Inhibitory Effect of Beer on the Clastogenicity of N-nitroso Compounds

Abstract

We investigated the effect of beer on the clastogenicity of N-nitroso compounds, such as N-methyl-N’-nitro-N-nitrosoguanidine (MNNG) and N-methyl-N-nitrosourea (MNU). To evaluate the clastogenicity and anticlastogenicity, we employed in vitro micronucleus (MN) assay in Chinese hamster V79 cells. MNNG (0.5, 1, 3, and 5 μM) or MNU (0.05, 0.1, 0.3, and 0.5 mM) lead to a dose-dependent increase in the frequency of MN cells in V79 cells. Two types of beer, Lager and Black, were tested for their anticlastogenicity, and both beer were found to reduce the frequency of MN cells induced by 5 μM MNNG or 0.3 mM MNU. Furthermore, we performed fractionation of beer components by column chromatography on cation- and anion-exchange resins, and fractions obtained were tested for their anti-clastogenicity against 5 μM MNNG. In the presence of bases fraction (53 μg/mL) or ampholytes fraction (7 μg/mL), the MN frequency significantly decreased compared to MNNG alone. These results suggest that certain base(s) and ampholyte(s), but not phenolic compounds, are responsible for the anticlastogenicity of beer.