Formation of a carcinogenic aromatic amine from an azo dye by human skin bacteria in vitro

Abstract

<jats:p> Azo dyes represent the major class of dyestuffs. They are metabolised to the corresponding amines by liver enzymes and the intestinal microflora following incorporation by both experimental animals and humans. For safety evaluation of the dermal exposure of consumers to azo dyes from wearing coloured textiles, a possible cleavage of azo dyes by the skin microflora should be considered since, in contrast to many dyes, aromatic amines are easily absorbed by the skin. A method for measuring the ability of human skin flora to reduce azo dyes was established. In a standard experiment, 3610<jats:sup>11</jats:sup> cells of a culture of Staphylococcus aureus wereincubatedinsyntheticsweat (pH 6.8, final volume 20 mL) at 288C for 24 h with Direct Blue 14 (C.I. 23850, DB 14). The reaction products were extracted and analysed using HPLC. The reduction product o-tolidine (3,3'-dimethylbenzidine, OT) could indeed be detected showing that the strain used was able to metabolise DB 14 to the corresponding aromatic amine. In addition to OT, two further metabolites of DB 14 were detected. Using mass spectrometry they were identified as 3,3'-dimethyl-4-amino-4'-hydroxybiphenyl and 3,3'-di methyl-4-aminobiphenyl. The ability to cleave azo dyes seems to be widely distributed among human skin bacteria, as, under these in vitro conditions, bacteria isolated from healthy human skin and human skin bacteria from strain collections also exhibited azo reductase activity. Further studies are in progress in order to include additional azo dyes and coloured textiles. At the moment, the meaning of the results with regard to consumer health cannot be finally assessed. </jats:p>

Functional role of Trp-105 of Enterococcus faecalis azoreductase (AzoA) as resolved by structural and mutational analysis

“…Many synthetic azo dyes can be converted to potentially carcinogenic aromatic amines after reduction (Platzek et al, 1999). Because of the widespread use of azo dyes, human intestinal micro-organisms are exposed to these compounds (Hanauer, 1996).…”

Synthesis of PEDOT/ZnO Photocatalyst: Validation of Photocatalytic Activity by Degradation of Azo RR45 Dye Under Solar and UV-A Irradiation

“…8, inset) which is characteristic of pure PEDOT and confirms its amorphous nature 40 . That peak appears for samples with higher concentration of polymer in composite, PEDOT/ZnO (1-3) and (1)(2)(3)(4)(5). The XRD results show that the increase in the polymer ratio in composite significantly affects the surface of ZnO photocatalyst.…”

“…Morphology of pure PEDOT polymers differ among themselves as it is observed that polymers form the aggregated particles. The size of primary particles seems to be larger for PEDOT (1)(2)(3)(4)(5) (Fig. 6c) than that of the other two samples PEDOT (1-2) (Fig.…”

Application of a Novel Micro-Cloud Point Extraction for Preconcentration and Spectrophotometric Determination of Azo Dyes

“…Environmental pollution with dyes can have dire effect on animal, plants, and human health. [4][5][6][7] One of the most important families of dyes is azo dyes that contain −N=N− bond in their structures. 8 So far azo dyes have found many applications.…”