Risk evaluation of the Alternaria mycotoxin tenuazonic acid in foods for adults and infants and subsequent risk management

Development of a high-throughput UHPLC-MS/MS method for the analysis of Fusarium and Alternaria toxins in cereals and cereal-based food

A QuEChERS (quick, easy, cheap, effective, rugged, and safe)-based multi-mycotoxin method was developed, analyzing 24 (17 free and 7 modified) Alternaria and Fusarium toxins in cereals via ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). A modified QuEChERS approach was optimized for sample preparation. Quantification was conducted using a combination of stable isotope dilution analysis (SIDA) for nine toxins and matrix-matched calibration for ten toxins. Quantification via a structurally similar internal standard was conducted for four analytes. Alternariol-9-sulfate (AOH-9-S) was measured qualitatively. Limits of detection (LODs) were between 0.004 µg/kg for enniatin A1 (ENN A1) and 3.16 µg/kg for nivalenol (NIV), while the limits of quantification were between 0.013 and 11.8 µg/kg, respectively. The method was successfully applied to analyze 136 cereals and cereal-based foods, including 28 cereal-based infant food products. The analyzed samples were frequently contaminated with Alternaria toxins, proving their ubiquitous occurrence. Interestingly, in many of those samples, some modified Alternaria toxins occurred, mainly alternariol-3-sulfate (AOH-3-S) and alternariol monomethyl ether-3-sulfate (AME-3-S), thus highlighting the importance of including modified mycotoxins in the routine analysis as they may significantly add to the total exposure of their parent toxins. Over 95% of the analyzed samples were contaminated with at least one toxin. Despite the general contamination, no maximum or indicative levels were exceeded.

The fate of Alternaria toxin tenuazonic acid (TeA) during the processing chain of wheat flour products and risk control strategies for mycotoxins

The fate of Alternaria toxin tenuazonic acid (TeA) during the processing chain of wheat flour products was systemically evaluated. TeA was analyzed by liquid chromatography-mass spectrometry (LC-MS/MS) in wheat grains and the corresponding wheat flour products produced throughout the whole chain. The results indicated that TeA contamination in wheat grains largely determines the level of TeA toxin present in byproducts, semi-finished products, and finished products of the processing of four types of simulated processed wheat flour products (e.g., dry noodles, steamed breads, baked breads, and biscuits). The different food processing techniques had different effects on the fate of TeA. Wheat flour processing can reduce the TeA content in wheat grains by 58.7-83.2 %, indicating that wheat flour processing is a key step in reducing the TeA content in the food chain. Among the four types of wheat flour products, the decreases in TeA content in biscuits (69.8-76.7 %) were greater than those in dry noodles (15.5-22.3 %) and steamed breads (24.9-43.6 %). In addition, the decreasing effect of TeA was especially obvious in the wheat flour product chain with a high level of contamination. The processing factors (PFs) for TeA were as low as 0.20 for the four wheat processing methods and as high as 1.24 for the dry noodle processing method. At the average and 95th percentiles, dietary exposure to TeA in Chinese consumers including infants and young children did not exceed the relevant threshold value of toxicological concern (TTC) of TeA (1.5 µg/kg body weight per day), indicating an acceptable health risk for Chinese consumers via wheat flour products. These findings provide new insight into the fate of TeA in the food chain and mycotoxin control on the safety of wheat flour products and public health.

Comprehensive identification and risk assessment of regulated and emerging mycotoxins in infant foods and related raw materials and risk management advice: A case study of an infant food company in China

This study evaluated muti-mycotoxins in 199 samples including processed infant foods and raw materials collected randomly from an infant food company and assessed their role in dietary exposure in infants and young children via probabilistic risk assessment. Approximately 79.6 % (74/93) of the processed infant foods and 65.1 % (69/106) of the raw materials were contaminated by mycotoxins, with a mean occurrence level of 3.66-321.8 µg/kg. Deoxynivalenol (DON) and tenuazonic acid (TeA) were the more prevalent mycotoxins detected, based on their higher frequencies and levels across samples. Co-occurrence of more than two mycotoxins was detected in 61.3 % (57/93) of the processed infant foods and 53.8 % (57/106) of the raw materials. Wheat flour and derived products (e.g., infant noodles and infant biscuits) were contaminated with higher contamination levels and a greater variety of mycotoxins than other samples (e.g., infant cereal and rice grains). The estimated daily exposure to OTA, DON, ZEN, and TEN was lower than the corresponding reference health-based guidance values, indicating acceptable health risks. However, the estimated dietary exposure to alternariol monomethyl ether (AME), alternariol (AOH), and tenuazonic acid (TeA) exceeded the corresponding thresholds of toxicological concern values, indicating potential dietary intake risks. Among the various samples, cereals and cereal-based infant foods emerged as the primary contributors to mycotoxin exposure. Further research is advised to address the uncertainties surrounding the toxicity associated with emerging Alternaria mycotoxins and to conduct cumulative risk assessments concerning multiple mycotoxin exposure in infants and young children.

Development and validation of a simultaneous quantitative analytical method for two Alternaria toxins and their metabolites in plasma and urine using ultra-high-performance liquid chromatography-tandem mass spectrometry

Much more attention has been paid to the contamination of Alternaria toxins because of food contamination and the threat to human health. In this study, an ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed for the simultaneous detection of the prototypical alternariol, alternariol monomethylether, and the metabolites 4-oxhydryl alternariol, and alternariol monomethylether 3-sulfate ammonium salt of Alternaria toxins. The positive samples were used as matrix samples to optimize the different experimental conditions. 0.01% formic acid solution and acetonitrile were used as the mobile phase, and analytes were scanned in negative electron spray ionization under multiple reaction monitoring, and quantitative determination by isotope internal standard method. Application of this method to samples of human plasma and urine showed the detection of the above analytes. The results showed that the recoveries were from 80.40% to 116.4%, intra-day accuracy was between 0.6% and 8.0%, and inter-day accuracy was between 1.1% and 12.1%. The limit of detection of the four analytes ranged from 0.02 to 0.6 µg/L in urine, and 0.02 to 0.5 µg/L in plasma, respectively. Thus, the developed method was rapid and accurate for the simultaneous detection of analytes and provided a theoretical basis for the risk assessment of Alternaria toxins for human exposure.

Probabilistic Risk Assessment of Combined Exposure to Deoxynivalenol and Emerging Alternaria Toxins in Cereal-Based Food Products for Infants and Young Children in China

Deoxynivalenol (DON) and emerging Alternaria toxins often co-occur in cereal-based products, but the current risk assessment is commonly conducted for only one type of mycotoxin at a time. Compared to adults, infants and young children are more susceptible to mycotoxins through food consumption, especially with cereal-based food products which are the main source of exposure. This study aimed to perform a probabilistic risk assessment of combined exposure to DON and three major Alternaria toxins, namely including alternariol monomethyl ether (AME), alternariol (AOH), and tenuazonic acid (TeA) through consumption of cereal-based foods for Chinese infants and young children. A total of 872 cereal-based food products were randomly collected and tested for the occurrence of DON and three major Alternaria toxins. The results on mycotoxin occurrence showed the DON, TeA, AOH, and AME was detected in 56.4%, 47.5%, 7.5%, and 5.7% of the samples, respectively. Co-contamination of various mycotoxins was observed in 39.9% of the analyzed samples. A preliminary cumulative risk assessment using the models of hazard index (HI) and combined margin of exposure (MoET) was performed on DON and Alternaria toxins that were present in cereal-based food products for infants and young children in China for the first time. The results showed that only 0.2% and 1.5%, respectively, of individuals exceeded the corresponding reference value for DON and TeA, indicating a low health risk. However, in the case of AME and AOH, the proportion of individuals exceeding the reference value was 24.1% and 33.5%, respectively, indicating the potential health risks. In the cumulative risk assessment of AME and AOH, both HI and MoET values indicated a more serious risk than that related to individual exposure. Further research is necessary to reduce the uncertainties that are associated with the toxicities of the Alternaria toxins and cumulative risk assessment methods.

Characteristics of Fungal Communities and Internal Mildew Occurrence during the Stages of Planting and Storing of Sunflower Seed in China

Internally mildewed sunflower seeds pose a significant risk to human health. To control internal mildew, it is imperative to study its source in the main production area of China, which has been little investigated. Here, high-throughput sequencing was used to characterize the fungal and fungus-seed communities. Alpha diversity and ANOSIM analyses showed mildew did not alter the fungal compositions significantly. STAMP analysis showed that the sunflower seeds were most vulnerable to internal mildew during the field-planting stage. Alternaria was the predominant mildew-causing pathogen of sunflower seeds for consumption, which may originate from seed transmission and colonize at the seed-development stage. Finally, only a few seeds developed internal mildew with a worrisome level of Alternaria contamination in the humid field climate. NMDS analysis showed that climatic factors also played important roles in shaping microbial change during storage, with a relative humidity (RH) of 67% being the critical threshold in normal-temperature warehouses. Internal mildew never occurred below the RH threshold for the microbial community structure, which hardly changed after an average storage duration. The results indicated that a combination of field management to combat Alternaria, pretreatment with 5 KGy γ-irradiation and drying at the time of storage will minimize or prevent internal mildew. This work also provides an empirical framework for studies of mildewing in other shelled seeds.

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.

An enhanced open sandwich immunoassay by molecular evolution for noncompetitive detection of Alternaria mycotoxin tenuazonic acid

Open sandwich enzyme-linked immunosorbent assay (OS-ELISA), a novel noncompetitive immunoassay format, has shown great potential in rapid detection for small molecules compared with traditional competitive format. Here, an enhanced OS-ELISA towards the mycotoxin tenuazonic acid (TeA) was developed for the first time based on heavy chain variable region (V_H) and light chain variable region (V_L) from the hybridoma cells (3F10) producing anti-TeA monoclonal antibody (mAb). The established OS-ELISA exhibited a limit of detection of 0.08 ng/mL, and was 13 times more sensitive than mAb-based indirect competitive ELISA (ic-ELISA). The proposed assay was also applied to detect TeA contents in juice, flour and tomato ketchup samples with satisfactory recoveries of 87.6%-111.3%. Finally, the great accuracy of the established OS-ELISA method was validated by the standard ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS).

Natural occurrence of Alternaria mycotoxins in wheat and potential of reducing associated risks using magnolol

BACKGROUND

Wheat is one of three major food crops in China. Alternaria species can cause spoilage of wheat with consequent mycotoxin accumulation. Alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA) are the most common and frequently studied mycotoxins. There are limited regulations placed on Alternaria mycotoxin concentrations worldwide due to the lack of toxicity data available. More data on the levels of mycotoxin contamination are also needed. It is also important to reduce the risks of Alternaria mycotoxins.

RESULTS

One hundred and thirty-two wheat samples were collected from Hebei Province, China, and analyzed for AOH, AME, and TeA. Tenuazonic acid was found to be the predominant Alternaria mycotoxin, especially in flour samples. Studying Alternaria species that cause black-point disease of wheat indicated that Alternaria alternata and Alternaria tenuissima were the dominant species. Most of the Alternaria strains studied produced more than one mycotoxin and TeA was produced at the highest concentration, which may have resulted in the high level of TeA contamination in the wheat samples. Furthermore, magnolol displayed obvious antifungal and antimycotoxigenic activity against Alternaria. This is the first report on the antimycotoxigenic activity of magnolol against Alternaria species.

CONCLUSION

The Alternaria mycotoxin contamination levels in wheat and wheat products from Hebei Province, China, were correlated with the toxigenic capacity of the Alternaria strains colonizing the wheat. Considering its safety, magnolol could be developed as a natural fungicide in wheat, or as a natural alternative food preservative based on its strong antifungal and antimycotoxigenic activity against Alternaria strains. © 2020 Society of Chemical Industry.

Development of a chemiluminescence immunoassay for detection of tenuazonic acid mycotoxin in fruit juices with a specific camel polyclonal antibody

The natural mycotoxin tenuazonic acid (TeA) in foods is identified as the most toxic mycotoxin among the over 70 kinds of secondary toxic metabolites produced by Alternaria alternata. Some hapten-antibody-mediated immunoassays have been developed for TeA detection in food samples, but these methods show unsatisfactory sensitivity and specificity. In this study, a rationally designed hapten for TeA mycotoxin generated with computer-assisted modeling was prepared to produce a highly specific camel polyclonal antibody, and an indirect competitive chemiluminescence enzyme immunoassay (icCLEIA) was established with a limit of detection of 0.2 ng mL-1 under optimized conditions. The cross-reactivity results showed that several analogs and some common mycotoxins had negligible recognition by the anti-TeA polyclonal antibody. The average recoveries spiked in fruit juices were determined to be 92.7% with an acceptable coefficient of variation, and good correlations between icCLEIA and liquid chromatography tandem mass spectrometry (LC-MS/MS) results were obtained in spiked samples. This developed icCLEIA for TeA detection with significantly improved sensitivity and satisfactory specificity is a promising alternative for environmental monitoring and food safety.

Mycotoxin Occurrence, Exposure and Health Implications in Infants and Young Children in Sub-Saharan Africa: A Review

Infants and young children (IYC) remain the most vulnerable population group to environmental hazards worldwide, especially in economically developing regions such as sub-Saharan Africa (SSA). As a result, several governmental and non-governmental institutions including health, environmental and food safety networks and researchers have been proactive toward protecting this group. Mycotoxins, toxic secondary fungal metabolites, contribute largely to the health risks of this young population. In SSA, the scenario is worsened by socioeconomic status, poor agricultural and storage practices, and low level of awareness, as well as the non-establishment and lack of enforcement of regulatory limits in the region. Studies have revealed mycotoxin occurrence in breast milk and other weaning foods. Of concern is the early exposure of infants to mycotoxins through transplacental transfer and breast milk as a consequence of maternal exposure, which may result in adverse health effects. The current paper presents an overview of mycotoxin occurrence in foods intended for IYC in SSA. It discusses the imperative evidence of mycotoxin exposure of this population group in SSA, taking into account consumption data and the occurrence of mycotoxins in food, as well as biomonitoring approaches. Additionally, it discusses the health implications associated with IYC exposure to mycotoxins in SSA.

Quantification of multi-mycotoxin in cereals (maize, maize porridge, sorghum and wheat) from Limpopo province of South Africa

Mycotoxins are secondary metabolites that are produced by filamentous mycotoxigenic fungi belonging to the Alternaria, Aspergillus, Fusarium and Penicillium genera amongst others. Multi-class mycotoxins were extracted from 55 cereal samples and analysed using liquid chromatography-tandem mass spectrometry. The adopted extraction method for maize, maize porridge, sorghum and wheat was comprehensively validated. This method was further tested to determine the natural occurrence of mycotoxins in foodstuffs. Twelve (12) out of 22 mycotoxins were detected in maize, maize porridge, sorghum and wheat, including α-zearalenol (α-ZEL) (89%), fumonisin B₃ (FB₃) (84%), fumonisin B₁ (FB₁) (80%), tenuazonic acid (TeA) (78%), ochratoxin B (42%), deoxynivalenol (DON) (12%), ochratoxin A (11%), 3-acetyldeoxynivalenol (7%), sterigmatocystin (STG) (6%), 15-acetyldeoxynivalenol (2%), cyclopiazonic acid (CPA) (2%) and aflatoxin B₂ (2%). The data revealed high incidence rate of α-ZEL (range: 6.5-70.5 µg kg^-1) in all matrices. Maize samples had high mycotoxin co-occurrence compared to other matrices. All recovered mycotoxins in food commodities were within the maximum regulatory limits, with the exception of fumonisins (FB₁ and FB₃) exceeded the South African and European Commission regulation, and the highest concentration was 2153 µg kg^-1 in maize. It is essential to monitor the level of emerging mycotoxins in food commodities from rural areas as trace amount of CPA (< limit of quantification), STG (range: 0.30-0.74 µg kg^-1) were detected and high concentration of TeA (292.7 µg kg^-1) was detected in sorghum. The occurrence of these mycotoxins further encourages frequent analyses, their co-occurrence in the samples poses a significant threat to public health and more emphasis should thus be placed on reducing the contamination levels of these toxins in staples.

Chemiluminescent Enzyme Immunoassay and Bioluminescent Enzyme Immunoassay for Tenuazonic Acid Mycotoxin by Exploitation of Nanobody and Nanobody-Nanoluciferase Fusion

The isolation of nanobodies (Nbs) from phage display libraries is an increasingly effective approach for the generation of new biorecognition elements, which can be used to develop immunoassays. In this study, highly specific Nbs against the Alternaria mycotoxin tenuazonic acid (TeA) were isolated from an immune nanobody phage display library using a stringent biopanning strategy. The obtained Nbs were characterized by classical enzyme-linked immunosorbent assay (ELISA), and the best one Nb-3F9 was fused with nanoluciferase to prepare an advanced bifunctional fusion named nanobody-nanoluciferase (Nb-Nluc). In order to improve the sensitivity and reduce the assay time, two different kinds of luminescent strategies including chemiluminescent enzyme immunoassay (CLEIA) and bioluminescent enzyme immunoassay (BLEIA) were established, respectively, on the basis of the single Nb and the fusion protein Nb-Nluc for TeA detection. The two-step CLEIA was developed on the basis of the same nanobody as ELISA, only with simple substrate replacement from 3,3',5,5'-tetramethylbenzidine (TMB) to luminol. In contrast with CLEIA, the novel BLEIA was conducted in one-step new strategy on the basis of Nb-Nluc and bioluminescent substrate coelenterazine-h (CTZ-h). Their half maximal inhibitory concentration (IC50) values were similar to 8.6 ng/mL for CLEIA and 9.3 ng/mL for BLEIA, which was a 6-fold improvement in sensitivity compared with that of ELISA (IC50 of 54.8 ng/mL). Both of the two assays provided satisfactory recoveries ranging from 80.1%-113.5% in real samples, which showed better selectivity for TeA analogues and other common mycotoxins. These results suggested that Nbs and Nb-Nluc could be used as useful reagents for immunodetection and that the developed CLEIA/BLEIA have great potential for TeA analysis.

Chemotaxonomic Profiling of Canadian Alternaria Populations Using High-Resolution Mass Spectrometry

Alternaria spp. occur as plant pathogens worldwide under field and storage conditions. They lead to food spoilage and also produce several classes of secondary metabolites that contaminate the food production chain. From a food safety perspective, the major challenge of assessing the risk of Alternaria contamination is the lack of a clear consensus on their species-level taxonomy. Furthermore, there are currently no reliable DNA sequencing methods to allow for differentiation of the toxigenic potential of these fungi. Our objective was to determine which species of Alternaria exist in Canada, and to describe the compounds they make. To address these issues, we performed metabolomic profiling using liquid chromatography high-resolution mass spectrometry (LC-HRMS) on 128 Canadian strains of Alternaria to determine their chemotaxonomy. The Alternaria strains were analyzed using principal component analysis (PCA) and unbiased k-means clustering to identify metabolites with significant differences (p < 0.001) between groups. Four populations or 'chemotypes' were identified within the strains studied, and several known secondary metabolites of Alternaria were identified as distinguishing metabolites, including tenuazonic acid, phomapyrones, and altenuene. Though species-level identifications could not be concluded for all groups through metabolomics alone, A. infectoria was able to be identified as a distinct population.

Fungal Diversity and Mycotoxins in Low Moisture Content Ready-To-Eat Foods in Nigeria

Low moisture content ready-to-eat foods vended in Nigerian markets could be pre-packaged or packaged at point of sale. These foods are widely and frequently consumed across Nigeria as quick foods. Despite their importance in the daily diets of Nigerians, a comprehensive study on the diversity of fungi, fungal metabolite production potential, and mycotoxin contamination in the foods has not yet been reported. Therefore, this study assessed the diversity of fungi in 70 samples of low moisture content ready-to-eat foods [cheese balls, garri (cassava-based), granola (a mix of cereals and nuts) and popcorn] in Nigeria by applying a polyphasic approach including morphological examination, genera/species-specific gene marker sequencing and secondary metabolite profiling of fungal cultures. Additionally, mycotoxin levels in the foods were determined by LC-MS/MS. Fungal strains (n = 148) were recovered only from garri. Molecular analysis of 107 representative isolates revealed 27 species belonging to 12 genera: Acremonium, Allophoma, Aspergillus, Cladosporium, Fusarium, Microdochium, Penicillium, Sarocladium, Talaromyces, and Tolypocladium in the Ascomycota, and Fomitopsis and Trametes in the Basidiomycota. To the best of our knowledge Allophoma, Fomitopsis, Microdochium, Tolypocladium, and Trametes are reported in African food for the first time. A total of 21 uncommon metabolites were found in cultures of the following species: andrastin A and sporogen AO1 in Aspergillus flavus; paspalin in A. brunneoviolaceus; lecanoic acid and rugulusovin in A. sydowii; sclerotin A in P. citrinum and Talaromyces siamensis; barceloneic acid, festuclavine, fumigaclavine, isochromophilons (IV, VI, and IX), ochrephilone, sclerotioramin, and sclerotiorin in P. sclerotium; epoxyagroclavine, infectopyron, methylorsellinic acid and trichodermamide C in P. steckii; moniliformin and sporogen AO1 in P. copticola; and aminodimethyloctadecanol in Tolypocladium. Twenty-four mycotoxins in addition to other 73 fungal and plant toxins were quantified in the foods. In garri, cheeseballs, popcorn and granola were 1, 6, 12, and 23 mycotoxins detected, respectively. Deoxynivalenol, fumonisins, moniliformin, aflatoxins and citrinin contaminated 37, 31, 31, 20, and 14% of all food samples, respectively. Overall, citrinin had the highest mean concentration of 1481 μg/kg in the foods, suggesting high citrinin exposures in the Nigerian populace. Fungal and mycotoxin contamination of the foods depend on pre-food and post-food processing practices.

From field to process: How storage selects toxigenic Alternaria spp. causing mouldy core in Red Delicious apples

Apple is a major crop in Argentina where 50% of the production is derived to by-products. Industries process either recently harvested apples or fruit stored for up to 9 months. This crop is susceptible to fungal diseases both external and internal, such as mouldy core (MC). The incidence of fungal pathogens changes during storage, as well as the risk associated with their presence since some contaminants belong to mycotoxigenic genera. The objective of this study was to characterize the fungal contaminants of Red Delicious apple fruit in Argentina evaluating their evolvement from field to process, with main interest on MC causal agents and mycotoxigenic species. A total of 240 apples were analysed; 140, recently harvested and intended for fresh consumption (C), and 100 stored for 9 months in a refrigerated chamber (0-3 °C) and destined to industrialization (I). The 86% of fresh consumption apples showed external fungal lesions, and only 14% were undamaged; MC incidence was 34%. High biodiversity was observed; Penicillium was the predominant genus (54%), followed by Alternaria spp. (41%). Only 3% of industrialization fruit were undamaged, 48% had external lesions and 51% MC. However, biodiversity was lower in these apples. Alternaria spp. was recovered from 60% of apples, mainly causing MC, while Penicillium spp. took second place (34%). All the Alternaria isolates belonged to Section Alternaria with A. tenuissima as the predominant species-group. Alternariol was synthesised by 75% of the isolates, while both alternariol monomethyl-ether and tenuazonic acid by 76%. From the 100 I apples, 93 were contaminated with at least one of these mycotoxins. Alternaria was the main causal agent of MC in Argentinean Red Delicious apples, and fruit affected by this disease might be incorporated into the process line, with a consequent risk of mycotoxin contamination in apple by-products.

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.

Alternaria host-specific (HSTs) toxins: An overview of chemical characterization, target sites, regulation and their toxic effects

Alternaria causes pathogenic disease on various economically important crops having saprophytic to endophytic lifecycle. Pathogenic fungi of Alternaria species produce many primary and secondary metabolites (SMs). Alternaria species produce more than 70 mycotoxins. Several species of Alternaria produce various phytotoxins that are host-specific (HSTs) and non-host-specific (nHSTs). These toxins have various negative impacts on cell organelles including chloroplast, mitochondria, plasma membrane, nucleus, Golgi bodies, etc. Non-host-specific toxins such as tentoxin (TEN), Alternaric acid, alternariol (AOH), alternariol 9-monomethyl ether (AME), brefeldin A (dehydro-), Alternuene (ALT), Altertoxin-I, Altertoxin-II, Altertoxin-III, zinniol, tenuazonic acid (TeA), curvularin and alterotoxin (ATX) I, II, III are known toxins produced by Alternaria species. In other hand, Alternaria species produce numerous HSTs such as AK-, AF-, ACT-, AM-, AAL- and ACR-toxin, maculosin, destruxin A, B, etc. are host-specific and classified into different family groups. These mycotoxins are low molecular weight secondary metabolites with various chemical structures. All the HSTs have different mode of actions, biochemical reactions, and signaling mechanisms to causes diseases in the host plants. These HSTs have devastating effects on host plant tissues by affecting biochemical and genetic modifications. Host-specific mycotoxins such as AK-toxin, AF-toxin, and AC-toxin have the devastating effect on plants which causes DNA breakage, cytotoxic, apoptotic cell death, interrupting plant physiology by mitochondrial oxidative phosphorylation and affect membrane permeability. This article will elucidate an understanding of the disease mechanism caused by several Alternaria HSTs on host plants and also the pathways of the toxins and how they caused disease in plants.

Effect of Wheat Milling Process on the Distribution of Alternaria Toxins

Alternaria toxins are mycotoxins produced by various Alternaria species which, besides the Fusarium species, represent the principal contaminants of wheat worldwide. As currently, only limited information on the behaviour of Alternaria toxins during processing of cereals is available, the objective of this study was to investigate the effect of the dry milling process of wheat on Alternaria toxins distribution. Alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA) content were analysed by high performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in all milling fractions of untreated (control), fungicide-treated, Alternaria tenuissima inoculated and commercial wheat sample. After dry milling process, in last break and milling flows and by-products, increased concentration of examined Alternaria toxins was detected. TeA was quantified in almost all milling fractions in all tested wheat samples, while AOH and AME were detectable mostly in last break and milling flows and by-products. In respect to the contamination with Alternaria toxins, white flour can be considered as relatively safe product. Since Alternaria toxins are concentrated mainly in the peripheral parts of the kernel, a special attention should be given to their content in low-grade flours and milling by-products.

Quantitation of Six Alternaria Toxins in Infant Foods Applying Stable Isotope Labeled Standards

Alternaria fungi are widely distributed saprophytes and plant pathogens. As pathogens, Alternaria fungi infect crops and vegetables and cause losses in the fields and during postharvest storage. While farmers suffer from declining yields, consumers are endangered by the formation of secondary metabolites, because some of these exhibit a pronounced toxicological potential. The evaluation of the toxicological capabilities is still ongoing and will contribute to a valid risk assessment. Additionally, data on the incidence and the quantity of Alternaria mycotoxins found in food products is necessary for dietary exposure evaluations. A sensitive LC-MS/MS method for the determination of the Alternaria mycotoxins alternariol (AOH), alternariol monomethylether (AME), tentoxin (TEN), altertoxin I (ATX I), alterperylenol (ALTP), and tenuazonic acid (TA) was developed. AOH, AME, and TA were quantified using stable-isotopically labeled standards. TEN, ATX I, and ALTP were determined using matrix matched calibration. The developed method was validated by using starch and fresh tomato matrix and resulted in limits of detection ranging from 0.05 to 1.25 μg/kg for starch (as a model for cereals) and from 0.01 to 1.36 μg/kg for fresh tomatoes. Limits of quantification were determined between 0.16 and 4.13 μg/kg for starch and between 0.02 and 5.56 μg/kg for tomatoes. Recoveries varied between 83 and 108% for starch and between 95 and 111% for tomatoes. Intra-day precisions were below 4% and inter-day precisions varied from 3 to 8% in both matrices. Various cereal based infant foods, jars containing vegetables and fruits as well as tomato products for infants were analyzed for Alternaria mycotoxin contamination (n = 25). TA was the most frequently determined mycotoxin and was detected in much higher contents than the other toxins. AME and TEN were quantified in many samples, but in low concentrations, whereas AOH, ATX I, and ALTP were determined rarely, among which AOH had higher concentration. Some infant food products were highly contaminated with Alternaria mycotoxins and the consumption of these individual products might pose a risk to the health of infants. However, when the mean or median is considered, no toxicological risk was obvious.

Development of a QuEChERS-Based UHPLC-MS/MS Method for Simultaneous Determination of Six Alternaria Toxins in Grapes

A simple and reliable analytical method for the simultaneous determination of alternariol (AOH), altenuene (ALT), tentoxin (TEN), altenusin (ALS), tenuazonic acid (TeA), and alternariol monomethyl ether (AME) in grapes was developed by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure with the extraction by acetonitrile and purification by sodium chloride (0.5 g) and anhydrous magnesium sulfate (0.5 g) was established to recover the six Alternaria toxins. After validation by determining the linearity (R² > 0.99), recovery (77.8–101.6%), sensitivity (limit of detection in the range of 0.03–0.21 μg kg⁻¹, and limit of quantification in the range of 0.09–0.48 μg kg⁻¹), and precision (relative standard deviation (RSD) ≤ 12.9%), the analytical method was successfully applied to reveal the contamination state of Alternaria toxins in grapes. Among 56 grape samples, 40 (incidence of 71.4%) were contaminated with Alternaria toxins. TEN was the most frequently found mycotoxin (37.5%), with a concentration range of 0.10–1.64 μg kg⁻¹, followed by TeA (28.6%) and AOH (26.8%). ALT (10.7%), AME (3.6%), and ALS (5.4%) were also detected in some samples. To the best of our knowledge, this is the first report about the Alternaria toxins contamination in grapes in China.

Polyphasic characterization of Epicoccum sorghinum: A tenuazonic acid producer isolated from sorghum grain

Epicoccum sorghinum isolates from sorghum grain grown in Brazil were characterized using a polyphasic approach based on morphological, genetic and physiologic features. A considerable intraspecific variability was observed. The phylogenetic analysis showed that the 53 isolates studied formed four distinct clades, and their morphological features revealed a high variability in culture. The four clades could not be distinguished clearly by morphology or enzyme production patterns. The tenuazonic acid (TeA) production capability of 11 isolates was also determined and revealed a good agreement with the phylogeny results. All of the 11 isolates were revealed as TeA producers, indicating a potential toxicological risk to sorghum crops. This is the first study to provide a detailed morphological description of E. sorghinum isolates from sorghum grains in Brazil and it clearly confirms the wide genetic and phenotypic variability previously reported for this species in other countries.

Occurrence of Alternaria mycotoxins and quantification of viable Alternaria spp. during the food processing of tomato products in Spain

The occurrence of two Alternaria mycotoxins, alternariol (AOH) and alternariol monomethyl ether (AME) and the presence of conidia from Alternaria spp., were investigated throughout the food production chain of two businesses, one which uses organic fruit and the other non-organic. For this purpose, a propidium monoazide (PMA) treatment followed by a quantitative Real Time PCR (qPCR) was used to detect and quantify viable conidia exclusively. Results demonstrated that 68.4% of the total raw fruit analysed was contaminated with viable Alternaria spp. Regarding the mycotoxin occurrence, only a few samples were contaminated with AME, while 35% of raw tomatoes tested positive for AOH in the organic producer and 21% in the non-organic producer. AOH was present in samples analysed before heat treatment, while almost no mycotoxins were found in the final products of the organic producer. However, in the non-organic producer, 47% of the tomato concentrates were contaminated.

Influence of environmental factors on tenuazonic acid production by Epicoccum sorghinum: An integrative approach of field and laboratory conditions

Sorghum is the fifth most cultivated and consumed grain in the world. However, this grain is frequently contaminated with toxins from fungi. The present study evaluated the effects of environmental factors on tenuazonic acid (TeA) production by Epicoccum sorghinum in the field and in controlled laboratory conditions. In this study, 50 sorghum grain samples were collected from summer and autumn growing seasons and analyzed for TeA contamination using LC-MS/MS. To further understand the ecophysiology of this fungus, an isolated strain of E. sorghinum from the field was investigated for its development and TeA production under controlled environmental conditions in the laboratory. In the ecophysiological investigation, the effects of water activity (0.90, 0.95, 0.99) and temperature (18, 22, 26 and 30 °C) were evaluated on the radial growth, enzymatic production and expression of TAS1, which is the gene involved in TeA production. Results showed that in the field, the summer season presented the highest TeA average level in the grains (587.8 μg/kg) compared to level found in the autumn (440.5 μg/kg). The ecophysiological investigation confirmed that E. sorghinum produces more actively TeA under environmental conditions simulating the summer season. Optimum growth, maximum TAS1 gene expression, and higher extracellular enzymatic production were observed at 26 °C with a water activity of 0.99. Pearson correlation analyses showed that the production of TeA highly correlates with fungal growth. The present study demonstrates that abiotic factors in a combined approach of field and laboratory conditions will assist in predicting the driving environmental factors that could affect growth of E. sorghinum and TeA production in sorghum grains.

Emerging Fusarium and Alternaria Mycotoxins: Occurrence, Toxicity and Toxicokinetics

Emerging Fusarium and Alternaria mycotoxins gain more and more interest due to their frequent contamination of food and feed, although in vivo toxicity and toxicokinetic data are limited. Whereas the Fusarium mycotoxins beauvericin, moniliformin and enniatins particularly contaminate grain and grain-based products, Alternaria mycotoxins are also detected in fruits, vegetables and wines. Although contamination levels are usually low (µg/kg range), higher contamination levels of enniatins and tenuazonic acid may occasionally occur. In vitro studies suggest genotoxic effects of enniatins A, A1 and B1, beauvericin, moniliformin, alternariol, alternariol monomethyl ether, altertoxins and stemphyltoxin-III. Furthermore, in vitro studies suggest immunomodulating effects of most emerging toxins and a reproductive health hazard of alternariol, beauvericin and enniatin B. More in vivo toxicity data on the individual and combined effects of these contaminants on reproductive and immune system in both humans and animals is needed to update the risk evaluation by the European Food Safety Authority. Taking into account new occurrence data for tenuazonic acid, the complete oral bioavailability, the low total body clearance in pigs and broiler chickens and the limited toxicity data, a health risk cannot be completely excluded. Besides, some less known Alternaria toxins, especially the genotoxic altertoxins and stemphyltoxin III, should be incorporated in risk evaluation as well.

Determination of Exposure to the Alternaria Mycotoxin Tenuazonic Acid and Its Isomer allo-Tenuazonic Acid in a German Population by Stable Isotope Dilution HPLC-MS(3)

The content of the Alternaria toxin tenuazonic acid and its isomer allo-tenuazonic acid was quantitated in urine of a German cohort (n = 48) using a newly developed and successfully validated solid phase extraction based stable isotope dilution HPLC-MS(3) method. Tenuazonic acid was detected in all of the samples and quantifiable in 97.9% of these samples in a range of 0.16-44.4 ng/mL (average = 6.58 ng/mL) or 0.07-63.8 ng/mg creatinine (average = 8.13 ng/mg creatinine). allo-Tenuazonic acid was for the first time detected in human urine (95.8% of the samples positive) and quantitated in 68.8% of the samples in a range of 0.11-5.72 ng/mL (average = 1.25 ng/mL) or 0.08-10.1 ng/mg creatinine (average = 1.52 ng/mg creatinine), representing 3.40-25.0% of the sum of both isomers (average = 12.4%). Food-frequency questionnaires were used to document food consumption of study participants to correlate mycotoxin exposure to nutritional habits. Although no statistically significant correlation between consumption of a specific food and urinary excretion of tenuazonic acid could be determined, a trend regarding elevated intake of cereal products and higher excretion of tenuazonic acid was evident. On the basis of these results, a provisional mean daily intake (PDI) for both tenuazonic acid and allo-tenuazonic acid was calculated, being 0.183 and 0.025 μg/kg body weight, respectively. A combined mean PDI for both isomers amounts to 0.208 μg/kg body weight with the highest individual PDI for one of the participants (1.582 μg/kg body weight) slightly exceeding the threshold of toxicological concern assumed for tenuazonic acid by the European Food Safety Authority of 1.500 μg/kg body weight. This is the first study to investigate the tenuazonic acid content in human urine of a larger sample cohort enabling the calculation of PDIs for tenuazonic acid and allo-tenuazonic acid.

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.