Azo reduction of trypan blue to a known carcinogen by a cell-free extract of a human intestinal anaerobe

Azo Dyes and Their Metabolites: Does the Discharge of the Azo Dye into Water Bodies Represent Human and Ecological Risks?

“…Although original Trypan Blue is not mutagenic, it was reduced by the cell-free extract of an intestinal anaerobe, Fusobacterium sp.2, to a mutagenic product, O-toluidine (3,3'-dimethylbenzidine) (Hartman et al, 1978;. In addition to Trypan Blue, Benzopurpurine 4B and Chlorazol Violet N were also shown to be Ames-positive frame-shift mutagens, but only in the presence of metabolizing systems capable of effecting azo reduction.…”

“…In addition to Trypan Blue, Benzopurpurine 4B and Chlorazol Violet N were also shown to be Ames-positive frame-shift mutagens, but only in the presence of metabolizing systems capable of effecting azo reduction. The activity of these dyes may therefore be attributed to the benzidine metabolite, O-toluidine, which is generated because these amines are themselves indirect frame-shift agents (Hartman, et al, 1978;Matsushima et al, 1978). As mentioned above, the benzidine produced after the reduction of some dyes can induce bladder cancer in humans and tumors in some experimental animals (Combes & Haveland-Smith, 1982;Chung, 1983).…”

“…Reductive cleavage of the azo linkages is probably the most toxicologically important metabolic reaction of azo compounds. This reaction can be catalyzed by mammalian enzymes, especially in the liver (Walker, 1970;Kennelly et al, 1982) or by intestinal (Chung et al, 1978;Hartman et al, 1978) or skin bacteria such as Staphylococcus aureus (De France, 1986;Platzek et al, 1999;Golka et al, 2004). Azo compounds can reach the intestine directly after oral ingestion or via the bile after parenteral administration.…”

Binding of benzidine, N-acetylbenzidine, N, N'-diacetylbenzidine and Direct Blue 6 to rat liver DNA.

“…It has been suggested that the carcinogenicity of this and similar dyes results from reductive cleavage of the diazo bonds with consequent release of free BZ (10,(21)(22)(23). Such reduction can occur as a result of action by gut microflora (22) or possibly by mammalian liver enzymes (24,25). Covalent binding of DBU6 to rat liver DNA occurred in animals dosed with [ring-3H]DBU6 either by gavage or by IP injection.…”

Rapid Ultrasound Assisted Reduction of Azo Dyes for Screening Banned Aromatic Amines

“…In some cases, the azo chromophore may undergo reductive cleavage, releasing mutagenic or carcinogenic aromatic amines into the environment. These aromatic amines create acute and chronic diseases in humans [1,2], other terrestrial [3][4][5][6][7] and aquatic living organisms [8,9]. Azo bond stability and the type of aromatic amines present in a dye play a decisive part in the acceptance of a dyed product.…”