Structural activity relationship between Salmonella-mutagenicity and nitro-orientation of nitroazaphenanthrenes

Hiroshi Tokiwa, Nobuyuki Sera, Kiyoshi Fukuhara, Hideo Utsumi, Shigeki Sasaki, Naoki Miyata

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Nitroazaphenanthrenes (NAphs) and their N-oxides (NAphOs) were synthesized as derivatives with nitrogen atoms in the 1, 4, and 9 positions of phenanthrene rings, and as nitrated derivatives substituted at the 1, 2, 3, 4, 5, 6, 7, and 8 positions of phenanthrene rings. To determine the structure activity relationship of these derivatives, all 19 isomers were bioassayed with Salmonella tester strains. NAphs substituted at the 4, 6, 7 and 8 positions were mutagenic for TA98, and 1-, 2-, and 3-N-9-AphOs, 6-N-1-AphO and 6-N-4-AphO were mutagenic for TA98 and TA100 without the S9 mix, while 5-N-1-AphO and 5-N-9-AphO were non- or weakly mutagenic. Nitrated derivatives, 6-N-4-Aph, 6-N-9-Aph, 6-N-1-AphO, and 6-N-4-AphO, were powerful mutagens for TA98 and TA100. Mutagenicity was enhanced by mutant strains producing nitroreductase, such as YG1021 and 1026, and by those producing O-acetyltransferase, such as YG1024 and 1029. Nitro derivatives substituted at positions 4 and 5 in the phenanthrene rings were perpendicular, while those at positions 2, 3, 6 and 7 were coplanar to the phenanthrene rings. NAphs substituted at the 1 and 8 positions were noncoplanar due to steric hindrance of the aromatic proton at the peri position. On the other hand, 1,5- and 1,8-dinitro-4-azaphenanthrenes showed high mutagenicity for strains TA98 and TA100 in the absence of the S9 mix, and were strongly enhanced by nitroreductase and O-acetyltransferase, over-producing mutants. Therefore, it was found that the mutagenic potency of NAphs and NAphOs was closely associated with the chemical properties and orientation of nitro substitution of aromatic rings.

Original languageEnglish
Pages (from-to)19-25
Number of pages7
JournalChemico-Biological Interactions
Issue number1
Publication statusPublished - Jul 25 2003

All Science Journal Classification (ASJC) codes

  • Toxicology


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