Metabolism of benzidine and benzidine-congener based dyes by human, monkey and rat intestinal bacteria

Abstract

Summary Anaerobic bacterial suspensions isolated from human, monkey and rat feces and intestinal contents metabolized a benzidine-based azo dye, Direct Black 38, a 3,3′-dimethylbenzidine-based dye, Direct Red 2 and a 3,3′-dimethoxybenzidine-based dye, Direct Blue 15 to their respective free amines. Azo reduction of Direct Black 38, Direct Red 2 and Direct Blue 15 by anaerobic intestinal bacteria was measured spectrophotometrically. Benzidine, 3,3-dimethylbenzidine and 3,3′-dimethoxybenzidine formed from the azo dyes by intestinal bacteria were isolated and identified by gas chromatography/mass spectrometry. The results suggest that anaerobic intestinal bacteria may play a significant role in the metabolism of dyes derived from benzidine or its congeners and in the etiology of urinary bladder cancer.