Bacterial Reduction of Azo Compounds as a Model Reaction for the Degradation of Azo-Containing Polyurethane by the Action of Intestinal Flora

Two types of model compounds containing an azo aromatic group were synthesized, and their reduction kinetics in an anaerobic culture of intestinal flora was investigated for insight into the degradation mechanism of the azo-containing polyurethane which can be specifically degraded by the action of azo reductases which are released by intestinal floras. A water-soluble azo compound, 3,3′ -azodibenzenemethanol (ADM), was readily reduced into its hydrazo form and then to the amine form, 3-aminobenzenemethanol (ABM). The reduction rate from azo to hydrazo was much faster than that from hydrazo to amine. In the case of a water-insoluble azo compound, 3,3′-azodibenzenemethanol bis(N-phenylcarbamate) (ADM-PC), in which the hydroxy groups of ADM were capped by N-phenylcarbamoyl groups, the reduction was stopped in the first step, and only the hydrazo form was produced. These data indicated that the azo-containing polyurethane which is hydrophobic in nature should be degraded by the azo-hydrazo reduction of the azo groups without the chain breakage occurring.