Ciprofloxacin by-products in seawater environment in the presence and absence of gilt-head bream

Abstract

The widespread use of pharmaceuticals has caused a growing concern on the presence of pharmaceuticals such as the antibiotic ciprofloxacin (CIPRO) in the aquatic environment, since they may exert adverse effects on non-target organisms, including fish. In order to study the uptake, distribution in different tissues (liver, muscle, brain and gill) and biofluids (plasma and bile), metabolism and elimination of CIPRO in gilt-head bream (Sparus aurata), controlled dosing experiments for 8 days at 200 μg/L concentration were carried out. CIPRO was only observed in bile at concentration up to 315 ± 4 ng/mL, probably due to its low octanol-water partition coefficient (log P = -2.4 at pH 7.4) and the zwitterionic behavior (pKa₁ = 5.76 and pKa₂ = 8.68). CIPRO by-products (BPs) were also identified in seawater environment, both in presence and absence of fish. The analysis done by means of liquid chromatography-high resolution mass spectrometry (hybrid quadrupole-Orbitrap) permitted the annotation of up to 35 BPs of CIPRO in seawater and bile, from which 30 structures were reported for the first time. These results confirm that CIPRO is very susceptible to photolysis, and that it goes through various phase I and phase II metabolisms in the fish. All these results suggested that, for a complete characterization of CIPRO exposure, BPs should also be included in the biomonitoring campaigns since they might also be toxicologically relevant.

Keywords: By-products; Ciprofloxacin; Gilt-head bream; High-resolution mass spectrometry; Seawater.