Simultaneous determination of ochratoxin A and cyclopiazonic, mycophenolic, and tenuazonic acids in cornflakes by solid-phase microextraction coupled to high-performance liquid chromatography

One-Pot Preparation of Mixed-Mode Reversed-Phase Anion-Exchange Silica Sorbent and its Application in the Detection of Cyclopiazonic Acid in Feeds and Agricultural Products

A novel co-bonded octyl and pyridine silica (OPS) sorbent was prepared and applied for the solid phase extraction (SPE) of cyclopiazonic acid (CPA, a type of mycotoxin) in feed and agricultural products for the first time. A simple mixed-ligand one-pot reaction strategy was employed for OPS sorbent preparation. Nitrogen adsorption-desorption measurements, elemental analysis (EI), thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR) analysis demonstrated the successful immobilization of octyl and quaternary ammonium groups onto the surface of silica gel. The large specific surface area, high-density functional groups, and mixed-mode anion-exchange characteristics of these silica particles made them the ideal material for the efficient extraction of CPA. Additionally, the OPS sorbents displayed excellent batch-to-batch reproducibility, satisfactory reusability, and low cost. The SPE parameters were optimized to explore the ionic and hydrophobic interactions between CPA and the functional groups, and the ultra-high performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UPLC-MS/MS) parameters were optimized to obtain a desirable extraction efficiency and high sensitivity to CPA. Meanwhile, the OPS sorbent presented a satisfactory extraction selectivity and low matrix effect. Under the optimized conditions, our developed CPA detection method was used to determine CPA level in rice, wheat flour, corn flour, peanut, and feed samples, exhibiting a lower detection limit, better linearity, higher sensitivity, and satisfactory extraction recovery rate than previously reported methods. Therefore, our method can be preferentially used as a method for the detection of CPA in agricultural products and feeds.

Untargeted metabolomic analyses support the main phylogenetic groups of the common plant-associated Alternaria fungi isolated from grapevine (Vitis vinifera)

Alternaria, a cosmopolitan fungal genus is a dominant member of the grapevine (Vitis vinifera) microbiome. Several Alternaria species are known to produce a variety of secondary metabolites, which are particularly relevant to plant protection and food safety in field crops. According to previous findings, the majority of Alternaria species inhabiting grapevine belong to Alternaria sect. Alternaria. However, the phylogenetic diversity and secondary metabolite production of the distinct Alternaria species has remained unclear. In this study, our aim was to examine the genetic and metabolic diversity of endophytic Alternaria isolates associated with the above-ground tissues of the grapevine. Altogether, 270 Alternaria isolates were collected from asymptomatic leaves and grape clusters of different grapevine varieties in the Eger wine region of Hungary. After analyses of the nuclear ribosomal DNA internal transcribed spacer (ITS) and RNA polymerase second largest subunit (rpb2) sequences, 170 isolates were chosen for further analyses. Sequences of the Alternaria major allergen gene (Alt a 1), endopolygalacturonase (endoPG), OPA10-2, and KOG1058 were also included in the phylogenetic analyses. Identification of secondary metabolites and metabolite profiling of the isolates were performed using high-performance liquid chromatography (HPLC)-high-resolution tandem mass spectrometry (HR-MS/MS). The multilocus phylogeny results revealed two distinct groups in grapevine, namely A. alternata and the A. arborescens species complex (AASC). Eight main metabolites were identified in all collected Alternaria isolates, regardless of their affiliation to the species and lineages. Multivariate analyses of untargeted metabolites found no clear separations; however, a partial least squares-discriminant analysis model was able to successfully discriminate between the metabolic datasets from isolates belonging to the AASC and A. alternata. By conducting univariate analysis based on the discriminant ability of the metabolites, we also identified several features exhibiting large and significant variation between A. alternata and the AASC. The separation of these groups may suggest functional differences, which may also play a role in the functioning of the plant microbiome.

Diversity of Mycotoxins and Other Secondary Metabolites Recovered from Blood Oranges Infected by Colletotrichum, Alternaria, and Penicillium Species

This study identified secondary metabolites produced by Alternaria alternata, Colletotrichum gloeosporioides, and Penicillium digitatum in fruits of two blood orange cultivars before harvest. Analysis was performed by UHPLC-Q-TOF-MS. Three types of fruits were selected, asymptomatic, symptomatic showing necrotic lesions caused by hail, and mummified. Extracts from peel and juice were analyzed separately. Penicillium digitatum was the prevalent species recovered from mummified and hail-injured fruits. Among 47 secondary metabolites identified, 16, 18, and 13 were of A. alternata, C. gloeosporioides, and P. digitatum, respectively. Consistently with isolations, indicating the presence of these fungi also in asymptomatic fruits, the metabolic profiles of the peel of hail-injured and asymptomatic fruits did not differ substantially. Major differences were found in the profiles of juice from hail-injured and mummified fruits, such as a significant higher presence of 5,4-dihydroxy-3,7,8-trimethoxy-6C-methylflavone and Atrovenetin, particularly in the juice of mummified fruits of the Tarocco Lempso cultivar. Moreover, the mycotoxins patulin and Rubratoxin B were detected exclusively in mummified fruits. Patulin was detected in both the juice and peel, with a higher relative abundance in the juice, while Rubratoxin B was detected only in the juice. These findings provide basic information for evaluating and preventing the risk of contamination by mycotoxins in the citrus fresh fruit supply chain and juice industry.

Homogeneous immunoassay for cyclopiazonic acid based upon mimotopes and upconversion-resonance energy transfer

Strains of Penicillium spp. are used for fungi-ripened cheeses and Aspergillus spp. routinely contaminate maize and other crops. Some of these strains can produce toxic secondary metabolites (mycotoxins), including the neurotoxin α-cyclopiazonic acid (CPA). In this work, we developed a homogeneous upconversion-resonance energy transfer (UC-RET) immunoassay for the detection of CPA using a novel epitope mimicking peptide, or mimotope, selected by phage display. CPA-specific antibody was used to isolate mimotopes from a cyclic 7-mer peptide library in consecutive selection rounds. Enrichment of antibody binding phages was achieved, and the analysis of individual phage clones revealed four different mimotope peptide sequences. The mimotope sequence, ACNWWDLTLC, performed best in phage-based immunoassays, surface plasmon resonance binding analyses, and UC-RET-based immunoassays. To develop a homogeneous assay, upconversion nanoparticles (UCNP, type NaYF₄:Yb³⁺, Er³⁺) were used as energy donors and coated with streptavidin to anchor the synthetic biotinylated mimotope. Alexa Fluor 555, used as an energy acceptor, was conjugated to the anti-CPA antibody fragment. The homogeneous single-step immunoassay could detect CPA in just 5 min and enabled a limit of detection (LOD) of 30 pg mL^-1 (1.5 μg kg^-1) and an IC₅₀ value of 0.36 ng mL^-1. No significant cross-reactivity was observed with other co-produced mycotoxins. Finally, we applied the novel method for the detection of CPA in spiked maize samples using high-performance liquid chromatography coupled to a diode array detector (HPLC-DAD) as a reference method.

'Kodo poisoning': cause, science and management

Many mycotoxigenic fungi infect the food crops and affect the quality of the produce due to production of mycotoxins. Kodo millet is one of the important minor millets cultivated in India, mostly confined to marginal lands and tribal regions but has high yield potential under good management. The grains are nutritious and have anti-oxidant properties besides having many medicinal properties. However, the consumption is often hindered by the condition called 'kodo poisoning' resulting from fungal contamination producing cyclopiazonic acid, a toxic fungal secondary metabolite. An attempt has been made here to review the limited information available on kodo poisoning, its causes and effects, and proposed management practices by which the contamination can be checked. Further research efforts are essential for identifying sources of natural resistance to fungal metabolite, induction of host resistance through antimicrobial compounds or microbial antagonism to the pathogens to achieve cleaner grains from this crop even under high humid and rainy conditions. By effective adoption of both pre- and post-harvest management the kodo millet grains can be made safe for human consumption and can be popularized as a nutritious grain.

Comparison of Flow Injection-MS/MS and LC-MS/MS for the Determination of Ochratoxin A

Two methods for measuring ochratoxin A in corn, oat, and grape juice were developed and compared. Flow injection (FI) and on-line liquid chromatography (LC) performances were evaluated separately, with both methods using a triple quadrupole tandem mass spectrometer (MS/MS) for quantitation. Samples were fortified with ¹³C uniformly labeled ochratoxin A as the internal standard (¹³C-IS) and prepared by dilution and filtration, followed by FI- and LC-MS/MS analysis. For the LC-MS/MS method, which had a 10 min run time/sample, recoveries of ochratoxin A fortified at 1, 5, 20, and 100 ppb in corn, oat, red grape juice, and white grape juice ranged from 100% to 117% with RSDs < 9%. The analysis time of the FI-MS/MS method was <60 s/sample, however, the method could not detect ochratoxin A at the lowest fortification concentration, 1 ppb, in all tested matrix sources. At 5, 20, and 100 ppb, recoveries by FI-MS/MS ranged from 79 to 117% with RSDs < 15%. The FI-MS/MS method also had ~5× higher solvent and matrix-dependent instrument detection limits (0.12–0.35 ppb) compared to the LC-MS/MS method (0.02–0.06 ppb). In the analysis of incurred corn and oat samples, both methods generated comparable results within ±20% of reference values, however, the FI-MS/MS method failed to determine ochratoxin A in two incurred wheat flour samples due to co-eluted interferences due to the lack of chromatographic separation.

Discovery of potential multi-target-directed ligands by targeting host-specific SARS-CoV-2 structurally conserved main protease

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has resulted in the current COVID-19 pandemic. Worldwide this disease has infected over 2.5 million individuals with a mortality rate ranging from 5 to 10%. There are several efforts going on in the drug discovery to control the SARS-CoV-2 viral infection. The main protease (MPro) plays a critical role in viral replication and maturation, thus can serve as the primary drug target. To understand the structural evolution of MPro, we have performed phylogenetic and Sequence Similarity Network analysis, that depicted divergence of Coronaviridae MPro in five clusters specific to viral hosts. This clustering was corroborated with the comparison of MPro structures. Furthermore, it has been observed that backbone and binding site conformations are conserved despite variation in some of the residues. These attributes can be exploited to repurpose available viral protease inhibitors against SARS-CoV-2 MPro. In agreement with this, we performed screening of ∼7100 molecules including active ingredients present in the Ayurvedic anti-tussive medicines, anti-viral phytochemicals and synthetic anti-virals against SARS-CoV-2 MPro as the primary target. We identified several natural molecules like δ-viniferin, myricitrin, taiwanhomoflavone A, lactucopicrin 15-oxalate, nympholide A, afzelin, biorobin, hesperidin and phyllaemblicin B that strongly binds to SARS-CoV-2 MPro. Intrestingly, these molecules also showed strong binding with other potential targets of SARS-CoV-2 infection like viral receptor human angiotensin-converting enzyme 2 (hACE-2) and RNA dependent RNA polymerase (RdRp). We anticipate that our approach for identification of multi-target-directed ligand will provide new avenues for drug discovery against SARS-CoV-2 infection.Communicated by Ramaswamy H. Sarma.

Mycotoxin Identification and In Silico Toxicity Assessment Prediction in Atlantic Salmon

The present study aimed to identify mycotoxins in edible tissues of Atlantic salmon (Salmo salar) using liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS). After using a non-targeted screening approach and a home-made spectral library, 233 mycotoxins were analyzed. Moreover, the occurrence of mycotoxins in fish filets was evaluated, and their potential toxicity was predicted by in silico methods. According to the obtained results, forty mycotoxins were identified in analyzed salmon samples, the predominant mycotoxins being enniatins (also rugulosin and 17 ophiobolins), commonly found in cereals and their by-products. Thus, mycotoxin carry-over can occur from feed to organs and edible tissues of cultivated fish. Moreover, the toxicity of detected mycotoxins was predicted by the in silico webserver ProTox-II, highlighting that special attention must be paid to some less reported mycotoxins due to their toxic predicted properties.

The Complex Essential Oils Highly Control the Toxigenic Fungal Microbiome and Major Mycotoxins During Storage of Maize

The contamination of maize with fungi and subsequent mycotoxins is a pivotal and long-standing safety concern in the maize industry. In this study, the inhibitory effects of the complex essential oils (cinnamaldehyde, citral, eugenol, and menthol, 3:3:2:2, v/v) on fungal growth and mycotoxins production in stored maize were evaluated using traditional plate counting, internal transcribed spacer 2 (ITS2) sequencing and liquid chromatography-tandem mass spectrometry. Complex essential oils (0.02%) significantly (p < 0.05) reduced the total fungi counts and the content of aflatoxin B₁, zearalenone, and deoxynivalenol in stored maize during 12 months of storage, and were more effective than propionic acid (0.2%). The fungal diversity of the control group was the highest with 113 operational taxonomic units. During storage of maize kernels, Aspergillus, Fusarium, Wallemia, Sarocladium, and Penicillium were main genera. At 0-6 months, the fungal diversity was high and Fusarium was predominant genus. However, at 7-11 months, the fungal diversity was low and Aspergillus was predominant genus. During the later stages of storage, the prevalence of Aspergillus in maize treated with essential oils was significantly lower than (p < 0.05) that observed in the propionic acid treated and control samples. The results of this study suggest that the complex essential oils may be employed successfully to control toxigenic fungi and subsequent contamination with mycotoxins in maize.

Cyclopiazonic acid: 50th anniversary of its discovery

In 1968, the mycotoxin cyclopiazonic acid (CPA) was first discovered and characterised as a chemical substance. Within the following five decades, much has been learned from the results of CPA research. CPA is produced by several Penicillium species (P. griseofulvum, P. camemberti, P. commune, P. dipodomyicola) and Aspergillus species (A. flavus, A. oryzae and A. tamarii). It is widespread on naturally contaminated agricultural raw materials. CPA has been reported to occur in food commodities (e.g. oilseeds, nuts, cereals, dried figs, milk, cheese and meat products) and to possess toxicological significance. CPA is also frequently detected in peanuts and maize; the presence of CPA and aflatoxins in maize and peanuts contaminated with A. flavus suggests that synergism may occur. CPA is toxic to several animal species, such as rats, pigs, guinea pigs, poultry and dogs. After ingesting CPA-contaminated feeds, test animals display severe gastrointestinal upsets and neurological disorders. Organs affected include the liver, kidney, heart, and digestive tract, which show degenerative changes and necrosis. Biologically, CPA is a specific inhibitor of sarco(endo)plasmic reticulum Ca2+-ATPase. Data from toxicological evaluation of aflatoxins and CPA in broiler chickens demonstrate that both aflatoxins and CPA alone and the aflatoxin-CPA combination can adversely affect broiler health. The effects of aflatoxins and CPA combination were additive in most cases.

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

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

Multi-Mycotoxin Analysis in Durum Wheat Pasta by Liquid Chromatography Coupled to Quadrupole Orbitrap Mass Spectrometry

A simple and rapid multi-mycotoxin method for the determination of 17 mycotoxins simultaneously is described in the present survey on durum and soft wheat pasta samples. Mycotoxins included in the study were those mainly reported in cereal samples: ochratoxin-A (OTA), aflatoxin B₁ (AFB₁), zearalenone (ZON), deoxynivalenol (DON), 3-and 15-acetyl-deoxynivalenol (3-AcDON and 15-AcDON), nivalenol (NIV), neosolaniol (NEO), fusarenon-X, (FUS-X), T-2 toxin (T-2) and HT-2 toxin (HT-2), fumonisin B₁ and B₂ (FB₁ and FB₂), and four emerging mycotoxins: three enniatins (ENA, ENA₁, and ENB), and beauvericin (BEA). Twenty-nine samples were analyzed to provide an overview on mycotoxin presence: 27 samples of durum wheat pasta, and two samples of baby food. Analytical results concluded that trichothecenes showed the highest incidence, mainly DON, NIV, and HT-2 toxin, followed by ZON and ENB, while NEO, FUS-X, OTA, AFB₁, and FUM were not detected in any sample. The highest contents corresponded to ENB and ranged from 91.15 µg/kg to 710.90 µg/kg.

Determination of Ochratoxin A in Wheat and Maize by Solid Bar Microextraction with Liquid Chromatography and Fluorescence Detection

Solid bar microextraction (SBME), followed by liquid chromatography with fluorescence detection (HPLC-FLD), for the quantification of ochratoxin A in wheat and maize was developed. Ground wheat and maize grains were extracted with acetonitrile-water-acetic acid (79:20:1, v/v/v), followed by defatting with cyclohexane, and subjected to SBME-LC-FLD analysis. SBME devices were constructed by packing 2 mg sorbent (C18) into porous polypropylene micro-tubes (2.5 cm length, 600 μm i.d., and 0.2 μm pore size). SBME devices were conditioned with methanol and placed into 5 mL stirred sample solutions for 70 min. After extraction, OTA was desorbed into 200 μL of methanol for 15 min, the solution was removed in vacuum, the residue was dissolved in 50 μL of methanol-water (1:1, v/v) and ochratoxin A content was determined by HPLC-FLD. Under optimized extraction conditions, the limit of detection of 0.9 μg·kg⁻¹ and 2.5 μg·kg⁻¹ and the precision of 3.4% and 5.0% over a concentration range of 1 to 100 μg·kg⁻¹ in wheat and maize flour, respectively, were obtained.

Durum wheat in conventional and organic farming: yield amount and pasta quality in Southern Italy

Five durum wheat cultivars were grown in a Mediterranean area (Southern Italy) under conventional and organic farming with the aim to evaluate agronomic, technological, sensory, and sanitary quality of grains and pasta. The cultivar Matt produced the best pasta quality under conventional cropping system, while the quality parameters evaluated were unsatisfactory under organic farming. The cultivar Saragolla showed the best yield amount and pasta quality in all the experimental conditions, thus proving to be the cultivar more adapt to organic farming. In all the tested experimental conditions, nivalenol (NIV) and deoxynivalenol (DON) occurrence was very low and the other mycotoxins evaluated were completely absent. These data confirm the low risk of mycotoxin contamination in the Mediterranean climate conditions. Finally, it has been possible to produce high-quality pasta in Southern Italy from durum wheat grown both in conventional and organic farming.

Biosensors for secondary metabolites, two case studies: ochratoxin A and microcystin

Secondary metabolites are chemical compounds that are not directly involved in the normal growth, development or reproduction of organisms. Due to the toxicity shown by some of these compounds, their presence can represent a threat to human health. Reliable detection systems able to control their presence are required, as a tool to ensure public health. This chapter offers an overview of different techniques developed for the detection of toxic secondary metabolites, taking ochratoxin A and microcystins as two representative examples. While ochratoxin A is a mycotoxin produced by several species of fungi, microcystins are cyanotoxins released by certain strains of cyanobacteria. Biosensor-based strategies are emphasized as powerful screening tools.

Comparison of off- and in-line solid-phase extraction for enhancing sensitivity in capillary electrophoresis using ochratoxin as a model compound

This paper proposes and compares two approaches based on off- and in-line solid-phase extraction (SPE), intended to enhance sensitivity in capillary electrophoresis with ultraviolet detection (CE-UV) using as a model the determination of ochratoxin A (OA) in river water samples. In the off-line SPE mode, the reversed-phase sorbent (octadecilsylane, C(18)) selectively retains the target analyte (OA) and allows large volumes of the sample (70 mL) to be introduced and subsequently eluted in a small volume (0.1 mL) of an appropriate solution. In the in-line SPE mode, a custom-made microcartridge is inserted near the inlet of the capillary, which is filled with the same C(18) sorbent. This solid phase selectively retains OA present in a sample volume as low as approximately 640 microL for subsequent elution with ca. 135 nL of an appropriate eluent. The limit of detection (LOD) obtained with the in-line SPE method was 1 ng L(-1), which is 3 orders of magnitude lower than that obtained with CE-UV and roughly 1 order lower than that provided by the off-line SPE-CE-UV method.

Photolysis of cyclopiazonic acid to fluorescent products

Cyclopiazonic acid (CPA) is a mycotoxin produced by some of the same species of fungi that produce the more widely known aflatoxins. As a consequence it has been found previously that CPA and the aflatoxins may co-occur in commodities under certain conditions. CPA, which is a substituted indole, has a chromophore with absorptions in the ultraviolet (UV) region (223 nm, 278 nm). Quantification of CPA is commonly accomplished by liquid chromatographic separation followed by detection of one of the UV absorbances. CPA has not previously been described as fluorescent, and it likely is not. However, herein we report that, following exposure to high intensity UV light in a photochemical reactor, fluorescent products of CPA are produced. In methanol or aqueous acetonitrile these products have an excitation maximum of 372 nm and an emission maximum of 462 nm. Upon exposure to UV light for extended periods a decrease in the absorbance of CPA at 223 nm and 278 nm and a concomitant increase in fluorescence was observed. CPA and aflatoxin B1 were separated by reverse-phase liquid chromatography and the eluant was subjected to post-column photolysis, which allowed the fluorescence detection of both toxins. The ability to photolyse CPA and detect this toxin by fluorescence may open up new avenues for determination of this mycotoxin alone or together with the aflatoxins.

LC-MS/MS multi-method for mycotoxins after single extraction, with validation data for peanut, pistachio, wheat, maize, cornflakes, raisins and figs

Mycotoxin analysis is usually carried out by high performance liquid chromatography after immunoaffinity column cleanup or in enzyme-linked immunosorbent assay tests. These methods normally involve determination of single compounds only. EU legislation already exists for the aflatoxins, ochratoxin A and patulin in food, and legislation will come into force for deoxynivalenol, zearalenone and the fumonisins in 2007. To enforce the various legal limits, it would be preferable to determine all mycotoxins by routine analysis in different types of matrices in one single extract. This would also be advantageous for HACCP control purposes. For this reason, a multi-method was developed with which 33 mycotoxins in various products could be analysed simultaneously. The mycotoxins were extracted with an acetonitrile/water mixture, diluted with water and then directly injected into a LC-MS/MS system. The mycotoxins were separated by reversed-phase HPLC and detected using an electrospray ionisation interface (ESI) and tandem MS, using MRM in the positive ion mode, to increase specificity for quality control. The following mycotoxins could be analysed in a single 30-min run: Aflatoxins B1, B2, G1 and G2, ochratoxin A, deoxynivalenol, zearalenone, T-2 toxin, HT-2 toxin, alpha-zearalenol, alpha-zearalanol, beta-zearalanol, sterigmatocystin, cyclopiazonic acid, penicillic acid, fumonisins B1, B2 and B3, diacetoxyscirpenol, 3- and 15-acetyl-deoxynivalenol, zearalanone, ergotamin, ergocornin, ergocristin, alpha-ergocryptin, citrinin, roquefortin C, fusarenone X, nivalenol, mycophenolic acid, alternariol and alternariol monomethyl ether. The limit of quantification for the aflatoxins and ochratoxin A was 1.0 microg kg(-1) and for deoxynivalenol 50 microg kg(-1). The quantification limits for the other mycotoxins were in the range 10-200 microg kg(-1). The matrix effect and validation data are presented for between 13 and 24 mycotoxins in peanuts, pistachios, wheat, maize, cornflakes, raisins and figs. The method has been compared with the official EU method for the determination of aflatoxins in food and relevant FAPAS rounds. The multi-mycotoxin method has been proven by the detection of more than one mycotoxin in maize, buckwheat, figs and nuts. The LC-MS/MS technique has also been applied to baby food, which is subject to lower limits for aflatoxin B1 and ochratoxin A, ergot alkaloids in naturally contaminated rye and freeze-dried silage samples.

Enzyme immunoassay for mycophenolic acid in milk and cheese

Mycophenolic acid (MPA) was reacted with N-hydroxysuccinimide and conjugated to keyhole limpet hemocyanin (KLH), and to horseradish peroxidase (HRP), respectively. The MPA-KLH was used to produce anti-MPA antiserum in rabbits. A competitive direct enzyme immunoassay (EIA) for MPA was established with anti-MPA antiserum and MPA-HRP conjugate. The mean 50% inhibition and detection limit of MPA standard curves (n = 103) were 197 +/- 67 and 81 +/- 48 pg/mL, respectively. The EIA was specific for MPA and its synthetic 2-morpholinoethyl ester, mycophenolate mofetil (91% relative cross-reactivity). Raw bulk milk and pasteurized milk, with and without beta-glucuronidase pretreatment, were analyzed by EIA. No MPA was found in milk, at a detection limit of 100 pg/mL (recovery 58-66% at 0.125-2 ng/mL). Blue-veined cheese from the German market (n = 53) was analyzed by EIA, and the detection limit was at 0.5 ng/g (recovery 68-79% at 5-100 ng/g). All but two cheeses contained MPA, although mostly (66%) at levels of <10 ng/g. MPA at 400-1200 ng/g was found in Roquefort cheeses. Highest levels (4-11 microg/g) were found in a German soft cheese preparation. MPA levels in mycelium-rich parts of cheese were 3 times higher than in mycelium-free parts.

Alternaria mycotoxins: an overview of chemical characterization, producers, toxicity, analysis and occurrence in foodstuffs

Microfungi of the genus Alternaria are ubiquitous pathogens and saprophytes. Many species of the genus Alternaria commonly cause spoilage of various food crops in the field or post-harvest decay. Due to their growth even at low temperatures, they are also responsible for spoilage of these commodities during refrigerated transport and storage. Several Alternaria species are known producers of toxic secondary metabolites - Alternaria mycotoxins. A. alternata produces a number of mycotoxins, including alternariol, alternariol monomethyl ether, altenuene, altertoxins I, II, III, tenuazonic acid and other less toxic metabolites. Tenuazonic acid is toxic to several animal species, e.g. mice, chicken, dogs. Alternariol, alternariol monomethyl ether, altenuene and altertoxin I are not very acutely toxic. There are several reports on the mutagenicity and genotoxicity of alternariol, and alternariol monomethyl ether. Alternariol has been identified as a topoisomerase I and II poison which might contribute to the impairment of DNA integrity in human colon carcinoma cells. Analytical methods to determine Alternaria toxins are largely based on procedures, involving cleanup by solvent partitioning or solid phase extraction, followed by chromatographic separation techniques, in combination with ultraviolet, fluorescence, electrochemical and mass spectroscopic detection. A large number of Alternaria metabolites has been reported to occur naturally in food commodities (e.g. fruit, vegetables, cereals and oil plants). Alternariol, alternariol monomethyl ether and tenuazonic acid were frequently detected in apples, apple products, mandarins, olives, pepper, red pepper, tomatoes, tomato products, oilseed rape meal, sunflower seeds, sorghum, wheat and edible oils. Alternariol and alternariol monomethyl ether were detected in citrus fruit, Japanese pears, prune nectar, raspberries, red currant, carrots, barley and oats. Alternariol monomethyl ether and tenuazonic acid were detected in melon. Natural occurrence of alternariol has been reported in apple juice, cranberry juice, grape juice, prune nectar, raspberry juice, red wine and lentils.

Solid phase microextraction of macrolide, trimethoprim, and sulfonamide antibiotics in wastewaters

In this work, we optimize a solid phase microextraction (SPME) method for the simultaneous collection of antibiotics (sulfonamides, macrolides, and trimethoprim) present in wastewaters. The performance of the SPME method is compared to a solid phase extraction (SPE) method. Analytes in both cases were quantified by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) with electrospray ionization. The advantages offered by SPME in this application are: decreased sample volume requirements, ease of sample processing and extraction, decreased cost, and most importantly, elimination of electrospray matrix effects. Despite having higher limits of quantification (16-1380 ng/L in influent and 35-260 ng/L in effluent), nearly all of the compounds found to be present in Edmonton Gold Bar wastewater by SPE were measurable by SPME (i.e., sulfamethoxazole, trimethoprim, erythromycin, and clarithromycin), with values similar to those obtained using the former method. Limits of quantification for the SPE method for the measured compounds were 4.7-15 ng/L and 0.86-6.1 ng/L for influent and effluent, respectively.

Determination of Ochratoxin A in wine at sub ng/mL levels by solid-phase microextraction coupled to liquid chromatography with fluorescence detection

Solid-phase microextraction (SPME), using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber, interfaced with liquid chromatography-fluorescence detection (LC-FD) has been applied to the determination of Ochratoxin A (OTA) in wine samples. Compared to the most widely adopted extraction/clean-up procedure based on immunoaffinity columns (IAC), the solventless extraction is simpler and cost-effective, requiring the simple immersion of the fiber in diluted wine samples. Furthermore, a fast LC separation is achieved under isocratic conditions. The linear range investigated in wine was 0.25-8 ng/mL; at fortification levels of 0.5 and 2 ng/mL, within-day intra-laboratory precision (repeatability) values, expressed as RSD%, were 5.9 and 5.1, respectively, whereas between days (n = 4) precision was 8.5 and 7.1%, respectively. The limit of detection (LOD) at a signal-to-noise (S/N) ratio of 3 was 0.07 ng/mL; the limit of quantification (LOQ) calculated at S/N = 10 was 0.22 ng/mL, well below the European regulatory level of 2 ng/mL. The potential of the method has been demonstrated by the analysis of a number of different wine samples.

Ochratoxin a determination in beer by solid-phase microextraction coupled to liquid chromatography with fluorescence detection: a fast and sensitive method for assessment of noncompliance to legal limits

A solid-phase microextraction-liquid chromatography-fluorescence detection (SPME-LC-FD) method for the determination of ochratoxin A (OTA) in commercial beer samples was developed for the first time using a 60 microm thick poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber. The procedure required a very simple sample pretreatment, an isocratic elution, and provides a selective extraction. All of the factors influencing fiber adsorption (extraction time, temperature, pH, and salt addition) and desorption of the analyte (desorption and injection time and desorption solvent mixture composition) have been investigated. The linear range investigated in beer was 0.03-2 ng/mL; within-day and between-days relative standard deviation in beer were 4.3 and 5.9%, respectively. The limit of quantification in spiked beer was 53 pg mL(-)(1), well below all European regulatory levels.

Polypyrrole modified stainless steel frits for on-line micro solid phase extraction of ochratoxin A

Polypyrrole (PPy) was electrochemically synthesized on stainless steel frits as a sorbent for the micro solid phase extraction (muSPE) of ochratoxin A (OTA). Using 20 microl of standard solution under a fast flow rate of 0.5 ml/min, 80% recovery of OTA was achieved in the concentration range from 0.1-10 pg/mul. This good recovery was achieved within a short residence time of 1.2 s. A binding capacity of 1 ng OTA was estimated for each PPy-modified frit, or 2 ng OTA for two frits in series. The bound OTA could be pulsed eluted (PE) with 20 microl of 1% triethylamine in acetonitrile. On-line coupling of this PPy-on-a-frit and PE technique to high performance liquid chromatography (HPLC) was straightforward. On-line muSPE-PE-HPLC results clearly demonstrated the capability of PPy-on-a-frit to bind OTA in the presence of red wine, beer, and orange juice components.

Simultaneous immunoaffinity column cleanup and HPLC analysis of aflatoxins and ochratoxin A in Spanish bee pollen

Bee pollen is a major substrate for mycotoxins growth when no prompt and adequate drying is performed by the beekeeper after collection by bees. Regulatory limits for aflatoxins and ochratoxin A are currently in force in the European Union for a rising list of foodstuffs, but not for this. An immunoaffinity column cleanup process has been applied prior to the analysis of aflatoxins B(1), B(2), G(1), and G(2) and ochratoxin A (OTA). Optimization of the HPLC conditions has involved both a gradient elution and a wavelength program for the separation and fluorimetric quantitation of all five mycotoxins at their maximum excitation and emission values of wavelength in a single run. The higher limit of detection (mug/kg) was 0.49 for OTA and 0.20 for aflatoxin B(1). Repeatability (RSDr) at the lower limit tested ranged from 9.85% for OTA to 6.23% for aflatoxin G(2), and recoveries also at the lower spiked level were 73% for OTA and 81% for aflatoxin B(1). None of the 20 samples assayed showed quantifiable values for the five mycotoxins.