PubMed · 4666191
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F B Coon, F J Baur, L R Symmes. 1972. International aflatoxin check sample program: 1971 study.. https://pubmed.ncbi.nlm.nih.gov/4666191/
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Aflatoxin (AF) contamination poses a severe global threat to food and medicinal material safety, yet existing research focuses on terminal AF metabolites while neglecting residual biosynthetic precursors, leading to potential underestimation of contamination risks. In this study, a UPLC-MS/MS method was established for the simultaneous quantification of six AFs and their five precursors in lotus seeds, with optimization of mass spectrum parameters, chromatographic separation conditions, and sample pretreatment. Method validation confirmed linearity (R2 > 0.99), LODs (0.03-0.36 μg/kg), and recoveries (76.53%-120.0%, RSD < 15%). Analysis of 41 natural lotus seed samples revealed a 63.4% AF contamination rate, dominated by B-group AFs, while O-methylsterigmatocystin (OMST) and versicolorin hemiacetal (VOH) were identified as the primary co-residual precursors with co-occurrence rates ≥ 50%. Notably, AFM1 was predominantly detected in natural samples with AFB1 concentrations exceeding 100 μg/kg. Artificial inoculation experiments further demonstrated that sterilization and sealing conditions modulated AF biosynthesis in lotus seeds, with non-sterilized and non-sealed groups showing delayed fungal metabolism and lower toxin accumulation. A significant linear correlation was observed between AFM1 and AFB1 levels (r = 0.94) in infected samples, demonstrating their accumulation levels are coupled with fungal overall metabolic flux. Given the high co-occurrence rate of OMST/VOH with AFB1 in natural samples, their individual and combined toxicities require in-depth investigation. This work deciphers matrix-specific AF dynamics in lotus seeds, supporting regulatory standard refinement (e.g., precursor inclusion) and targeted control (e.g., time-sensitive drying after harvest). Further studies will focus on exploring the molecular mechanisms of substrate-dependent AF synthesis.
Twenty-five varieties of dates (Phoenix dactylifera) were examined at different maturation stages for total microbial counts, aflatoxins and aflatoxigenic Aspergillus sp. and lactic acid bacteria. The samples were examined as fresh and under simulated storage condition of high humidity. Microbial counts were high at the first stage of maturation (Kimri) and increased sharply at the second stage (Rutab), then decrease significantly at the final dried stage of maturation (Tamr). Aflatoxins were detected in 12% of the samples although aflatoxigenic Aspergillus were detected in 40% of the varieties examined, all at Kimri stage only. Lactic acid bacteria were present only at the Rutab stage in some varieties including all varieties in which aflatoxins or aflatoxigenic Aspergillus were detected. No aflatoxins or aflatoxigenic Aspergillus were detected at the final edible stage of maturation.
The kinetics of reduction of AFB(1) to AFB(2) and AFG(1) to AFG(2) by lactic acid has been investigated in dilute aqueous acidic solutions (pH 3.35-4.50) as a function of the concentrations of lactic acid, AFB(1), AFG(1) and hydrogen ion at 37 degrees C. The rate of the reaction was found to be first order with respect to the concentrations of lactic acid and aflatoxins and independent on hydrogen ion concentration. The experimental results are interpreted in terms of mechanisms involving an initial formation of transient oxonium intermediate, which tends to polarize the olefinic (C=C) carbon, which in turn causes the hydride abstraction from alpha-carbon atom of lactic acid in rate determining step. The proposed mechanisms involve an overall transfer of two protons and two electrons from lactic acid to AFB(1) and AFG(1) to give the corresponding reduced less toxic products AFB(2) and AFG(2) and the oxidised product pyruvic acid.