Comparison of extraction and clean-up procedures for analysis of zearalenone in corn, rice and wheat grains by high-performance liquid chromatography with photodiode array and fluorescence detection

Identification of type B trichothecenes and zearalenone in Chilean cereals by planar chromatography coupled to mass spectroscopy

High-performance thin-layer chromatography (HPTLC) and HPTLC coupled with mass spectrometry (MS) methods were described for the simultaneous determination of zearalenone (ZEA); type B trichothecenes (TCT-B); nivalenol (NIV) and deoxynivalenol (DON) along with its acetylated derivatives: 3-acetyldeoxynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON). The extract samples were cleaned-up with Bond Elut Mycotoxin^® solid-phase extraction cartridges. Then, separation was performed on HPTLC silica gel 60 F₂₅₄ plates using toluene, ethyl acetate and formic acid (1:8:1 v/v/v) as mobile phase. Derivatisation was then performed with 10% aluminium trichloride in 50% methanol. Mycotoxin standards and spiked cereals grains were identified by UV spots at 366 nm, with retention factors (R_F) of 0.20 (NIV), 0.39 (DON), 0.45 (15-ADON), 0.50 (3-ADON) and 0.60 (ZEA). Some parameters of validation were determined. Calibration data (n = 5) fitted a linear regression model with determination coefficients, R² > 0.99. The recovery was determined in triplicate at two levels, ranging from 84.3 ± 2.2% to 114.2 ± 11.7%. Detection limits ranged from 80 to 120 μg kg^-1 and quantification limits ranged from 120.0 to 200 μg kg^-1. The analysis by HPTLC/electrospray (ESI)-MS in negative mode confirmed the presence of TCT-B and ZEA standards in Chilean cereals with mass signals at m/z 355, 371, 337, and 317 for DON, NIV, 3-ADON and 15-ADON, and ZEA, respectively.

Contamination of Wheat, Barley, and Maize Seeds with Toxigenic Fusarium Species and Their Mycotoxins in Tunisia

Background

Fusarium is a worldwide distributed fungal genus. It includes different species pathogenic to cereals among others crops. Some of these species can also produce toxic compounds toward animals and humans.

Objective

In this work, occurrence of fumonisins B1+B2, zearalenone, type A trichothecenes (T-2 and HT-2 toxins), and type B trichothecenes (deoxynivalenol[DON] and nivalenol[NIV]) was studied in 65 samples of stored and freshly harvested wheat, barley, and maize collected in Tunisia.

Methods

Mycotoxins analyses were performed by using gas chromatography for type B trichothecenes and HPLC for other mycotoxins. Obtained results were compared with the presence of mycotoxigenic species considered responsible for their synthesis by using species-specific polymerase chain reaction (PCR).

Results

Fumonisins occurred in 20.83% of wheat, 40% of barley, and 57.14% of maize samples, at levels exceeding European limits and suggesting a risk in Tunisian cereals, especially maize. Zearalenone, DON, NIV, and T-2+HT-2 toxins were detected at lower values in only wheat and barley samples. PCR protocols showed the predominance of F. verticillioides especially in maize, and occurrence of F. equiseti and F. graminearum in wheat and barley, and F. proliferatum in only two maize samples. A very consistent correlation was found between the detection of F. verticillioides and the contamination by fumonisins, as well as between the presence of F. graminearum and the contamination by zearalenone, DON, and NIV in the analyzed cereals.

Conclusions

Consequently, the detection of Fusarium species with the current PCR assays strategy in wheat, barley, and maize grains may be considered predictive of their potential mycotoxin risk in these matrices.

Highlights

This work is the first to report information on the occurrence of fumonisins, trichothecene, and ZEN, together with their potentially producing Fusarium species in wheat, barley, and maize in Tunisia. The high level of fumonisins in cereals, especially maize, stresses the importance of the control and the regularization of these mycotoxins for food safety.

A Novel Magnetic Molecular Imprinted Polymer for Selective Extraction of Zearalenone from Cereal Flours before Liquid Chromatography-Tandem Mass Spectrometry Determination

Zearalenone (ZEN) is a nonsteroidal estrogenic mycotoxin produced by various Fusarium species and commonly occurring in corn and other cereals. Even though its acute toxicity is low, still the estrogenic activity of ZEN and metabolites is a matter of concern. In this work, a new magnetic molecularly imprinted polymer (mMIP) for the selective extraction of ZEN from cereal flours is presented. The mMIP was synthesized previously using quercetin as dummy template, and here we wanted to test its applicability to complex food samples. Analyte determination was carried out by high-performance liquid chromatography coupled to tandem mass spectrometry. The selectivity of the mMIP and the main validation method parameters were assessed. In particular, even in samples as complex as cereals, matrix effect was negligible. Although the mMIP showed cross-selectivity towards both ZEN-related and quercetin-related compounds, nonetheless ZEN recovery was > 95% for the two lower spiking levels, and the quantification limit was 0.14 ng g⁻¹, i.e., ca. 500 times lower than the maximum limit fixed for most cereals by European law. Therefore, the material, also in comparison with a commercial sorbent, appears suitable for the application in food analysis, also to isolate ZEN at trace levels.

Contamination of barley seeds with Fusarium species and their toxins in Spain: an integrated approach

Fusarium is a globally distributed fungal genus that includes different species pathogenic to cereals among others crops. Some of these Fusarium species can also produce toxic compounds towards animals and humans. In this work, the presence of the most important Fusarium toxins was determined in barley seeds from Spain, sampled according to European Union requirements. The results obtained were compared with the presence of mycotoxigenic species considered responsible for their synthesis by using species-specific polymerase chain reaction protocols. Fumonisins B(1) and B(2), zearalenone, trichothecenes type A (T-2 and HT-2) and trichothecenes type B (deoxynivalenol and nivalenol) were analysed by using high-performance liquid chromatography. Deoxynivalenol and zearalenone were detected in 72% and 38% of the barley samples, respectively, at levels below European Union limits in all cases. However, the co-occurrence of both toxins in 34% of the samples suggested that synergistic activity of these two mycotoxins should be evaluated. Nivalenol and HT-2/T-2 were detected at low levels in 17% and 10% of the samples, respectively. Fumonisins occurred in 34% of the samples at levels up to 300 µg/kg. This suggested that they might represent a risk in Spanish barley, and to our knowledge, this is the first report on the presence of fumonisins in barley in this country. The species-specific polymerase chain reaction assays to detect mycotoxin-producing Fusarium species showed a very consistent correlation between F. verticillioides detection and fumonisin contamination as well as F. graminearum presence and zearalenone, deoxynivalenol and nivalenol contamination in barley samples. The approach used in this study provided information of mycotoxin contamination of barley together with the identification of the fungal species responsible for their production. Detection of the species with the current polymerase chain reaction assay strategy may be considered predictive of the potential mycotoxin risk in this matrix.

Deoxynivalenol and zearalenone in Fusarium-contaminated wheat in Mexico City

Fusarium spp. invasion causes head blight, a destructive disease in the world's main wheat-growing areas, and deoxynivalenol (DON) and zearalenone (ZEA) contamination in cereal-based products. No data are available on the relationship between Fusarium spp. on commercial wheat samples in Mexico City and the presence of mycotoxins. A total of 30 wheat samples were subject to a PCR method involving genes of the trichothecene and zearalenone biosynthesis pathways to detect the presence of Fusarium. Detection and quantification of DON and ZEA was performed using liquid chromatography coupled to UV detection. PCR indicated the presence of the Tri5 and PKS4 genes in 16.7 and 23.3% of samples, respectively. DON and ZEA contamination was found in 51.2 and 71.4% of samples, respectively, where a positive amplification was obtained. This work presents up-to-date information on mycotoxin contamination in Mexico, where improved contamination/exposure data and firm control/monitoring measures are needed.

Transformation of zearalenone to zearalenone-sulfate by Aspergillus spp

The primary goal of this research was to assess the biotransformation of zearalenone (ZEA), an oestrogenic mycotoxin, into ZEA-sulfate by some Aspergillus section Nigri isolates. A. niger isolates were shown to be able to convert ZEA after 72 h of incubation at different ZEA concentrations (5 to 150 µg/ml). The product formula corresponding to ZEA-sulfate was determined by accurate mass measurement. This conjugate was shown to be less oestrogenic than ZEA using a MCF-7 proliferation assay. This study demonstrated that A. niger has the ability to transform ZEA over a broad range of ZEA concentrations (5 to 150 µg/ml) and that sulfonation could lead to a less toxic compound. These results are significant as little is known about the ability of fungi, and especially A. niger, to detoxify ZEA by sulfonation. This study could lead to a way of detoxifying feed naturally contaminated with mycotoxins.

An overview of conventional and emerging analytical methods for the determination of mycotoxins

Mycotoxins are a group of compounds produced by various fungi and excreted into the matrices on which they grow, often food intended for human consumption or animal feed. The high toxicity and carcinogenicity of these compounds and their ability to cause various pathological conditions has led to widespread screening of foods and feeds potentially polluted with them. Maximum permissible levels in different matrices have also been established for some toxins. As these are quite low, analytical methods for determination of mycotoxins have to be both sensitive and specific. In addition, an appropriate sample preparation and pre-concentration method is needed to isolate analytes from rather complicated samples. In this article, an overview of methods for analysis and sample preparation published in the last ten years is given for the most often encountered mycotoxins in different samples, mainly in food. Special emphasis is on liquid chromatography with fluorescence and mass spectrometric detection, while in the field of sample preparation various solid-phase extraction approaches are discussed. However, an overview of other analytical and sample preparation methods less often used is also given. Finally, different matrices where mycotoxins have to be determined are discussed with the emphasis on their specific characteristics important for the analysis (human food and beverages, animal feed, biological samples, environmental samples). Various issues important for accurate qualitative and quantitative analyses are critically discussed: sampling and choice of representative sample, sample preparation and possible bias associated with it, specificity of the analytical method and critical evaluation of results.

Molecular imprinted polymers as synthetic receptors for the analysis of myco- and phyco-toxins

Continuous exposure to low doses of myco- and phyco-toxins poses severe risks to human health. Contemporary analytical methods have the sensitivity required for contamination detection and quantification, but direct application of these methods on real samples can be rarely performed because of matrix complexity. Thus, selective analytical methods, relying on intelligent functional materials are needed. Recent years have seen the increasing use of molecular imprinted polymers in contaminant analysis because these materials seem to be particularly suitable for applications where analyte selectivity is essential. In this review, several applications of molecular imprinted polymers in myco- and phyco-toxin contamination analysis will be discussed.

Variability and characterization of mycotoxin-producing Fusarium spp isolates by PCR-RFLP analysis of the IGS-rDNA region

In the present report, a total of 75 Fusarium spp isolates (35 of the Gibberella fujikuroi species complex, 26 of F. oxysporum, 7 of F. graminearum, 5 of F. culmorum, 1 of F. cerealis, and 1 of F. poae) from different hosts were characterized morphologically, physiologically and genetically. Morphological characterization was performed according to macroscopic and microscopic aspects. Physiological characterization was based on their ability to produce fumonisin B1 (FB1), fumonisin B2 (FB2), zearalenone (ZEA) and type B trichothecenes (deoxynivalenol, nivalenol and 3-acetyldeoxynivalenol). FB1, FB2, and ZEA were determined by liquid chromatography and trichothecenes by gas chromatography. Molecular characterization of isolates was carried out using an optimized and simple method for isolation of DNA from filamentous fungi and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) of the intergenic spacer region (IGS) of the rDNA. The results indicated that G. fujikuroi complex isolates can be divided into low and high fumonisin producers. The haplotypes obtained with HhaI, EcoRI, AluI, PstI and XhoI enzymes provided very characteristic groupings of G. fujikuroi isolates as a function of host type and fumonisin producing capacity. F. graminearum, F. culmorum and F. cerealis isolates were high ZEA and type B trichothecene producers, while F. oxysporum and the G. fujikuroi complex isolates did not show this ability. The haplotypes obtained with CfoI, AluI, HapII, XhoI, EcoRI and PstI enzymes permitted to discern these five Fusarium species and G. fujikuroi complex isolates but the restriction patterns of the IGS region did not show any relationship with the geographic origin of isolates.

Molecularly imprinted polymers applied to the clean-up of zearalenone and α-zearalenol from cereal and swine feed sample extracts

A molecularly imprinted polymer prepared using 1-allylpiperazine (1-ALPP) as the functional monomer, trimethyltrimethacrylate (TRIM) as the crosslinker and the zearalenone (ZON)-mimicking template cyclododecanyl-2,4-dihydroxybenzoate (CDHB) has been applied to the clean-up and preconcentration of this mycotoxin (zearalenone) and a related metabolite, alpha-zearalenol (alpha-ZOL), from cereal and swine feed sample extracts. The extraction of ZON and alpha-ZOL from the food samples was accomplished using pressurized liquid extraction (PLE) with MeOH/ACN (50:50, v/v) as the extraction solvent, at 50 degrees C and 1500 psi. The extracted samples were cleaned up and preconcentrated through the MIP cartridge and analyzed using HPLC with fluorescence detection (lambda (exc)=271/ lambda (em)=452 nm). The stationary phase was a polar endcapped C18 column, and ACN/MeOH/water 10/55/35 (v/v/v, 15 mM ammonium acetate) at a flow rate of 1.0 mL min(-1) was used as the mobile phase. The method was applied to the analysis of ZON and alpha-ZOL in wheat, corn, barley, rye, rice and swine feed samples fortified with 50, 100 and 400 ng g(-1) of both mycotoxins, and it gave recoveries of between 85 and 97% (RSD 2.1-6.7%, n=3) and 87-97% (RSD 2.3-5.6%, n=3) for alpha-ZOL and ZON, respectively. The method was validated using a corn reference material for ZON.

Characterization of Fusarium spp. isolates by PCR-RFLP analysis of the intergenic spacer region of the rRNA gene (rDNA)

In the present study, 44 Fusarium spp. isolates (5 Fusarium culmorum, 7 Fusarium graminearum, 1 Fusarium cerealis, 1 Fusarium poae, 26 Fusarium oxysporum, and 4 Gibberella fujikuroi species complex) were characterized morphologically, physiologically and genetically. All except one (Dutch Collection: CBS 620.72) were isolated from different hosts grown in various Spanish localizations. Morphological characterization was made according to macroscopic and microscopic aspects. Physiological characterization was based on their ability to produce zearalenone (ZEA) and type B trichothecenes (deoxynivalenol, nivalenol and 3-acetyldeoxynivalenol). ZEA was determined by liquid chromatography and trichothecenes by gas chromatography. Confirmation was carried out by liquid chromatography-ion trap-mass spectrometry (ZEA) or gas chromatography-mass spectrometry (trichothecenes). Molecular characterization of isolates was performed using an optimized, simple and low-cost method for isolation of DNA from filamentous fungi and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) of the intergenic spacer region (IGS) of the rRNA gene (rDNA). The results indicate that F. graminearum, F. culmorum and F. cerealis isolates were high ZEA and type B trichothecene producers, the F. poae isolate produced very low level of nivalenol while F. oxysporum and the G. fujikuroi complex isolates did not show this ability. Restriction patterns of the IGS region did not show any relationship with the host, geographic origin of the isolate and mycotoxin-producing capacity. However, the haplotypes obtained with six restriction enzymes (CfoI, AluI, HapII, XhoI, EcoRI and PstI) permitted to discern the six assayed Fusarium species. Therefore, this is a rapid and suitable methodology that allows closely related strains to group and to estimate the genetic relationships between the groups.

Fumonisin B1, fumonisin B2, zearalenone and ochratoxin A contamination of maize in Croatia

Mycotoxins are products of moulds that frequently contaminate maize. In this study the presence of mycotoxins fumonisin B1 (FB1), fumonisin B2 (FB2), zearalenone (ZEA) and ochratoxin A (OTA) was determined in 49 maize grain samples collected in autumn 2002. The most frequent finding was that of FB1(100%), followed by ZEA (84%) and OTA (39%), while FB2 was found only in three samples. The co-occurrence of two and three mycotoxins was found in 55 and 37% of samples, respectively. The concentrations (mean +/- SD) of FB1, ZEA and OTA in positive samples were 459.8 +/- 310.7, 3.84 +/- 6.68 and 1.47 +/- 0.38 microg kg(-1), respectively, and the concentrations of FB2 in three positive samples were 68.4, 109.2 and 3084.0 microg kg(-1). Although such low concentrations of mycotoxins are not a significant source of exposure in countries with a European diet, a few samples with extreme values indicate that thorough control is needed.

Occurrence of mycotoxin in Farro samples from southern Italy

The occurrence of nine mycotoxins and of contamination by pre- and postharvest fungal pathogens of cereals was investigated in samples of stored Triticum monococcum L., Triticum dicoccon Schrank (emmer), and Triticum spelta L. (spelt). In Italy, all three species are collectively referred to as farro. The samples examined were harvested in summer 2000 from eight different sites in southern Italy. Conventional fluorimetric and diode array-based high-performance liquid chromatography (HPLC) analyses and HPLC-mass spectrometry analyses were used to identify fumonisin B1 in five samples (up to 70.00 microg/ kg), ochratoxin A in seven samples (up to 4.07 microg/kg), and beauvericin in three samples (up to 4.44 mg/kg). Enniatin B was detected in one sample (30.00 microg/kg), but no zearalenone or fusaproliferin was found. Deoxynivalenol and aflatoxins were not evaluated. The potentially mycotoxigenic fungal species detected were Alternaria alternata, Fusarium proliferatum, Fusarium tricinctum, Penicillium verrucosum, and Penicillium chrysogenum. This is the first report of the natural occurrence of mycotoxins in farro samples.

Determination of zearalenone from wheat and corn by pressurized liquid extraction and liquid chromatography-electrospray mass spectrometry

Zearalenone (ZON) was extracted from wheat and corn by using pressurized liquid extraction (PLE) and the PLE extracts were analyzed using liquid-chromatography-mass spectrometry (LC-MS) without further clean-up procedures. A statistical design approach was applied to evaluate the influence of several extraction parameters such as temperature (40 degrees C; 80 degrees C; 120 degrees C), time (5 min; 10 min) and solvent extraction mixture [acetonitrile-water (9:1, v/v); methanol-water (8:2, v/v); methanol-acetonitrile (1:1, v/v)] on fortified cereals. The results showed a strong influence of the solvent composition on recovery of ZON. Quantification of the analytes was performed by LC-MS analysis of the raw extract using matrix-matched standard curves. The method performance was tested in the selected conditions (80 degrees C; 5 min; two cycles; methanol-acetonitrile) on samples which had been previously used for an international proficiency test. Compared to the assigned value, the recovered ZON was 118% [relative standard deviation (RSD)=5.2%, n=3)] and 107% (RSD=2.2%, n=3) in wheat and corn, respectively. Therefore, PLE can be used for ZON extraction, achieving good performances and allowing for an automated handling of the sample extraction step. Successively, the influence of temperature and number of cycles was investigated on naturally contaminated corn. From these results it could be concluded that fortified experiments perfectly mimicked naturally contaminated samples.