Cyclic voltammetry of phenazines and quinoxalines including mono- and di-N-oxides. Relation to structure and antimicrobial activity.

Cyclic voltammetry data were obtained for eight phenazines and phenazine-N-oxides, and eleven quinoxalines and quinoxaline-N-oxides: 1,6-phenazine-diol-5,10-dioxide (iodinin), iodinin copper complex, 6-methoxy-1-phenazinol-5,10-dioxide 1,6-dimethoxyphenazine-5-oxide, 1,6-phenazinediol, 1,6-dimethoxyphenazine, quinoxaline-1,4-dioxide, 2-methylquinoxaline-1,4-dioxide, 2,3-diphenylquinoxaline-1,4-dioxide, 2-carboxyquinoxaline-1,4-dioxide, 5-hydroxyquinoxaline-1,4-dioxide, 5-hydroxy-8-methoxyquinoxaline-1,4-dioxide, 2-methylquinoxaline, 2,3-diphenylquinoxaline, 5-hydroxyquinoxaline, 5-hydroxy-8-methoxyquinoxaline and 2-(2-quinoxalinylmethylene)hydrazine carboxylic acid methyl ester-1,4-dioxide (Carbadox). The di-N-oxides exhibit the most positive E1/2 values within each class. Reversible first wave reductions were observed for iodinin, iodinin copper complex, 1,6-dimethoxyphenazine-5-oxide, 1,6-dimethoxyphenazine, quinoxaline-1,4-dioxide, 2-methylquinoxaline-1,4-oxide and 2,3-diphenylquinoxaline-1,4-dioxide. The results are correlated with structure. Some relationships exist between reduction potential and reported antimicrobial activity. A possible mechanism of drug action is addressed.