The antiseptic action of compounds of the apocyanine, carbocyanine and isocyanine series

Abstract

The present work is a direct continuation of that previously communicated, and has for its object the investigation of relationships between chemical constitution and antiseptic properties of organic compounds belonging to the apocyanine, carbocyanine and isocyanine series ; the two latter classes of dyes have attained great practical importance on account of their use as photographic “ sensitisers.” The sensitisers, like many of the more potent antiseptic members of the acridine series, are quaternary alkyl salts ; as in the case of the acridine series of antiseptics also, the amino derivatives are active, and the introduction of acidic radicals into the amino groups has the effect in the one case of destroying the antiseptic properties of the compound and in the other of removing its sensitising action (Pope). Pope suggested that the photo-sensitising action may be connected with the presence of some such group as the following :— - N - C = CH -C = N - I I I / R R I a group which is also present in acriflavine as well as in the more recently investigated and highly antiseptic styryl and anil compounds. But, so far as we know, none of these sensitizers have been investigated hitherto for their antiseptic action. Antiseptic power was estimated by the same methods as those used for the acridine group, since with compounds of the present series also, the lethal action on bacteria is exerted slowly and is preceded by bacteriostatic effects. Thus the substance to be tested, in a volume not exceeding 0.1 c. c., was added to 1 c. c. of the culture medium, which consisted ( a ) of a watery solution containing 0•35 per cent, sodium chloride, and 0.7 per cent, bacteriological peptone, the hydrogen-ion concentration of the mixture being adjusted by the addition of caustic soda to yield a P H value between 7.2 and 7.8 as indicated by the usual indicators ; and ( b ) sterile ox serum, which had been previously heated for several hours at 56° C., in order to destroy normal bactericidal power, as well as accidental contaminating organisms. The organisms employed in the tests were Staphylococcus aureus and a single strain of B . coli , the inoculation dose being 0.1 c. c. of a 1 : 1000 dilution in saline of a 24 hours’ culture in peptone water.