Simultaneous analysis of Alternaria toxins and citrinin in tomato: an optimised method using liquid chromatography-tandem mass spectrometry

Development and validation of stable isotope dilution LC-MS/MS method for simultaneous quantification of four Alternaria toxins in 15 food commodities

Alternaria toxins (ATs) are produced from Alternaria species that result in crop losses and harmful impacts on human health. A stable isotope dilution LC-MS/MS method was established to quantify four ATs in 15 food commodities: alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN), and tenuazonic acid (TeA). Based on systematically optimization of detection conditions and pre-processing steps, the limits of detection and limits of quantification of the four ATs ranged from 0.1 to 10 μg/kg and 0.2 to 30 μg/kg, respectively. The results showed that the recoveries of the four ATs were 72.0%-119.1%. The intra-precision and inter-precision ranged from 0.7% to 11.1% and 1.1% to 13.1%, respectively. The method was successfully applied to the determination of four ATs in 35 food samples, suggesting that this method could provide meaningful occurrence data to support the assessment of emerging ATs in food commodities.

High-Coverage UHPLC-MS/MS Analysis of 67 Mycotoxins in Plasma for Male Infertility Exposure Studies

Mycotoxins are a class of exogenous metabolites that are major contributors to foodborne diseases and pose a potential threat to human health. However, little attention has been paid to trace mycotoxin co-exposure situations in vivo. To address this, we devised a novel analytical strategy, both highly sensitive and comprehensive, for quantifying 67 mycotoxins in human plasma samples. This method employs isotope dilution mass spectrometry (IDMS) for approximately 40% of the analytes and utilizes internal standard quantification for the rest. The mycotoxins were classified into three categories according to their physicochemical properties, facilitating the optimization of extraction and detection parameters to improve analytical performance. The lowest limits of detection and quantitation were 0.001-0.5 μg/L and 0.002-1 μg/L, respectively, the intra-day precision ranged from 1.8% to 11.9% RSD, and the intra-day trueness ranged from 82.7-116.6% for all mycotoxins except Ecl, DH-LYS, PCA, and EnA (66.4-129.8%), showing good analytical performance of the method for biomonitoring. A total of 40 mycotoxins (including 24 emerging mycotoxins) were detected in 184 plasma samples (89 from infertile males and 95 from healthy males) using the proposed method, emphasizing the widespread exposure of humans to both traditional and emerging mycotoxins. The most frequently detected mycotoxins were ochratoxin A, ochratoxin B, enniatin B, and citrinin. The incidence of exposure to multiple mycotoxins was significantly higher in infertile males than in healthy subjects, particularly levels of ochratoxin A, ochratoxin B, and citrinin, which were significantly increased. It is necessary to carry out more extensive biological monitoring to provide data support for further study of the relationship between mycotoxins and male infertility.

Development of Acid Hydrolysis-Based UPLC–MS/MS Method for Determination of Alternaria Toxins and Its Application in the Occurrence Assessment in Solanaceous Vegetables and Their Products

In this work, we proposed an acid hydrolysis-based analytical method for the detection of Alternaria toxins (ATs) in solanaceous vegetables and their products with solid-phase extraction (SPE) and ultrahigh-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS). This study was the first to reveal that some compounds in the eggplant matrix bind to altenusin (ALS). Validation under optimal sample preparation conditions showed that the method met the EU criteria, exhibiting good linearity (R2 > 0.99), matrix effects (−66.6–−20.5%), satisfying recovery (72.0–107.4%), acceptable precision (1.5–15.5%), and satisfactory sensitivity (0.05–2 µg/kg for limit of detection, 2–5 µg/kg for limit of quantification). Out of 393 marketed samples, only 47 samples were detected, ranging from 0.54–806 μg/kg. Though the occurrence ratio (2.72%) in solanaceous vegetables could be negligible, the pollution status in solanaceous vegetable products was much more serious, and the incidences were 41.1%. In the 47 contaminated samples, the incidences were 4.26% for alternariol monomethyl ether (AME), 6.38% for alternariol (AOH) and altenuene (ALT), 42.6% for tentoxin (TEN), and 55.3% for tenuazonic acid (TeA).

Validation and application of an immunochromatographic test to detect four macrolides and two lincosamides in raw cow milk

In this study, an immunochromatographic test (using the Charm QUAD2® Test) was used to screen for residual macrolides and lincosamides in raw cow's milk. The validation parameters (selectivity/specificity, detection capability (CCβ), and ruggedness) were in agreement with the requirements of[EC] 2021. The selectivity of the immunochromatographic test was verified by the negative results of microbiological tests. The false-positive rate was 0%. The CCβ values of the immunochromatographic test for various antibiotics in milk were as follows: erythromycin 0.02 mg/kg, spiramycin 0.1 mg/kg, tilmicosin 0.025 mg/kg, tylosin 0.05 mg/kg, lincomycin 0.15 mg/kg, and pirlimycin 0.15 mg/kg. The determined CCβ values were lower than the respective maximum residue limits (MRLs; regulatory limits in Japan) for milk, except for lincomycin (equal to the MRL). The presence of antibiotic groups other than macrolides and lincosamides did not interfere with the specificity of the test. It showed no significant difference in lot-to-lot repeatability. The results obtained by the two researchers showed no significant differences. Finally, the test was applied to milk samples obtained from a tylosin-treated cow. The outcome was positive and in agreement with the results of the chemical analytical and microbiological methods. Therefore, this validated immunochromatographic test is expected to be suitable for routine analysis to ensure milk safety.

Development of a Novel LC-MS/MS Multi-Method for the Determination of Regulated and Emerging Food Contaminants Including Tenuazonic Acid, a Chromatographically Challenging Alternaria Toxin

The regulation of food contaminants in the European Union (EU) is comprehensive, and there are several compounds in the register or being added to the recommendation list. Recently, European standard methods for analysis have also been issued. The quick analysis of different groups of analytes in one sample requires a number of methods and the simultaneous use of various instruments. The aim of the present study was to develop a method that could analyze several groups of food contaminants: in this case, 266 pesticides, 12 mycotoxins, 14 alkaloid toxins, and 3 Alternaria toxins. The main advantage of the herein described approach over other methods is the simultaneous analysis of tenuazonic acid (TEA) and other relevant food contaminants. The developed method unites the newly published standard methods such as EN 15662:2018, EN 17194:2019, EN 17256:2019, EN 17425:2021, EN 17521:2021, which describes the analysis of both regulated and emerging contaminants. The developed method is based on a QuEChERS sample preparation, followed by LC-MS/MS analysis under alkaline mobile phase conditions. The pH of the aqueous eluent was set to 8.3, which resulted in baseline separation among ergot alkaloids and their corresponding epimers, a symmetric chromatographic peak shape for analyzing TEA and fit-for-purpose sensitivity for MS/MS detection in both positive and negative ionization modes. Those compounds, which possess the corresponding isotopically labeled internal standards (ISTD), allowed for direct quantification by the developed method and no further confirmation was necessary. This was proven by satisfactory analyses of a number of quality control (QC), proficiency test (PT), and validation samples.

Simultaneous detection of multiple phenolic compounds in fish by gas chromatography-mass spectrometry following a modified QuEChERS cleanup

Phenolic compounds can cause health problems in humans through the food chain. Considering that fish play an important role in human diets, we established a rapid, simple and high-throughput method for the determination of 18 phenolic compounds in fish based on a modified QuEChERS sample preparation method combined with GC-MS. The average recovery of the 18 phenolic compounds was 81.3-116% at 3 spiked levels, and the relative standard deviations, RSD_r and RSD_wR, were in the range of 1.1-11.3% and 1.5-12.2%, respectively. The limit of detection was 2.0-10.1 μg/kg. Satisfactory linear relationships (R² > 0.998) were observed for the phenolic compounds in their corresponding concentration ranges. Moreover, the established method exhibited a high sensitivity, good stability, and reliability. The development of this method has an important theoretical and practical significance for establishing standards and to control the residue levels of phenolic compounds in fish.

Determination of Alternaria Toxins in Food by SPE and LC-IDMS: Development and In-House Validation of a Candidate Method for Standardisation

Alternaria toxins (ATs) are frequently found contaminants in foodstuffs (e.g., alternariol), often reaching high concentrations (e.g., tenuazonic acid). They can spoil a wide variety of food categories (e.g., cereals, vegetables, seeds and drinks) and storage at fridge temperatures does not prevent the growth of Alternaria fungi. Therefore, reliable and validated analytical methods are needed to protect human health and to ensure a transparent and fair trade. This paper describes new technical features that improved a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of ATs in tomato, wheat and sunflower seeds. This analytical method should be simple to implement in different laboratories across the EU and thus be an attractive candidate for standardisation. The major element for improvement was the use of isotopically labelled internal standards, only recently commercially available, thereby reducing the sample handling and improving the accuracy of the results. In addition, the sample extraction and the solid-phase extraction (SPE) enrichment/clean-up were fine-tuned, whereas a more suitable analytical column (XSelect HSS T3) with improved selectivity was also employed. Overall, this method shows adequate precision (repeatability < 5.7% RSD; intermediate precision < 7.0% RSD) and trueness (recoveries ranging from 74% to 112%). The limits of quantification in wheat (the most analytically demanding matrix) vary between 0.19 and 1.40 µg/kg. These figures were deemed satisfactory by the European Committee for Standardization (CEN) and have formed the basis for a subsequent interlaboratory validation study. The corresponding standard was published by CEN in 2021.

Monitoring Alternaria toxins in Italian food to support upcoming regulation

The collection of occurrence data on Alternaria toxins in food and feed across the European countries is required since 2012 by the European Commission, endorsing the relevant scientific opinion by the EFSA CONTAM Panel. Within this framework, occurrence data for Alternaria toxins (Alternariol, Alternariol monomethyl ether, Tenuazonic acid, Tentoxin, and Altenuene) in 97 samples of cereal foods, tomato products, and sunflower seeds have been provided as requested by the Italian national monitoring programme (years 2017-2020). To this purpose, an LC-MS/MS method was set up and validated, obtaining fit for purpose sensitivity, recoveries (70-120%), repeatability (≤20%) and within laboratory reproducibility (≤26%). Occurrence data showed that oilseeds were the most contaminated food group with levels of Tenuazonic acid up to 16752 µg/kg and Tentoxin up to 570 µg/kg, whereas for the other mycotoxin/commodities combinations, the percentage of left censored data (below the limit of quantification) ranged from 74 to 100%.

Progress and Challenges in Quantifying Carbonyl-Metabolomic Phenomes with LC-MS/MS

Carbonyl-containing metabolites widely exist in biological samples and have important physiological functions. Thus, accurate and sensitive quantitative analysis of carbonyl-containing metabolites is crucial to provide insight into metabolic pathways as well as disease mechanisms. Although reversed phase liquid chromatography electrospray ionization mass spectrometry (RPLC-ESI-MS) is widely used due to the powerful separation capability of RPLC and high specificity and sensitivity of MS, but it is often challenging to directly analyze carbonyl-containing metabolites using RPLC-ESI-MS due to the poor ionization efficiency of neutral carbonyl groups in ESI. Modification of carbonyl-containing metabolites by a chemical derivatization strategy can overcome the obstacle of sensitivity; however, it is insufficient to achieve accurate quantification due to instrument drift and matrix effects. The emergence of stable isotope-coded derivatization (ICD) provides a good solution to the problems encountered above. Thus, LC-MS methods that utilize ICD have been applied in metabolomics including quantitative targeted analysis and untargeted profiling analysis. In addition, ICD makes multiplex or multichannel submetabolome analysis possible, which not only reduces instrument running time but also avoids the variation of MS response. In this review, representative derivatization reagents and typical applications in absolute quantification and submetabolome profiling are discussed to highlight the superiority of the ICD strategy for detection of carbonyl-containing metabolites.

Production of Alternaria Toxins in Yellow Peach (Amygdalus persica) upon Artificial Inoculation with Alternaria alternate

The yellow peach (Amygdalus persica), an important fruit in China, is highly susceptible to infection by Alternaria sp., leading to potential health risks and economic losses. In the current study, firstly, yellow peaches were artificially inoculated with Alternariaalternate. Then, the fruits were stored at 4 °C and 28 °C to simulate the current storage conditions that consumers use, and the Alternaria toxins (ATs) contents from different parts of the fruits were analyzed via ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The results showed that the growth of A. alternate and the ATs production were dramatically affected by the storage temperature. At 28 °C, the fungi grew rapidly and the lesion diameter reached about 4.0 cm within 15 days of inoculation, while, at 4 °C, the fungal growth was noticeably inhibited, with no significant change in the lesion diameter. To our surprise, high contents of ATs were produced under both storage conditions even though the fungal growth was suppressed. With an increase in the incubation time, the amounts of ATs showed a steady tendency to increase in most cases. Remarkably, alternariol monomethyl ether (AME), alternariol (AOH), and tenuazonic acid (TeA) were detected in the rotten tissue and also in the surrounding tissue, while a large amount of TeA could also be found in the healthy tissue. To the best of our knowledge, this is the first report regarding the production of ATs by the infection of Alternaria sp. in yellow peach fruits via artificial inoculation under regulated conditions, and, based on the evidence herein, it is recommended that ATs be included in monitoring and control programs of yellow peach management and food safety administration.

Rapid Detection and Quantification of Patulin and Citrinin Contamination in Fruits

Patulin (PAT) and citrinin (CTN) are the most common mycotoxins produced by Penicillium and Aspergillus species and are often associated with fruits and fruit by-products. Hence, simple and reliable methods for monitoring these toxins in foodstuffs are required for regular quality assessment. In this study, we aimed to establish a cost-effective method for detection and quantification of PAT and CTN in pome fruits, such as apples and pears, using high-performance liquid chromatography (HPLC) coupled with spectroscopic detectors without the need for any clean-up steps. The method showed good performance in the analysis of these mycotoxins in apple and pear fruit samples with recovery ranges of 55–97% for PAT and 84–101% for CTN, respectively. The limits of detection (LOD) of PAT and CTN in fruits were 0.006 µg/g and 0.001 µg/g, while their limits of quantification (LOQ) were 0.018 µg/g and 0.003 µg/g, respectively. The present findings indicate that the newly developed HPLC method provides rapid and accurate detection of PAT and CTN in fruits.

Tea: Transfer of Mycotoxins from the Spiked Matrix into an Infusion

Recent surveys report the occurrence of Aspergillus and Penicillium metabolites (aflatoxins (AFLs), ochratoxin A (OTA), cyclopiazonic and mycophenolic acids (MPA), sterigmatocystin (STC), citrinin), Fusarium (trichothecenes, zearalenone (ZEA), fumonisins (FBs), enniatins (ENNs)) and Alternaria (alternariol (AOH), its methyl ether (AME), tentoxin (TE), and tenuazonic acid (TNZ)) toxins in dry Camellia sinensis and herbal tea samples. Since tea is consumed in the form of infusion, correct risk assessment needs evaluation of mycotoxins’ transfer rates. We have studied the transfer of AFLs, OTA, STC, deoxynivalenol (DON), ZEA, FBs, T-2, and HT-2 toxins, AOH, AME, TE, ENN A and B, beauvericin (BEA), and MPA from the spiked green tea matrix into an infusion under variation of preparation time and water characteristics (total dissolved solids (TDS) and pH). Analytes were detected by HPLC-MS/MS. The main factors affecting transfer rate proved to be mycotoxins’ polarity, pH of the resulting infusion (for OTA, FB2, and MPA) and matrix-infusion contact period. The concentration of mycotoxins increased by 20–50% within the first ten minutes of infusing, after that kinetic curve changed slowly. The concentration of DON and FB2 increased by about 10%, for ZEA, MPA, and STC it stayed constant, while for T-2, TE, AOH, and AFLs G1 and G2 it went down. Maximum transfer correlated well with analytes polarity. Maximum transfer of ENNs, BEA, STC, ZEA, and AOH into infusion was below 25%; AFLs—25–45%; DON, TE, and T-2 toxins 60–90%, FB1—80–100%. The concentration of OTA, MPA, and FB2 in the infusion depended on its pH. At pH about four, 20%, 40%, and 60% of these toxins transferred into an infusion, at pH about seven, their concentrations doubled. Water TDS did not affect transfer significantly.

A high sensitive platinum-modified colloidal gold immunoassay for tenuazonic acid detection based on monoclonal IgG

Due to the threat of tenuazonic acid (TA) to public health, it is urgent to establish rapidly effective and sensitive assay methods for TA. In this study, a TA-specific IgG monoclonal antibody (McAb) with high affinity (Kaff was 1.72 × 10¹⁰ L/mol) was screened, and the developed icELISA for TA detection has IC₅₀ of 2.50 ng/mL and LOD of 0.17 ng/mL. Platinum-modified gold nanoparticle (Au@PtNP) was optimized as Au@Pt_0.4NP, and the resulted Au@Pt_0.4NP-McAb probe was designed to catalyze precipitation-type tetramethylbenzidine for visual detection of trace TA with visual LOD of 0.39 ng/mL. The sensitivity of this established Au@Pt_0.4NP-McAb strip was highly increased when compared with the existing colloidal gold strip. The developed strip was used to detect trace TA in apple juice and tomato ketchup which were consistent with the results from UHPLC-MS/MS. Therefore, this developed strip could be used for rapid detection of trace TA in real samples.

A Dilute and Shoot Strategy for Determining Alternaria Toxins in Tomato-Based Samples and in Different Flours Using LC-IDMS Separation

Alternaria toxins are emerging mycotoxins whose regulation and standardization are in progress by the European Commission and the European Committee for Standardization. This paper describes a dilute and shoot approach to determine five Alternaria toxins in selected food samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The strategy involves sample extraction with acidified aqueous methanol, followed by a solvent change accomplished via sample evaporation and reconstitution. The quantification is based on isotope dilution, applying all corresponding isotopically labeled internal standards to compensate possible matrix effects of the analysis. The main advantages of the present method over other existing methods includes simple and effective sample preparation, as well as detection with high sensitivity. The five-fold sample dilution can decrease matrix effects, which were evaluated with both external and internal standard methods. The results demonstrated a limit of quantification lower than 1.0 µg/kg for all five analytes for the first time. The newly presented method showed acceptable accuracy (52.7-111%) when analyzing naturally contaminated and spiked standard samples at the described levels. The method was validated for tomato-based and flour samples (wheat, rye, and maize). The absolute recovery ranged from 66.7% to 91.6% (RSD < 10%). The developed method could be an alternative approach for those laboratories that exclude sample cleanup and pre-concentration of state-of-the-art instruments with enhanced sensitivity.

Microfiltration results in the loss of analytes and affects the in vitro genotoxicity of a complex mixture of Alternaria toxins

Alternaria molds produce a variety of chemically diverse secondary metabolites with potentially adverse effects on human health. However, data on occurrence in food and human exposure is inconsistent for some of these mycotoxins. Membrane filtration is a frequent step in many sample preparation procedures for LC-MS-based methods analyzing food contaminants. Yet, little is known about the possibility of adsorptive phenomena that might result in analyte losses. Thus, we treated a complex extract of Alternaria toxins with several types of syringe filters and unraveled the impact on its chemical composition by LC-MS/MS. We observed significant, and in some cases complete, losses of compounds due to filtration. Particularly, two key Alternaria toxins, alternariol (AOH) and its monomethyl ether (AME), were heavily affected. As a comparison with published food surveys indicating a correlation of the type of filtration used with lower incidence reports in food, our results point at a possible underestimation of AME in past exposure assessment. Also, perylene quinones were greatly affected by filtration, underlining the importance to take this into consideration during analytical method development. Furthermore, we applied the comet assay in HT-29 cells to elucidate the impact of filtration on the genotoxicity of the extract. We observed strong coincidences with the loss of epoxide-carrying metabolites and also an intriguing induction of oxidative DNA damage by yet toxicologically uncharacterized Alternaria toxins. In conclusion, we highlight potential issues with sample filtration and call for a critical re-evaluation of previous food occurrence data in the light of the results at hand.

Recent advances in analytical methods for the determination of citrinin in food matrices

Citrinin is a toxic small organic molecule produced as a secondary metabolite by fungi types Penicillium, Monascus and Aspergillus and is known to contaminate various food commodities during postharvest stages of food production. During the last 10 years, most reported methods for citrinin analysis employed enzyme-linked immunosorbent assays or high-performance liquid chromatography. Over this same time period, liquid extraction, solid-phase extraction, dispersive liquid-liquid microextraction and QuEChERS were the most cited sample preparation and clean-up methods. In this review the advantages and disadvantages of the various sample preparation, separation and detection methods for citrinin analysis over the last decade are evaluated. Furthermore, current trends, emerging technologies and the future prospects of these methods are discussed.

Development and Validation of a QuEChERS-Based Liquid Chromatography Tandem Mass Spectrometry Multi-Method for the Determination of 38 Native and Modified Mycotoxins in Cereals

Here, a reliable and sensitive method for the determination of 38 (modified) mycotoxins was developed. Using a QuEChERS-based extraction method [acetonitrile/water/formic acid (75:20:5, v/v/v)], followed by two runs of high performance liquid chromatography tandem mass spectrometry with different conditions, relevant mycotoxins in cereals were analyzed. The method was validated according to the performance criteria defined by the European Commission (EC) in Commission Decision no. 657/2002. Limits of quantification ranged from 0.05 to 150 μg/kg. Good linearity (R² > 0.99), recovery (61-120%), repeatability (RSDr < 15%), and reproducibility (RSDR < 20%) were obtained for most mycotoxins. However, validation results for Alternaria toxins and fumonisins were unsatisfying. Matrix effects (-69 to +59%) were compensated for using standard addition. Application on reference materials gave correct results while analysis of samples from local retailers revealed contamination, especially with deoxynivalenol, deoxynivalenol-3-glucoside, fumonisins, and zearalenone, in concentrations up to 369, 58, 1002, and 21 μg/kg, respectively.

Advances in Analysis and Detection of Major Mycotoxins in Foods

Mycotoxins are the most widely studied biological toxins, which contaminate foods at very low concentrations. This review describes the emerging extraction techniques and the current and alternatives analytical techniques and methods that have been used to successfully detect and identify important mycotoxins. Some of them have proven to be particularly effective in not only the detection of mycotoxins, but also in detecting mycotoxin-producing fungi. Chromatographic techniques such as high-performance liquid chromatography coupled with various detectors like fluorescence, diode array, UV, liquid chromatography coupled with mass spectrometry, and liquid chromatography-tandem mass spectrometry, have been powerful tools for analyzing and detecting major mycotoxins. Recent progress of the development of rapid immunoaffinity-based detection techniques such as immunoassays and biosensors, as well as emerging technologies like proteomic and genomic methods, molecular techniques, electronic nose, aggregation-induced emission dye, quantitative NMR and hyperspectral imaging for the detection of mycotoxins in foods, have also been presented.

Determination of Alternaria Toxins in Sunflower Oil by Liquid Chromatography Isotope Dilution Tandem Mass Spectrometry

Alternaria toxins have gained attention as a potential health risk and can be classified as emerging mycotoxins. As a result, they are candidates to be regulated by the European Commission. This paper describes a liquid chromatography tandem mass spectrometric (LC-MS/MS) method for analyzing five Alternaria toxins in sunflower oil, which is a rather different type of sample to those matrices investigated in earlier published papers. An optimal sample preparation condition was achieved when samples were dissolved in n-hexane and extracted with methanol/water mixture, followed by sample pre-concentration with solvent evaporation. This study is the first focusing only on this lipophilic matrix and in using all corresponding isotopically labeled internal standards (ISTD) to compensate the matrix effect that strongly influences the LC-MS/MS analysis of toxins. Target compounds were separated on Zorbax Extend C-18 column enabling the analysis at alkaline pH of 8.8 that was necessary to obtain appropriate peak shape of tenuazonic acid and to separate the analytes at baseline. The method was validated according to the EU 2002/657/EC Decision and all the analytical performance characteristics met the requirements. The recovery was between 74% and 122% in fortified sunflower oil samples and the precision varied from 9% to 22%. The method was successfully demonstrated for sunflower seed quality check (QC) samples. Finally, 16 different sunflower oil samples were measured; and tenuazonic acid and tentoxin toxins were detected at levels close to LOQ concentrations.

Determination of Alternaria toxins in drinking water by ultra-performance liquid chromatography tandem mass spectrometry

A sensitive and reliable analytical method has been developed and validated for the determination of five Alternaria toxins, including tenuazonic acid (TeA), alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), and tentoxin (TEN), in drinking water using a one-step enrichment and clean-up strategy followed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Drinking water samples were preprocessed using excess sodium sulfite to remove residual chlorine, and the pH was adjusted by formic acid. Analytes were concentrated and purified from the water samples using hydrophilic-lipophilic balanced (HLB) solid-phase extraction (SPE) cartridges. Chromatographic separation was performed on an Acquity HSS C₁₈ column using 0.1 mM ammonium carbonate and methanol as the mobile phase. The average recoveries at three spiked levels (0.1, 0.5, and 1 ng/L for TeA, AOH, and ALT; 0.01, 0.05, and 0.1 ng/L for TEN and AME) were 76.1-106.5%, with an intra-day precision less than 15.5% and inter-day precision of 11.8-16.5%. The limits of detection (LODs) were 0.05 ng/L for TeA, AOH, and ALT and 0.005 ng/L for TEN and AME. The limits of quantification (LOQs) were 0.1 ng/L for TeA, AOH, and ALT and 0.01 ng/L for TEN and AME. The developed method was applied to monitor 289 drinking water samples collected in Beijing from 2015 to 2017, and TeA and TEN were found in 28 samples, with concentrations ranging from 0.16 to 2.7 ng/L and 0.21 to 2.2 ng/L, respectively.

Interaction of Dihydrocitrinone with Native and Chemically Modified Cyclodextrins

Citrinin (CIT) is a nephrotoxic mycotoxin produced by Aspergillus, Penicillium, and Monascus genera. It appears as a contaminant in grains, fruits, and spices. After oral exposure to CIT, its major urinary metabolite, dihydrocitrinone (DHC) is formed, which can be detected in human urine and blood samples. Cyclodextrins (CDs) are ring-shaped molecules built up from glucose units. CDs can form host-guest type complexes with several compounds, including mycotoxins. In this study, the complex formation of DHC with native and chemically modified beta- and gamma-cyclodextrins was tested at a wide pH range, employing steady-state fluorescence spectroscopic and modeling studies. The weakly acidic environment favors the formation of DHC-CD complexes. Among the CDs tested, the quaternary-ammonium-γ-cyclodextrin (QAGCD) formed the most stable complexes with DHC. However, the quaternary-ammonium-β-cyclodextrin (QABCD) induced the strongest enhancement in the fluorescence signal of DHC. Our results show that some of the chemically modified CDs are able to form stable complexes with DHC (logK = 3.2–3.4) and the complex formation can produce even a 20-fold increase in the fluorescence signal of DHC. Considering the above-listed observations, CD technology may be a promising tool to increase the sensitivity of the fluorescence detection of DHC.

Mycotoxin Contamination of Beverages Obtained from Tropical Crops

This review is mainly centered on beverages obtained from tropical crops, including tea, nut milk, coffee, cocoa, and those prepared from fruits. After considering the epidemiological data found on the matrices above, the focus was given to recent methodological approaches to assess the most relevant mycotoxins. Aspects such as singularities among the mycotoxin and the beverage in which their were found, and the economic effects and repercussions that the mycotoxin-tainted ingredients have on the beverage industry were pointed out. Finally, the burden of their consumption through beverages, including risk and health effects on humans, was addressed as well.

Rapid determination of Alternaria mycotoxins in tomato samples by pressurised liquid extraction coupled to liquid chromatography with fluorescence detection

A sensitive and reliable method using pressurised liquid extraction (PLE) followed by molecularly imprinted solid phase extraction (MISPE) and high performance liquid chromatography with fluorescence detection (HPLC-FLD) has been developed for the analysis of alternariol (AOH) and alternariol monomethyl ether (AME) in tomato samples. Influence of several extraction parameters that affect PLE efficiency were evaluated for the simultaneous extraction of both mycotoxins in the selected samples. AOH and AME were optimally extracted using MeOH/water (25:75, v/v) at 70°C as solvent, a pressure of 1000 psi and a single extraction cycle. The resulting PLE extracts were pre-concentrated by molecularly imprinted solid phase extraction (MISPE) cartridges followed of analysis by HPLC with fluorescence detection (λ_exc = 258, λ_em = 440 nm). The proposed method was applied to the analysis of AOH and AME in fortified tomato samples (20-72 µg· kg-1) with recoveries of 84-97% (RSD < 8%, n = 6) for AOH and 67-91% (RSD < 13%, n = 6) for AME. The detection limit for AOH and AME were 7 and 15 µg· kg^-1, respectively. The ensuing PLE-MISPE-HPLC-FLD method was validated for the analysis of both mycotoxins in tomato samples in accordance with European Commission Decision 2002/657/EC.

Tracking emerging mycotoxins in food: development of an LC-MS/MS method for free and modified Alternaria toxins

Mycotoxins produced by Alternaria fungi are ubiquitous food contaminants, but analytical methods for generating comprehensive exposure data are rare. We describe the development of an LC-MS/MS method covering 17 toxins for investigating the natural occurrence of free and modified Alternaria toxins in tomato sauce, sunflower seed oil, and wheat flour. Target analytes included alternariol (AOH), AOH-3-glucoside, AOH-9-glucoside, AOH-3-sulfate, alternariol monomethyl ether (AME), AME-3-glucoside, AME-3-sulfate, altenuene, isoaltenuene, tenuazonic acid (TeA), tentoxin (TEN), altertoxin I and II, alterperylenol, stemphyltoxin III, altenusin, and altenuic acid III. Extensive optimization resulted in a time- and cost-effective sample preparation protocol and a chromatographic baseline separation of included isomers. Overall, adequate limits of detection (0.03–9 ng/g) and quantitation (0.6–18 ng/g), intermediate precision (9–44%), and relative recovery values (75–100%) were achieved. However, stemphyltoxin III, AOH-3-sulfate, AME-3-sulfate, altenusin, and altenuic acid III showed recoveries in wheat flour below 70%, while their performance was stable and reproducible. Our pilot study with samples from the Austrian retail market demonstrated that tomato sauces (n = 12) contained AOH, AME, TeA, and TEN in concentrations up to 20, 4, 322, and 0.6 ng/g, while sunflower seed oil (n = 7) and wheat flour samples (n = 9) were contaminated at comparatively lower levels. Interestingly and of relevance for risk assessment, AOH-9-glucoside, discovered for the first time in naturally contaminated food items, and AME-3-sulfate were found in concentrations similar to their parent toxins. In conclusion, the established multi-analyte method proved to be fit for purpose for generating comprehensive Alternaria toxin occurrence data in different food matrices.

Graphical abstract

Co-occurrence of toxigenic moulds, aflatoxins, ochratoxin A, Fusarium and Alternaria mycotoxins in fresh sweet peppers (Capsicum annuum) and their processed products

Forty-five samples of a landrace of sweet pepper (Capsicum annuum) widely cultivated in Basilicata (Italy) were screened for 17 mycotoxins and potential toxigenic fungal species. Two different LC-MS/MS methods were used for the determination of aflatoxins, ochratoxin A (OTA), Fusarium mycotoxins zearalenone (ZEA), fumonisins (FB1 and FB2), nivalenol (NIV), deoxynivalenol (DON), T-2 and HT-2 toxins and Alternaria mycotoxins altenuene (ALT), alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TTX) and tenuazonic acid (TeA). Frequency of potential toxigenic fungal species occurrence was: 87% Aspergillus Sect. Nigri; 58% Aspergillus Sect. Flavi; 38% Aspergillus Sect. Circumdati; 42% Alternaria spp.; 33% Penicillium spp. and 20% Fusarium spp. Frequency of mycotoxin occurrence and mean of positives were: 51% OTA, 29.5 µg/kg, 5 samples above the EU limit of 20 µg/kg; 31% aflatoxins, 12.8 µg/kg, two samples above the EU limit of 5 µg/kg for aflatoxin B1; 91% ZEA, 1.4 µg/kg; 78% FB2, 7.6 µg/kg; 58% FB1, 22.8 µg/kg; 38% NIV, 39.5 µg/kg; 36% DON, 6.9 µg/kg; 20% T-2 toxin, 5.6 µg/kg and 22% HT-2 toxin, 13.8 µg/kg. For the Alternaria mycotoxins, 100% of samples contained TeA, 4817.9 µg/kg; 93% TTX, 29.7 µg/kg; 56% AOH, 114.4 µg/kg; 33% AME, 13.0 µg/kg and 9% ALT, 61.7 µg/kg. Co-occurrence of mycotoxins in each sample ranged from 2 to 16 mycotoxins (mean 7). No statistical correlation was found between moulds and their mycotoxins occurrence. Within the four groups of peppers collected herein (fresh, dried, grounded and fried) higher percentages of contamination and mycotoxin levels were measured in grounded peppers, whereas much lower values were observed for fried peppers. The high percentages of positive samples and the high levels of some mycotoxins observed in this study confirm the susceptibility of peppers to mycotoxin contamination and claims for an improvement of the conditions used during production and drying process.

Determination of four Alternaria alternata mycotoxins by QuEChERS approach coupled with liquid chromatography-tandem mass spectrometry in tomato-based and fruit-based products

A liquid chromatography-tandem mass spectrometry method for the determination of four Alternaria toxins, i.e. alternariol, alternariol monomethyl ether, tentoxin, and tenuazonic acid in tomato-based and fruit-based products was developed using a QuEChERs approach for the extraction of the mycotoxins. To optimise the QuEChERs extraction, several parameters were tested: types of QuEChERs pouches, sample weights, quantities of added water, use of dispersive SPE as a purification step, types of solvent and conditions of shaking. The method showed good linearity (R² > 0.997) and precision (RSD% < 10) for all analytes. Tenuazonic acid showed very good recovery (98.8%-108.9%) for tomato-based products, as well as for fruit-based products. The method was successfully applied to 57 samples collected from the Italian market. Tenuazonic acid was found in appreciable concentrations in some products. The highest value was found in a tomato sauce sample (814 μg/kg).

Delphinidin protects colon carcinoma cells against the genotoxic effects of the mycotoxin altertoxin II

Alternaria spp. are ubiquitous molds that are able to produce toxic secondary metabolites which may contaminate food globally. One of those is the mycotoxin altertoxin II (ATX-II), a genotoxic and mutagenic compound. In recent years, different flavonoids that may co-occur with mycotoxins in food were demonstrated to temper toxic effects of molds, mostly through their anti-oxidant properties. Thus, in this study, we assessed the influence of the berry anthocyanidin delphinidin on the toxicity of ATX-II in HT-29 colon carcinoma cells. We performed coupled SRB/WST-1 cytotoxicity assays which revealed only weak antagonistic interactions, and single-cell gel electrophoresis ("comet") assays, where we observed a potent protective effect of delphinidin on the DNA-damaging properties of ATX-II. Furthermore, we investigated the mechanism for this interaction. In the DCF assay delphinidin was found to reduce intracellular oxidative stress levels, which might contribute partly to the latter protection. However, LC-MS experiments showed that co-incubation of the mycotoxin with either delphinidin or its potential degradation product phloroglucinol aldehyde significantly decreased ATX-II concentrations in aqueous solutions, indicating that a direct chemical reaction of ATX-II with these components is likely responsible for the observed loss of toxicity. Our results indicate that delphinidin - and possibly other anthocyanins as well - might play a role in the protection of the gut from Alternaria-induced genotoxicity.

Isolation, characterization and toxicological potential of Alternaria-mycotoxins (TeA, AOH and AME) in different Alternaria species from various regions of India

Alternaria species produce various sorts of toxic metabolites during their active growth and causes severe diseases in many plants by limiting their productivity. These toxic metabolites incorporate various mycotoxins comprising of dibenzo-α-pyrone and some tetramic acid derivatives. In this study, we have screened out total 48 isolates of Alternaria from different plants belonging to different locations in India, on the basis of their pathogenic nature. Pathogenicity testing of these 48 strains on susceptible tomato variety (CO-3) showed 27.08% of the strains were highly pathogenic, 35.41% moderately pathogenic and 37.5% were less pathogenic. Phylogenetic analysis showed the presence of at least eight evolutionary cluster of the pathogen. Toxins (TeA, AOH and AME) were isolated, purified on the basis of column chromatography and TLC, and further confirmed by the HPLC-UV chromatograms using standards. The final detection of toxins was done by the LC-MS/MS analysis by their mass/charge ratio. The present study develops an approach to classify the toxicogenic effect of each of the individual mycotoxins on tomato plant and focuses their differential susceptibility to develop disease symptoms. This study represents the report of the natural occurrence and distribution of Alternaria toxins in various plants from India.

The Preparation and Identification of a Monoclonal Antibody against Citrinin and the Development of Detection via Indirect Competitive ELISA

Citrinin (CTN) is a hepato-nephrotoxic mycotoxin produced by fungi genera of Aspergillus, Monauscus, and Penicillium. CTN contaminates grains, fruits, juices and vegetables, and causes various toxic effects to humans and animals. It has small molecular weight, which is non-immunogenic to animals. Thus, CTN was conjugated to bovine serum albumin (BSA) and ovalbumin (OVA), respectively, by amide bonds using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). Mice were immunized with CTN-BSA conjugates, and spleen cells of the immunized mice were fused with Sp2/0 myeloma cells to obtain 21H27 hybriodoma cell. Ascitic fluid of hybridoma cell was produced in mice abdomen, and purified using caprylic/ammonium sulfate precipitation method. The 21H27 anti-CTN mcAb was the IgG2a antibody subclass, and cross-reactivity results indicated that anti-CTN mcAb is specific to CTN with high affinity (2.0 × 10⁸ L/mol). Indirect competitive ELISA (ic-ELISA) results showed that the linear range of detection was 0.01–5.96 ng/mL and the IC₅₀ was 0.28 ng/mL with a lower detection limit (LOD) of 0.01 ng/mL. The average recovery was 93.8% ± 1.6% with a coefficient variation of 1.0%–4.3%. Hence, anti-CTN mcAb secreted by 21H27 hybridoma cell was successfully produced and can be used to detect CTN contaminated feed and foodstuffs.

AlternariaMycotoxins in Food and Feed: An Overview

Alternariais one of the major mycotoxigenic fungal genera with more than 70 reported metabolites.Alternariamycotoxins showed notably toxicity, such as mutagenicity, carcinogenicity, induction of DNA strand break, sphingolipid metabolism disruption, or inhibition of enzymes activity and photophosphorylation. This review reports on the toxicity, stability, metabolism, current analytical methods, and prevalence ofAlternariamycotoxins in food and feed through the most recent published research. Half of the publications were focused on fruits, vegetables, and derived products—mainly tomato and apples—while cereals and cereal by-products represented 38%. The most studied compounds were alternariol, alternariol methyl ether, tentoxin, and tenuazonic acid, but altenuene, altertoxins (I, II, and III), and macrosporin have been gaining importance in recent years. Solid-liquid extraction (50%) with acetonitrile or ethyl acetate was the most common extraction methodology, followed by QuEChERS and dilution-direct injection (both 14%). High- and ultraperformance liquid chromatography coupled with tandem mass spectrometry was the predominant determination technique (80%). The highest levels of alternariol and alternariol methyl ether were found in lentils, oilseeds, tomatoes, carrots, juices, wines, and cereals. Tenuazonic acid highest levels were detected in cereals followed by beer, while alternariol, alternariol methyl ether, tenuazonic acid, and tentoxin were found in legumes, nuts, and oilseeds.

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.

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.

Core-Shell Columns in High-Performance Liquid Chromatography: Food Analysis Applications

The increased separation efficiency provided by the new technology of column packed with core-shell particles in high-performance liquid chromatography (HPLC) has resulted in their widespread diffusion in several analytical fields: from pharmaceutical, biological, environmental, and toxicological. The present paper presents their most recent applications in food analysis. Their use has proved to be particularly advantageous for the determination of compounds at trace levels or when a large amount of samples must be analyzed fast using reliable and solvent-saving apparatus. The literature hereby described shows how the outstanding performances provided by core-shell particles column on a traditional HPLC instruments are comparable to those obtained with a costly UHPLC instrumentation, making this novel column a promising key tool in food analysis.

Developments in mycotoxin analysis: an update for 2014-2015

This review summarises developments in the determination of mycotoxins over a period between mid-2014 and mid-2015. In tradition with previous articles of this series, analytical methods to determine aflatoxins, Alternaria toxins, ergot alkaloids, fumonisins, ochratoxins, patulin, trichothecenes and zearalenone are covered in individual sections. Advances in proper sampling strategies are discussed in a dedicated section, as are new methods used to analyse botanicals and spices and newly developed LC-MS based multi-mycotoxin methods. The critical review aims to briefly discuss the most important developments and trends in mycotoxin determination as well as to address shortcomings of current methodologies.

Detection and Quantitative Analysis of the Non-cytotoxic allo-Tenuazonic Acid in Tomato Products by Stable Isotope Dilution HPLC-MS/MS

Tenuazonic acid (1) is a mycotoxin produced mainly by fungi of the genus Alternaria. It occurs in a variety of agricultural products. allo-Tenuazonic acid (2) is an isomer of 1 that is not chromatographically separated from 1 in most analytical methods. Therefore, both isomers are quantitated as a sum parameter. In this study a QuEChERS (quick, easy, cheap, effective, rugged and safe) based stable isotope dilution HPLC-MS/MS method including the chromatographic separation of both isomers was developed and applied to 20 tomato products from the German market. All products showed contamination with both toxins. 1 was found in a range from 5.3 ± 0.1 to 550 ± 15 μg/kg (average = 120 μg/kg) and 2 in a range from 1.5 ± 0.4- to 270 ± 0.8 μg/kg (average = 58 μg/kg). 2 represents 7.0-44% of the sum of both isomers (average = 29%). This is the first reported occurrence of 2 in food samples. To evaluate and compare the cytotoxicities of 1 and 2, both compounds were isolated from a synthetic racemic mixture. 1 showed moderate cytotoxic effects on HT-29 cells starting at 100 μM, whereas 2 exhibited no activity. 2 was not produced in liquid cultures of Alternaria alternata in yeast extract sucrose (YES) medium, but could be detected in small amounts in tomato puree inoculated with the fungus.