Genotoxicity testing of extracts from aflatoxin-contaminated peanut meal, following chemical decontamination

One of the most important concerns in the decontamination of aflatoxin-cont aining feed commodities is the safety of the products for food-producing an imals and for human consumption of products derived from these animals. A n ew method, based on the use of florisil and C18 solid phase extraction colu mns, was developed for the preparation of extracts from decontaminated pean ut meal, which allowed testing with in vitro genotoxicity assays without in terference of the residual aflatoxin B-1. Recovery of degradation products in the extracts was evaluated by the use of radiolabelled [C-14]-aflatoxin B-1 (AFB(1)) added to naturally-contaminated peanut meal (3.5 mg AFB(1)/kg) . The meal was treated by a small-scale version of an industrial decontamin ation process based on ammoniation. Following decontamination, more than 90 % of the label could not be extracted from the meal. AFB(1) accounted for a bout 10% of the radiolabel present in the extractable fraction, indicating a total AFB(1) reduction of more than 99%. Decontamination of the meal by a number of other small- and industrial-scale ammonia-based processes result ed in similar efficiencies. Application of the extraction procedure resulte d in AFB(1)-rich and AFB(1)-poor fractions, the latter containing half of t he extractable decontamination products but less than 1% of the residual AF B(1). Testing in the Salmonella/microsome mutagenicity assay (TA 100, with S9-mix) of the original crude extracts and AFB(1)-rich fractions prepared f rom non-treated and decontaminated mala, showed the positive results expect ed from the AFB(1) contents as determined by HPLC analysis. Analysis and te sting of the AFB(1)-poor fractions showed that the various decontamination processes not only resulted in a successful degradation of AFB(1) but also did not produce other potent mutagenic compounds. Slight positive results o btained with these extracts were similar for the untreated and treated meal s and may be due to unknown compounds originally present in the meal. Resul ts obtained wit an unscheduled DNA synthesis (UDS) and Comet assay with rat hepatocytes supported this conclusion. Positive results obtained with the micronucleus assay, using immortalized mouse hepatocytes (GKB), did not cle arly reflect the mycotoxin levels and require further examination. It is co ncluded that newly developed extraction procedure yields highly reproducibl e fractions and hence is very suitable for examining the possible formation of less potent degradation products of aflatoxins in short-term genotoxici ty tests.