title: Anti-mutagenic structural modification by fluorine-substitution in highly mutagenic 4-methylquinoline derivatives.
abstract: We have previously shown that fluorine-substitution at position 3 of quinoline deprived this molecule of mutagenicity, possibly due to interference with the yield of its metabolically activated form, the 1,4-hydrated 2,3-epoxide (enamine epoxide), which is directly responsible for the mutagenic modification of DNA. To further explore the possibility of a method for anti-mutagenic modification of mutagens by fluorine-substitution, 4-methylquinoline (4-MeQ), the most mutagenic form of all the quinoline derivatives examined so far, was used as a target in the present study. Five mono- and di-fluorinated derivatives of 4-MeQ, 2-fluoro-4-methylquinoline (2-F-4-MeQ), 6-F-4-MeQ, 7-F-4-MeQ, 2,6-difluoro-4-methylquinoline (2, 6-diF-4-MeQ), and 2,7-diF-4-MeQ, were subjected to analysis of their structure-mutagenicity relationships. The 2-fluorinated derivatives (2-F-4-MeQ, 2,6-diF-4-MeQ, and 2,7-diF-4-MeQ) were all non-mutagenic in the Ames test. 7-F-4-MeQ was as highly mutagenic as, and 6-F-4-MeQ was less mutagenic than non-fluorinated 4-MeQ. Metabolic studies were also conducted with 4-MeQ, 2-F-4-MeQ, 6-F-4-MeQ, and 7-F-4-MeQ, using a liver microsomal enzyme fraction prepared from the 3-methylcholanthrene-treated rat. The HPLC analytical data showed that, although the metabolic patterns (hydroxylation at 4-methyl group as a main metabolic pathway and 3-hydroxylation as a minor pathway) of these four F-MeQs were similar to one another, only the 3-hydroxy metabolite of 2-F-4-MeQ was not produced under the present experimental conditions employed. These results suggest that fluorine-substitution at position 2 of 4-MeQ inhibited the formation of the enamine epoxide in the pyridine moiety and deprived this molecule of mutagenicity as in the case of quinoline.
authors.affiliation: Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuho-ku, Nagoya, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kato
authors.forename: A
authors.initials: A
authors.lastname: Hakura
authors.forename: T
authors.initials: T
authors.lastname: Mizutani
authors.forename: K
authors.initials: K
authors.lastname: Saeki
mesh_terms: D000818:Animals; D016587:Antimutagenic Agents / Q000737:chemistry* / Q000378:metabolism; D001711:Biotransformation; D005461:Fluorine / Q000737:chemistry; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D008954:Models, Biological; D009152:Mutagenicity Tests; D009153:Mutagens / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity*; D011804:Quinolines / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013329:Structure-Activity Relationship
chemical_list: D016587:Antimutagenic Agents; D009153:Mutagens; D011804:Quinolines; D005461:Fluorine