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- Enantioselective Degradation of Enantiomers of Fluoxetine Followed by HPLC- FDPublication . Ribeiro, Ana R.; Maia, Alexandra S.; Moreira, Irina S.; Afonso, Carlos; Castro, Paula M.L.; Tiritan, Maria E.Environmental fate assessment of chiral pharmaceuticals is an important issue and little information is known about enantioselectivity in the environment. This kind of information is important for regulamentation of pharmaceutical industry and chiral switching processes. Fluoxetine (FLX), an anti-depressant worldwide used, is a chiral pharmaceutical prescribed in racemic form, and its main metabolite norfluoxetine (NFLX) is also chiral. In this study, enantioselective degradation of rac-FLX and degradation of its enantiomers separately, in a minimal salts medium inoculated by a bacterium consortium was examined both at light and dark conditions. Theassays were performed in a shaker at aerobic and ambient temperature conditions. The analytical method used was an enantioselective HPLC-FD method using a vancomycin-based chiral stationary phase in reversed mode to monitor enantiomers of FLX and NFLX. No degradation of enantiomers of FLX in the abiotic controls was observed. In theall assays (R)-FLX was degraded faster and totally until day 24th while (S)-FLX remained up to 20% of its initial concentration until the end of the experiment (38 days). NFLX wasdetected in all biotic experiments.
- Biodegradation of fluoroquinolones by a bacterial consortiumPublication . Maia, Alexandra S.; Duque, Anouk F.; Ribeiro, Ana R.; Tiritan, Maria E.; Castro, Paula M. L.The present concern in pharmaceuticals in the environment is well known and research studies in this area have been regularly reported. Pharmaceuticals reach the environment by several ways but mostly due to their incorrect disposal and the incomplete elimination during the treatment processes in Wastewater Treatment Plants (WWTP). These residues continuously enter aquatic environments and many of them are resistant to degradation, being so called as pseudo-persistent pollutants. In aquatic compartments, pharmaceutical residues reach concentrations in the ng L-1 to µg L-1 range. This work describes the biodegradation of four fluoroquinolones, Ofloxacin (OFL), Norfloxacin (NOR), Ciprofloxacin (CPF) and Moxifloxacin (MOX), by a bacterial consortium constituted by three bacterial species isolated in our labs, namely F11, FP1 and S2, known to degrade different aromoatic fluorinated compounds. The experiments were conducted in batch mode using a mineral medium supplemented with acetate and 10 mg l-1 of each compound or 10 mg l-1 of a mix of the compounds. The bacterial consortium was capable of aerobic biodegradation of OFL, NOR and CPF during successive feedings of the compounds to the medium, as measured by monitoring removal of the compounds by HPLC-FD and fluoride release by potenciometry. Degradation profile of the fluoroquinolones used in this study indicated that intermediate metabolites were accumulated. Two of the initial constituting strains, F11, belonging to the α-proteobacteria group, and S2, belonging to the Actinobacteria group, were recovered from the medium, F11 predominating in cultures fed with moxifloxacin whereas S2 was mostly found in the remaining cultures. Degradation by single bacteria is under evaluation.
- HPLC-FD Method Validation for Determination of Several Fluoroquinolones in Biodegradation AssaysPublication . Maia, Alexandra S.; Ribeiro, Ana R.; Castro, Paula M. L.; Tiritan, Maria E.The present concern in pharmaceuticals in the environment is well known and research studies in this area have been regularly reported [1]. Pharmaceuticals reach the environment by several ways but mostly due to their incorrect disposal and the incomplete elimination during the treatment processes in Wastewater Treatment Plants (WWTP). These residues continuously enter aquatic environments and many of them are resistant to degradation, being so called as pseudo-persistent pollutants [2]. In aquatic compartments, pharmaceutical residues reach concentrations in the ng/L to µg/L range [3]. Antibiotics are a class extensively studied due to its implications on development of multi-resistant bacteria. This work describes a validated HPLC (High Performance Liquid Chromatography) method with Fluorescence Detection for monitorization of biodegradation of four fluoroquinolones: Ofloxacin (OFL), Norfloxacin (NOR), Ciprofloxacin (CPF) and Moxifloxacin (MOX). The separation of the target pharmaceuticals was performed at 38ºC using a Luna 3µ PFP(2) 100 A (150 x 4.60 mm) column in isocratic mode with a mixture of 0.1% triethylamine (TEA) in water acidified to pH = 2.2 with trifluoroacetic acid (TFA) and ethanol as mobile phase. The validated method demonstrated selectivity, linearity (r2>0.999) and precision (intra-day: 0.71>RSD>2.51; inter-day: 1.11>RSD>2.74) in the range of 0.5 µg/mL – 12 µg/mL. The quantification limits were 5 ng/mL for OFL, NOR and CPF and 20 ng/mL for MOX. The biodegradation study was performed during 15 days using a microbial consortia constituted by three bacterial species known to degrade fluorinated compounds. The OFL presented higher extent of degradation than CPF and MOX.