Bioconcentration And Metabolism Of Fluoroquinolones(FQs) In Common Carp(Cyprinus Carpio)

Fluoroquinolones（FQs）are a group of chemosynthetic antibiotics that are widely used in the prevention and treatment of various human and animal diseases.With the extensive use of FQs,there are a series of environmental problems.For example,FQs have been frequently detected in water,which may cause side effects on aquatic organisms.And the residues of FQs in aquatic products have aroused wide concern,which may accumulate in human bodies through food chains.However,reports on the bioconcentration patterns and biotransformation mechanisms of FQs in aquatic organisms are still limited.Therefore,in this study,FQs were selected as target compounds,common carp（Cyprinus carpio）were selected as test species,and we investigated the bioconcentration patterns and biotransformation pathways of FQs in common carp tissues.The main research contents and results are as follows:（1）Bioconcentration of FQs in common carp was studied under controlled laboratory conditions.Concentrations of eight FQs in common carp hepatopancreas,kidney and muscle were determined by UPLC-MS/MS.The results showed that all the compounds were detected during the uptake and depuration periods,and a similar bioconcentration trend of FQs was observed over the whole period.Among them,moxifloxacin had the biggest concentration,up to 295.12 ng/g（wet weight,ww）.（2）The bioconcentration curve was fitted by the double-box model,and we obtained bioconcentration kinetic parameters of FQs in common carp tissues,including uptake rate constant（k₁）,depuration rate constant（k₂）,half-lives(t_1/2)and bioconcentration factor（BCF）,which were in the range of 0.007³.599 L/（kg·d）,0.051⁰.283 d^-1,2.4¹0.7 d and 0.04³9.55 L/kg,respectively.The BCF values of each FQs were decreased in the following order.MOX>enrofloxacin（ENR）>enoxacin（ENO）≈balofloxacin（BAL）≈fleroxacin（FLE）≈ofloxacin（OFL）≈lomefloxacin（LOM）≈sparfloxacin（SPA）,which may be related with the characteristic substitutions of the target compounds and the metabolic ability.The BCF values in each tissue showed the following pattern:hepatopancreas>kidney>muscle,which may be correlated with the phospholipid content in each tissue.（3）The present study investigated the biotrasformation pathway of ENR in common carp hepatopancreas.The results showed that there were eight metabolites of ENR in common carp hepatopancreas,and the main metabolite was ciprofloxacin（CIP）.Subsequently,the metabolic pathway of ENR in common carp hepatopancreas was presumed,including desethylation,piperazine ring cleavage,de-acetylene,defluorination,hydroxylation,N-formylation and methylation.