Detection of Ochratoxin A in wheat samples in different regions of India

Genotoxic effects of the ochratoxin A (OTA), its main metabolite (OTα) per se and in combination with fumonisin B1 in HepG2 cells and human lymphocytes

Ochratoxin A (OTA) and fumonisin B₁ (FB₁) are mycotoxins distributed in a wide variety of foods for human or animal consumption and are classified as possible carcinogens for humans. This study aimed to evaluate the cytotoxic, cytostatic and genotoxic effects of OTA and its main metabolite, ochratoxin α (OTα), FB₁ and three combinations of OTA and FB₁ at moderate and environmental doses. Cell viability was evaluated through MTT assay and the trypan blue exclusion method. The cytostatic and genotoxic effects were evaluated through the cytokinesis-block micronucleus assay. The results showed synergistic time- and concentration-dependent cytotoxic effects of one of the combinations of OTA and FB₁. In contrast, significant differences were observed in the micronuclei (MN) frequency from OTA, OTα and coexposure of OTA + FB₁. Some of these combinations increased the frequency of nuclear buds, nucleoplasmic bridges, donut-shaped nuclei, necrotic and apoptotic cells and MN in mononucleated cells. In conclusion, OTA and its main metabolite OTα, as well as the co-exposure of OTA and FB₁, cause stable DNA damage at environmentally relevant concentrations, which was greater in metabolically competent cells. More studies are needed to understand the chemical interactions that occur due to the joint presence of mycotoxins, which occurs commonly.

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.

Occurrence and preventive strategies to control mycotoxins in cereal-based food

Mycotoxins contamination in cereal-based food is ubiquitous according to systematic review of the scientific documentation of worldwide mycotoxin contamination in cereal and their products between 2008 and 2018, thus representing food safety issue especially in developing tropical countries. Food processing plays a vital role to prevent mycotoxin contamination in food. Therefore, it is with great urgency to develop strategies to inhibit fungi growth and mycotoxin production during food processing. This review begins by discussing physicochemical properties of five most common mycotoxins (aflatoxins, fumonisins, ochratoxins, deoxynivalenol, and zearalenone) found in cereal grains, regulation for mycotoxins in food, and their potential negative impact on human health. The fate of mycotoxins during major cereal-based food processing including milling, breadmaking, extrusion, malting, and brewing was then summarized. In the end, traditional mitigation strategies including physical and chemical and potential application of biocontrol agent and essential oil nanoemulsions that can be applied during food processing were discussed. It indicated that no single method is currently available to completely prevent mycotoxin contamination in cereal foods.

Determination of aflatoxins and ochratoxin A in wheat from different regions of Turkey by HPLC with fluorescence detection

This study examines the occurrence of aflatoxins (AFS) and ochratoxin A (OTA) in bread and durum wheat samples. A total of 141 samples were collected from eleven different regions of Turkey. An analytical method based on liquid extraction, immunoaffinity column (IAC) clean-up followed by high performance liquid chromatography (HPLC) was used for the determination of AFs and OTA levels. As a result, AFs and OTA were detected in 2% and 9.2% of wheat samples at concentrations varying from 0.21 to 0.44 µg kg−1 and from 0.1 to 3.2 µg kg−1, respectively. Aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) were found positive in samples ranging between 0.21–0.35 µg kg−1 and 0.094 µg kg−1, respectively. However, none of the samples contained aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2). The study also recommended that contamination levels in wheat and wheat-based products should be routinely monitored in greater sample numbers to insure food safety.

An HPLC-FLD method to measure ochratoxin A in teff (Eragrostis tef) and wheat (Triticum spp.) destined for the local Ethiopian market

Wheat (Triticum spp.) is among the top cereal grains in terms of production and consumption in Ethiopia. It can be typically infected with ochratoxin A (OTA) producing fungi both in the field and during storage resulting in animal and human health problems. While there is a wealth of information on the presence of OTA in wheat, the incidence of OTA in teff (Eragrostis tef), a cereal grain produced and consumed traditionally in Ethiopia and Eretria, remains insufficient. The purpose of this study was to develop and validate a high performance liquid chromatography (HPLC) method for OTA analysis in teff and wheat flours and to analyse the characteristic distribution of OTA in teff and wheat flours samples destined for local consumption in Ethiopia using a survey-approach. Wheat and teff flour samples were examined for OTA contamination. OTA was detected in 20% of the teff flour samples and in 50% of the wheat flour samples with median contamination levels of 1.04 μg/kg (limit of detection (LOD) = 0.78 μg/kg) and 7.23 μg/kg (LOD = 0.58 μg/kg) respectively. The validated method for OTA detection and quantification in teff and wheat using HPLC meets the European Union performance criteria for OTA (EC 2006/401) and the Eurachem Guideline validation requirements. An insight into the occurrence of OTA in teff is very valuable because the cereal might provide a lower OTA risk alternative for wheat in Ethiopia. In addition, for the world market, an insight into the occurrence of OTA in teff is important in the light of an increasing interest in teff as a gluten free cereal.

Cetylpyridinium chloride functionalized silica-coated magnetite microspheres for the solid-phase extraction and pre-concentration of ochratoxin A from environmental water samples with high-performance liquid chromatographic analysis

A new method based on cetylpyridinium chloride coated ferroferric oxide/silica magnetic microspheres as an efficient solid-phase adsorbent was developed for the extraction and enrichment of ochratoxin A. The determination of ochratoxin A was obtained by high-performance liquid chromatography with fluorescence detection. In the presence of cetylpyridinium chloride, the adsorption capacity of ferroferric oxide/silica microspheres was 5.95 mg/g for ochratoxin A. The experimental parameters were optimized, including the amounts of ferroferric oxide/silica microspheres (20 mg) and cetylpyridinium chloride (0.18 mL, 0.5 mg/mL), pH value of media (9), ultrasonic time (5 min), elution solvent and volume [2(1 + 1) mL (washed twice, 1 mL each time) 1% acetic acid acetonitrile]. Under optimal experiment conditions, ochratoxin A had good linearity in the range of 2.5-250.0 ng/L in water samples with correlation coefficient of the calibration curve 0.9995. The limit of detection for ochratoxin A was 0.83 ng/L, and the recoveries were 89.8-96.8% with the relative standard deviation of 1.5-3.5% in environmental water samples. Furthermore, ferroferric oxide/silica microspheres show excellent reusability during extraction procedures for no less than six times.

Highly sensitive colorimetric aptasensor for ochratoxin A detection based on enzyme-encapsulated liposome

A simple, low-cost, and sensitive liposome-based colorimetric aptasensor has been developed to detect ochratoxin A (OTA). Specifically, a dumbbell-shaped probe was designed, including magnetic beads (MBs), double-stranded DNA (dsDNA), and enzyme-encapsulated liposome. The dsDNA formed by the hybridization between OTA aptamer and its complementary probe. And the dsDNA was used to contact the MBs and the enzyme-encapsulated liposome. In the presence of OTA, the aptamer preferred to combine with OTA to form G-quadruplex, resulting in the release of the detection probe and the enzyme-encapsulated liposome. Each liposome contained a large amount of HRP. Thus, when the liposome was lysed by adding the mixed solution of 3,3',5,5'-tetramethylbenzidine (TMB) and H₂O₂, a large number of HRP were released. HRP could catalyze the H₂O₂-mediated oxidation of TMB and hence resulted in the color change from colorless to blue with the OTA concentration varying, and this variation can be observed by naked eyes easily. The result showed that the absorption intensity at 652 nm enhanced with the increase of OTA concentration ranging from 0.05 to 2.0 ng mL^-1, and the limit of detection was calculated to be 0.023 ng mL^-1 (S/N = 3). The developed colorimetric aptasensor has been applied to detect OTA concentration in corn samples with satisfied results.

Mycotoxin Cocktail in the Samples of Oilseed Cake from Early Maturing Cotton Varieties Associated with Cattle Feeding Problems

Cottonseed cake in South East Asia has been associated with health issues in ruminants in the recent years. The present study was carried out to investigate the health issues associated with cottonseed cake feeding in dairy animals in Pakistan. All the cake samples were confirmed to be from early maturing cotton varieties (maturing prior to or during Monsoon). A survey of the resource persons indicated that the feeding problems with cottonseed cake appeared after 4-5 months of post-production storage. All the cake samples had heavy bacterial counts, and contaminated with over a dozen different fungal genera. Screening for toxins revealed co-contamination with toxic levels of nearly a dozen mycotoxins including aflatoxin B1 + B2 (556 to 5574 ppb), ochratoxin A + B (47 to 2335 ppb), cyclopiazonic acid (1090 to 6706 ppb), equisetin (2226 to 12672 ppb), rubrofusarin (81 to 1125), tenuazonic acid (549 to 9882 ppb), 3-nitropropionic acid (111 to 1032 ppb), and citrinin (29 to 359 ppb). Two buffalo calves in a diagnostic feed trial also showed signs of complex toxicity. These results indicate that inappropriate processing and storage of the cake, in the typical conditions of the subcontinent, could be the main contributory factors regarding the low quality of cottonseed cake.

VHH phage-based competitive real-time immuno-polymerase chain reaction for ultrasensitive detection of ochratoxin A in cereal

Phage display-mediated immuno-polymerase chain reaction (PD-IPCR) is an ultrasensitive detection technology that combines the advantages of immuno-PCR and phage display. The phage particle, which displayed antibody fragments including single-chain fragment variable (scFv), variable domain of heavy-chain antibodies (VHH), and antigen-binding fragment (Fab) on the surface can be directly used in IPCR, supplying both the detection antibody and deoxyribonucleic acid (DNA) template. In this work, we used ochratoxin A (OTA) as a model system to study the capacity of PD-IPCR in the detection of toxic small molecular weight compounds, especially mycotoxins. An alpaca-derived VHH library was constructed and subjected to four cycles of panning. In total, 16 clones with four unique sequences were selected by competitive binding with OTA. The clone VHH-28 resulted in the lowest 50% inhibitory concentration of 0.31 ng/mL in the phage enzyme-linked immunosorbent assay (ELISA) and was selected to develop the VHH phage-based real-time immuno-PCR (RT-IPCR). The detection limit of the VHH phage-based RT-IPCR was 3.7 pg/L, with a linear range of 0.01-1000 pg/mL. This method was compared with conventional ELISA, and validation results indicated the reliability of VHH phage-based RT-IPCR in the detection of OTA in cereal samples. This study provides a new idea for the ultrasensitive detection of mycotoxins and other toxic small molecular weight compounds.

Occurrence and molecular detection of toxigenic Aspergillus species in food grain samples from India

BACKGROUND

The aim of this study was to detect the presence of different mycotoxigenic Aspergillus species in major food grains from southern states of India, namely maize, paddy, groundnut and sorghum. A total of 200 isolates recovered from 320 grain samples from four southern states were tested for their toxin chemotypes using high-performance liquid chromatography (HPLC), high-performance thin layer chromatography (HPTLC) and polymerase chain reaction (PCR) methods. The diversity and distribution of the isolates were recorded in terms of their frequency, density, importance value index and diversity indices.

RESULTS

Among the different grain samples tested, 83% of groundnut, 69% of maize, 57% of sorghum and 29% of paddy samples had aflatoxin B1 (AFB1) levels above the allowed limit, while 82% of maize, 70% of sorghum, 42% of paddy and 17% of groundnut samples had ochratoxin A (OTA) concentrations higher than the permitted threshold (5 µg kg⁻¹).

CONCLUSION

Since the southern states of India are temperate regions, environmental factors, especially temperature and relative humidity, may be responsible for the high levels of mycotoxins present in the grains studied. Therefore there is a need to generate awareness among farmers and consumers about the possible adverse health effects of high levels of mycotoxins present in different food grains.