Alternaria toxins in wheat during the 2004 to 2005 Argentinean harvest

Alternariol Monomethyl-Ether Induces Toxicity via Cell Death and Oxidative Stress in Swine Intestinal Epithelial Cells

Alternariol monomethyl-ether (AME), together with altenuene and alternariol, belongs to the Alternaria mycotoxins group, which can contaminate different substrates, including cereals. The aim of the present study was to obtain a deeper understanding concerning the effects of AME on pig intestinal health using epithelial intestinal cell lines as the data concerning the possible effects of Alternaria toxins on swine are scarce and insufficient for assessing the risk represented by Alternaria toxins for animal health. Our results have shown a dose-related effect on IPEC-1 cell viability, with an IC50 value of 10.5 μM. Exposure to the toxin induced an increase in total apoptotic cells, suggesting that AME induces programmed cell death through apoptosis based on caspase-3/7 activation in IPEC-1 cells. DNA and protein oxidative damage triggered by AME were associated with an alteration of the antioxidant response, as shown by a decrease in the enzymatic activity of catalase and superoxide dismutase. These effects on the oxidative response can be related to an inhibition of the Akt/Nrf2/HO-1 signaling pathway; however, further studies are needed in order to validate these in vitro data using in vivo trials in swine.

Occurrence of Alternaria secondary metabolites in milling oats and its de-hulled fractions from harvest years 2017 to 2021

In this study, secondary metabolites produced by Alternaria were investigated for their presence in milling oats. For this purpose, pre-cleaned milling oat samples (n = 193), intended for human consumption, out of harvest years 2017 to 2021 originating from different northern European countries were analysed by LC-MS/MS. Alternariol and alternariol methyl ether were positively identified in 38% of the samples with mean values of 2.1 µg/kg and 1.2 µg/kg, respectively. The highest concentrations of 50.5 µg/kg alternariol and 24.2 µg/kg of alternariol methyl ether were detected in a Latvian sample. Tenuazonic acid was found in 45% of all samples, with a mean concentration of 28.9 µg/kg and a maximum concentration of 1430 µg/kg, also in a Latvian sample. Tentoxin was detected in 49% of all samples with a mean value of 1.7 µg/kg. The Alternaria metabolite most frequently detected in 96% of all samples was infectopyrone with a mean concentration of 593 µg/kg and a maximum value reaching up to 3990 µg/kg in a German sample. In addition, eight oat samples were selected to investigate to what extent the Alternaria metabolites are distributed between the oat hulls and the oat kernels. After de-hulling, approximately 23% of Alternaria metabolites were found in the remaining oat kernels. According to the results, alternariol, infectopyrone and altersetin were present in the kernels with the lowest proportion of 10%-20% on average, respectively. The values for tentoxin showed that about 60% of tentoxin was contained in the hulls, while almost 40% remained in the oat kernel. This suggests that potential health risks posed by Alternaria secondary metabolites and metabolites of other fungal genera in milling oats can be reduced by de-hulling.

Molecular Characterization of Phospholipase C in Infection Structure Differentiation Induced by Pear Fruit Surface Signals, Stress Responses, Secondary Metabolism, and Virulence of Alternaria alternata

Fungal pathogens use plant surface physiochemical signals to trigger specific developmental processes. To assess the role of phospholipase C (PLC) in mediating plant stimuli sensing of Alternaria alternata, the function of three PLC genes was characterized by constructing ΔAaPLC mutants. Here we showed that fruit wax-coated surfaces significantly induced appressorium formation in A. alternata and mutants. Germination of ΔAaPLC mutants did not differ from the wild type. Deletion of AaPLC1 led to the decrease of appressorium formation and infected hyphae, but the degree of reduction varies between the different types of waxes, with the strongest response to pear wax. Appressorium formation and infected hyphae of the ΔAaPLC1 mutant on dewaxed onion epidermis mounted with pear wax (θ4) were reduced by 14.5 and 65.7% after 8 h incubation, while ΔAaPLC2 and ΔAaPLC3 formed the same infection hyphae as wild type. In addition, AaPLC1 mutation caused pleiotropic effects on fungal biological function, including growth deficiency, changes in stress tolerance, weakening of pathogenicity to the host, as well as destruction of mycotoxin synthesis. Both AaPLC2 and AaPLC3 genes were found to have some effects on stress response and mycotoxin production. Taken together, AaPLC genes differentially regulate the growth, stress response, pathogenicity, and secondary metabolism of A. alternata.

General toxicity and genotoxicity of alternariol: a novel 28-day multi-endpoint assessment in male Sprague-Dawley rats

Alternariol (AOH) is one of the toxins of Alternaria, and it has been widely detected in a variety of foods. It has been reported to be cytotoxic, dermally toxic, genotoxic, and potentially carcinogenic in vitro. However, in vivo toxicity data are lacking. This study used a novel in vivo 28-day multi-endpoint (Pig-a assay + micronucleus test + comet assay) genotoxicity evaluation system to evaluate the general toxicity and genotoxicity of AOH. A total of 42 male Sprague-Dawley rats were randomly distributed into three AOH-treated groups (5.51, 10.03, and 22.05 µg/kg bw), one AOH high-dose recovery group (AOH-HR, 22.05 µg/kg bw), one positive control group (N-ethyl-N-nitrosourea, 40 mg/kg bw), and two vehicle control groups (corn oil and PBS). Treatments were administered by oral gavage for 28 consecutive days. Histopathological lesions were observed in the liver, kidney, and spleen in all AOH-treated groups. No statistical difference was found in each genotoxicity index within 28 days in the AOH-treated groups compared with those in the corn oil group. On day 42, in the AOH-HR group, the rate of Pig-a mutant phenotype reticulocytes (RET^CD59-) significantly increased. On day 56, both RET^CD59- and the rate of Pig-a mutant phenotype erythrocytes (RBC^CD59-) were significantly reduced. These findings indicated that AOH might cumulatively induce genetic mutations.

Distinction of Alternaria Sect. Pseudoalternaria Strains among Other Alternaria Fungi from Cereals

Species of the genus Alternaria are ubiquitous and frequently isolated from various plants, including crops. There are two phylogenetically and morphologically close Alternaria sections: the relatively well-known Infectoriae and the rarely mentioned Pseudoalternaria. Currently, the latter includes at least seven species that are less studied and sometimes misidentified. To perform precise identification, two primers (APsF and APsR) were designed and a sect. Pseudoalternaria-specific PCR method was developed. Thirty-five Russian A. infectoria-like strains were then examined. Five strains were found to be the members of the sect. Pseudoalternaria. Additionally, specificity of the previously developed primer set (Ain3F and Ain4R) was checked. It was found to be highly specific for sect. Infectoriae and did not amplify sect. Pseudoalternaria DNA. Identification of strains of the sect. Pseudoalternaria was supported and refined by phylogenetic reconstruction based on analysis of two loci, the glyceraldehyde-3-phosphate dehydrogenase gene (gpd), and the plasma membrane ATPase gene (ATP). These fungi belonged to Alternaria kordkuyana and A. rosae, which were the first detection of those taxa for the Eastern Europe. Alternaria kordkuyana was isolated from cereal seeds and eleuthero leaves. Alternaria rosae was obtained from oat seed. All strains of sect. Pseudoalternaria were not able to produce alternariol mycotoxin, as well as the majority of A. sect. Infectoriae strains.

Natural Occurrence of Alternaria Fungi and Associated Mycotoxins in Small-Grain Cereals from The Urals and West Siberia Regions of Russia

Alternaria fungi dominate the grain microbiota in many regions of the world; therefore, the detection of species that are able to produce mycotoxins has received much attention. A total of 178 grain samples of wheat, barley and oat obtained from the Urals and West Siberia regions of Russia in 2017–2019 were included in the study. Grain contamination with Alternaria fungi belonging to sections Alternaria and Infectoriae was analysed using qPCR with specific primers. The occurrence of four mycotoxins produced by Alternaria, AOH, AME, TEN, and TeA, was defined by HPLC-MS/MS. Alternaria DNA was found in all analysed grain samples. The prevalence of DNA of Alternaria sect. Alternaria fungi (range 53 × 10⁻⁴–21,731 × 10⁻⁴ pg/ng) over the DNA of Alternaria sect. Infectoriae (range 11 × 10⁻⁴‒4237 × 10⁻⁴ pg/ng) in the grain samples was revealed. Sixty-two percent of grain samples were contaminated by at least two Alternaria mycotoxins. The combination of TEN and TeA was found most often. Eight percent of grain samples were contaminated by all four mycotoxins, and only 3% of samples were free from the analysed secondary toxic metabolites. The amounts varied in a range of 2–53 µg/kg for AOH, 3–56 µg/kg for AME, 3–131 µg/kg for TEN and 9–15,000 µg/kg for TeA. To our knowledge, a new global maximum level of natural contamination of wheat grain with TeA was detected. A positive correlation between the amount of DNA from Alternaria sect. Alternaria and TeA was observed. The significant effects of cereal species and geographic origin of samples on the amounts of DNA and mycotoxins of Alternaria spp. in grain were revealed. Barley was the most heavily contaminated with fungi belonging to both sections. The content of AOH in oat grain was, on average, higher than that found in wheat and barley. The content of TEN in the grain of barley was lower than that in wheat and similar to that in oat. The content of TeA did not depend on the cereal crop. The effect of weather conditions (summer temperature and rainfall) on the final fungal and mycotoxin contamination of grain was discussed. The frequent co-occurrence of different Alternaria fungi and their mycotoxins in grain indicates the need for further studies investigating this issue.

Occurrence of Alternaria and Other Toxins in Cereal Grains Intended for Animal Feeding Collected in Slovenia: A Three-Year Study

In recent years, the less-studied Alternaria mycotoxins have attracted increasing interest due to the lack of survey data and their ability to cause toxic effects in animals and humans. To fill the gap, the aim of this three-year survey was to investigate the presence and co-occurrence of Alternaria and other mycotoxins in a total of 433 cereal grain samples from Slovenian farms and agricultural cooperatives from 2014 to 2016. Using the multi-mycotoxin method, 14 mycotoxins were determined. In 53% of 433 analysed samples, contamination with at least one mycotoxin was found. Deoxynivalenol (DON) and tenuazonic acid (TeA) were present in 32% and 26% of cereal grain samples, respectively, whereas alternariol (AOH), tentoxin (TEN), alternariol monomethyl ether (AME), 3- and 15-acetyldeoxynivalenol (3- and 15-AcDON), and zearalenone (ZEN) were present in fewer than 15% of the samples. Ochratoxin A (OTA) was found in one rye sample, while diacetoxyscirpenol (DAS), HT-2 and T-2 toxin, and fumonisins B1 and B2 (FB1 and FB2) were not detected. The highest maximum and median concentrations of Alternaria toxins were determined in spelt in 2016 (TeA, 2277 µg/kg and 203 µg/kg, respectively), and those of Fusarium toxins in wheat in 2015 (DON, 4082 µg/kg and 387 µg/kg, respectively). The co-occurrence of two or more mycotoxins was found in 43% of the positive samples. The correlations between Alternaria toxins were very weak but statistically significant (r: 0.15-0.17, p: 0.0042-0.0165). A well-known correlation between Fusarium toxins DON and ZEN was weak and highly significant (r = 0.28, p < 0.0001).

Molecular Identification and Mycotoxin Production by Alternaria Species Occurring on Durum Wheat, Showing Black Point Symptoms

Black point is a fungal disease of wheat, mainly associated with mycotoxigenic Alternaria species. Affected wheat kernels are characterized by dark brown discolouration of the embryo region and reduction of grain quality. Potential risk is the possible accumulation of Alternaria mycotoxins, alternariol (AOH), alternariol-monomethyl ether (AME), tenuazonic acid (TA), and altenuene (ALT), provided by haemato-toxic, genotoxic, and mutagenic activities. One hundred and twenty durum wheat samples belonging to 30 different genotypes grown in Bologna and Modena areas, in Italy, showing black point symptoms, were analyzed for Alternaria species and their mycotoxin contamination. Alternariol was selected as an indicator of the capability of the Alternaria species to produce mycotoxin in vivo in field conditions. The data showed that Alternaria species occurred in 118 out of 120 wheat kernels samples, with the incidence of infected kernels ranging between 1% and 26%. Moreover, AOH was detected by using a HPLC with a diode array detector (LC-DAD) in 98 out of 120 samples with values ranging between 24 and 262 µg Kg⁻¹. Ninety-two Alternaria representative strains, previously identified morphologically, were identified at species/section level using gene sequencing, and therefore were analyzed for their mycotoxin profiles. Eighty-four strains, phylogenetically grouped in the Alternaria section, produced AOH, AME, and TA with values up to 8064, 14,341, and 3683 µg g⁻¹, respectively, analyzed by using a LC-DAD. On the other hand, eight Alternaria strains, included in Infectoriae Section, showed a very low or no capability to produce mycotoxins.

Natural occurrence of Alternaria mycotoxins in malting barley grains in the main producing region of Argentina

BACKGROUND

Barley (Hordeum vulgare L.) is one of the most important cereals worldwide, and its quality is affected by fungal contamination such as species of the genus Alternaria. No information is available about the occurrence of Alternaria mycotoxins in Argentinean barley grains, which is of concern, because they can be transferred into malt and beer. The aim of this study was to analyze the occurrence of alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA) in malting barley grains from the main producing region of Argentina during the 2014 and 2015 growing seasons.

RESULTS

The most frequent mycotoxin was AOH (64%), which was detected at higher levels (712 μg kg^-1 ) compared with other studies, followed by TeA (37%, 1522 μg kg^-1 ), while AME was present in five samples in the 2015 growing season only, with a mean of 4876 μg kg^-1 . A similar frequency of mycotoxin occurrence was observed in both years (80.8 vs 85.3%), but more diverse contamination was found in 2015, which was characterized by lower accumulated precipitation. Nevertheless, AOH was more frequently found in 2014 than in 2015 (80.8 and 47.1% respectively). A negative correlation between AOH concentration and temperature was observed. The susceptibility of different barley varieties to mycotoxin accumulation varied with the mycotoxin, geographical location and meteorological conditions.

CONCLUSION

The results obtained in the present work represent a tool for risk assessment of exposition to these mycotoxins and could be used by food safety authorities to determine the need for their regulation. Furthermore, the establishment of a hazard analysis and critical control point (HACCP) system to minimize fungal and mycotoxin contamination in barley from farm to processing could be apply to ensure food safety. © 2019 Society of Chemical Industry.

Co-Occurrence and Combinatory Effects of Alternaria Mycotoxins and other Xenobiotics of Food Origin: Current Scenario and Future Perspectives

Mycotoxins are low-molecular weight compounds produced by diverse genera of molds that may contaminate food and feed threatening the health of humans and animals. Recent findings underline the importance of studying the combined occurrence of multiple mycotoxins and the relevance of assessing the toxicity their simultaneous exposure may cause in living organisms. In this context, for the first time, this work has critically reviewed the most relevant data concerning the occurrence and toxicity of mycotoxins produced by Alternaria spp., which are among the most important emerging risks to be assessed in food safety, alone or in combination with other mycotoxins and bioactive food constituents. According to the literature covered, multiple Alternaria mycotoxins may often occur simultaneously in contaminated food, along with several other mycotoxins and food bioactives inherently present in the studied matrices. Although the toxicity of combinations naturally found in food has been rarely assessed experimentally, the data collected so far, clearly point out that chemical mixtures may differ in their toxicity compared to the effect of toxins tested individually. The data presented here may provide a solid foothold to better support the risk assessment of Alternaria mycotoxins highlighting the actual role of chemical mixtures on influencing their toxicity.

A microfluidic colorimetric immunoassay for sensitive detection of altenariol monomethyl ether by UV spectroscopy and smart phone imaging

A novel microfluidic colorimetric immunoassay was developed using gold nanoparticles (GNPs) for indicating different concentrations of altenariol monomethyl ether (AME), and UV spectroscopy and smart phone imaging for monitoring color change of the GNPs. Norland Optical Adhesive 81 (NOA 81) was used for simple and rapid fabrication of the microfluidic chip. AME-BSA modified magnetic nanoparticles (MNPs-BSA-AME) were used as capture probe and the self-magnetism for rapid separation and purification. AME monoclonal antibodies modified gold nanoparticles (GNP-mAbs) which dried on conjugate pad were used as detection probe and the self-catalyst for signal amplification. Under the optimal conditions, the proposed microfluidic colorimetric immunoassay was able to detect AME as low as 12.5 pg/mL for UV spectroscopy (574 nm), and 200 pg/mL for smart phone imaging. The total analysis time is less than 15 min. The immunoassay also has a lower cross-reactivity to AME analogues. It was also evaluated by analyzing fruit samples spiked with AME. The recoveries ranged from 91.19% to 94.15% for UV spectroscopy, and from 90.63% to 93.9% for smart phone imaging. This method can be used for rapid, sensitive, low-cost and portable point-of care testing (POCT) of other mycotoxins or haptens in food samples.

Alternaria toxins in Argentinean wheat, bran, and flour

Alternaria species have been reported to infect a wide variety of vegetables, fruits, and cereal crops. Wheat is one of the most consumed cereal worldwide. A sensitive HPLC-DAD methodology was applied to quantify alternariol (AOH), alternariol methyl ether (AME) and tenuazonic acid (TeA) in 65 samples of whole wheat, bran, and flour. The extraction methodology allowed extracting the three toxins simultaneously. Limits of detection in wheat were 3.4, 4.5, and 0.5 µg kg^-1 for AOH, AME and TeA, respectively. For bran, these data were 3.1, 4.5, and 12 µg kg^-1 and for flour 50, 70, and 14 µg kg^-1, respectively. The studied recoveries were higher than 70% and RSD was below 10%. Wheat and bran samples showed low AOH and AME contamination compared to TeA. The averages levels found for TeA in wheat, bran and flour were 19,190, 16,760, and 7360 µg kg^-1, respectively.

Mycotoxin production of Alternaria strains isolated from Korean barley grains determined by LC-MS/MS

Twenty-four Alternaria strains were isolated from barley grain samples. These strains were screened for the production of mycotoxins on rice medium using thin layer chromatography. All 24 strains produced at least one of the five mycotoxins (ALT, AOH, ATX-I, AME, and TeA). Three representative strains, namely EML-BLDF1-4, EML-BLDF1-14, and EML-BLDF1-18, were further analyzed using a new LC-MS/MS-based mycotoxin quantification method. This method was used to detect and quantify Alternaria mycotoxins. We used positive ion electrospray mass spectrometry with multiple reaction mode (MRM) for the simultaneous quantification of various Alternaria mycotoxins produced by these strains. Five Alternaria toxins (ALT, ATX-I, AOH, AME, and TeA) were detected and quantified. Sample preparation included methanol extraction, concentration, and injection into LC-MS/MS. Limit of detection ranged from 0.13 to 4μg/mL and limit of quantification ranged from 0.25 to 8μg/mL.

Alternaria Species and Their Associated Mycotoxins

The genus Alternaria includes more than 250 species. The traditional methods for identification of Alternaria species are based on morphological characteristics of the reproductive structures and sporulation patterns under controlled culture conditions. Cladistics analyses of "housekeeping genes" commonly used for other genera, failed to discriminate among the small-spored Alternaria species. The development of molecular methods achieving a better agreement with morphological differences is still needed. The production of secondary metabolites has also been used as a means of classification and identification. Alternaria spp. can produce a wide variety of toxic metabolites. These metabolites belong principally to three different structural groups: (1) the dibenzopyrone derivatives, alternariol (AOH), alternariol monomethyl ether (AME), and altenuene (ALT); (2) the perylene derivative altertoxins (ATX-I, ATX-II, and ATX II); and (3) the tetramic acid derivative, tenuazonic acid (TeA). TeA, AOH, AME, ALT, and ATX-I are the main. Certain species in the genus Alternaria produce host-specific toxins (HSTs) that contribute to their pathogenicity and virulence. Alternaria species are plant pathogens that cause spoilage of agricultural commodities with consequent mycotoxin accumulation and economic losses. Vegetable foods infected by Alternaria rot could introduce high amounts of these toxins to the human diet. More investigations on the toxic potential of these toxins and their hazard for human consumption are needed to make a reliable risk assessment of dietary exposure.

Spotlight on the Underdogs-An Analysis of Underrepresented Alternaria Mycotoxins Formed Depending on Varying Substrate, Time and Temperature Conditions

Alternaria (A.) is a genus of widespread fungi capable of producing numerous, possibly health-endangering Alternaria toxins (ATs), which are usually not the focus of attention. The formation of ATs depends on the species and complex interactions of various environmental factors and is not fully understood. In this study the influence of temperature (7 °C, 25 °C), substrate (rice, wheat kernels) and incubation time (4, 7, and 14 days) on the production of thirteen ATs and three sulfoconjugated ATs by three different Alternaria isolates from the species groups A. tenuissima and A. infectoria was determined. High-performance liquid chromatography coupled with tandem mass spectrometry was used for quantification. Under nearly all conditions, tenuazonic acid was the most extensively produced toxin. At 25 °C and with increasing incubation time all toxins were formed in high amounts by the two A. tenuissima strains on both substrates with comparable mycotoxin profiles. However, for some of the toxins, stagnation or a decrease in production was observed from day 7 to 14. As opposed to the A. tenuissima strains, the A. infectoria strain only produced low amounts of ATs, but high concentrations of stemphyltoxin III. The results provide an essential insight into the quantitative in vitro AT formation under different environmental conditions, potentially transferable to different field and storage conditions.

Natural Occurrence of Alternaria Toxins in the 2015 Wheat from Anhui Province, China

The exposure to Alternaria toxins from grain and grain-based products has been reported to be related to human esophageal cancer in China. In this study, a total of 370 freshly harvested wheat kernel samples collected from Anhui province of China in 2015 were analyzed for the four Alternaria toxins tenuazonic acid (TeA), tentoxin (TEN), alternariol (AOH) and alternariol monomethyl ether (AME) by high performance liquid chromatography-tandem mass spectrometry method (HPLC-MS/MS). TeA was the predominant toxin detected followed by TEN, AOH and AME. The concentrations of the four Alternaria toxins varied geographically. The samples from Fuyang district showed higher TEN concentration levels than the other regions studied (p < 0.05). Furthermore, 95% (352/370) of the wheat samples were positive for more than one type of Alternaria toxins. Positive correlation was observed between concentration levels of TeA and TEN, AOH and AME, TeA and AOH, and the total dibenzopyrone derivatives (AOH + AME) and TeA. Results indicate that there is a need to set the tolerance limit for Alternaria toxins in China, and more data on the contamination of these toxins in agro-products is required.

Development of a high performance liquid chromatography tandem mass spectrometry based analysis for the simultaneous quantification of various Alternaria toxins in wine, vegetable juices and fruit juices

An analytical method based on high performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) detection for the simultaneous quantification of 12 Alternaria toxins in wine, vegetable juices and fruit juices was developed. Excellent chromatographic performance was demonstrated for tenuazonic acid (TeA) in a multi-analyte method. This comprehensive study is also the first to report the determination of TeA, alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN) and altenuene (ALT), altertoxin I (ATX-I), altertoxin II (ATX-II), altenuisol (ATL), iso-altenuene (isoALT), altenuic acid III (AA-III) and the AAL toxins TB1 und TB2 in samples from the German market. Several types of HPLC columns were tested for the liquid chromatographic separation of the toxins of interest that widely differ in their polarities. The focus was on gaining suitable retention while avoiding derivatization steps especially for TeA and AA-III. Three atmospheric pressure ionization techniques used with liquid chromatography (electrospray, chemical and photo ionization) were tested to obtain the best selectivity and sensitivity. Samples were diluted with sodium hydrogen carbonate buffer and extracted on a diatomaceous earth solid phase extraction cartridge. Method validation was carried out by using tomato juice, citrus juice and white wine as blank matrices. Limits of detection ranged from 0.10 to 0.59μgL(-1) and limits of quantification ranged from 0.4-3.1μgL(-1) depending on the toxin and matrix. Recoveries were around 100±9% for all toxins except stemphyltoxin III (STTX-III) and altenusin (ALS) due to instability during sample clean up. Matrix-induced effects leading to ion suppression especially for ATX-I, ATX-II and AA-III were investigated. Relative standard deviations of repeatability (RSDr) and intermediate reproducibility (RSDR) were ≤9.3 and ≤17.1, respectively, for the toxins in different matrices at levels of 5 and 30μgL(-1). Finally, 103 commercially obtained wine and juice samples from the German market in 2015 were analysed. TeA was found most frequently (68% of all analysed samples) in concentrations of up to 60.0μgL(-1). AOH, AME and TEN were detected in fewer samples (37%, 16% and 30%) at lower concentrations of up to 8.2, 1.5 and 10.3μgL(-1), respectively. AA-III and ATL were detected for the first time in 3% and 17% of food all samples, in concentrations of up to 6.0μgL(-1) and 5.9μgL(-1), respectively.

Alternaria toxins of the alternariol type are not metabolised by human faecal microbiota

The metabolism of the Alternaria toxins alternariol (AOH), alternariol-9-O-methyl ether (AME) and altenuene (ALT) by the microbiota present in faeces from three human volunteers was studied. Faecal cultures were prepared as a 5% faeces suspension in brain-heart infusion broth and incubated with 50 μM of the toxins under anaerobic conditions for 72 h at 37 °C. The metabolism of AOH was also studied in pure bacterial cultures with either Escherichia coli DH5α or Lactobacillus plantarum BFE 5092 for 72 h at 37 °C. The three parent toxins were stable in uninoculated, heat-treated medium over a 72 h incubation period with a recovery of more than 90%. As a control for the activity of the faecal microbiota, the isoflavone daidzein was incubated with the faecal cultures and was transformed to its expected metabolites. In contrast, no metabolites of AOH, AME and ALT could be detected in the faecal cultures from the same volunteers, indicating that the gut microbiota was not capable of metabolising these substances. The Alternaria toxins could be shown to be at least partially bound to bacterial cells in a non-covalent manner, which may serve as a mechanism for their removal from the gut.

Characterization of Alternaria strains from Argentinean blueberry, tomato, walnut and wheat

Alternaria species have the ability to produce a variety of secondary metabolite, which plays important roles in food safety. Argentina is the second largest exporter of fresh and processed food products to Europe, however, few studies on Alternaria mycotoxins and other bioactive secondary metabolites have been carried out on Argentinean cereals, fruit and vegetables. Knowing the full chemical potential and the distribution of Alternaria spp. on crops, it is necessary to establish a toxicological risk assessment for food products for human consumption. In the present study, 87 Alternaria strains from different substrates (tomato, wheat, blueberries and walnuts) were characterized according to morphology and metabolite production. Aggressive dereplication (accurate mass, isotopic patterns and lists of all described compounds from Alternaria) was used for high-throughput evaluation of the chemical potential. Four strains belonged to the Alternaria infectoria sp.-grp., 6 to the Alternaria arborescens sp.-grp., 6 showed a sporulation pattern similar to that of "M" according to Simmons, 1 to that of Alternaria vaccinii, and the remaining 70 constituted a diverse group belonging to morphological groups "G" and "H". The cluster analysis yielded 16 almost identical dendrograms and grouped the Alternaria strains into four clusters and 11 singletons and outlier groups. The chemical analysis showed that AOH and AME were the most common metabolites produced, followed by TEN, ALXs and TeA. The A. infectoria sp.-grp. had no metabolites in common with the rest of the strains. Several secondary metabolites isolated from large-spored Alternaria species or other fungal genera were detected, such as dehydrocurvularin, pyrenochaetic acid and alternarienonic acid. The strains isolated from tomato produced lower amounts of metabolites than strains from blueberries, walnut and wheat, although individual strains from tomato produced the highest amount of some metabolites. The A. infectoria sp.-grp. was unique to cereals, whereas strains classified as belonging to the A. arborescens sp.-grp or having sporulation pattern "M" were only isolated from tomatoes. Otherwise, no clear association between substrate and identity could be found. The analyses in the study show that at least 75% of the Argentinean strains are able to produce potential mycotoxins.

Temperature and water stress impacts on growth and production of altertoxin-II by strains of Alternaria tenuissima from Argentinean wheat

Alternaria tenuissima is commonly isolated from wheat in Argentina. The objective of this study was to examine the effects of temperature (15-34 °C) and water activity (0.98, 0.95 aw) on growth and temporal altertoxin II (ALTX-II) production by two strains over 14-21 days on a milled wheat agar. It was shown that growth occurred over the whole temperature range tested and was optimum at 25-30 °C and 0.98 aw, and 30 °C at 0.95 aw. The incubation time did not show any significant effect on ALTX-II accumulation. The optimum conditions for ALTX-II production were 0.98 aw and 30 °C for both strains. The strains also accumulated significant amounts of this toxin at 34 °C. This is the first study to evaluate the ecology of growth and production of ALTX-II by strains of A. tenuissima.

Structure and tautomerism of tenuazonic acid--a synergetic computational and spectroscopic approach

All reasonable tautomers and rotamers of tenuazonic acid, which is considered to be of the highest toxicity amongst the Alternaria mycotoxins, were investigated by DFT calculations at different levels of theory in gas phase and in solution to obtain optimized geometries for further examinations. Calculated NMR spectra of tautomeric structures are being presented and compared to experimental data to finally achieve a synergetic computational and spectroscopic approach for structure elucidation of 3-acetyltetramic acids, affording the predominant tautomer of tenuazonic acid in aqueous solution. Furthermore we were able to simulate the less hindered rotation of the exocyclic acetyl group, which occurs after dissociation of tenuazonic acid in protic solvents.

Development of analytical methods for the determination of tenuazonic acid analogues in food commodities

Analogues of the Alternaria mycotoxin tenuazonic acid (TA, biosynthesized by the fungus from the amino acid isoleucine) derived from valine (ValTA), leucine (LeuTA), alanine (AlaTA) and phenylalanine (PheTA) were synthesized and characterized by mass spectrometry (MS) and (1)H nuclear magnetic resonance (NMR) spectroscopy. Concentrations of stock solutions were determined by quantitative (1)H NMR (qHNMR). Two analytical methods based on high performance liquid chromatography (HPLC) and MS detection were developed, one with derivatization with 2,4-dinitrophenylhydrazine (DNPH) and one without derivatization. Limits of detection (LODs) were between 1-3 μg/kg (with derivatization) and 50-80 μg/kg (without derivatization). Respective limits of quantitation (LOQs) were about three times higher. Beside TA, the analogues LeuTA (about 4% of TA content) and ValTA (about 10% of TA content) were found in highly contaminated sorghum infant cereals and sorghum grains. Other analogues were not detected. Quantification of LeuTA and ValTA was performed using [(13)C6,(15)N]-TA as internal standard and matrix matched calibration. Recovery was between 95±11% and 102±10% for both compounds. Precision (relative standard deviation of triplicate sorghum cereal analyses three times during 3 weeks) was 7% for TA (912±60 μg/kg), 17% for LeuTA (43±8 μg/kg) and 19% for ValTA (118±22 μg/kg). These results indicate that several TA-like compounds, which are not yet characterized in aspects of their toxic properties, were detected in sorghum based infant food highly contaminated with TA, already.

Alternaria toxins alternariol and alternariol monomethyl ether in grain foods in Canada

Alternaria alternata has been reported to be the most common fungus on Canadian Western wheat. The Alternaria toxins alternariol (AOH) and alternariol monomethyl ether (AME) are mutagenic in vitro and there is also limited evidence for carcinogenic properties. They have been found in wheat from Europe, Argentina, China and Australia, but they have not been looked for in Canadian grains or grain foods. In the present study, 83 samples of grain-based food sold in Canada, including flour, bran, breakfast cereals, infant cereals and bread, were analysed for AOH and AME using extraction with methanol, clean-up on combined aminopropyl/C18 solid phase extraction (SPE) columns, and liquid chromatography (LC) with tandem mass spectrometric (MS/MS) determination. The overall average recoveries of AOH and AME from a variety of spiked cereal foods (n = 13) were 45 ± 9% and 53 ± 9%, which could be attributed mainly to MS matrix effects The instrumental limits of detection (LOD) were 0.34 ng/g and 0.13 ng/g for AOH and AME, respectively, and the instrumental limits of quantitation (LOQ) were 1.1 and 0.43 ng/g. Of 83 samples analysed, 70 were positive for AOH (up to 63 ng/g, in a soft wheat bran) and 64 contained AME (up to 12 ng/g in a bran-based breakfast cereal). Of particular interest was the presence of AOH and/or AME in 27 out of 30 infant foods (up to 4.4 ng/g and 9.0 ng/g, respectively, in a sample of multigrain cereal).

Process development for the elucidation of mycotoxin formation in Alternaria alternata

The black mould Alternaria alternata produces a wide diversity of mycotoxins which are of particular health concern. Since no maximum allowable limits are set for Alternaria toxins in food and feed, prevention of Alternaria infestations and mycotoxin spoilage is the only way to avoid health risks. Thus, the understanding of mycotoxin biosynthesis is essential. For that purpose, a reliable batch process in a 2 L bioreactor was established which enables the study of several parameters influencing the production of the mycotoxins alternariol (AOH), alternariol monomethylether (AME) and tenuazonic acid (TA) by A. alternata DSM 12633. Modified Czapek-Dox medium was used with glucose as carbon source and ammonium and nitrate as nitrogen sources. Consumption of carbon and nitrogen sources as well as formation of the three mycotoxins were monitored; the average data of five independent fermentations was plotted and fitted using a logistic equation with four parameters. Maximum mycotoxin concentrations of 3.49 ± 0.12 mg/L AOH, 1.62 ± 0.14 mg/L AME and 38.28 ± 0.1 mg/L TA were obtained.In this system the effect of different aeration rates (0.53 vvm-0.013 vvm) was tested which exerted a great influence on mycotoxin production. The use of the semi-synthetic Czapek-Dox medium allowed the exchange of carbon and nitrogen sources for acetate and aspartic acid. The use of acetate instead of glucose resulted in the sole production of alternariol whereas the exchange of ammonium and nitrate for aspartate enhanced the production of both AOH and AME while TA production was not affected.

PCR detection of Alternaria spp. in processed foods, based on the internal transcribed spacer genetic marker

The genus Alternaria is considered one of the most important fungal contaminants of vegetables, fruits, and cereals, producing several mycotoxins that can withstand food processing methods. Conventional methods for Alternaria identification and enumeration are laborious and time-consuming, and they might not detect toxigenic molds inactivated by food processing. In this study, a PCR method has been developed for the rapid identification of Alternaria spp. DNA in foodstuffs, based on oligonucleotide primers targeting the internal transcribed spacer (ITS) 1 and ITS2 regions of the rRNA gene. The specificity of the Alternaria-specific primer pair designed (Dir1ITSAlt-Inv1ITSAlt) was verified by PCR analysis of DNA from various Alternaria spp., and also from several fungal, bacterial, yeast, animal, and plant species. The detection limit of the method was 10(2) CFU/ml in viable culture, heated culture, or experimentally inoculated tomato pulp. The applicability of the method for detection of Alternaria spp. DNA in foodstuffs was assessed by testing several commercial samples. Alternaria DNA was detected in 100% of spoiled tomato samples, 8% of tomato products, and 36.4% of cereal-based infant food samples analyzed.

Precise determination of the Alternaria mycotoxins alternariol and alternariol monomethyl ether in cereal, fruit and vegetable products using stable isotope dilution assays

Cereal, fruit and vegetable products were analyzed for contamination with the Alternaria mycotoxins alternariol (AOH) and alternariol monomethyl ether (AME) using stable isotope dilution assays (SIDAs). Both toxins were practically not detected in cereals and cereal products: AOH-one out of 13 samples at a content of 4.1 μg/kg; AME-two out of 13 samples at contents ranging between 0.2 and 0.6 μg/kg. However, if cereals for animal nutrition were analyzed, much higher values were found: AOH-five out of six samples (13-250 μg/kg); AME-six out of six samples (3-100 μg/kg). This finding may pose a potential problem concerning animal health. AOH and AME were frequently detected in vegetable products: AOH-5 out of 10 samples (2.6-25 μg/kg); AME-6 out of 10 samples (0.1-5 μg/kg). Tomato products were affected, especially. The highest content of AOH (25 μg/kg) and AME (5 μg/kg) were found in triple concentrated tomato paste. Special wines like "Trockenbeerenauslese" or "Spätlese" (affected by noble rot in the vineyard) contained AOH (4/6 samples; 1.2-4.9 μg/kg) and AME (4/6 samples; 0.1-0.3 μg/kg), but the values did not exceed the values of both toxins that were found generally in wines.

Degradation of the Alternaria mycotoxins alternariol, alternariol monomethyl ether, and altenuene upon bread baking

The stability of the Alternaria mycotoxins alternariol, alternariol monomethyl ether, and altenuene upon bread baking was investigated by model experiments using a spiked wholemeal wheat flour matrix. For alternariol and alternariol monomethyl ether, but not for altenuene, degradation products, formed through a sequence of hydrolysis and decarboxylation, could be identified in pilot studies. The simultaneous quantification of alternariol, alternariol monomethyl ether, altenuene, and the degradation products was achieved by a newly developed high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) multimethod. The obtained quantitative data indicate that the Alternaria mycotoxins are barely degraded during wet baking, while significant degradation occurs upon dry baking, with the stability decreasing in the order alternariol monomethyl ether>alternariol>altenuene. The novel degradation products could be detected after the wet baking of flour spiked with alternariol and in a sample survey of 24 commercial cereal based baking products.