Analysis of aflatoxins and ochratoxin a in chilli powder using ultrahigh performance liquid chromatography with fluorescence detection and tandem mass spectrometry

Chilli powder, a popular spice, is predominantly contaminated with aflatoxins (AFs) and ochratoxin A (OTA), posing a menace to public health. As no validated method exists for the simultaneous and direct analysis of AFs and OTA in chilli powder, it was imperative to develop one to ensure their effective monitoring and promote trade. In this research, we developed and validated a multi-mycotoxin analysis method that allows the simultaneous determination of AFs (AFB₁, AFB₂, AFG₁ and AFG₂) and OTA in chilli powder with high sensitivity, accuracy and precision. The optimised sample preparation workflow started with the extraction of chilli powder (25 g) with methanol-water (100 mL, 80:20). An aliquot (3 mL) was cleaned on a multi-mycotoxin, immunoaffinity column (AFLAOCHRA PREP^®) and analysed using ultrahigh performance liquid chromatography with fluorescence (UHPLC-FLD) and tandem mass spectrometric (LC-MS/MS) detection in a single chromatographic run. The method performance was evaluated through intra- and inter-laboratory validation (ILV) studies, and also by analysing a certified reference material. A direct analysis using UHPLC-FLD (without derivatisation) provided the limits of quantification (LOQ) of 0.25 and 1 ng/g for AFs and OTA, respectively, while the LOQ for all these mycotoxins in LC-MS/MS was 0.5 ng/g. These LOQs are much lower than the maximum levels (MLs) specified by the European Commission. The recoveries of these analytes at LOQ and higher levels were above 75% (RSD_r < 12%). The ILV study demonstrated satisfactory method-reproducibility (RSD_R < 25%). The analysis of the certified reference material provided accuracies of AFs and OTA in the range of 83-101%. The analysis by UHPLC-FLD and LC-MS/MS provided very similar results. The incurred levels of B1 in market samples were estimated with a precision-RSD of < 6%. Considering its efficiency and alignment with the regulatory requirements, this method can be implemented for the routine analysis of AFs and OTA in chilli powder.

Validation of HPLC and Enzyme-Linked Immunosorbent Assay (ELISA) Techniques for Detection and Quantification of Aflatoxins in Different Food Samples

BACKGROUND

In Jordan as in other worldwide countries, mycotoxins are considered a serious national problem in food supplies. As a result, almost all nations are setting and adopting different regulations targeting the control of mycotoxins levels in the domestic food supply, including the problem of reliable sampling and analysis methods.

OBJECTIVE

It is necessary to improve and give evidence of analytical abilities of laboratories within Jordan and developing countries enabling them to monitor mycotoxins effectively in food to overcome non-tariff obstacles.

METHODS

We analyzed 40 samples from wheat, corn, dried fig and dried coffee beans for total aflatoxin content using High Pressure Liquid Chromatography (HPLC) and Enzyme Linked Immunesorbent Assay (ELISA) methods.

RESULTS

40% of samples from wheat, 60% from corn, 30% from dried fig, and 50% from dried coffee beans were found positive when speaking of total aflatoxins, with average values between 1.14 and 4.12 μg/kg. Obtained results allow considering all tested food samples as fit for human consumption if compared with the labeled regulatory limit of allowed aflatoxins in the European Union. In detail, the limit of detection and the limit of quantification for methods used in this study were significantly lower than the maximum limits established by the European Union.

HIGHLIGHTS

The procedure used in this study is suitable for detection of mycotoxins at very low concentration.

Microarray-Based Immunoassay for Parallel Quantification of Multiple Mycotoxins in Oat

Because multianalyte methods are highly desirable in order to keep analysis time and costs low, the biosensor development increasingly focuses on parallel analysis of several mycotoxins. Here, we describe an indirect competitive immunoassay on regenerable, reusable glass microchips for the parallel determination of aflatoxins, ochratoxin A, deoxynivalenol, and fumonisin B1 in oat extracts, using a fully automated flow-through device with chemiluminescence readout.

The inhibitory potential of Zataria multiflora and Syzygium aromaticum essential oil on growth and aflatoxin production by Aspergillus flavus in culture media and Iranian white cheese

Antifungal activity of essential oils (EOs) of Zataria multiflora (thyme) and Syzygium aromaticum (clove) against Aspergillus flavus growth and aflatoxin B₁ production was studied in potato dextrose agar (PDA) and potato dextrose broth (PDB), as well as in Iranian white cheese as a food model. The results showed that the inhibitory potential of EOs in the PDB medium is more than PDA medium. Clove EO on PDB medium prevented fungal growth and aflatoxin B₁ production at 300 and 100 ppm, respectively. However, the thyme EO was not able to inhibit fungal growth completely and showed the strongest inhibition effect at 400 ppm. EOs also had more inhibitory activity in laboratory culture media than the food environments. EOs in all concentrations reduced aflatoxin B₁ production and fungal growth in cheese, but only the clove EO at 150 ppm was able to prevent the fungal growth and aflatoxin B₁ production completely. Thyme EO reduced aflatoxin B₁ value to below detection threshold (2 ppb) at 10 μl. Our findings propose EOs as a natural inhibitor to control fungal contamination of foodstuffs such as Iranian white cheese.

Banana peel: an effective biosorbent for aflatoxins

This work reports the application of banana peel as a novel bioadsorbent for in vitro removal of five mycotoxins (aflatoxins (AFB1, AFB2, AFG1, AFG2) and ochratoxin A). The effect of operational parameters including initial pH, adsorbent dose, contact time and temperature were studied in batch adsorption experiments. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pHpzc) analysis were used to characterise the adsorbent material. Aflatoxins' adsorption equilibrium was achieved in 15 min, with highest adsorption at alkaline pH (6-8), while ochratoxin has not shown any significant adsorption due to surface charge repulsion. The experimental equilibrium data were tested by Langmuir, Freundlich and Hill isotherms. The Langmuir isotherm was found to be the best fitted model for aflatoxins, and the maximum monolayer coverage (Q0) was determined to be 8.4, 9.5, 0.4 and 1.1 ng mg(-1) for AFB1, AFB2, AFG1 and AFG2 respectively. Thermodynamic parameters including changes in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were determined for the four aflatoxins. Free energy change and enthalpy change demonstrated that the adsorption process was exothermic and spontaneous. Adsorption and desorption study at different pH further demonstrated that the sorption of toxins was strong enough to sustain pH changes that would be experienced in the gastrointestinal tract. This study suggests that biosorption of aflatoxins by dried banana peel may be an effective low-cost decontamination method for incorporation in animal feed diets.

A study of the interaction between rhodamine 6g and hydroxy propyl β-cyclodextrin by steady state fluorescence

The binding of rhodamine 6G and hydroxy propyl β-cyclodextrin (Hβ-CD) was investigated measuring fluorescence and absorption at pH 7.0. The solid inclusion complex of Rh6G and Hβ-CD has been studied by Ultraviolet (UV) spectroscopy, Fluorimetry, Fourier Transform Infrared (FTIR), (1)H Nuclear Magnetic Resonance ((1)HNMR) and in the Scanning Electron Microscope (SEM). Association constant K(g) and K(e) were determined by the enhancement of the fluorescence of rhodamine 6G in the presence of Hβ-CD. Fluorescence of Rh6G is generally enhanced, in complexes of Rh6G and β-Cyclodextrin in aqueous solutions. The free energy change for the ground state (ΔG(g)) and for the excited state (ΔG(e)) have also been determined. The experimental results indicated that the inclusion process is an exothermic and spontaneous.

Use of isotope-labeled aflatoxins for LC-MS/MS stable isotope dilution analysis of foods

Aflatoxins are a group of very carcinogenic mycotoxins that can be found on a wide range of food commodities including nuts, cereals, and spices. In this study, the first LC-MS/MS stable isotope dilution assay (SIDA) for the determination of aflatoxins in foods was developed. The development of this method was enabled by easily accessible isotope-labeled (deuterated) aflatoxins B2 and G2, which were synthesized by catalytic deuteration of aflatoxin B1 and G1, purified, and well-characterized by NMR and MS. All four aflatoxins of interest (B1, B2, G1, and G2) were quantified in food samples by using these two labeled internal standards. The response factors (RF) of the linear calibrations were revealed to be matrix independent for labeled aflatoxin B2/aflatoxin B2 and labeled aflatoxin G2/aflatoxin G2. For labeled aflatoxin B 2/aflatoxin B 1 and labeled aflatoxin B2/aflatoxin G1 matrix-matched calibration was performed for the model matrices almonds and wheat flour, showing significant differences of the RFs. Limits of detection (LOD) were determined by applying a statistical approach in the presence of the two model matrices, yielding 0.31 microg/kg (aflatoxin B1), 0.09 microg/kg (aflatoxin B2), 0.38 microg/kg (aflatoxin G1), and 0.32 microg/kg (aflatoxin G2) for almonds (similar LODs were obtained for wheat flour). Recovery rates were between 90 and 105% for all analytes. Coefficients of variation (CV) of 12% (aflatoxin B1), 3.6% (aflatoxin B2), 14% (aflatoxin G1), and 4.8% (aflatoxin G2) were obtained from interassay studies. For further validation, a NIST standard reference food sample was analyzed for aflatoxins B1 and B2. The method was successfully applied to determine trace levels of aflatoxins in diverse food matrices such as peanuts, nuts, grains, and spices. Aflatoxin contents in these samples ranged from about 0.5 to 6 microg/kg.

Detection of transcripts of the aflatoxin genes aflD, aflO, and aflP by reverse transcription–polymerase chain reaction allows differentiation of aflatoxin-producing and non-producing isolates of Aspergillus flavus and Aspergillus parasiticus

The aim of this study was to test the suitability of the RT-PCR (reverse transcription-polymerase chain reaction) technique to differentiate aflatoxin-producing from aflatoxin-non-producing strains of Aspergillus flavus and Aspergillus parasiticus. Total RNAs of 13 strains grown under inducing yeast extract-sucrose (YES) and non-inducing yeast extract-peptone (YEP) media, respectively, were analyzed by using specific primers based on the conserved regions of nine structural genes (aflD, aflG, aflH, aflI, aflK, aflM, aflO, aflP, and aflQ) and two regulatory genes aflS and aflR of the aflatoxin B1 biosynthetic pathway. Transcription was confirmed by the expression of the beta-tubulin gene. The expression of the majority aflatoxin biosynthetic genes including aflR and aflS of all strains varied with regard to the aflatoxin-producing ability and the growth conditions. Nonetheless, we found that the expression profile of the three genes aflD, aflO, and aflP was consistently correlated with a strain's ability to produce aflatoxins or not in YES as well as the inability to produce aflatoxins in YEP. The devised RT-PCR profiling method reflects aflatoxin concentrations ranging from 0.1 to 60 microg/ml of the culture filtrates as determined by fluorescence HPLC. The results are discussed in relation to the suitability of RT-PCR as well as cDNA-based array techniques in diagnostic laboratory settings where individual isolates are being tested for potential toxin production to identify toxigenic isolates of Aspergillus species.