In vitro cytotoxicity and genotoxicity induction by aflatoxin B1 (AFB1) from maize (ME) and tortillas (TE) produced by microwave nixtamalization were investigated in monkey kidney (Vero cells) using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the induction of lipid peroxidation, the oxidative damage by means of glutathione (GSH) depletion, and the Salmonella-microsomal screening system (Ames test). Our results showed that, at higher concentrations, both ME and TE extracts that contained varying amounts of aflatoxin caused a considerable decrease in Vero cell viability (up to 37%) after 4 h of exposure. Aflatoxins from ME induced greater oxidative damage by enhancing lipid peroxidation (up to 6.05 ± 0.14 μmol/mg protein) as compared to TE; however, TE also induced significant malondialdehyde formation in particular at the higher aflatoxin concentration tested (up to 2.7 ± 0.19 μmol/mg protein). The decrease in GSH level was also more pronounced in ME as compared to TE. Moreover, the Ames test results indicated that the mutagenic activity of TE was greatly reduced compared with that of ME based on his(-) → his(+) reversions in the Salmonella TA100 strain. According to these results, it is concluded that the microwave nixtamalization procedure reduced aflatoxins and their in vitro toxicity and mutagenic activity.
Practical application: In Mexico, aflatoxins are often found in maize destined for the tortilla industry; consequently, tortilla consumption invariably leads to an important intake of intact and/or modified aflatoxin molecules caused by the thermal-alkaline treatment used during production. Therefore, it is of the highest importance to check whether such intake has the potential to lead to higher risk for adverse human health effects. In view of these considerations, in vitro tests may thus be useful for predicting the potential cytotoxicity and genotoxicity of tortillas produced for human consumption using aflatoxin-contaminated maize.
Keywords: aflatoxins; cytotoxicity; genotoxicity; maize; tortillas.
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