Spectroscopic characterization and photoinduced processes of 4-oxoquinoline derivatives

Derivatives of 1,4-dihydro-4-oxoquinoline substituted at 4-pyridone or/and benzene moieties were synthesized (Q1–Q17), and characterized by UV/vis and FT-IR spectroscopy. In dimethylsulfoxide and acetonitrile solvents a significant influence of the substituent's character and position on the quinolone skeleton was observed on the absorption bands in the UVA region (315–400 nm). Electron-withdrawing substituents (nitro, cyano, acetyl or trifluoroacetyl) caused a red shift, resulting in the effective absorption of UVA light. Photoinduced generation of superoxide radical anion and singlet oxygen upon UVA irradiation was followed by EPR spectroscopy using in situ spin trapping technique; 4-hydroxy-2,2,6,6-piperidine (TMP) served for singlet oxygen (1O2) detection. An efficient generation of superoxide radical anions and singlet oxygen was observed predominantly for nitro-substituted quinolones. The effect of quinolones on proliferation of HL-60 cells was monitored, and the values of IC50 evidenced the highest inhibition in the presence of ethyl 1,4-dihydro-6-fluoro-8-nitro-4-oxoquinoline-3-carboxylate (Q17) and ethyl 1,4-dihydro-8-nitro-4-oxoquinoline-3-carboxylate (Q5).

► UV/vis and FT-IR characterization of 1,4-dihydro-4-oxoquinoline derivatives.
► Photoactivation of molecular oxygen in the presence of quinolones.
► EPR spin trapping technique confirmed photoinduced generation of O2−.
► Cytotoxic/antiproliferative effect of quinolones on the proliferation of HL-60 cells.