This result agrees with the study carried out by Osugi et al. (2009) and Ferraz et al. (2010), who demonstrated the mutagenic potential of the original dye. This result can be explained by the chemical structure of each dye, because a relevant property of environmental genotoxic mutagens is related to the high electrophilic character of the molecule or its derivative ( Osugi et al., 2009). This characteristic raises the possibility of a reaction with the

nucleophilic groups of DNA, leading to adduct generation. If this genotoxic effect is not reverted, it can induce a permanent mutation in the DNA, and this mutation could be detected by the Salmonella assay ( Pinto and Felzenszwalb, 2003 and Osugi et al., 2009). McCann and coworkers (1975) tested 61 aromatic amines and azo dyes using the Salmonella/microsome XL184 concentration mutagenicity test and observed a 90% correlation between carcinogenicity and mutagenicity ( McCann et al., 1975 and Chung, 1983). A necessary prerequisite for carcinogenicity may be the transformation of azo dyes by intestinal bacteria. In the gut, the metabolites of the azo dyes may then be reabsorbed from the digestive tract, and so

act adversely with the body tissue to originate tumors ( Chung, 1983). The MLA system was also used to evaluate the mutagenicity of the original dye DR1 and of the products obtained SB203580 order after biotransformation processes. MLA allows for differentiation of the large and small colonies. It is believed that small colonies are induced by chromosomal damage and large colonies by gene mutations (Hozier et al., 1981, Moore et al., 1985 and Jäger et al., 2004).

Accordingly it would be expected that Ames-positive samples should be characterized by an induction of large colonies in MLA (Jäger et al., 2004). However this was not observed in the present study: both the dye DR1 and its oxidation and reduction products were negative in the MLA, with a greater number of small as compared to large colonies. However Clements (2000) observed that colony size did not necessarily predict whether a chemical compound much was a mutagenic or clastogenic agent causing chromosomal breaks. According to Jäger et al. (2004), who carried out the MLA with nine textile dye products that showed positive results in the Ames test, only 60% of these induced genotoxic effects in the MLA (i.e. only six of the nine were positive in the MLA). Therefore there was no clear correlation between mutations in the Salmonella/microsome test and the induction of large colonies in the MLA ( Jäger et al., 2004). In conclusion, the azo dye Disperse Red 1 can be metabolized by hepatic enzymes generating mutagenic compounds such as nitrobenzene, which can contribute to the observed effect.