Survey of Alternaria Toxins and Other Mycotoxins in Dried Fruits in China

Regulation of nitrogen utilization and mycotoxin biosynthesis by the GATA transcription factor AaAreA in Alternaria alternata

Alternaria alternata is a prevalent postharvest pathogen that generates diverse mycotoxins, notably alternariol (AOH) and alternariol monomethyl ether (AME), which are recurrent severe contaminants. Nitrogen sources modulate fungal growth, development, and secondary metabolism, including mycotoxin production. The GATA transcription factor AreA regulates nitrogen source utilization. However, little is known about its involvement in the regulation of nitrogen utilization in A. alternata. To examine the regulatory mechanism of AaAreA on AOH and AME biosynthesis in A. alternata, we analyzed the impact of diverse nitrogen sources on the fungal growth, conidiation and mycotoxin production. The use of a secondary nitrogen source (NaNO3) enhanced mycelial elongation and sporulation more than the use of a primary source (NH4Cl). NaNO3 favored greater mycotoxin accumulation than did NH4Cl. The regulatory roles of AaAreA were further clarified through gene knockout. The absence of AaAreA led to an overall reduction in growth in minimal media containing any nitrogen source except NH4Cl. AaAreA positively regulates mycotoxin biosynthesis when both NH4Cl and NaNO3 are used as nitrogen sources. Subcellular localization analysis revealed abundant nuclear transport when NaNO3 was the sole nitrogen source. The regulatory pathway of AaAreA was systematically revealed through comprehensive transcriptomic analyses. The deletion of AaAreA significantly impedes the transcription of mycotoxin biosynthetic genes, including aohR, pksI and omtI. The interaction between AaAreA and aohR, a pathway-specific transcription factor gene, demonstrated that AaAreA binds to the aohR promoter sequence (5'-GGCTATGGAAA-3'), activating its transcription. The expressed AohR regulates the expression of downstream synthase genes in the cluster, ultimately impacting mycotoxin production. This study provides valuable information to further understand how AreA regulates AOH and AME biosynthesis in A. alternata, thereby enabling the effective design of control measures for mycotoxin contamination.

The characteristics, occurrence, and toxicological effects of alternariol: a mycotoxin

Alternaria species are mycotoxin-producing fungi known to infect fresh produce and to cause their spoilage. Humans get exposed to fungal secondary metabolites known as mycotoxin via the ingestion of contaminated food. Alternariol (AOH) (C14H10O5) is an isocoumarins produced by different species of Alternaria including Alternaria alternata. AOH is often found in grain, fruits and fruits-based food products with high levels in legumes, nuts, and tomatoes. AOH was first discovered in 1953, and it is nowadays linked to esophagus cancer and endocrine disruption due to its similarity to estrogen. Although considered as an emerging mycotoxin with no regulated levels in food, AOH occurs in highly consumed dietary products and has been detected in various masked forms, which adds to its occurrence. Therefore, this comprehensive review was developed to give an overview on recent literature in the field of AOH. The current study summarizes published data on occurrence levels of AOH in different food products in the last ten years and evaluates those levels in comparison to recommended levels by the regulating entities. Such surveillance facilitates the work of health risk assessors and highlights commodities that are most in need of AOH levels regulation. In addition, the effects of AOH on cells and animal models were summarized in two tables; data include the last two-year literature studies. The review addresses also the main characteristics of AOH and the possible human exposure routes, the populations at risk, and the effect of anthropogenic activities on the widespread of the mycotoxin. The commonly used detection and control methods described in the latest literature are also discussed to guide future researchers to focus on mitigating mycotoxins contamination in the food industry. This review aims mainly to serve as a guideline on AOH for mycotoxin regulation developers and health risk assessors.

Synergistic toxicity induced by the co-exposure of tenuazonic acid and patulin in Caenorhabditis elegans: Daf-16 plays an important regulatory role

Tenuazonic acid (TeA) and patulin (PAT), as the naturally occurring mycotoxins with various toxic effects, are often detected in environment and food chain, has attracted more and more attention due to their widespread and high contaminations as well as the coexistence, which leads to potential human and animals' risks. However, their combined toxicity has not been reported yet. In our study, C. elegans was used to evaluate the type of combined toxicity caused by TeA+PAT and its related mechanisms. The results showed that TeA and PAT can induce synergistic toxic effects based on Combination Index (CI) evaluation model (Chou-Talalay method), that is, the body length, brood size as well as the levels of ROS, CAT and ATP were significantly affected in TeA+PAT-treated group compared with those in TeA- or PAT-treated group. Besides, the expressions of oxidative (daf-2, daf-16, cyp-35a2, ctl-1, ctl-3, pmk-1, jnk-1, skn-1) and intestinal (fat-5, pod-2, egl-8, pkc-3, ajm-1, nhx-2) stress-related genes were disrupted, among which daf-16 displayed the most significant alternation. Further study on daf-16 gene defective C. elegans showed that the damages to the mutant nematodes were significantly attenuated. Since daf-2, daf-16, jnk-1 and pmk-1 are evolutionarily conserved, our findings could hint synergistic toxic effects of TeA+PAT on higher organisms.

Sensitive and selective alternariol analysis by a newly developed monoclonal antibody-based immunoassay

Alternariol is a toxic secondary metabolite produced by Alternaria fungi. Nowadays, this mycotoxin can be found in many products of plant origin at concerning concentrations. The aim of the present study was to develop a highly sensitive and selective immunochemical method for the analysis of alternariol. To this end, hapten synthesis was carried out from the scratch and specific high-affinity monoclonal antibodies to alternariol were generated by using, for the first time, alternariol bioconjugates with unambiguous linker tethering sites. A novel indirect enzyme-linked immunosorbent assay that incorporated a rationally designed heterologous conjugate was developed. The optimized assay showed an outstanding half-maximal inhibition concentration for alternariol below 0.04 ng/mL, and no cross-reactivity with alternariol monomethyl ether was observed. Very good recovery values and coefficients of variation were obtained from the analysis of alternariol-fortified fruit and cereal flour samples. Finally, alternariol was quantitatively determined in pears that had been previously infected with Alternaria alternata, showing excellent correlation with liquid chromatography results.

Mycotoxins from Alternaria Panax, the specific plant pathogen of Panax ginseng

Ginseng black spot, caused by Alternaria panax, is one of the most common diseases of Panax ginseng, which usually causes serious yield loss of ginseng plants. However, the pathogenic mechanism of A. panax has not been clarified clearly. Mycotoxins produced by phytopathogens play an important role in the process of infection. Previous study reported that dibutyl phthalate (DBP) identified from the metabolites of A. panax is a potent mycotoxin against P. ginseng. However, more evidence suggests that DBP is one of the constituents of plasticisers. To identify mycotoxins from A. panax and evaluate their phytotoxicity on the leaves of P. ginseng, different chromatographic, spectral and bioassay-guided methods were used together in this report. As a result, tyrosol (1), 3-hydroxy-3-(4-methoxyphenyl) propanoic acid (2), and 3-benzylpiperazine-2,5-dione (3) were isolated and characterised from the extract of A. panax, in which compounds 1 and 2 showed phytotoxic activity on ginseng leaves. Furthermore, DBP was confirmed to come from the residue of ethyl acetate through UPLC-MS/MS analysis, and displayed no phytotoxicity on ginseng leaves based on biological experiments. The results in this report first revealed that tyrosol (1), and 3-hydroxy-3-(4-methoxyphenyl) propanoic acid (2) not DBP were the potent mycotoxins of A. panax.

Saturated brine dissolution and liquid-liquid extraction combined with UPLC-MS/MS for the detection of typical Alternaria toxins in pear paste

BACKGROUND

Alternaria can infest pears to produce metabolites, which can contaminate pears and their processed products. Pear paste, one of the most important pear-based products, is popular among Chinese consumers especially for its cough relieving and phlegm removal properties. Although people are concerned about the risk of Alternaria toxins in many agro-foods and their products, little is known about the toxins in pear paste.

RESULTS

A method was developed for the determination of tenuazonic acid, alternariol, alternariol menomethyl ether, altenuene and tentoxin in pear paste by ultra-performance liquid chromatography tandem mass spectrometry with saturated sodium sulphate dissolution and acidified acetonitrile extraction. The mean recoveries of the five toxins were 75.3-113.8% with relative standard deviations of 2.8-12.2% at spiked levels of 1.0-100 μg kg-1 . Alternaria toxins were detected in 53 out of 76 samples, with a detection rate of 71.4%. Tenuazonic acid (67.1%), alternariol (35.5%), tentoxin (23.7%) and alternariol monomethyl ether (7.9%) were detected in all samples at concentrations of < limit of quantification (LOQ)-105.0 μg kg-1 , < LOQ-32.1 μg kg-1 , < LOQ-74.2 μg kg-1 and < LOQ-15.1 μg kg-1 , respectively. Altenuene was never found in pear paste samples. Tenuazonic acid, alternariol, tentoxin and alternariol menomethyl ether should be focused on due to their toxicity and detection rates.

CONCLUSION

To the best of our knowledge, this is the first report on the detection method and residue levels of Alternaria toxins in pear paste. The proposed method and research data can provide technical support for the Chinese government to continuously monitor and control Alternaria toxins in pear paste, especially tenuazonic acid. It can also provide a useful reference for related researchers. © 2023 Society of Chemical Industry.

A novel sample preparation method based on polarity grouping for comprehensive determination of 315 pesticides and other contaminants in wolfberry by liquid chromatography-tandem mass spectrometry

A novel sample preparation method based on polarity grouping was developed for the comprehensive determination of 315 undesirable low-weight organic pollutants ranging from polar to weakly polar in wolfberry. The method involves the swelling of the sample in ammonium acetate buffer, two-phase extraction, three-phase extraction, and dispersive solid phase extraction (D-SPE) with the assistance of low-temperature centrifugation and analysis by ultrahigh performance liquid chromatography coupled with electrospray ionization tandem mass (UHPLC-ESI-MS-MS) by using the multiple reaction monitoring mode. The recoveries of the analytes with wide range of polarity were satisfactory. The matrix-fortified standard calibration curves were compared for quantification. The results of linearity were satisfactory with linear regression coefficients (R) ranging from 0.9901 to 1.000. The limits of quantification ranged from 1 μg/kg to 10.0 μg/kg, indicating the compliance of products with legal tolerances. The average recoveries for spiked wolfberry were in the range of 69.3 %-145.2 % with RSD values of 0.2 %-28.6 %. The inter-day precision was in the range of 0.2 %-27.0 %. For over 90 % of the analytes, the recoveries were 70 %-120 % with RSD values below 20 %. The application of this method in routine monitoring programs would imply a drastic reduction of both effort and time.

Natural Occurrence of Alternaria Toxins in Citrus-Based Products Collected from China in 2021

A total of 181 citrus-based products, including dried fruits, canned fruits, and fruit juices, collected from China and from abroad in 2021 were analyzed for the four Alternaria toxins (ALTs): alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN), and tenuazonic acid (TeA) via ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS). Although the concentrations of the four ALTs varied by product and geographically, TeA was the predominant toxin followed by AOH, AME, and TEN. Products made in China showed higher levels of ALTs than those made abroad. Maximum levels of TeA, AOH, and AME in analyzed domestic samples were 4.9-fold, 1.3-fold, and 1.2-fold, respectively, higher than those in imported products. Furthermore, 83.4% (151/181) of the analyzed citrus-based products were contaminated with at least two or more ALTs. There were significant positive correlations between AOH and AME, AME and TeA, and TeA and TEN in all analyzed samples. More importantly, the solid and the condensed liquid products had higher concentrations of ALTs than the semi-solid product samples, as well as tangerines, pummelos, and grapefruits compared to the other kinds of citrus-based products. In conclusion, co-contamination with ALTs in commercially available Chinese citrus-based products was universal. Extensive and systematic surveillance of ALTs in citrus-based products, both domestic and imported, is required to obtain more scientific data for the determination of the maximum allowable concentrations of ALTs in China.

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).

Inhibitory effect of carvacrol against Alternaria alternata causing goji fruit rot by disrupting the integrity and composition of cell wall

Goji (Lycium barbarum L.) is a widely planted crop in China that is easily infected by the pathogenic fungus Alternaria alternata, which causes rot after harvest. Previous studies showed that carvacrol (CVR) significantly inhibited the mycelial growth of A. alternata in vitro and reduced Alternaria rot in goji fruits in vivo. The present study aimed to explore the antifungal mechanism of CVR against A. alternata. Optical microscopy and calcofluor white (CFW) fluorescence observations showed that CVR affected the cell wall of A. alternata. CVR treatment affected the integrity of the cell wall and the content of substances in the cell wall as measured by alkaline phosphatase (AKP) activity, Fourier transform-infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Chitin and β-1,3-glucan contents in cells decreased after CVR treatment, and the activities of β-glucan synthase and chitin synthase decreased. Transcriptome analysis revealed that CVR treatment affected cell wall-related genes in A. alternata, thereby affecting cell wall growth. Cell wall resistance also decreased with CVR treatment. Collectively, these results suggest that CVR may exert antifungal activity by interfering with cell wall construction, leading to impairment of cell wall permeability and integrity.

Volatile organic compounds produced by Bacillus velezensis L1 as a potential biocontrol agent against postharvest diseases of wolfberry

Volatile organic compounds (VOCs) produced by antagonistic microorganisms have good biocontrol prospects against postharvest diseases. Infection caused by Alternaria iridiaustralis and 10 other significant fungal diseases can be successfully inhibited by VOCs produced by an identified and screened endophytic strain L1 (Bacillus velezensis). This study revealed the in vivo and in vitro biocontrol effects of VOCs released by B. velezensis L1 on A. iridiaustralis, a pathogenic fungus responsible for rot of wolfberry fruit. The inhibition rates of VOCs of B. velezensis L1 on the mycelial growth of A. iridiaustralis in vitro were 92.86 and 90.30%, respectively, when the initial inoculum concentration on the plate was 1 × 10⁹ colony forming unit (CFU)/ml. Spore germination and sporulation were 66.89 and 87.96%, respectively. VOCs considerably decreased the wolfberry’s disease index and decay incidence in vivo. Scanning electron microscopy revealed that the morphological and structural characteristics of A. iridiaustralis could be altered by VOCs. Ten VOCs were identified through headspace-gas chromatography-ion mobility spectrometry. Pure chemical tests revealed that 2.3-butanedione had the strongest antifungal effects, totally inhibiting A. iridiaustralis in wolfberry fruit at a 60 μl/L concentration. The theory underpinning the potential application of VOCs from B. velezensis is provided herein. This is also the first study to document the antifungal capabilities of the B. velezensis strain on postharvest wolfberry fruit.

GRAPHICAL ABSTRACT

Investigation of fungal contamination in medicinal and edible Lycii Fructus through DNA metabarcoding

AIMS

Lycii Fructus (LF) is considered as a 'superfood' due to its health benefits and delicious tastes, which has gained popularity worldwide. However, LF is also a proper host for fungal growth due to its abundant nutrients. Fungal contamination seriously affects the quality and safety of LF and poses threats to consumer health.

METHODS AND RESULTS

In this study, a total of 15 LF samples were collected from five provinces in China, and were divided into five groups based on the collection areas. Fungal contamination in LF was investigated by targeting the internal transcribed spacer 2 region using Illumina Miseq PE300 platform, and the differences of fungal community in groups based on collection areas were compared. Results showed that the fungal contamination was detected in all the 15 LF samples. Ascomycota, Dothideomycetes, Pleosporales and Pleosporaceae were dominant at the phylum, class, order and family levels, respectively. At the genus level, Alternaria, Cladosporium and Fusarium were the three dominant genera. In all, 24 fungal species were identified. Among which, two species, namely Penicillium oxalicum and Trichothecium roseum, were potentially toxigenic.

CONCLUSIONS

All 15 LF samples were detected with fungal contamination. The differences of fungal community in LF samples collected from different areas were observed. DNA metabarcoding was demonstrated as an efficient method to monitor the fungal contamination in LF.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work comprehensively reveals the fungal diversity and composition in LF and provides early warning for potential mycotoxin contamination.

Contamination, Detection and Control of Mycotoxins in Fruits and Vegetables

Mycotoxins are secondary metabolites produced by pathogenic fungi that colonize fruits and vegetables either during harvesting or during storage. Mycotoxin contamination in fruits and vegetables has been a major problem worldwide, which poses a serious threat to human and animal health through the food chain. This review systematically describes the major mycotoxigenic fungi and the produced mycotoxins in fruits and vegetables, analyzes recent mycotoxin detection technologies including chromatography coupled with detector (i.e., mass, ultraviolet, fluorescence, etc.) technology, electrochemical biosensors technology and immunological techniques, as well as summarizes the degradation and detoxification technologies of mycotoxins in fruits and vegetables, including physical, chemical and biological methods. The future prospect is also proposed to provide an overview and suggestions for future mycotoxin research directions.

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%.

Screening of multi-mycotoxins in fruits by ultra-performance liquid chromatography coupled to ion mobility quadrupole time-of-flight mass spectrometry

A modified quick, easy, cheap, effective, rugged, and safe extraction procedure combined with ultra-performance liquid chromatographic separation and ion mobility quadrupole time-of-flight mass spectrometry was developed to determine the presence of 20 mycotoxins (i.e., Alternaria toxins, ochratoxin, patulin, aflatoxin and trichothecenes) in fruit samples from Xinjiang. A complete platform, including screening via an in-house library, confirmation and quantification using reference standards, was established, which provided accurate MS data and complete spectra containing the fragment ions for each analyte. To evaluate the performance of the developed method, satisfactory validation parameters, such as linearity (R² ≥ 0.9992), precision (RSDs ≤ 9.8%), recovery (81.2-99.2%), LOD (0.06-2.22 µg kg^-1), and LOQ (0.2-7.39 µg kg^-1), were obtained. The analysis of 130 fruit samples revealed nonnegligible contamination with mycotoxins; specifically, the highest levels of three Alternaria toxins were detected in jujube, wolfberries and raisins.

[Progress of sample preparation and analytical methods of dried fruit foods]

坚果、果脯等干果类食品含有丰富的营养成分,深受国内外广大消费者的喜爱。但这些食品在果实生产、加工、储运时会使用农药或产生霉变等,造成干果中农药、重金属、霉菌毒素或添加剂等有害成分残留,甚至超过国家限量要求,带来严重的食品安全问题。因此,加强干果类食品的质量监督具有重要的经济和社会意义。但干果类食品基质复杂,有害物质种类多,结构和性质差异大,含量低,其分析检测需要快速高效的样品前处理技术和准确灵敏的分析检测方法。该文主要综述了近十年来干果类食品中有害物质的样品前处理及分析检测方法研究进展。其中样品前处理方法主要包括各种场辅助萃取法、相分离法和衍生化萃取方法等。场辅助萃取法主要是借助超声波和微波场等外场(协同)作用加快干果中有害物质的溶出速度,提高其萃取效率。相分离法,包括固相(微)萃取、分散固相萃取和液相(微)萃取法等,具有溶剂消耗少、分离富集效率高的优势,是干果样品分析中较常使用的前处理方法。该文还重点介绍了干果中各类有害成分分析检测技术,主要包括色谱、原子光谱、无机质谱、电化学分析等常规实验室方法,以及一些适用于现场分析的快速检测技术,并以此为基础,展望了干果类食品中有害物质分析检测技术的发展趋势。

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.

Recent Advances in Mycotoxin Analysis and Detection of Mycotoxigenic Fungi in Grapes and Derived Products

Mycotoxins are secondary metabolites of filamentous fungi that can cause toxic effects in human and animal health. Most of the filamentous fungi that produce these mycotoxins belong to four genera, namely, Aspergillus, Penicillium, Fusarium, and Alternaria. Mycotoxigenic fungi, along with mycotoxins, create a constant and serious economic threat for agriculture in many terms, counting product losses due to crop contamination and food spoilage, as well malnutrition when considering nutritional quality degradation. Given the importance of robust and precise diagnostics of mycotoxins and the related producing fungi in the grape food chain, one of the most important agricultural sectors worldwide, the present review initially delivers a comprehensive presentation of mycotoxin reports on grape and derived products, including a wide range of commodities such as fresh grapes, raisins, wine, juices, and other processed products. Next, based on worldwide regulations’ requirements for mycotoxins, and referring to the relative literature, this work presents methodological approaches for mycotoxin determination, and stresses major methods for the detection of fungal species responsible for mycotoxin production. The principle of function and basic technical background on the available analytical and molecular biology techniques developed—including chromatography, mass spectrometry, immunochemical-based assays, biosensors, and molecular assays—is briefly given, and references for their application to grape and derived product testing are highlighted.

Transcriptomic Insights into the Antifungal Effects of Magnolol on the Growth and Mycotoxin Production of Alternaria alternata

Alternaria alternata is an important phytopathogen causing fruit black rot and also producing a variety of mycotoxins, such as alternariol (AOH) and alternariol monomethyl ether (AME) as two main contaminants. This could lead to economic losses of agricultural products as well as human health risks. In this study, magnolol extracted from the traditional Chinese herb, Mangnolia officinalis, exhibited an obvious antifungal property and could completely suppress the mycelial growth at 100 μM. Morphological differences of A. alternata were observed to be significantly shrunk and wrinkled after the exposure to magnolol. Furthermore, AOH and AME were no longer produced in response to 50 μM of magnolol. To uncover the antifungal and antimycotoxigenic mechanisms, the transcriptomic profiles of A. alternata—treated with or without magnolol—were evaluated. The clustered genes responsible for AOH and AME biosynthesis were obviously less transcribed under magnolol stress and this was further confirmed by qRT-PCR. The global regulators of carbon and nitrogen utilization, such as CreA and NmrA, were significantly down-regulated and this possibly caused the reduction in mycotoxins. In addition, fatty acid β-oxidation was regarded to contribute to polyketide mycotoxin production for the supply of precursor acetyl-CoA while the expression of these related genes was inhibited. The response to magnolol led to the marked alteration of oxidative stress and the down-expression of the mitogen-activated protein kinase (MAPK) signaling pathway from the transcriptome data and the determination of peroxidase (POD), superoxide dismutase (SOD) and glutathione (GSH) assays. This above might be the very reason for the growth supression and mycotoxin production of A. alternata by magnolol. This study provides new insights into its potential as an important active ingredient for the control of A. alternata and its mycotoxins in fruits and their products.

Levels of Alternaria Toxins in Selected Food Commodities Including Green Coffee

Alternaria toxins are emerging mycotoxins, candidates for regulation by European Authorities. Therefore, highly sensitive, confirmatory, and reliable analytical methodologies are required for their monitoring in food. In that context, an isotope dilution LC-MS/MS method was developed for the analysis of five Alternaria toxins (Altenuene, Alternariol, Alternariol monomethylether, Tentoxin, and Tenuazonic Acid) in a broad range of commodities including cereals and cereal-based products, tomato-based products, tree nuts, vegetable oils, dried fruits, cocoa, green coffee, spices, herbs, and tea. Validation data collected in two different laboratories demonstrated the robustness of the method. Underestimation of Tenuazonic Acid level in dry samples such as cereals was reported when inappropriate extraction solvent mixtures were used as currently done in several published methodologies. An investigation survey performed on 216 food items evidenced large variations of Alternaria toxins levels, in line with data reported in the last EFSA safety assessment. The analysis of 78 green coffee samples collected from 21 producing countries demonstrated that coffee is a negligible source of exposure to Alternaria toxins. Its wide scope of application, adequate sample throughput, and high sensitivity make this method fit for purpose for the regular monitoring of Alternaria toxins in foods.

Consumer preference for dried mango attributes: A conjoint study among Dutch, Chinese, and Indonesian consumers

Abstract

One way to add value to tropical fruit and increase its availability in the global market is to develop new, less perishable, products from fresh fruit. The purpose of this study is to compare the perception of key quality attributes and preferences of dried mango between consumers with different familiarity and health consciousness. This study surveyed respondents from China, Indonesia, and the Netherlands via an adaptive choice‐based conjoint method (n = 483) to evaluate intrinsic quality attributes that influenced consumer preference for dried mango. Consumers in different countries have different texture, taste, and color preferences for dried mango. The most important attribute for the Dutch and Chinese was “free from extra ingredients”, while for Indonesians, it was the texture. Familiarity with dried mango and health consciousness do not influence consumer preference of intrinsic attributes of dried mango. Different preferences of intrinsic attributes of dried mango between countries are related to cultural differences. This study provides useful insights for food manufacturers into the significance of key intrinsic quality attributes in developing dried mango.

Practical Application

Intrinsic quality parameters of dried mango are not perceived in the same way by every consumer and this is related to cultural differences. Crispy texture is important only for Indonesian consumers, while “free from extra ingredients” is the most important for Dutch and Chinese consumers. This information is relevant when developing dried mango products for the respective markets.

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.

The Effectiveness of Durian Peel as a Multi-Mycotoxin Adsorbent

Durian peel (DP) is an agricultural waste that is widely used in dyes and for organic and inorganic pollutant adsorption. In this study, durian peel was acid-treated to enhance its mycotoxin adsorption efficacy. The acid-treated durian peel (ATDP) was assessed for simultaneous adsorption of aflatoxin B₁ (AFB₁), ochratoxin A (OTA), zearalenone (ZEA), deoxynivalenol (DON), and fumonisin B₁ (FB₁). The structure of the ATDP was also characterized by SEM–EDS, FT–IR, a zetasizer, and a surface-area analyzer. The results indicated that ATDP exhibited the highest mycotoxin adsorption towards AFB₁ (98.4%), ZEA (98.4%), and OTA (97.3%), followed by FB₁ (86.1%) and DON (2.0%). The pH significantly affected OTA and FB₁ adsorption, whereas AFB₁ and ZEA adsorption was not affected. Toxin adsorption by ATDP was dose-dependent and increased exponentially as the ATDP dosage increased. The maximum adsorption capacity (Q_max), determined at pH 3 and pH 7, was 40.7 and 41.6 mmol kg⁻¹ for AFB₁, 15.4 and 17.3 mmol kg⁻¹ for ZEA, 46.6 and 0.6 mmol kg⁻¹ for OTA, and 28.9 and 0.1 mmol kg⁻¹ for FB₁, respectively. Interestingly, ATDP reduced the bioaccessibility of these mycotoxins after gastrointestinal digestion using an in vitro, validated, static model. The ATDP showed a more porous structure, with a larger surface area and a surface charge modification. These structural changes following acid treatment may explain the higher efficacy of ATDP in adsorbing mycotoxins. Hence, ATDP can be considered as a promising waste material for mycotoxin biosorption.

Stability of Mycotoxins in Individual Stock and Multi-Analyte Standard Solutions

Standard solutions of mycotoxins prepared in RP HPLC solvents from neat standards are usually used for analytical method development. Multi-mycotoxin HPLC-MS/MS methods necessitate stability estimation for the wide spectrum of fungal metabolites. The stability of individual diluted stock standard solutions of mycotoxins in RP-HPLC solvents and multi-analyte HPLC-MS/MS calibrants was evaluated under standard storage and analysis conditions. Individual stock standard solutions of aflatoxins, sterigmatocystin, A- and B-trichothecenes, zearalenone and its analogues, ochratoxin A, fumonisins, Alternaria toxins, enniatins and beauvericin, moniliformin, citrinin, mycophenolic, cyclopiazonic acids and citreoviridin were prepared in RP-HPLC solvents and stored at -18 °C for 14 months. UV-spectroscopy was utilized to monitor the stability of analytes, excluding fumonisins. The gradual degradation of α-, β-zearalenol and α-, β-zearalanol in acetonitrile was detected. Aflatoxins and sterigmatocystin, zearalenone, Alternaria toxins, enniatins and beauvericin, citrinin, mycophenolic, cyclopiazonic acids and citreoviridin can be referred to as stable. The concentration of the majority of trichothecenes should be monitored. Diluted multi-mycotoxin standard in water/methanol (50/50 v/v) solutions acidified with 0.1% formic acid proved to be stable in silanized glass at 23 °C exposed to light for at least 75 h (CV≤10%). An unexpected manifestation of MS/MS signal suppression/enhancement was discovered in the course of multi-mycotoxin standard solution stability evaluation.

Advances in Occurrence, Importance, and Mycotoxin Control Strategies: Prevention and Detoxification in Foods

Mycotoxins are toxic substances that can infect many foods with carcinogenic, genotoxic, teratogenic, nephrotoxic, and hepatotoxic effects. Mycotoxin contamination of foodstuffs causes diseases worldwide. The major classes of mycotoxins that are of the greatest agroeconomic importance are aflatoxins, ochratoxins, fumonisins, trichothecenes, emerging Fusarium mycotoxins, enniatins, ergot alkaloids, Alternaria toxins, and patulin. Thus, in order to mitigate mycotoxin contamination of foods, many control approaches are used. Prevention, detoxification, and decontamination of mycotoxins can contribute in this purpose in the pre-harvest and post-harvest stages. Therefore, the purpose of the review is to elaborate on the recent advances regarding the occurrence of main mycotoxins in many types of important agricultural products, as well as the methods of inactivation and detoxification of foods from mycotoxins in order to reduce or fully eliminate them.

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

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

Contamination of fresh and dried tomato by Alternaria toxins in southern Italy

In the present investigation, fresh and dried tomato samples from markets and packinghouses located in Apulia region (southern Italy) were analysed for Alternaria toxins. All samples proved to be contaminated by tenuazonic acid (TeA); in particular, dried tomatoes were contaminated in the range 425-81,592 µg/kg, while fresh tomatoes were in the range 11-4560 µg/kg. The second most abundant toxin was alternariol monomethyl ether (AME), followed by tentoxin (TEN) and alternariol (AOH). Overall dried tomatoes were more contaminated than fresh ones, although this seemed not directly related to the presence of sodium chloride, utilized in the drying process. Five representative Alternaria isolates within those collected from samples proved to be one Alternaria arborescens (A215) and four Alternaria alternata. Within the latter species, one strain belonged to morphotype tenuissima (A216), and three to alternata (A214, A217 and A218). They were confirmed to produce TeA, AOH, and AME in vitro. This study demonstrates the possible risk for consumers' health related to the consumption of contaminated fresh and dried tomatoes, and thus the need for suitable control strategies.

Alternaria mycotoxins in grains from Albania: alternariol, alternariol monomethyl ether, tenuazonic acid and tentoxin

The presence of four Alternaria toxins in maize and wheat harvested in 2014 and 2015 in Albania was investigated. In total, 45 samples of maize and 71 samples of wheat were collected from the country’s main producing regions. The presence of alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA) and tentoxin (TTX) was studied by an LC-MS/MS method. The incidence of Alternaria toxins in maize was 45.2% in the year 2014 and 7.1% in 2015, and the contamination rate in wheat was 82.9% in 2014 and 86.1% in 2015. Considering maize and wheat samples together, 65.2 and 64.0% of samples were contaminated by Alternaria toxins in the harvesting years 2014 and 2015, respectively. The occurrence rate was much higher in wheat than in maize, but the concentrations were higher in maize. The highest concentration of total Alternaria toxins in maize was 1,283 μg/kg (mean 243.0 μg/kg, median 110.2 μg/kg), while the maximum concentration in wheat was 175.7 μg/kg (mean 29.9 μg/kg, median 16.5 μg/kg). TeA was the major Alternaria mycotoxin detected. It was found in 70 out of 116 samples (60.3%). Chronic exposure of the adult population in Albania to Alternaria toxins through cereal consumption was assessed by the estimated daily intake (EDI) taking into account daily consumption of wheat and maize of 380 and 4.9 g, respectively. The main contribution to chronic dietary exposure was by TeA originating from wheat, with EDIs of 88.6-94.1 ng/kg body weight (bw) per day in 2014 and 152.7-155.5 ng/kg bw per day in 2015. TTX EDIs were 7.8- 34.0 and 10.6-38.7 ng/kg bw per day in 2014 and 2015, respectively. The contribution of AOH and AME originating from wheat was 0-31.7 ng/kg bw per day. The contribution of Alternaria toxins through maize consumption was significantly lower.

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.

Development and Application of a QuEChERS-Based Liquid Chromatography Tandem Mass Spectrometry Method to Quantitate Multi-Component Alternaria Toxins in Jujube

A simple, rapid and efficient methodology was developed and validated for the analysis of four Alternaria toxins in jujube: Tenuazonic acid, alternariol, alternariol monomethyl ether, and tentoxin. Under the optimized extraction procedure, chromatographic conditions, and instrumental parameters, the four toxins were effectively extracted via a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, and quantified by ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Matrix-matched calibrations ranging from 0.01 to 0.5 μg mL⁻¹ were conducted for the quantification due to the matrix effect. A blank jujube sample was spiked at 40, 80 and 160 μg kg⁻¹, obtaining recoveries in the range of 83.5–109.6%. Limits of detection and limits of quantification were in the range of 0.14–0.26 and 0.47–0.87 μg kg⁻¹, respectively. Finally, the developed method was applied for the quantification of the four toxins in 14 jujube samples, including black spot-infected and uninfected samples. Results showed that the predominant toxin detected in all the samples was tenuazonic acid, the content of which was associated with the infection level; alternariol, alternariol monomethyl ether, and tentoxin were detected in all the infected samples and some of the uninfected samples with rather low contents.