Structure–activity relations of azafluorenone and azaanthraquinone as antimicrobial compounds

Antimicrobial activities of two azafluorenones, four 1-azaanthraquinones, five 2-azaanthraquinones, and one 2-azaquinone were tested. Several azaanthraquinones possessed broad, potent activity, while the azafluorenones demonstrated weak activity. The following structure–activity relationship was postulated: (1) activity decreased in the order 2-azaanthraquinones > 1-azaanthraquinones > azafluorenones; and (2) a hydroxyl group at the peri-carbonyl group enhanced activity. In addition, correlations among reduction potential, hydrophobic parameter, and antimicrobial activity were discussed.