1. Determination of ﬂumequine, nalidixic acid and oxolinic acid in shrimps by high-performance liquid chromatography with ﬂuorescence detection
Ute Schroder • Anke Machetzki. Eur Food Res Technol (2007) 225:627–635
The quinolones ﬂumequine and oxolinic acid are synthetic antibacterial agents which are still administered preferentially in the Asian aquaculture. They are widely used for the prevention and treatment of infectious diseases in farmed ﬁsh and shrimps. Studies show that they act mainly against Gram-negative organisms by inhibiting bacterial enzyme DNA Gyrase, a type II topoisomerase. DNA Gyrase is an essential enzyme which is responsible for DNA replication, recombination and transcription and so required for bacteria cell growth and division [7, 8]. The use of drugs can lead to residues in edible tissue which may cause toxic effects on consumers. To protect consumers’ health the European Union established maximum residues limits (MRL’s based on the wet weight) in the Council Regulation 2377/90/EEC for veterinary drugs in foodstuffs, also for several quinolones. The MRL of oxolinic acid in ﬁsh is ﬁxed at 100 µg/kg and the MRL of ﬂumequine in ﬁsh is ﬁxed actually at 600 µg/kg. Shrimps must be classiﬁed according to the mentioned European regulation in the category “other species used for food production”. In this case, the MRL of ﬂumequine is 200 µg/kg. Unfortunately, this category does not exist for oxolinic acid. In the year 2004 the Joint FAO/WHO Expert Committee on Food Additives recommended for ﬂumequine a MRL of 500 µg/kg for Black Tiger shrimp muscle (P. monodon) and trout muscle with skin in their natural proportions. TheMRL is temporary until 2006 when detailed description of a regulatory method including validation data will be available. The identical recommendation for shrimp and trout was the reason to take the MRL of oxolinic acid for ﬁsh also for shrimp in this paper.
2. Extraction and Determination of Oxytetracycline Hydrochloride and Oxolinic Acid in Fish Feed by Derivative Spectrophotometry of First Order
M. Inés Toral & Sandra L. Orellana & César A. Soto & Pablo Richter. Food Anal. Methods (2011) 4:497–504
Oxytetracycline (OTC), an antibacterial broad-spectrum antibiotic belonging to the family of tetracyclines (TCAs), is widely used in aquaculture. Its mechanism of action is to inhibit the synthesis of bacterial proteins being fixed to 30S ribosome subunit (Chopra and Roberts 2001). Its structure presents a hydronaphthacene skeleton containing four fused rings, showing acid–base properties due to the presence of amino and hydroxyl groups. In general, chelating properties of TCAs are due to the presence of ketone and enol groups, and their antibacterial activity and pharmacokinetic properties are influenced by the chelation of metal ions (Arias et al. 2005). Oxolinic acid (OA) is another synthetic antibiotic used regularly in the salmon industry. It belongs to the family of quinolones, which have in common the presence of a 4-quinolone-3-carboxylate ring. The first action site described for these antibiotics was the bacterial enzyme DNA gyrase, a bacterial topoisomerase II. Quinolones inhibit some of the catalytic activities of DNA gyrase in bacteria (Hooper 1999). In this context, quinolones exert their toxicity on the bacterial cell, stabilizing the double strand of DNA that has been broken by the DNA gyrase so that the subsequent ligation cannot occur. Also, they show acid–base properties by possessing carboxylic acid group with a pKa close to 7.0 (Luetzhoft et al. 2000; Turiel et al. 2003).
3. Simultaneous Determination of Trimethoprim, Sulfadiazine, Florfenicol and Oxolinic Acid in Surface Water by Liquid Chromatography Tandem Mass Spectrometry
L. K. Sørensen*, T. H. Elbæk. Chromatographia 2004, 60, September (No. 5/6)
The recoveries of sulfadiazine and oxolinic acid were clearly inﬂuenced by the pH used for SPE. The true recoveries of oxolinic acid and sulfadiazine began to decline rapidly at pH values above 6 and 7 respectively (Fig. 3). It was therefore decided to keep the pH in the range 5.0–5.2 to keep signal enhancement at a low level and to obtain suﬃcient recovery of sulfadiazine and oxolinic acid. The mean apparent recoveries which combine true recoveries and matrix eﬀects on signal responses were 87, 97, 106 and 80% for trimethoprim, sulfadiazine, ﬂorfenicol and oxolinic acid in the pH range 5.0–5.2. The data on apparent recovery demonstrated the importance of a precise pH control of sample solutions in order to obtain reproducible results, especially for oxolinic acid (Fig. 4).