechanisms of wheat to F. graminearum.

Background ions into exclusion list: A new strategy to enhance the efficiency of DDA data collection for high-throughput screening of chemical contaminations in food

Foods contaminated with hazardous compounds, could pose potential risks for human health. To date, there is still a big challenge in accurate identification. In this study, a novel data-dependent acquisition (DDA) approach, based on a combination of inclusion list and exclusion list, was proposed to acquire more effective MS/MS spectra. This strategy was successfully applied in a large-scale screening survey to detect 50 mycotoxins in oats, 155 veterinary drugs in dairy milk, and 200 pesticides in tomatoes. Compared with traditional acquisition modes, this new strategy has higher detection rate, particularly at ultra-low concentration by eliminating background influence, thereby generating the MS/MS spectra for more potential hazardous materials instead of matrix interference. Additionally, the obtained MS/MS spectra are simpler and more likely to be traced back than DIA. Moreover, this new strategy would be more comprehensively applied in food safety monitoring with the improvement of HRMS and post-acquisition techniques.

Structure-toxicity relationships, toxicity mechanisms and health risk assessment of food-borne modified deoxynivalenol and zearalenone: A comprehensive review

Mycotoxin, as one of the most common pollutants in foodstuffs, poses great threat to food security and human health. Specifically, deoxynivalenol (DON) and zearalenone (ZEN)-two mycotoxin contaminants with considerable toxicity widely existing in food products-have aroused broad public concerns. Adding to this picture, modified forms of DON and ZEN, have emerged as another potential environmental and health threat, owing to their higher re-transformation rate into parent mycotoxins inducing accumulation of mycotoxin in humans and animals. Given this, a better understanding of the toxicity of modified mycotoxins is urgently needed. Moreover, the lack of toxicity data means a proper risk assessment of modified mycotoxins remains challenging. To better evaluate the toxicity of modified DON and ZEN, we have reviewed the relationship between their structures and toxicities. The toxicity mechanisms behind modified DON and ZEN have also been discussed; briefly, these involve acute, subacute, chronic, and combined toxicities. In addition, this review also addresses the global occurrence of modified DON and ZEN, and summarizes novel methods-including in silico analysis and implementation of relative potency factors-for risk assessment of modified DON and ZEN. Finally, the health risk assessment of modified DON and ZEN has also been discussed comprehensively.

Deoxynivalenol: Mechanisms of action and its effects on various terrestrial and aquatic species

Deoxynivalenol, a type B trichothecene mycotoxin produced by Fusarium species of fungi, is a ubiquitious contaminant of cereal grains worldwide. Chronic, low dose consumption of feeds contaminated with DON is associated with a wide range of symptoms in terrestrial and aquatic species including decreased feed intake and feed refusal, reduced weight gain, and altered nutritional efficiency. Acute, high dose exposure to DON may be associated with more severe symptoms such as vomiting, diarrhea, intestinal inflammation and gastrointestinal hemorrhage. The toxicity of DON is partly related to its ability to disrupt eukaryotic protein synthesis via binding to the peptidyl transferase site of the ribosome. Moreover, DON exerts its effects at the cellular level by activating mitogen activated protein kinases (MAPK) through a process known as the ribotoxic stress response (RSR). The outcome of DON-associated MAPK activation is dose and duration dependent; acute low dose exposure results in immunostimulation characterized by the upregulation of cytokines, chemokines and other proinflammatory-related proteins, whereas longer term exposure to higher doses generally results in apoptosis, cell cycle arrest, and immunosuppression. The order of decreasing sensitivity to DON is considered to be: swine > rats > mice > poultry ≈ ruminants. However, studies conducted within the past 10 years have demonstrated that some species of fish, such as rainbow trout, are highly sensitive to DON. The aims of this review are to explore the effects of DON on terrestrial and aquatic species as well as its mechanisms of action, metabolism, and interaction with other Fusarium mycotoxins. Notably, a considerable emphasis is placed on reviewing the effects of DON on different species of fish.

The Occurrence of Mycotoxins in Raw Materials and Fish Feeds in Europe and the Potential Effects of Deoxynivalenol (DON) on the Health and Growth of Farmed Fish Species-A Review

The first part of this study evaluates the occurrence of mycotoxin patterns in feedstuffs and fish feeds. Results were extrapolated from a large data pool derived from wheat (n = 857), corn (n = 725), soybean meal (n = 139) and fish feed (n = 44) samples in European countries and based on sample analyses by liquid chromatography/tandem mass spectrometry (LC-MS/MS) in the period between 2012-2019. Deoxynivalenol (DON) was readily present in corn (in 47% of the samples) > wheat (41%) > soybean meal (11%), and in aquafeeds (48%). Co-occurrence of mycotoxins was frequently observed in feedstuffs and aquafeed samples. For example, in corn, multi-mycotoxin occurrence was investigated by Spearman's correlations and odd ratios, and both showed co-occurrence of DON with its acetylated forms (3-AcDON, 15-AcDON) as well as with zearalenone (ZEN). The second part of this study summarizes the existing knowledge on the effects of DON on farmed fish species and evaluates the risk of DON exposure in fish, based on data from in vivo studies. A meta-analytical approach aimed to estimate to which extent DON affects feed intake and growth performance in fish. Corn was identified as the ingredient with the highest risk of contamination with DON and its acetylated forms, which often cannot be detected by commonly used rapid detection methods in feed mills. Periodical state-of-the-art mycotoxin analyses are essential to detect the full spectrum of mycotoxins in fish feeds aimed to prevent detrimental effects on farmed fish and subsequent economic losses for fish farmers. Because levels below the stated regulatory limits can reduce feed intake and growth performance, our results show that the risk of DON contamination is underestimated in the aquaculture industry.

Two Different Inoculation Methods Unveiled the Relative Independence of DON Accumulation in Wheat Kernels from Disease Severity on Spike after Infection by Fusarium Head Blight

Fusarium head blight (FHB) causes wheat yield loss and mycotoxin (deoxynivalenol, DON) accumulation in wheat kernel. Developing wheat cultivars with overall resistance to both FHB spread within a spike and DON accumulation in kernels is crucial for ensuring food security and food safety. Here, two relatively novel inoculation methods, bilateral floret inoculation (BFI) and basal rachis internode injection (BRII), were simultaneously employed to evaluate disease severity and DON content in kernels in a segregating population of recombinant inbred lines (RILs) developed from Ning 7840 (carrying Fhb1) and Clark (without Fhb1). Under both inoculation methods, four contrasting combinations of disease severity and DON content were identified: high severity/high DON (HSHD), high severity/low DON (HSLD), low severity/high DON (LSHD) and low severity/low DON (LSLD). Unexpectedly, the BRII method clearly indicated that disease severity was not necessarily relevant to DON concentration. The effects of Fhb1 on disease severity, and on DON concentrations, agreed very well across the two methods. Several lines carrying Fhb1 showed extremely higher severity and (or) DON content under both inoculation methods. The “Mahalanobis distance” (MD) method was used to rate overall resistance of a line by inclusion of both disease severity and DON content over both methods to select LSLD lines.

Mycotoxins-Biomonitoring and Human Exposure

Mycotoxins are secondary metabolites produced by fungal species that commonly have a toxic effect on human and animal health. Different foodstuff can be contaminated and are considered the major source of human exposure to mycotoxins, but occupational and environmental exposure can also significantly contribute to this problem. This review aims to provide a short overview of the occurrence of toxigenic fungi and regulated mycotoxins in foods and workplaces, following the current literature and data presented in scientific papers. Biomonitoring of mycotoxins in plasma, serum, urine, and blood samples has become a common method for determining the exposure to different mycotoxins. Novel techniques are more and more precise and accurate and are aiming toward the simultaneous determination of multiple mycotoxins in one analysis. Application of liquid chromatography (LC) methodologies, coupled with tandem mass spectrometry (MS/MS) or high-resolution mass spectrometry (HRMS) has become a common and most reliable method for determining the exposure to mycotoxins. Numerous references confirm the importance of mycotoxin biomonitoring to assess the exposure for humans and animals. The objectives of this paper were to review the general approaches to biomonitoring of different mycotoxins and the occurrence of toxigenic fungi and their mycotoxins, using recent literature sources.

Mycotoxin and Gut Microbiota Interactions

The interactions between mycotoxins and gut microbiota were discovered early in animals and explained part of the differences in susceptibility to mycotoxins among species. Isolation of microbes present in the gut responsible for biotransformation of mycotoxins into less toxic metabolites and for binding mycotoxins led to the development of probiotics, enzymes, and cell extracts that are used to prevent mycotoxin toxicity in animals. More recently, bioactivation of mycotoxins into toxic compounds, notably through the hydrolysis of masked mycotoxins, revealed that the health benefits of the effect of the gut microbiota on mycotoxins can vary strongly depending on the mycotoxin and the microbe concerned. Interactions between mycotoxins and gut microbiota can also be observed through the effect of mycotoxins on the gut microbiota. Changes of gut microbiota secondary to mycotoxin exposure may be the consequence of the antimicrobial properties of mycotoxins or the toxic effect of mycotoxins on epithelial and immune cells in the gut, and liberation of antimicrobial peptides by these cells. Whatever the mechanism involved, exposure to mycotoxins leads to changes in the gut microbiota composition at the phylum, genus, and species level. These changes can lead to disruption of the gut barrier function and bacterial translocation. Changes in the gut microbiota composition can also modulate the toxicity of toxic compounds, such as bacterial toxins and of mycotoxins themselves. A last consequence for health of the change in the gut microbiota secondary to exposure to mycotoxins is suspected through variations observed in the amount and composition of the volatile fatty acids and sphingolipids that are normally present in the digesta, and that can contribute to the occurrence of chronic diseases in human. The purpose of this work is to review what is known about mycotoxin and gut microbiota interactions, the mechanisms involved in these interactions, and their practical application, and to identify knowledge gaps and future research needs.

Co-Occurrence and Levels of Mycotoxins in Fish Feeds in Kenya

This study determined the presence, levels and co-occurrence of mycotoxins in fish feeds in Kenya. Seventy-eight fish feeds and ingredients were sampled from fish farms and fish feed manufacturing plants and analysed for 40 mycotoxins using high-performance liquid chromatography-high resolution mass spectrometry. Twenty-nine (73%) mycotoxins were identified with 76 (97%) samples testing positive for mycotoxins presence. Mycotoxins with the highest prevalences were enniatin B (91%), deoxynivalenol (76%) and fumonisin B1 (54%) while those with the highest maximum levels were sterigmatocystin (<30.5-3517.1 µg/kg); moniliformin (<218.9-2583.4 µg/kg) and ergotamine (<29.3-1895.6 µg/kg). Mycotoxin co-occurrence was observed in 68 (87%) samples. Correlations were observed between the fumonisins; enniatins B and zearalenone and its metabolites. Fish dietary exposure estimates ranged between <0.16 and 43.38 µg/kg body weight per day. This study shows evidence of mycotoxin presence and co-occurrence in fish feeds and feed ingredients in Kenya. Fish exposure to these levels of mycotoxins over a long period of time may lead to adverse health effects due to their possible additive, synergistic or antagonist toxic effects. Measures to reduce fish feed mycotoxin contamination should be taken to avoid mycotoxicosis in fish and subsequently in humans and animals through residues.

Investigation of age-related differences in toxicokinetic processes of deoxynivalenol and deoxynivalenol-3-glucoside in weaned piglets

Age-related differences in toxicokinetic processes of deoxynivalenol (DON) and deoxynivalenol-3-glucoside (DON3G) were studied. DON3G [55.7 µg/kg bodyweight (BW)] and an equimolar dose of DON (36 µg/kg BW) were administered to weaned piglets (4 weeks old) by single intravenous and oral administration in a double two-way cross-over design. Systemic and portal blood was sampled at different time points pre- and post-administration and plasma concentrations of DON, DON3G and their metabolites were quantified using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) methods. Data were processed using tailor-made compartmental toxicokinetic (TK) models to accurately estimate TK parameters. Results were statistically compared to data obtained in a previous study on 11-week-old pigs using identical experimental conditions. Significant age-related differences in intestinal and systemic exposure to both DON and DON3G were noted. Most remarkably, a significant difference was found for the absorbed fraction of DON3G, after presystemic hydrolysis to DON, in weaned piglets compared to 11-week-old piglets (83% vs 16%, respectively), assumed to be mainly attributed to the higher intestinal permeability of weaned piglets. Other differences in TK parameters could be assigned to a higher water/fat body ratio and longer gastrointestinal transit time of weaned piglets. Results may further refine current risk assessment concerning DON and DON3G in animals. Additionally, since piglets possibly serve as a human paediatric surrogate model, results may be extrapolated to human infants.

Changes in masked forms of deoxynivalenol and their co-occurrence with culmorin in cereal-based products: A systematic review and meta-analysis

This study was aimed to evaluate the fate of D3G, 3-ADON, and 15-ADON during various processing steps (milling, fermentation, baking and cooking with water) of different cereal-based products, as well as the co-occurrence of culmorin (CUL) and its derivatives (15-Hydroxy-CUL and 5-Hydroxy-CUL. Some databases such as Science Direct, PubMed, Scopus, and Embase were screened to collect the relevant published papers between January 1983 to October 2018, and 23 articles with 319 data were included. The baking resulted in reductions in the concentration of all types of investigated masked mycotoxins, i.e., 15-ADON (-25%) > 3-ADON (-15%) > D3G (-6%). Also, rank order of CUL and its derivatives based on occurrence was CUL (70%) > 15-Hydroxy-CUL (47%) > 5-Hydroxy-CUL (15%) and their rank based on their concentration was 5-Hydroxy-CUL (99.21 µg/kg) > CUL (48.84 µg/kg) > 15-Hydroxy-CUL (9.39 µg/kg) > Hydroxy -CUL (0.06 µg/kg) > 12-Hydroxy-CUL (0.05 µg/kg) > 14-Hydroxy-CUL (0.01 µg/kg).

Yesterday masked, today modified; what do mycotoxins bring next?

Mycotoxins are secondary metabolites produced by toxigenic fungi in crops worldwide. In (micro)organisms such as plants, fungi, bacteria, or animals they may be further metabolised and modified, but this is also true for food processing, which may lead to a wide range of masked mycotoxin forms. These often remain undetected by analytical methods and are the culprits for underestimates in risk assessments. Furthermore, once ingested, modified mycotoxins can convert back to their parent forms. This concern has raised the need for analytical methods that can detect and quantify modified mycotoxins as essential for accurate risk assessment. The promising answer is liquid chromatography-mass spectrometry. New masked mycotoxin forms are now successfully detected by iontrap, time-of-flight, or high-resolution orbitrap mass spectrometers. However, the toxicological relevance of modified mycotoxins has not been fully clarified.

Monitoring and evaluation of the interaction between deoxynivalenol and gut microbiota in Wistar rats by mass spectrometry-based metabolomics and next-generation sequencing

Published evidence has demonstrated the several toxic characteristics of mycotoxins and their considerable risk to human and animal health. One of the most common uncertainties regards whether if very low concentrations of the mycotoxin deoxynivalenol (DON), easily consumed within the Mediterranean Diet, can cause metabolic alterations; some of them produced by the interaction between DON and gut microbiota. Accordingly, faecal samples were collected from Wistar rats that had consumed the mycotoxin DON at low levels (60 and 120 μg kg^-1 body weight of DON per day), and were analysed by ultra-high performance liquid chromatography coupled with tandem mass spectrometry detection, in order to monitor the mycotoxin DON and its metabolite de-epoxy deoxynivalenol (DOM-1). The obtained results showed an evolution in DON excretion and the metabolite DOM-1 which has less toxic properties, over the course of the days of the study. To elucidate whether intestinal microbiota had a role in the observed detoxification process, the changes in microbial gut biodiversity were explored through 16s rRNA high throughput sequencing. No main changes were detected but significant increase in Coprococcus genus relative abundance was found. Further studies are needed to confirm if intestinal microbiota composition and function are affected by low mycotoxin concentrations.

Modified Fusarium Mycotoxins in Cereals and Their Products-Metabolism, Occurrence, and Toxicity: An Updated Review

Mycotoxins are secondary fungal metabolites, toxic to humans, animals and plants. Under the influence of various factors, mycotoxins may undergo modifications of their chemical structure. One of the methods of mycotoxin modification is a transformation occurring in plant cells or under the influence of fungal enzymes. This paper reviews the current knowledge on the natural occurrence of the most important trichothecenes and zearalenone in cereals/cereal products, their metabolism, and the potential toxicity of the metabolites. Only very limited data are available for the majority of the identified mycotoxins. Most studies concern biologically modified trichothecenes, mainly deoxynivalenol-3-glucoside, which is less toxic than its parent compound (deoxynivalenol). It is resistant to the digestion processes within the gastrointestinal tract and is not absorbed by the intestinal epithelium; however, it may be hydrolysed to free deoxynivalenol or deepoxy-deoxynivalenol by the intestinal microflora. Only one zearalenone derivative, zearalenone-14-glucoside, has been extensively studied. It appears to be more reactive than deoxynivalenol-3-glucoside. It may be readily hydrolysed to free zearalenone, and the carbonyl group in its molecule may be easily reduced to α/β-zearalenol and/or other unspecified metabolites. Other derivatives of deoxynivalenol and zearalenone are poorly characterised. Moreover, other derivatives such as glycosides of T-2 and HT-2 toxins have only recently been investigated; thus, the data related to their toxicological profile and occurrence are sporadic. The topics described in this study are crucial to ensure food and feed safety, which will be assisted by the provision of widespread access to such studies and obtained results.

Humans significantly metabolize and excrete the mycotoxin deoxynivalenol and its modified form deoxynivalenol-3-glucoside within 24 hours

For the first time, a comprehensive human intervention study was conducted to unravel the urinary excretion profile and metabolism of the fungal metabolite deoxynivalenol (DON) and its modified form deoxynivalenol-3-glucoside (DON-3-glucoside). Twenty volunteers were restricted in consuming cereals and cereal-based foods for 4 days. At day 3, a single bolus of 1 µg/kg body weight of DON and a single bolus of 1 µg/kg body weight of DON-3-glucoside after a washing-out period of two months was administered, and a 24-h urine collection was performed. The urine was analysed for DON, DON-3-glucoside, 3-ADON, 15-ADON, deepoxy-deoxynivalenol (DOM-1), deoxynivalenol-3-glucuronide (DON-3-glucuronide) and deoxynivalenol-15-glucuronide (DON-15-glucuronide). The urinary biomarker-analysis revealed that DON and DON-3-glucoside were rapidly absorbed, distributed, metabolized and excreted. Sixty-four % of the administered DON and 58% of DON-3-glucoside was recovered in the urine collected within 24 h. DON-15-glucuronide was the most prominent urinary biomarker followed by free DON and DON-3-glucuronide. Moreover, correlations among the presence of DON-15-glucuronide and DON-3-glucuronide were observed (within 24 hours (r = 0.61)). The DOM-1 detected in the urine was higher after the DON-3-glucoside administration. The obtained results are imperative to construct a standardized method to estimate DON-intake by means of urinary biomarkers.

UDP-Glucosyltransferases from Rice, Brachypodium, and Barley: Substrate Specificities and Synthesis of Type A and B Trichothecene-3-O-β-d-glucosides

Trichothecene toxins are confirmed or suspected virulence factors of various plant-pathogenic Fusarium species. Plants can detoxify these to a variable extent by glucosylation, a reaction catalyzed by UDP-glucosyltransferases (UGTs). Due to the unavailability of analytical standards for many trichothecene-glucoconjugates, information on such compounds is limited. Here, the previously identified deoxynivalenol-conjugating UGTs HvUGT13248 (barley), OsUGT79 (rice) and Bradi5g03300 (Brachypodium), were expressed in E. coli, affinity purified, and characterized towards their abilities to glucosylate the most relevant type A and B trichothecenes. HvUGT13248, which prefers nivalenol over deoxynivalenol, is also able to conjugate C-4 acetylated trichothecenes (e.g., T-2 toxin) to some degree while OsUGT79 and Bradi5g03300 are completely inactive with C-4 acetylated derivatives. The type A trichothecenes HT-2 toxin and T-2 triol are the kinetically preferred substrates in the case of HvUGT13248 and Bradi5g03300. We glucosylated several trichothecenes with OsUGT79 (HT-2 toxin, T-2 triol) and HvUGT13248 (T-2 toxin, neosolaniol, 4,15-diacetoxyscirpenol, fusarenon X) in the preparative scale. NMR analysis of the purified glucosides showed that exclusively β-D-glucosides were formed regio-selectively at position C-3-OH of the trichothecenes. These synthesized standards can be used to investigate the occurrence and toxicological properties of these modified mycotoxins.

Effect of gaseous ozone treatments on DON, microbial contaminants and technological parameters of wheat and semolina

Deoxynivalenol (DON) is an important mycotoxin produced by several species of Fusarium. It occurs often in wheat grain and is frequently associated with significant levels of its modified form DON-3-glucoside (DON-3-Glc). Ozone (O₃) is a powerful disinfectant and oxidant, classified as GRAS (Generally Recognised As Safe), that reacts easily with specific compounds including the mycotoxins aflatoxins, ochratoxin A, trichothecenes and zearalenone. It degrades DON in aqueous solution and can be effective for decontamination of grain. This study reports the efficacy of gaseous ozone treatments in reducing DON, DON-3-Glc, bacteria, fungi and yeasts in naturally contaminated durum wheat. A prototype was used to dispense ozone continuously and homogeneously at different concentrations and exposure time, in 2 kg aliquots of durum wheat. The optimal conditions, which do not affect chemical and rheological parameters of durum wheat, semolina and pasta, were identified (55 g O₃ h^-1 for 6 h). The measured mean reductions of DON and DON-3-Glc in ozonated wheat were 29% and 44%, respectively. Ozonation also produced a significant (p < 0.05) reduction of total count (CFU/g) of bacteria, fungi and yeasts in wheat grains.

Metabolic profile of the masked mycotoxin T-2 toxin-3-glucoside in rats (in vitro and in vivo) and humans (in vitro)

The metabolic profile of T-2 toxin-3-glucoside (T2-Glc) in humans and rats was investigated using ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF). When rat and human liver microsomes were incubated with T2-Glc, a total of five metabolites were detected. T2-Glc exposed a higher metabolic stability in rats and human than T-2 toxin (T-2). The metabolism of T2-Glc by the intestinal microbiota of human and rats was also investigated, and three metabolites were observed. T2-Glc was reconverted to T-2 during incubation with fresh faeces. Furthermore, in vivo metabolism of T2-Glc in rats after oral administration was carried out, and three metabolites were detected in rat urine and faeces (T-2, HT-2 toxin and 3'-OH-T2-Glc). In vivo metabolism results indicated that T2-Glc was mainly metabolised in the gastro-intestinal tract with a low absorption level in rats. The results demonstrated that hydroxylation (C-3' and C-4'), hydrolysis (C-4 and C-8) and deconjugation are the main metabolic pathways of T2-Glc in mammals.

Modified mycotoxins: An updated review on their formation, detection, occurrence, and toxic effects

Modified mycotoxins are metabolites that normally remain undetected during the testing for parent mycotoxin. These modified forms of mycotoxins can be produced by fungi or generated as part of the defense mechanism of the infected plant. In some cases, they are formed during food processing. The various processing steps greatly affect mycotoxin levels present in the final product (free and modified), although the results are still controversial regarding the increase or reduction of these levels, being strongly related to the type of process and the composition of the food in question. Evidence exists that some modified mycotoxins can be converted into the parent mycotoxin during digestion in humans and animals, potentially leading to adverse health effects. Some of these formed compounds can be even more toxic, in case they have higher bioaccessibility and bioavailability than the parent mycotoxin. The modified mycotoxins can occur simultaneously with the free mycotoxin, and, in some cases, the concentration of modified mycotoxins may exceed the level of free mycotoxin in processed foods. Even though toxicological data are scarce, the possibility of modified mycotoxin conversion to its free form may result in a potential risk to human and animal health. This review aims to update information on the formation, detection, occurrence, and toxic effects caused by modified mycotoxin.

Risks to human and animal health related to the presence of deoxynivalenol and its acetylated and modified forms in food and feed

Deoxynivalenol (DON) is a mycotoxin primarily produced by Fusarium fungi, occurring predominantly in cereal grains. Following the request of the European Commission, the CONTAM Panel assessed the risk to animal and human health related to DON, 3-acetyl-DON (3-Ac-DON), 15-acetyl-DON (15-Ac-DON) and DON-3-glucoside in food and feed. A total of 27,537, 13,892, 7,270 and 2,266 analytical data for DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside, respectively, in food, feed and unprocessed grains collected from 2007 to 2014 were used. For human exposure, grains and grain-based products were main sources, whereas in farm and companion animals, cereal grains, cereal by-products and forage maize contributed most. DON is rapidly absorbed, distributed, and excreted. Since 3-Ac-DON and 15-Ac-DON are largely deacetylated and DON-3-glucoside cleaved in the intestines the same toxic effects as DON can be expected. The TDI of 1 μg/kg bw per day, that was established for DON based on reduced body weight gain in mice, was therefore used as a group-TDI for the sum of DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside. In order to assess acute human health risk, epidemiological data from mycotoxicoses were assessed and a group-ARfD of 8 μg/kg bw per eating occasion was calculated. Estimates of acute dietary exposures were below this dose and did not raise a health concern in humans. The estimated mean chronic dietary exposure was above the group-TDI in infants, toddlers and other children, and at high exposure also in adolescents and adults, indicating a potential health concern. Based on estimated mean dietary concentrations in ruminants, poultry, rabbits, dogs and cats, most farmed fish species and horses, adverse effects are not expected. At the high dietary concentrations, there is a potential risk for chronic adverse effects in pigs and fish and for acute adverse effects in cats and farmed mink.

Glucuronidation of deoxynivalenol (DON) by different animal species: identification of iso-DON glucuronides and iso-deepoxy-DON glucuronides as novel DON metabolites in pigs, rats, mice, and cows

The Fusarium mycotoxin deoxynivalenol (DON) is a frequent contaminant of cereal-based food and feed. Mammals metabolize DON by conjugation to glucuronic acid (GlcAc), the extent and regioselectivity of which is species-dependent. So far, only DON-3-glucuronide (DON-3-GlcAc) and DON-15-GlcAc have been unequivocally identified as mammalian DON glucuronides, and DON-7-GlcAc has been proposed as further DON metabolite. In the present work, qualitative HPLC–MS/MS analysis of urine samples of animals treated with DON (rats: 2 mg/kg bw, single bolus, gavage; mice: 1 mg/kg bw, single i.p. injection; pigs: 74 µg/kg bw, single bolus, gavage; cows: 5.2 mg DON/kg dry mass, oral for 13 weeks) revealed additional DON and deepoxy-DON (DOM) glucuronides. To elucidate their structures, DON and DOM were incubated with human (HLM) and rat liver microsomes (RLM). Besides the expected DON/DOM-3- and 15-GlcAc, minor amounts of four DON- and four DOM glucuronides were formed. Isolation and enzymatic hydrolysis of four of these compounds yielded iso-DON and iso-DOM, the identities of which were eventually confirmed by NMR. Incubation of iso-DON and iso-DOM with RLM and HLM yielded two main glucuronides for each parent compound, which were isolated and identified as iso-DON/DOM-3-GlcAc and iso-DON/DOM-8-GlcAc by NMR. Iso-DON-3-GlcAc, most likely misidentified as DON-7-GlcAc in the literature, proved to be a major DON metabolite in rats and a minor metabolite in pigs. In addition, iso-DON-8-GlcAc turned out to be one of the major DON metabolites in mice. DOM-3-GlcAc was the dominant DON metabolite in urine of cows and an important DON metabolite in rat urine. Iso-DOM-3-GlcAc was detected in urine of DON-treated rats and cows. Finally, DON-8,15-hemiketal-8-glucuronide, a previously described by-product of DON-3-GlcAc production by RLM, was identified in urine of DON-exposed mice and rats. The discovery of several novel DON-derived glucuronides in animal urine requires adaptation of the currently used methods for DON-biomarker analysis.

T-2 Toxin-3α-glucoside in Broiler Chickens: Toxicokinetics, Absolute Oral Bioavailability, and in Vivo Hydrolysis

Due to the lack of information on bioavailability and toxicity of modified mycotoxins, current risk assessment on these modified forms assumes an identical toxicity of the modified form to their respective unmodified counterparts. Crossover animal trials were performed with intravenous and oral administration of T-2 toxin (T-2) and T-2 toxin-3α-glucoside (T2-G) to broiler chickens. Plasma concentrations of T2-G, T-2, and main phase I metabolites were quantified using a validated liquid chromatography-tandem mass spectrometry method with a limit of quantitation for all compounds of 0.1 ng/mL. Resulting plasma concentration-time profiles were processed via two-compartmental toxicokinetic models. No T-2 triol and only traces of HT-2 were detected in the plasma samples after both intravenous and oral administration. The results indicate that T-2 has a low absolute oral bioavailability of 2.17 ± 1.80%. For T2-G, an absorbed fraction of the dose and absolute oral bioavailability of 10.4 ± 8.7% and 10.1 ± 8.5% were observed, respectively. This slight difference is caused by a minimal (and neglectable) presystemic hydrolysis of T2-G to T-2, that is, 3.49 ± 1.19%. Although low, the absorbed fraction of T2-G is 5 times higher than that of T-2. These differences in toxicokinetics parameters between T-2 and T2-G clearly indicate the flaw in assuming equal bioavailability and/or toxicity of modified and free mycotoxins in current risk assessments.

Do Plant-Bound Masked Mycotoxins Contribute to Toxicity?

Masked mycotoxins are plant metabolites of mycotoxins which co-contaminate common cereal crops. Since their discovery, the question has arisen if they contribute to toxicity either directly or indirectly through the release of the parent mycotoxins. Research in this field is rapidly emerging and the aim of this review is to summarize the latest knowledge on the fate of masked mycotoxins upon ingestion. Fusarium mycotoxins are the most prevalent masked mycotoxins and evidence is mounting that DON3Glc and possibly other masked trichothecenes are stable in conditions prevailing in the upper gut and are not absorbed intact. DON3Glc is also not toxic per se, but is hydrolyzed by colonic microbes and further metabolized to DOM-1 in some individuals. Masked zearalenone is rather more bio-reactive with some evidence on gastric and small intestinal hydrolysis as well as hydrolysis by intestinal epithelium and components of blood. Microbial hydrolysis of ZEN14Glc is almost instantaneous and further metabolism also occurs. Identification of zearalenone metabolites and their fate in the colon are still missing as is further clarification on whether or not masked zearalenone is hydrolyzed by mammalian cells. New masked mycotoxins continuously emerge and it is crucial that we gain detailed understanding of their individual metabolic fate in the body before we can assess synergistic effects and extrapolate the additive risk of all mycotoxins present in food.

Masked trichothecene and zearalenone mycotoxins withstand digestion and absorption in the upper GI tract but are efficiently hydrolyzed by human gut microbiota in vitro

SCOPE

Cereal grains are commonly contaminated with Fusarium mycotoxins and their plant-derived masked metabolites. The fate of masked mycotoxins in the human gut is poorly understood. Here we assess the metabolism and transport of glucoside metabolites of common trichothecenes (deoxynivalenol, nivalenol, T-2 toxin) and zearalenone compounds (zearalenone, α- and β-zearalenol) in the human gut in vitro.

METHODS AND RESULTS

Masked mycotoxins were incubated with artificial digestive juices and absorption was assessed in differentiated Caco-2/TC7 cells. Colonic metabolism was studied using fecal batch cultures from five donors and mycotoxins were detected using LC-MS/MS. All masked mycotoxins were stable under upper GI tract conditions and no absorption was observed. Free trichothecenes were absorbed intact whereas free zearalenone compounds were absorbed and metabolized to undetected compounds by Caco-2/TC7 cells. Human gut microbiota efficiently hydrolyzed all masked mycotoxins. Trichothecenes were fully recovered as parent mycotoxins whereas 40-70% of zearalenone compounds were further metabolized to unknown metabolites.

CONCLUSION

Our results demonstrate that masked trichothecenes will reach the colon intact to be released as parent mycotoxins by gut microbiota, hence contributing to mycotoxin exposure. Masked zearalenone compounds are metabolized by gut microbiota and epithelial cells and the identity and toxicity of metabolites remain to be determined.

Fate of Fusarium Toxins during Brewing

Some information is available about the fate of Fusarium toxins during the brewing process, but only little is known about the single processing steps in detail. In our study we produced beer from two different barley cultivars inoculated with three different Fusarium species, namely, Fusarium culmorum, Fusarium sporotrichioides, and Fusarium avenaceum, producing a wide range of mycotoxins such as type B trichothecenes, type A trichothecenes, and enniatins. By the use of multi-mycotoxin LC-MS/MS stable isotope dilution methods we were able to follow the fate of Fusarium toxins during the entire brewing process. In particular, the type B trichothecenes deoxynivalenol, 3-acetyldeoxynivalenol, and 15-acetyldeoxynivalenol showed similar behaviors. Between 35 and 52% of those toxins remained in the beer after filtration. The contents of the potentially hazardous deoxynivalenol-3-glucoside and the type A trichothecenes increased during mashing, but a rapid decrease of deoxynivalenol-3-glucoside content was found during the following steps of lautering and wort boiling. The concentration of enniatins greatly decreased with the discarding of spent grains or finally with the hot break. The results of our study show the retention of diverse Fusarium toxins during the brewing process and allow for assessing the food safety of beer regarding the monitored Fusarium mycotoxins.

Fate of deoxynivalenol and deoxynivalenol-3-glucoside during cereal-based thermal food processing: a review study

Deoxynivalenol (DON), the most commonly occurring trichothecene in nature, may affect animal and human health through causing diarrhea, vomiting, gastrointestinal inflammation, and immunomodulation. DON-3-glucoside (DON-3G) as a major plant metabolite of the mycotoxin is another "emerging" food safety issue in recent years. Humans may experience potential health risks by consuming DON-contaminated food products. Thus, it is crucial for human and animal health to study also the degradation of DON and DON-3G during thermal food processing. Baking, boiling, steaming, frying, and extrusion cooking are commonly used during thermal food processing and have promising effects on the reduction of mycotoxins in food. For DON, however, the observed effects of these methods, as reported in numerous studies, are ambiguous and do not present a clear picture with regard to reduction or transformation. This review summarized the influence of thermal processing on the stability of DON and the formation of degradation/conversion products. Besides this, also a release of DON and DON-3G from food matrix as well as the release of DON from DON-3G during processing is discussed. In addition, some conflicting findings as reported from the studies on thermal processing as well as cause-effect relationships of the different thermal procedures are explored. Finally, the potential toxic profiles of DON degradation products are discussed as well when data are available.

Deoxynivalenol and Its Modified Forms: Are There Major Differences?

Considering the diverse toxic effects of the Fusarium toxin deoxynivalenol (DON), its common occurrence in wheat-based products, and its stability during processing, DON constitutes an increasing health concern for humans and animals. In addition to the parent compound DON, human and animal exposure encompasses the acetylated fungal metabolites 3-acetyl-deoxynivalenol (3ADON) and 15-acetyl-deoxynivalenol (15ADON) as well as the plant-derived DON-glucoside (DON3G) and the bacterial product de-epoxy-DON (DOM-1). In the current study we used the well-established Caco-2 cell model to compare the effects of these naturally occurring forms of DON on cell viability and markers of barrier integrity, as well as on the release of the pro-inflammatory chemokine chemokine CXC motif ligand (CXCL8). Results show that 3ADON is less potent in inducing adverse effects on barrier integrity when compared to DON, whereas 15ADON appears to be slightly more potent than DON. In contrast, DON3G and DOM-1 exerted no measurable adverse effects on the intestinal barrier. It was also demonstrated that galacto-oligosaccharides (GOS) are able to protect epithelial cells against DON and its acetylated forms, which suggests that GOS are beneficial food additives in the protection of vulnerable segments of the human population against adverse effects of DON and its derivatives.

Masked mycotoxins: does breeding for enhanced Fusarium head blight resistance result in more deoxynivalenol-3-glucoside in new wheat varieties?

From economic and environmental points of view, enhancing resistance to Fusarium head blight (FHB) in wheat is regarded as the best option to reduce fungal colonisation and the concomitant mycotoxin contamination. This review focuses on the effect of FHB resistance on deoxynivalenol (DON) and the masked metabolite deoxynivalenol-3-glucoside (DON-3-glucoside) in wheat. Based on published information complemented with our own results we draw the following conclusions: (1) All investigated wheat cultivars can convert DON to DON-3-glucoside. Hence, detoxification of DON to DON-3-glucoside is not a new trait introduced by recent resistance breeding against FHB. (2) The amount of DON-3-glucoside relative to DON contamination can be substantial (up to 35%) and is among other things dependent on genetic and environmental factors. (3) Correlation analyses showed a highly significant relationship between the amount of FHB symptoms and DON contamination: breeding for FHB resistance reduces DON contamination. (4) DON contamination data are highly correlated with DON-3-glucoside concentration data: in other words, reduction of DON content through resistance breeding results in a concomitant reduction in DON-3-glucoside content. (5) The DON-3-glucoside/DON ratio increases with decreasing DON contamination: the most resistant lines with the lowest DON contamination show the highest relative level of DON-3-glucoside to DON. In summary, introgressing FHB resistance reduces both DON and DON-3-glucoside levels in the grain, but the reduction is lower for the masked toxin. DON-3-glucoside can represent a possible hazard to human and animal health, especially in wheat samples contaminated with DON close to permitted limits.

Toxicology of deoxynivalenol and its acetylated and modified forms

Mycotoxins are the most frequently occurring natural contaminants in human and animal diet. Among them, deoxynivalenol (DON), produced by Fusarium, is one of the most prevalent and thus represents an important health risk. Recent detection methods revealed new mycotoxins and new molecules derivated from the "native" mycotoxins. The main derivates of DON are the acetylated forms produced by the fungi (3- and 15-acetyl-DON), the biologically "modified" forms produced by the plant (deoxynivalenol-3-β-D-glucopyranoside), or after bacteria transformation (de-epoxy DON, 3-epi-DON and 3-keto-DON) as well as the chemically "modified" forms (norDON A-C and DON-sulfonates). High proportions of acetylated and modified forms of DON co-occur with DON, increasing the exposure and the health risk. DON and its acetylated and modified forms are rapidly absorbed following ingestion. At the molecular level, DON binds to the ribosome, induces a ribotoxic stress leading to the activation of MAP kinases, cellular cell-cycle arrest and apoptosis. The toxic effects of DON include emesis and anorexia, alteration of intestinal and immune functions, reduced absorption of the nutrients as well as increased susceptibility to infection and chronic diseases. In contrast to DON, very little information exists concerning the acetylated and modified forms; some can be converted back to DON, their ability to bind to the ribosome and to induce cellular effects varies according to the toxin. Except for the acetylated forms, their toxicity and impact on human and animal health are poorly documented.