Identification of biotransformation products of disperse dyes with rat liver microsomes by LC-MS/MS and theoretical studies with DNA: Structure-mutagenicity relationship using Salmonella/microsome assay

Abstract

Azo dyes are known as a group of substances with DNA damage potential that depend on the nature and number of azo groups connected to aromatic rings (benzene and naphthalene), chemical properties, e.g. solubility and reactive functional groups, which significantly affect their toxicological and ecological risks. In this paper, we used in vitro models to evaluate the metabolism of selected textile dyes: Disperse Red 73 (DR 73), Disperse Red 78 (DR 78) and Disperse Red 167 (DR 167). To evaluate the mutagenic potential of the textile dyes, the Salmonella mutagenicity assay (Ames test) with strains TA 98 and TA 100 in the presence and absence of the exogenous metabolic system (S9) was used. DR73 was considered the most mutagenic compound, inducing both replacement base pairs (TA 100) and also changing frameshift (TA 98) mutations that are reduced in the presence of the S9 mixture. Furthermore, we used rat liver microsomes in the same experimental conditions of the S9 mixture to metabolize the dyes and the resultant solutions were analyzed using a liquid chromatography coupled to a quadrupole linear ion trap mass spectrometry (LC-MS/MS) to investigate the metabolites formed by the in vitro biotransformation. Based on this experiment, we detected and identified two biotransformation products for each textile dye substrate analyzed. Furthermore, to evaluate the interaction and reactivity of these compounds with DNA, theoretical calculations were also carried out. The results showed that the chemical reaction occurred preferentially at the azo group and the nitro group, indicating that there was a reduction in these groups by the CYP P450 enzymes presented in the rat microsomal medium. Our results clearly demonstrated that the reduction of these dyes by biological systems is a great environmental concern due to increased genotoxicity for the body of living beings, especially for humans.

Influence of auxochrome group in disperse dyes bearing azo groups as chromophore center in the biotransformation and molecular docking prediction by reductase enzyme: Implications and assessment for environmental toxicity of xenobiotics

“…Thus, these results show that Disperse Red 73 possesses superior reactivity relative to the other two dyes (Table S1). This finding, in essence, brings valuable information to the fore besides being in agreement with the mutagenic effect evaluated and obtained through the use of Salmonella typhimurium (Ames test) described by Franco et al (Franco et al, 2018).…”

“…DR 78 and DR 167 exhibited low mutagenic activity in both the absence and presence of metabolic activity (P-450). Based on the above results, the Salmonella / microsome test can be used as an important tool to predict the effects of the ingestion of azo dyes dispersed on human health, clearly indicating that the dyes can be biotransformed (Franco et al, 2018).…”

Biotransformation of disperse dyes using nitroreductase immobilized on magnetic particles modified with tosyl group: Identification of products by LC-MS-MS and theoretical studies conducted with DNA

“…The dyes and their metabolites were entirely optimized at DFT level for the subsequent PM6 semi-empirical affinity calculations with B-DNA. After that, the reaction mechanism simulation was carried out through the application of the QM/MM techniques (Franco et al, 2018). This methodology has exhibited significantly good performance in the treatment of large systems with high level of theory.…”

“…The dyes that bear azo groups are chromophore, and are characterized by very low solubility in water. The presence of CN-and Clsubstituents in ortho position relative to nitro groups in the molecule interferes in the mutagenicity of these compounds (Franco et al, 2018). Salmonella/microsome assay (Franco et al, 2018) conducted on the TA 98 and TA 100 strains with and without liver microsomal fractions (S9) (Zbaida and Levine, 1990) indicated that DR 73 exhibited the highest mutagenicity among the dyes.…”

“…The interaction and reactivity of these compounds with DNA have also been evaluated by theoretical calculations; the results of these calculations indicated that DR 73, DR 78, and DR 167 may be hazardous to both human beings and the environment. The reason being that their biotransformation can produce harmful compounds, such as amines, which have been categorically disapproved by the International Agency for Research on Cancer (Franco et al, 2018;Brown and De Vito, 1993;Chung and Cerniglia, 1992).…”