Determination of five Alternaria toxins in wolfberry using modified QuEChERS and ultra-high performance liquid chromatography-tandem mass spectrometry

CRISPR-Cas12a-driven aptasensor for sensitive detection of alternariol by using a personal glucose meter

Alternariol (AOH) has attracted much attention as an emerging toxin in edible herbs that can pose potential carcinogenic risks to human. However, the rapid detection of AOH to ensure food safety remains a challenge. Here, a CRISPR-Cas12a-mediated aptamer-based sensor (aptasensor) was proposed for the sensitive quantification of AOH by using a personal glucose meter. First, fluorescent probes were used to validate crRNA sequences that could activate Cas12a trans-cleavage activity. Owing to the high affinity of aptamer, different concentrations of AOH were able to release different levels of Cas12a cleavage activity to cut magnetic bead-modified invertase probes. The free invertase was collected to catalyze hydrolysis of sucrose to glucose. After optimizing a series of key parameters, the constructed aptasensor with dual signal amplification of Cas12a and invertase allowed for highly-sensitive AOH detection in a linear range of 0.45-3000 ng/mL with a detection limit of 0.048 ng/mL. In addition, this aptasensor was successfully applied in edible herb samples with satisfactory recovery rates of 92.19-102.40 %. This CRISPR-Cas12a-mediated aptasensing platform provides a simple and powerful alternative for rapid quantitative detection of AOH, which is of great significance for food safety.

Determination of five alternaria toxins in peppermint by dispersive solid-phase extraction coupled with ultra-high performance liquid chromatography-tandem mass spectrometry based on MOF-808-TFA

An efficient and rapid ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MSMS) method was developed for simultaneous determination of 5 alternaria toxins (ATs) in edible and medicinal plant - peppermint using MOF-808-trifluoroacetic acid (MOF-808-TFA) as the adsorbent. Characterization methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 adsorption-desorption demonstrated that the synthesized MOF-808-TFA had a regular ortho-octahedral configuration and high specific surface area. Under the optimal conditions, the 5 ATs showed good linearity (R2 ≥ 0.9993) in their respective concentration ranges. The limits of quantifications (LOQs) of the method ranged from 0.21 to 0.48 μg/L, and the recoveries were 77.8-118.2 %, with the relative standard deviations (RSDs) less than 8.9 %.

Determination of twelve mycotoxins in red and green Sichuan peppers using QuEChERS method with LC-MS/MS

The detection of mycotoxins in Sichuan peppers is crucial for ensuring food safety. Hence, an efficient detection approach based on the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method followed by LC-MS/MS (liquid chromatography-tandem mass spectrometry) was established for the analysis of various mycotoxins in dried red and green Sichuan peppers. Samples were extracted with a solution containing 99 % acetonitrile and 1 % formic acid. A new adsorbent, namely, ENVI-Carb, and primary secondary amines were used as purifying agents. The proposed method demonstrated good linearity (R2 ≥ 0.999), satisfactory recovery (77.3 %-109.2 %), and good repeatability (intraday and interday relative standard deviations ≤9.7 %) in dried red and green Sichuan peppers. Its limits of detection in red and green Sichuan peppers were 0.2-0.6 and 0.1-0.7 μg/kg, respectively. The established method can effectively eliminate complex matrix interference and provides an effective approach for the high-throughput detection of mycotoxins in various complex food matrices.

Development and application of an efficient, accurate, and environmentally friendly liquid chromatography-tandem mass spectrometry method for the determination of five Alternaria toxins in wheat

The contamination of Alternaria toxins poses a potential risk to human health. This study developed a rapid, efficient, and environmentally friendly method for the simultaneous determination of five types of Alternaria toxins in wheat using high-precision and stable isotope liquid chromatography tandem mass spectrometry. The comparison between dilution method and solid-phase extraction method shows that the former achieves satisfactory results with a simple and convenient sample purification method. The quantitative limit range is 0.88 to 1.68 μg/kg. The recoveries are between 81.40% and 102.68%, with RSD less than 11.95%. The method was used to analyze 60 samples from the main wheat producing areas in China. The results showed that Tenuzonic acid had the highest detection rate (100%), followed by Tentoxin (95%), Alternariol (66.67%), and Alternariol monomethyl ether (53.33%). There is a certain pollution risk that needs to be taken seriously and monitoring should be strengthened.

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.

The combination of metabolome and transcriptome clarifies the inhibition of the Alternaria toxin accumulation by methyl ferulate

As one of the most typical pathogens in fruit postharvest diseases, Alternaria alternata (A. alternata) can produce Alternaria toxins (ATs) aggravating fruit decay and harming human health. In this study, ATs (tenuazonic acid, alternariol monomethyl ether, and alternariol) production was inhibited effectively by 200 and 8000 mg/L MF (methyl ferulate) in vitro and in vivo. 1-Octen-3-ol and 3-octanol were the potential iconic volatile organic compounds of ATs (R2 > 0.99). MF induced oxidative stress, resulting in physiological and metabolic disorders, membrane lipid oxidation and cell damage. It decreased precursors and energy supply by disturbing amino acid metabolism, ABC transporters, citrate cycle, pentose and glucuronate interconversions to regulate ATs synthesis. MF down-regulated the genes related to ATs synthesis (PksJ, AaTAS1, and OmtI), transport (AaMFS1 and MFS), and pathogenicity to affect ATs production and virulence. This study provided a theoretical basis for the control of ATs production.

Biocontrol potential and growth-promoting effect of endophytic fungus Talaromyces muroii SD1-4 against potato leaf spot disease caused by Alternaria alternata

BACKGROUND

Alternaria alternata is the primary pathogen of potato leaf spot disease, resulting in significant potato yield losses globally. Endophytic microorganism-based biological control, especially using microorganisms from host plants, has emerged as a promising and eco-friendly approach for managing plant diseases. Therefore, this study aimed to isolate, identify and characterize the endophytic fungi from healthy potato leaves which had great antifungal activity to the potato leaf spot pathogen of A. alternata in vitro and in vivo.

RESULTS

An endophytic fungal strain SD1-4 was isolated from healthy potato leaves and was identified as Talaromyces muroii through morphological and sequencing analysis. The strain SD1-4 exhibited potent antifungal activity against the potato leaf spot pathogen A. alternata Lill, with a hyphal inhibition rate of 69.19%. Microscopic and scanning electron microscope observations revealed that the strain SD1-4 grew parallel to, coiled around, shrunk and deformed the mycelia of A. alternata Lill. Additionally, the enzyme activities of chitinase and β-1, 3-glucanase significantly increased in the hyphae of A. alternata Lill when co-cultured with the strain SD1-4, indicating severe impairment of the cell wall function of A. alternata Lill. Furthermore, the mycelial growth and conidial germination of A. alternata Lill were significantly suppressed by the aseptic filtrate of the strain SD1-4, with inhibition rates of 79.00% and 80.67%, respectively. Decrease of leaf spot disease index from 78.36 to 37.03 was also observed in potato plants treated with the strain SD1-4, along with the significantly increased plant growth characters including plant height, root length, fresh weight, dry weight, chlorophyll content and photosynthetic rate of potato seedlings.

CONCLUSION

The endophyte fungus of T. muroii SD1-4 isolated from healthy potato leaves in the present study showed high biocontrol potential against potato leaf spot disease caused by A. alternata via direct parasitism or antifungal metabolites, and had positive roles in promoting potato plant growth.

High-throughput extraction and automatic purification of alternariol from edible and medicinal herbs based on aptamer-functionalized magnetic nanoparticles

Mycotoxin contamination is widespread in plants and herbs, posing serious threats to the consumer and human health. Of them, alternariol (AOH) has attracted great attention as an "emerging" mycotoxin in medicinal herbs. However, a specific and high-throughput extraction method for AOH is currently lacking. Thus, developing an efficient pre-treatment technique for AOH detection is extremely vital. Here, a novel automated magnetic solid-phase extraction method was proposed for the highly efficient extraction of AOH. Combining the aptamer-functionalized magnetic nanoparticles (AMNPs) and the automatic purification instrument, AOH could be extracted in medicinal herbs in high throughput (20 samples) and a short time (30 min). The main parameters affecting extraction were optimized, and the method was finally carried out by incubation AMNPs with 3 mL of sample solution for 10 min, and then desorption in 75% methanol for liquid-phase detection. Under optimal conditions, good reproducibility, stability, and selectivity were realized with an adsorption capacity of 550.84 ng/mg. AOH extraction in three edible herbs showed good resistance to matrix interference with recovery rates from 86% to 111%. In combination with AMNPs and the automatic purification instrument, high-throughput and labor-free extraction of AOH in different complex matrices was achieved, which could be extended in other complex matrices.

Simultaneous determination of triazole fungicides in animal-origin food by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry

A method for the simultaneous determination of 21 triazole fungicides in animal-origin foods was established by using UPLC-MS/MS. The dilution solvent, extraction solvent, and QuEChERS purification adsorbent composition, were optimized. The response value of the target compound was the highest and the chromatographic peak shape was optimal under the following conditions: water-acetonitrile as the mobile phase, acetonitrile to extract the target compound, C18 (100 mg) as the adsorbent, and water-acetonitrile as the diluent. Our method was validated under electrospray ionization (ESI) + conditions with six animal-origin foods. The 21 triazole fungicides showed good linear relationships (0.1-20 μg∙L-1, R2 > 0.99). The limits of detection and quantitation ranged from 0.1 to 0.3 μg∙kg-1 and 0.3 to 0.9 μg∙kg-1, respectively. The average recoveries ranged from 72.0% to 114.8% with RSDs < 9.9%. Therefore, our method was suitable for the determination of pesticide residues in commercially available animal-origin samples.

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.

Construction of electrochemical and electrochemiluminescent dual-mode aptamer sensors based on ferrocene dual-functional signal probes for the sensitive detection of Alternariol

In this study, a novel dual-mode aptamer sensor was developed using Fca-DNA₂ as the quenching electrochemiluminescence (ECL) and electrochemical (EC) signal response probe, and Ru-MOF/Cu@Au NPs were used as the ECL substrate platform to detect Alternariol (AOH) via a competitive reaction between AOH and Fca-DNA₂. Compared with the conventional aptamer sensor with a single detection signal, this dual-mode aptamer sensor has the following advantages: (1) Electrodeposition-based rapid synthesis Ru-MOF on the electrode surface. (2) The Signal amplification substance Cu@Au NPs can synergistically catalyze Triethanolamine (TEOA) to amplify ECL behavior. (3) The aptamer sensor employs the dual-functional material Fca, which can detect both ECL and EC signals, increasing the result accuracy. Both ECL and EC methods have excellent detection performance for AOH in the detection range of 0.1 pg/mL to 100 ng/mL, with detection limits of 0.014 and 0.083 pg/mL, respectively, and are expected to be used for sensitive AOH detection in real samples.

Scope of Onsite, Portable Prevention Diagnostic Strategies for Alternaria Infections in Medicinal Plants

Medicinal plants are constantly challenged by different biotic inconveniences, which not only cause yield and economic losses but also affect the quality of products derived from them. Among them, Alternaria pathogens are one of the harmful fungal pathogens in medicinal plants across the globe. Therefore, a fast and accurate detection method in the early stage is needed to avoid significant economic losses. Although traditional methods are available to detect Alternaria, they are more time-consuming and costly and need good expertise. Nevertheless, numerous biochemical- and molecular-based techniques are available for the detection of plant diseases, but their efficacy is constrained by differences in their accuracy, specificity, sensitivity, dependability, and speed in addition to being unsuitable for direct on-field studies. Considering the effect of Alternaria on medicinal plants, the development of novel and early detection measures is required to detect causal Alternaria species accurately, sensitively, and rapidly that can be further applied in fields to speed up the advancement process in detection strategies. In this regard, nanotechnology can be employed to develop portable biosensors suitable for early and correct pathogenic disease detection on the field. It also provides an efficient future scope to convert innovative nanoparticle-derived fabricated biomolecules and biosensor approaches in the diagnostics of disease-causing pathogens in important medicinal plants. In this review, we summarize the traditional methods, including immunological and molecular methods, utilized in plant-disease diagnostics. We also brief advanced automobile and efficient sensing technologies for diagnostics. Here we are proposing an idea with a focus on the development of electrochemical and/or colorimetric properties-based nano-biosensors that could be useful in the early detection of Alternaria and other plant pathogens in important medicinal plants. In addition, we discuss challenges faced during the fabrication of biosensors and new capabilities of the technology that provide information regarding disease management strategies.

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).

Fe3O4@COF(TAPT-DHTA) Nanocomposites as Magnetic Solid-Phase Extraction Adsorbents for Simultaneous Determination of 9 Mycotoxins in Fruits by UHPLC-MS/MS

In this study, a simple and efficient magnetic solid-phase extraction (MSPE) strategy was developed to simultaneously purify and enrich nine mycotoxins in fruits, with the magnetic covalent organic framework nanomaterial Fe₃O₄@COF(TAPT-DHTA) as an adsorbent. The Fe₃O₄@COF(TAPT-DHTA) was prepared by a simple template precipitation polymerization method, using Fe₃O₄ as magnetic core, and 1,3,5-tris-(4-aminophenyl) triazine (TAPT) and 2,5-dihydroxy terephthalaldehyde (DHTA) as two building units. Fe₃O₄@COF(TAPT-DHTA) could effectively capture the targeted mycotoxins by virtue of its abundant hydroxyl groups and aromatic rings. Several key parameters affecting the performance of the MSPE method were studied, including the adsorption solution, adsorption time, elution solvent, volume and time, and the amount of Fe₃O₄@COF(TAPT-DHTA) nanomaterial. Under optimized MSPE conditions, followed by analysis with UHPLC-MS/MS, a wide linear range (0.05-200 μg kg^-1), low limits of detection (0.01-0.5 μg kg^-1) and satisfactory recovery (74.25-111.75%) were achieved for the nine targeted mycotoxins. The established method was further successfully validated in different kinds of fruit samples.

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.

Recent advances in simultaneous detection strategies for multi-mycotoxins in foods

Mycotoxin contamination has become a challenge in the field of food safety testing, given the increasing emphasis on food safety in recent years. Mycotoxins are widely distributed, in heavily polluted areas. Food contamination with these toxins is difficult to prevent and control. Mycotoxins, as are small-molecule toxic metabolites produced by several species belonging to the genera Aspergillus, Fusarium, and Penicillium growing in food. They are considered teratogenic, carcinogenic, and mutagenic to humans and animals. Food systems are often simultaneously contaminated with multiple mycotoxins. Due to the additive or synergistic toxicological effects caused by the co-existence of multiple mycotoxins, their individual detection requires reliable, accurate, and high-throughput techniques. Currently available, methods for the detection of multiple mycotoxins are mainly based on chromatography, spectroscopy (colorimetry, fluorescence, and surface-enhanced Raman scattering), and electrochemistry. This review provides a comprehensive overview of advances in the multiple detection methods of mycotoxins during the recent 5 years. The principles and features of these techniques are described. The practical applications and challenges associated with assays for multiple detection methods of mycotoxins are summarized. The potential for future development and application is discussed in an effort, to provide standards of references for further research.

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.

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.

Detection of seven Alternaria toxins in edible and medicinal herbs using ultra-high performance liquid chromatography-tandem mass spectrometry

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A modified QuEChERS-UPLC-MS/MS method was established to investigate alternaria mycotoxins.

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The method was applied to 260 edible and medicinal herb samples.

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28.46% of samples were contaminated by at least one toxin.

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AME with a high occurrence in analyzed herbs.

Alternaria mycotoxins are ubiquitous mycotoxins that contaminate food and animal feed. Here, an UPLC-MS/MS was developed and used for the detection of seven Alternaria mycotoxins in 19 different edible and medicinal herbs. Extensive optimization resulted in a simple and convenient sample preparation procedure with satisfactory extraction and a lower matrix effect. LOQs ranged from 0.01 to 2.0 ng/mL. Recoveries varied between 71.44% and 112.65%, with RSD less than 12%. The method was successfully applied for use in the mycotoxin analysis of 260 samples. A high percentage (28.46%) of samples were contaminated by 1–5 mycotoxins. Alternariol mono methylether was the predominant mycotoxin with high percentage of positive samples (37.5%), followed by alternariol (22.5%), alternariol (17.5%), tentoxin (10.83%), altertoxin Ⅰ (7.5%), and altenusin (4.17%). Collectively, the natural incidence data obtained from this study will help with better, validated risk assessments and efforts towards more comprehensive, future regulation.

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.

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.

Simultaneous Detection of Seven Alternaria Toxins in Mixed Fruit Puree by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry Coupled with a Modified QuEChERS

The presence of Alternaria toxins (ATs) in fruit purees may cause potential harm to the life and health of consumers. As time passes, ATs have become the key detection objects in this kind of food. Based on this, a novel and rapid method was established in this paper for the simultaneous detection of seven ATS (tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene, tentoxin, altenusin, and altertoxin I) in mixed fruit purees using ultra-high performance liquid chromatography-tandem mass spectrometry. The sample was prepared using the modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method to complete the extraction and clean-up steps in one procedure. In this QuEChERS method, sample was extracted with water and acetonitrile (1.5% formic acid), then salted out with NaCl, separated on an ACQUITY UPLC BEH C₁₈ with gradient elution by using acetonitrile and 0.1% formic acid aqueous as eluent, and detected by UPLC-MS/MS under positive (ESI⁺) and negative (ESI⁻) electrospray ionization and MRM models. Results showed that the seven ATs exhibited a good linearity in the concentration range of 0.5–200 ng/mL with R² > 0.9925, and the limits of detection (LODs) of the instrument were in the range of 0.18–0.53 μg/kg. The average recoveries ranged from 79.5% to 106.7%, with the relative standard deviations (RSDs) no more than 9.78% at spiked levels of 5, 10, and 20 μg/kg for seven ATs. The established method was applied to the determination and analysis of the seven ATs in 80 mixed fruit puree samples. The results showed that ATs were detected in 31 of the 80 samples, and the content of ATs ranged from 1.32 μg/kg to 54.89 μg/kg. Moreover, the content of TeA was the highest in the detected samples (23.32–54.89 μg/kg), while the detection rate of Ten (24/31 samples) was higher than the other ATs. Furthermore, the other five ATs had similar and lower levels of contamination. The method established in this paper is accurate, rapid, simple, sensitive, repeatable, and stable, and can be used for the practical determination of seven ATs in fruit puree or other similar samples. Moreover, this method could provide theory foundation for the establishment of limit standard of ATs and provide a reference for the development of similar detection standard methods in the future.

Antifungal Activity and Biocontrol Mechanism of Fusicolla violacea J-1 against Soft Rot in Kiwifruit Caused by Alternaria alternata

Alternaria alternata is the main pathogenic species of various crops, including kiwifruit (Actinidia cinensis). In this study, an antagonistic fungus, J-1, with high antifungal activity against A. alternata was isolated from A. cinensis “Hongyang.” The strain J-1 was identified as Fusicolla violacea via morphological identification and DNA sequencing. This study aimed to evaluate the antifungal activity and potential mechanism of the strain J-1 against A. alternata. The strain J-1 exhibited antifungal activity against A. alternata, with an inhibition rate of 66.1% in vitro. Aseptic filtrate (AF) produced by the strain J-1 could suppress the mycelial growth and conidia germination of A. alternata at the inhibition rates of 66.8% and 80%, respectively, as well as suppress the spread of Alternaria rot in fresh kiwifruit. We observed that many clusters of spherical protrusions appeared at the mycelial tips of A. alternata after treatment with 200 mL L⁻¹ AF of J-1. Scanning electron microscopy analysis results showed that the mycelial structures were bent and/or malformed and the surfaces were rough and protuberant. Variations in temperature, pH, and storage time had little effect on the antifungal activity of the AF. Moreover, the AF could damage the integrity of cell membranes and cause intracellular content leakage. Meanwhile, the chitinase and β-1,3-glucanase enzyme activities increased significantly, indicating that the function of A. alternata cell wall was seriously injured. Eleven antimicrobial metabolites were identified by gas chromatography–mass spectrometry (GC–MS). The strain J-I and its AF exhibited well broad-spectrum antifungal activity against Diaporthe eres, Epicoccum sorghinum, Fusarium graminearum, Phomopsis sp., and Botryosphaeria dothidea, with inhibition rates ranging from 34.4% to 75.1% and 42.7% to 75.2%, respectively. Fusicolla violacea J-1 is a potential biocontrol agent against A. alternata and other fungal phytopathogens.

Assessment of Human Exposure to Five Alternaria Mycotoxins in China by Biomonitoring Approach

This biomonitoring study was conducted to investigate the concentration levels of five Alternaria mycotoxins in urine samples from 269 healthy volunteers living in the Yangtze River Delta, China. Alternariol (AOH), alternariol monomethyl ether (AME), tenuazonic acid (TeA) and tentoxin (TEN) were detected in 38.3%, 48.7%, 63.9% and 23.4% of urine samples with the concentrations ranging from 0.057 to 45.8 ng/mL, 0.020 to 0.802 ng/mL, 0.050 to 80.6 ng/mL and 0.021 to 0.939 ng/mL, respectively. Altenuene (ALT) was not detected in any urine sample. Based on the urinary concentrations, the probable daily intake (PDI) values of Alternaria mycotoxins were calculated, and 100%, 99.2-100%, 0.372% and 1.12% of participants exceeded the threshold of toxicological concern (TTC) values for AOH, AME, TeA and TEN, respectively. This study revealed high potential health risks related to the contaminations of major Alternaria mycotoxins in China and highlighted the necessity for more toxicological studies to provide better basis for further comprehensive risk assessments.

A Novel Multiplex Mycotoxin Surface-Enhanced Raman Spectroscopy Immunoassay Using Functional Gold Nanotags on a Silica Photonic Crystal Microsphere Biochip

A novel multiplex mycotoxin surface-enhanced Raman spectroscopy (SERS) immunoassay was established for the first time on different artificial antigen-modified silica photonic crystal microspheres (SPCMs), which can be integrated into a biochip array to achieve multiplex detection using corresponding antibody-functionalized gold nanoparticles (AuNPs) as the SERS nanotag. The unique optical structure of SPCMs is helpful to find the detection spots easily, accommodate a large amount of probe molecules, and enhance the Raman signal intensity. Such enhancement was confirmed by the simulation result, showing the electric field enhancing effect in SPCMs with AuNPs being 7 times. A competitive SERS immunoassay was established using antigen-modified SPCMs and mycotoxins to compete for binding antibody-functionalized SERS nanotags, displaying broad linear detection ranges of 0.001-0.1 ng/mL for aflatoxin B₁ (AFB₁), 0.01-10 ng/mL for ochratoxin A (OTA), and 0.001-0.1 ng/mL for zearalenone (ZEN) and low detection limits of 0.82 pg/mL for AFB₁, 1.43 pg/mL for OTA, and 1.00 pg/mL for ZEN. In the spiked cereal samples, recovery rates of the method were measured in the range of 70.35-118.04% for the three mycotoxins, which was in agreement with that of the traditional enzyme-linked immunosorbent assay method. The SERS immunoassay for mycotoxin detection also showed high specificity and good repeatability and reproducibility. The new microsphere-based SERS immunoassay biochip only requires a one-step reaction and overcomes the disadvantages of fluorescence and chemiluminescence background signals. The work paves the way for further developing SERS-based microsphere suspension arrays for new targets.

Alternaria Mycotoxins: An Overview of Toxicity, Metabolism, and Analysis in Food

The genus Alternaria is widely distributed in the environment. Numerous species of the genus Alternaria can produce a variety of toxic secondary metabolites, called Alternaria mycotoxins. In this review, natural occurrence, toxicity, metabolism, and analytical methods are introduced. The contamination of these toxins in foodstuffs is ubiquitous, and most of these metabolites present genotoxic and cytotoxic effects. Moreover, Alternaria toxins are mainly hydroxylated to catechol metabolites and combined with sulfate and glucuronic acid in in vitro arrays. A more detailed summary of the metabolism of Alternaria toxins is presented in this work. To effectively detect and determine the mycotoxins in food, analytical methods with high sensitivity and good accuracy are also reviewed. This review will guide the formulation of maximum residue limit standards in the future, covering both toxicity and metabolic mechanism of Alternaria toxins.

g-C3N4/Fe3O4 Nanocomposites as Adsorbents Analyzed by UPLC-MS/MS for Highly Sensitive Simultaneous Determination of 27 Mycotoxins in Maize: Aiming at Increasing Purification Efficiency and Reducing Time

According to known studies, numerous mycotoxins have been found simultaneously in foods and have a certain expansion toxicity, so the simultaneous detection of multiple mycotoxins is absolutely critical. In this article, multifunctional magnetic g-C₃N₄/Fe₃O₄ nanocomposites have been fabricated to employ as modified QuEChERS adsorbents. In addition, they were also used in conjunction with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), an accurate quantitative approach, to analyze 27 mycotoxins in maize. The improved method not only has a powerful adsorption effect on the complex matrix by g-C₃N₄/Fe₃O₄ but also enables magnetic separation from the sample solution. Experiments proved that this method can exhibit good linearity under the appropriate and optimal external environment (r² ≥ 0.9954), high sensitivity (the threshold of detection limit is 0.0004-0.6226 μg kg^-1, and the threshold of quantification limit is 0.0014-2.0753 μg kg^-1), adequate recoveries (77.81-115.21%), and excellent repeatability (with a threshold of intraday precision of 1.5-10.8% and interday precision in the range of 2.9-12.5%). In practice this method has been used to evaluate a variety of mycotoxins in maize specimens, and certain actual outcomes have been achieved.

The Role of Suspension Array Technology in Rapid Detection of Foodborne Pollutants: Applications and Future Challenges

Food safety is an important livelihood issue, which has always been focused attention by countries and governments all over the world. As food supply chains are becoming global, food quality control is essential for consumer protection as well as for the food industry. In recent years, a great part of food analysis is carried out using new techniques for rapid detection. As the first biochip technology that has been approved by the Food and Drug Administration (FDA), there is an increasing interest in suspension array technology (SAT) for food and environmental analysis with advantages of rapidity, high accuracy, sensitivity, and throughput. Therefore, it is important for researchers to understand the development and application of this technology in food industry. Herein, we summarized the principle and composition of SAT and its application in food safety monitoring. The utility of SAT in detection of foodborne microorganisms, residues of agricultural and veterinary drugs, genetically modified food and allergens in recent years is elaborated, and the further development direction of SAT is envisaged.

Pesticide multi-residues in Dendrobium officinale Kimura et Migo: Method validation, residue levels and dietary exposure risk assessment

Dendrobium officinale Kimura et Migo (D. officinale) is a dual-use plant with both botanical medicine and food applications, drawing increasing attentions. Pesticides are inevitably applied on D. officinale in commercial artificial-sheltered cultivation, yet little is known about pesticide residue levels in D. officinale. A modified high through-put QuEChERS method coupled with HPLC-MS/MS was developed and validated to detect 76 pesticides in D. officinale. Graphitized multi-wall carbon nanotubes (g-MWCNTs) was selected as the clean-up sorbent, showing relative weak affinity to triazole fungicide having planar structure in their molecular and low matrix effects of pesticides in D. officinale samples compared to MWCNTs and pesticarb. The validated method was applied to analyze pesticide residues in 86 real D. officinale samples collected from three main producing provinces. 43 different pesticides were detected with highest residue of 6.11 mg/kg for dimethomorph. Given possible health risks related to pesticide residues, accordingly, risk assessment of human exposure to pesticides via intake of D. officinale was thus performed, indicating that the pesticide residue in fresh or dry D. officinale would not cause potential risk to human health either in the long-term or short-term. This work improved our understanding of potential exposure risk of pesticide multi-residues in D. officinale.

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.

Evaluation of Two Fully Automated Setups for Mycotoxin Analysis Based on Online Extraction-Liquid Chromatography-Tandem Mass Spectrometry

Mycotoxins are secondary metabolites of fungi species widely known for their potentially toxic effects on human health. Considering their frequent presence in crops and their processed food, monitoring them on food-based matrices is now an important topic. Within such a context, the sample preparation step is usually mandatory before the chromatographic analysis, due to the complexity of matrices such as nuts, cereals, beverages, and others. For these reasons, we herein present the evaluation of two greener setups, based on the automation and miniaturization of the sample preparation step for mycotoxin analysis in different beverages. Firstly, we describe an analytical method based on a multidimensional assembly, coupling a lab-made microextraction column (508 µm i.d. × 100 mm) to a UPLC–MS/MS for the analysis of ochratoxin A in beverages. This configuration used a synthesized sorbent phase containing C18-functionalized graphene–silica particles, which exhibited excellent extraction performance, as well as being reusable and cheaper than commercially available extractive phases. Sequentially, a second setup, based on a multidimensional capillary LC coupled to MS/MS, was assessed for the same purpose. In this case, a graphene oxide-based capillary extraction column (254 µm i.d. × 200 mm) was used as the first dimension, while a C18 analytical capillary column performed the mycotoxin separation in beverages. Although this second one has similarities with the first, we focused mainly on the benefits related to the link between a miniaturized/automated sample preparation device with a capillary LC–MS/MS system, which made our analysis greener. Additionally, the chromatographic efficiency could even be enhanced.