Genotoxicity of quinocetone, cyadox and olaquindox in vitro and in vivo.

Quinocetone (QCT) and Cyadox (CYA) are important derivative of heterocyclic N-oxide quinoxaline (QdNO), used actively as antimicrobial feed additives in China. Here, we tested and compared the genotoxic potential of QCT and CYA with olaquindox (OLA) in Ames test, HGPRT gene mutation (HGM) test in V79 cells, unscheduled DNA synthesis (UDS) assay in human peripheral lymphocytes, chromosome aberration (CA) test, and micronucleus (MN) test in mice bone marrow. OLA was found genotoxic in all 5 assays. In Ames test, QCT produced His(+) mutants at 6.9 µg/plate in Salmonella typhimurium TA 97, at 18.2 µg/plate in TA 100, TA 1535, TA 1537, and at 50 µg/plate in TA 98. CYA produced His(+) mutants at 18.2 µg/plate in TA 97, TA 1535, and at 50 µg/plate in TA 98, TA 100 and TA 1537. QCT was found positive in HGM and UDS assay at concentrations ≥10 µg/ml while negative results were reported in CA test and MN test. Collectively, we found that OLA was more genotoxic than QCT and CYA. Genotoxicity of QCT was found at higher concentration levels in Ames test, HGM and UDS assays while CYA showed weak mutagenic potential to bacterial cells in Ames test.