Relationship between azo dye structure and rat hepatic azoreductase activity

Abstract The rate of reduction was determined for a variety of azo dyes using the rat hepatic azoreductase enzyme system. In decreasing order, the rates of reduction for the azo dyes expressed as nmol of arylamine product formed/min/0.25 g of liver were amaranth (33.2), azosulfamide (32.5), orange G (12.4), 1,2‐dimethyl‐4‐ p ‐(carboxyphenylazo)‐5‐hydroxybenzene (CPA) (9.27), brilliant crystal scarlet (8.00), sulfachrysoidine (7.27), and Sudan I (1.03). A comparison of the partition coefficient with its rate of reduction indicated that the water‐soluble azo dyes were reduced more rapidly than the lipid‐soluble ones. Furthermore, higher rates of reduction were observed for those dyes containing electron‐withdrawing groups on the aromatic rings.