Directphotochemistryofthreefluoroquinoloneantibacterials:Norfloxacin,ofloxacin,andenrofloxacinKristineH.Wammera,*,AndrewR.Kortea,RachelA.Lundeena,JacobE.Sundberga,KristopherMcNeillb,WilliamA.ArnoldcaDepartmentofChemistry,UniversityofSt.Thomas,2115SummitAve.,St.Paul,MN55105,USAbInstituteforBiogeochemistryandPollutantDynamics,ETHZurich,8092Zurich,SwitzerlandcDepartmentofCivilEngineering,UniversityofMinnesota,500PillsburyDr.SE,Minneapolis,MN55455,USAarticleinfoArticlehistory:Received8June2012Receivedinrevisedform12October2012Accepted13October2012Availableonline22October2012Keywords:FluoroquinolonesQuantumyieldPhotolysisAntibacterialactivityabstractFluoroquinolone(FQ)antibacterialcompoundsarefrequentlydetectedintheaquaticenvironment,andphotodegradationisexpectedtoplayanimportantroleinFQfateinsomesunlitsurfacewaters.ThisstudyinvestigatedthedirectaquaticphotochemistryofthreeFQs:norfloxacin,ofloxacin,andenrofloxacin.ThedirectphotolysisrateofeachdrugexhibitedstrongpHdependencewhenexposedtosimulatedsunlight.ForeachFQ,directphotolysisratesandtotallightabsorbancewereusedtocalculatequantumyieldsforeachofthreeenvironmentallyrelevantprotonationstates:acationic,azwitterionic,andananionicform.Ineachcase,quantumyieldsofthespeciesvariedsignificantly.Thequantumyieldforthezwitterionicformwas2e3timeshigherthanthatoftheanionicformandoveranorderofmagnitudehigherthanthatofthecationicform.AntibacterialactivityassayswereusedtodeterminewhetherthelossofparentFQduetophotolysisledtolossofactivity.Norfloxacinandofloxacinphotoproductswerefoundtobeinactive,whereasenrofloxacinphotoproductswerefoundtoretainsignificantactivity.TheseresultsareimportantforaidinginpredictionsofthepotentialimpactsofFQsinsurfacewaters.ª2012ElsevierLtd.Allrightsreserved.1.IntroductionFluoroquinolones(FQs)areaclassofantibacterialcompoundsusedextensivelyinbothhumanandveterinarymedicine.FQshavebeenfoundinhospitalwastewaters(atconcentrationsrangingfromapproximately60e120,000ng/L),inwastewatertreatmentplant(WWTP)effluents(w2e580ng/L)andinsurfacewaters(w5e1300ng/L)throughouttheworld,includingintheUnitedStates(Kolpinetal.,2002;RenewandHuang,2004),Italy(Andreozzietal.,2003),Switzerland(Gigeretal.,2003;Goletetal.,2003),Finland(Vienoetal.,2007),Sweden(Lindbergetal.,2006),Germany(Hartmannetal.,1999),China(Xuetal.,2009),andAustralia(Watkinsonetal.,2009).ResearchaboutwhichprocessesaremostlikelytocontroltheenvironmentalfateofFQsinaquaticenvironmentsisneededtoassesspotentiallong-termimpacts.ThepresenceofFQsandotherantibacterialcompoundsintheenvironmentisofconcernprimarilyduetothepossibilitythatlong-termexposuretosub-therapeuticdosesmayprovideselectivepressureforantibiotic-resistantorganisms(Ku¨mmerer,2009).ThereisalsoconcernthatFQsmayinhibitphotosynthesisinplants(Aristildeetal.,2010).PreviousworkhasshownthatphotodegradationisexpectedtoplayanimportantroleinFQfateinsomesunlitsurfacewaters(Schmitt-Kopplinetal.,1999;Andreozzietal.,2003;Knappetal.,2005;LamandMabury,2005;Sturinietal.,2010;Lietal.,2011),andinparticularmaybesignificantrelativetootherabiotic*Correspondingauthor.Tel.:þ16519625574;fax:þ16519625209.E-mailaddress:khwammer@stthomas.edu(K.H.Wammer).Availableonlineatwww.sciencedirect.comjournalhomepage:www.elsevier.com/locate/watreswaterresearch47(2013)439e4480043-1354/$eseefrontmatterª2012ElsevierLtd.Allrightsreserved.http://dx.doi.org...
