Mutagenic evaluation of antischistosomal drugs and their derivatives in Neurospora crassa.

The mutagenic activities of lucanthone, hycanthone, niridazole, and the indazole analogs of lucanthone (IA-3 and IA-5) or hycanthone (IA-4 and IA-6) were studied by assaying for the induction of specific locus mutations in the ad-3 region of N. crassa. The results show that lucanthone, hycanthone, and their indazole analogs (IA-3 through IA-6) are all mutagenic in N. crassa when conidia are treated with any of these compounds. On a per mole basis, hycanthone is the least toxic and mutagenic, whereas IA-3 is the most toxic and mutagenic compound among the six closely related agents. In general, compounds with a methyl group at the C-4 position are more mutagenic than compounds with a methanol group; 6-chloroindazole analogs are more mutagenic and more toxic than nonchlorinated analogs. Niridazole is not mutagenic when conidial suspensions are treated. However, the mutation frequency increased more than 50-fold when niridazole was added to the medium used to grow vegetative cultures. Thus, it appears that the mutagenic activity of this latter compound requires metabolic activation.