Twelve 4- and 5-nitroimidazole derivatives, including metronidazole and two of its metabolites, tinidazole, dimetridazole, and nimorazole, were tested for antitrichomonad action on Tritrichomonas foetus (KV 1 ) and Trichomonas vaginalis (ATCC 30001) for mutagenicity on a nitroreductase-positive (TA 100) and a nitroreductase-deficient (TA 100-FR 1 ) strain of Salmonella typhimurium , as well as for the reducibility of the nitro group by T. foetus homogenates. Compounds with activity <1% of that of metronidazole are regarded as inactive. All antitrichomonad compounds induce mutations and can be reduced. S. typhimurium TA 100 gave mutations under both aerobiosis and anaerobiosis; TA 100-FR 1 , however, gave mutations only under anaerobiosis. Certain compounds that are reducible, and the nonreducible derivatives, were inactive. Metronidazole and its inactive 4-nitro analogue were reduced in a four-electron process in ferredoxin- or methyl viologen-mediated reactions with the same velocity. The results underscore the role of the reduction of the nitro group in the antitrichomonad and in the mutagenic activity of nitroimidazoles.

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