A comparison of the bactericidal and photobactericidal activities of aminoacridines and bis(aminoacridines).

An attempt was made to increase the activity of some antibacterial acridines in two ways: (a) via the use of bis-aminacrines (analogues of 1,6-bis-[9-acridinamino]hexane), in order to increase the potential for DNA intercalation and (b) via photoactivation, as several acridines are known to produce the cytotoxin singlet oxygen on irradiation. The bactericidal activity of the simple aminoacridines was much higher than that of the corresponding bis-acridine compounds. In addition, on low-power illumination of the compounds in liquid culture, many of the monomeric compounds exhibited marked increases in activity against both Gram-negative and Gram-positive bacteria, whereas the bis-acridines showed little or no increase.