In vitro genotoxicity evaluation of 4-carboxyl-2,6-dinitrophenylazohydroxynaphthalenes using human lymphocytes

The genotoxicity of a new monoazo dye series, 4-carboxyl-2,6-dinitrophenylazohydroxynaphthalenes has been evaluated using human lymphocytes by alkaline comet assay. Freshly isolated human lymphocytes were exposed to the dyes (AZ-01, -02, -03 and -04) at concentrations ranging from 0 to 500 μM for 3 h at 37 °C. Appropriate negative (culture medium) and positive (100 μM methyl methane sulfonate) controls were set up alongside with the dye-treated cells. Comet assay was performed to assess the extent of DNA damage. The four dyes gave varying results with respect to the parameters of DNA damage studied. AZ-01 showed concentration-dependent DNA damage (% Tail DNA) while lower concentrations (31.25–62.5 μM) did not produce any significant difference in the tail extent moment. AZ-02, the positional isomer of AZ-01, gave non-genotoxic effects at lower concentrations for the two DNA parameters. AZ-03 and AZ-04 (possessing additional C-7 substituents) did not produce significant genotoxic effect at all concentrations relative to the negative control. Two of these monoazo dyes show the potential of being used as edible colorants. The results revealed that genotoxicity of congeneric dyes bear a direct relationship to their chemical structure.