Mutagenic activity of benzofurans and naphthofurans in the Salmonella/microsome assay: 2-nitro-7-methoxy-naphtho[2,1-b]furan (R7000), a new highly potent mutagenic agent.

A series of benzofurans and naphthofurans was examined through the Salmonella/microsome assay. (i) With one possible exception, only 2-nitro derivatives give a mutagenic response. However, it appears that the mutagenic potency depends notably on the nature and the position of the other substituents in the molecule. (ii) The mutagenic response occurs in strains TA1537, TA1538, TA98 and TA100 but not in strain TA1535. Reversion of the missense mutation of TA1535 is thus induced only in presence of the plasmid pKM101. (iii) This mutagenic response is at least partially dependent on the bacterial nitroreductase activities and is usually lower in presence of activating mixture from rat liver. (iv) One of the compounds tested, 2-nitro-7-methoxynaphtho[2,1-b]furan (R7000), may be the most potent mutagen examined so far in the Salmonella/microsome assay. It yields about 200 000 revertants/nanomole on strain TA100 in the standard plate test. The relation between structure, mutagenic potency and other biological activities of the compounds are briefly discussed.