Anti-trypanosomal activity of certain phenyldiazoamino- and phenylazoamino-phenanthridinium compounds.

Red phenyldiazoaminophenanthridinium and purple phenylazoaminophenanthridinium compounds, most of which were obtained as isomeric pairs, were tested in mice for curative and prophylactic action against Trypanosoma congolense. Several of the individual compounds showed a high degree of activity, the red isomer of each pair usually being more active therapeutically and prophylactically than the purple one, although high prophylactic effect was not always associated with high therapeutic potency. The most interesting isomeric pair was that consisting of metamidium, 7-(m-amidinophenyldiazoamino)-2-amino-10-ethyl-9-phenylphenanthridinium chloride hydrochloride (red isomer) and x-(m-amidinophenylazo)-2,7-diamino-10-ethyl-9-phenylphenanthridinium chloride hydrochloride (purple isomer). Among the individual compounds, the one with the greatest curative action was the red isomer of metamidium, now known as isometamidium. Its 10-methyl homologue was slightly less active and its p-amidino-isomer was considerably less active. The compounds with the greatest prophylactic action were 2,7-di(m-amidinophenyldiazoamino)-10-ethyl-9-phenylphenanthridinium chloride dihydrochloride trihydrate, its 10-methyl homologue, and the red m-amidino-isomers mentioned above. The only other compounds to show appreciable prophylactic action were three guanidino-substituted phenyldiazoaminophenanthridines, although they were less active than metamidium at low doses. One of these, 2-amino-10-ethyl-7-(m-guanidinophenyldiazoamino)-9-phenylphenanthridinium chloride hydrochloride, was also very active therapeutically.