[Oxidation and reduction of nitroarene as environmental mutagens]

Newly synthesized dinitrobenzo[a]pyrenes and 6-aza analogues of 1- and 3-nitrobenzo[a]pyrenes showed strong mutagenic activity in Salmonella assays (TA98 and TA98NR). Nitroreduction is essential for metabolic activation of nitroarene. The structure activity relationships of mono-, di- and trinitrophenanthrene were studied. Electrochemical ease of nitroreduction and dihedral angles of nitro substituents to aromatic rings is found to be important factor to determine their mutagenic potency. Nitroarene is oxidatively metabolized to form hydroxylated and nitrosubstituted derivatives and the same oxidative products were obtained by the reaction of nitroarene with chemically generated superoxide anion radical, suggesting the participation of superoxide in metabolic oxidation of nitroarene. Catalytic activity of nitroarene as a mediator in the reductive activation of molecular oxygen was also evaluated by using potential step chronocoulometry method. The potential relevence of toxicity caused by redox cycling could be solved by using this method.