| Abstract
| - A series of fluoroquinolones (FQs), including enoxacin (ENX), pefloxacin (PFX), norfloxacin (NFX), itsN(4‘)-acetyl derivative (ANFX), ofloxacin (OFX), and rufloxacin (RFX) have been investigated to determinetheir potential as DNA photosensitizers via thymine cyclobutane dimer (T<>T) formation in DNA. Atfluoroquinolone concentrations and light doses insufficient to produce direct single strand breaks, ENX, PFX,and NFX were able to produce T<>T dimers in DNA, revealed by enzymatic treatment with T4 endonucleaseV. By contrast, ANFX, OFX, and RFX were inefficient in this assay. The absolute values of the tripletenergies of ENX, PFX, NFX, ANFX, OFX, and RFX were estimated by means of laser flash photolysis,using flurbiprofen, 4-biphenylcarboxylic acid, and naproxen as energy acceptors. They were found to be 273,269, 269, 265, 262, and 253 kJ/mol, respectively. Other triplet excited state properties of the FQs, includingquantum yields and lifetimes, were also studied. All the results indicate that the threshold ET value requiredfor a given compound to become a potential DNA photosensitizer via T<>T formation is in the range definedby the triplet energies of NFX and ANFX (265−269 kJ/mol). This provides the basis for an alert rule: anychemical (drugs, cosmetics, pesticides, etc.) with higher ET has to be considered with regard to its potentialphotogenotoxicity.
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