Comparison of the genetic activity of 5-nitroimidazole derivatives in Escherichia coli, Neurospora crassa, Saccharomyces cerevisiae and Drosophila melanogaster.

5-nitroimidazoles, including metronidazole (compound 1) and 3 analogues (compounds 2, 3 and 4) of actual or potential chemotherapeutic use were assayed for genetic activity in test systems detecting forward and back mutations in Escherichia coli K-12/343/113, forward mutations in Neurospora crassa heterokaryon 12, mitotic gene conversion in the heteroallelic diploid yeast strain Saccharomyces cerevisiae D4 and sex-linked recessive lethals in Drosophila melanogaster. Whereas metronidazole exhibits moderate mutagenic activity in E. coli, two of the analogues, compounds 2 and 3 are strongly mutagenic even at concentrations that do not inactive the colony forming ability of the cells. The analogue compound 4 does not show any effect toward E. coli under the present experimental conditions. Similar results were obtained with N. crassa, with S. cerevisiae and with Drosophila in which compound 2 exhibits the highest effect, while compound 4 is non-mutagenic in all assays. These biological effects have been partly explained on the basis of differences in the chemical structure of the compounds.