Genotoxicity of fluoroquinolines and methylquinolines.

Quinoline in the presence of microsomal activation exhibits mutagenic activity in Salmonella typhimurium TA100 and induces unscheduled DNA synthesis (UDS) in rat hepatocytes. Structure-activity studies were performed to determine those positions on quinoline critically associated with its genotoxicity. In assays performed to determine the ability of 2-, 4-, 6- and 8-methylquinoline to induce UDS, only 4- and 8-methylquinoline produced a positive response. This represents an improved correlation for these methylquinolines with tumorigenic activity as compared to that previously observed with mutagenic activity in S. typhimurium TA100. The complete isomeric series of fluoroquinolines were evaluated as mutagens in S. typhimurium TA100 and for their potential to induce UDS in rat hepatocytes. The only isomers that did not exhibit significant mutagenic activity were 2- and 3-fluoroquinoline. Among these isomeric fluoroquinolines 5-, 6-, 7- and 8-fluoroquinoline are capable of inducing UDS. No significant effect on UDS was observed for 2-, 3- or 4-fluoroquinoline. These data indicate that positions 1-3 in quinoline are critical sites associated with its genotoxicity.