Mutagenesis Advance Access originally published online on December 14, 2006
Mutagenesis 2007 22(1):43-47; doi:10.1093/mutage/gel057
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Mutagenicity of UV-irradiated maltol in Salmonella typhimurium
1 Kureha Corporation Biomedical Research Laboratories 3-26-2, Hyakunin-cho, Shinjuku, Tokyo 169-8503, Japan 2 School of Life Science, Tokyo University of Pharmacy and Life Science 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
We investigated the photomutagenicity of maltol (3-hydroxy-2-methyl-4H-pyran-4-one) in bacterial cells. Maltol has a caramel-butterscotch odour and is used as a food additive to impart flavour to bread and cakes. Unirradiated maltol was not mutagenic up to 5 mg/plate in the Ames test. When maltol was irradiated with either UVA (a black light, 320400 nm, 230 µW/cm2) for 530 min or UVC (a germicidal lamp, 610 µW/cm2) for 3 min in sodium phosphate buffer (pH 7.4) prior to the exposure of bacterial cells, it was mutagenic to Salmonella typhimurium TA100, TA104 and TA97. Mutagenic activation of maltol by UVA-irradiation was more evident in neutral and alkaline conditions (pH 7.09.0) than in acidic conditions. On the other hand, photomutagenicity was not observed when maltol was irradiated with UVA in 100 mM NaCl solution or water. The mutagenic photoproduct was stable for at least 60 min after UVA-irradiation. However, addition of thiol compounds (cysteine or glutathione) to the UVA-irradiated maltol diminished the mutagenicity. Mutational spectrum analysis revealed that the predominant base-substitutions induced were G:C
T:A transversions and G:C
A:T transitions. An increase of 8-hydroxydeoxyguanosine formation in salmon sperm DNA exposed to maltol and UVA in vitro was detected by HPLC-ECD, but it was too small to explain the photomutagenicity. We are considering the formation of DNA adducts as the photomutagenic mechanism.
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