液相色谱-三重四级杆复合线性离子阱质谱法分析恩诺沙星在鲤鱼(Cyprinus carpio)中的代谢产物

采用液相色谱-三重四级杆复合线性离子阱质谱(HPLC/Q-TRAP MS),在正离子检测模式下,对鲤鱼(Cyprinus carpio)腹腔注射恩诺沙星给药后肝脏中的代谢产物进行分析.根据保留时间和各色谱峰质谱裂解规律,推测了恩诺沙星在鲤鱼肝脏中的代谢产物,同时,根据二级质谱碎片离子推测代谢途径及代谢产物结构.结果显示,恩诺沙星进入鲤鱼肝脏后,除以恩诺沙星原形药物(M0)和N-去乙基代谢产物环丙沙星(M2)形式存在外,还有少量恩诺沙星脱羧代谢产物(M1)和恩诺沙星羟基化代谢产物(M3-1和M3-2).该研究可为深入了解恩诺沙星在水生动物体内代谢产物及代谢机理提供理论基础,为在水产养殖生产中科学、合理地使用恩诺沙星提供参考.

Analysis on the Metabolites of Enrofloxacin in the Carp Liver by Using HPLC/Q-TRAP MS

Enrofloxacin is one of the third-generation synthetic broad-spectrum antibiotics in the class of quinolone, and has been widely used in the prevention and treatment of animal infectious diseases. Previous pharmacokinetics studies have been mainly focused on the metabolites of enrofloxacin in fungi and animals, but little is known about the metabolic pathways and the metabolites in fish. Our study aimed for better understanding of this drug in aquatic animals because it would provide a theoretical basis for the proper use of enrofloxacin in aquaculture. In our experiment carps (Cyprinus carpio) were orally administered a single dose of 30 mg/kg body weight enrofloxacin. Liver samples from the control group and the 24 h post-administration group were collected for the metabolite analysis. Following intraperitoneal injection, enrofloxacin and its metabolites in the liver of carp were analyzed using a positive liquid chromatography coupled with Q-Trap mass spectrometry (HPLC/Q-TRAP MS). Based on the retention time and MS/MS spectra, we surmised the possible metabolites of enrofloxacin in the liver, and also proposed the potential metabolic pathways and the structures of metabolites by analyzing the fragmentation pathway. The results revealed that most of enrofloxacin remained in the form of the parent drug, and that a small portion of enrofloxacin was converted into metabolites in the liver. Besides the parent drug enrofloxacin (M0) and the known metabolite ciprofloxacin (M2), a very small amount of decarboxylation (M1) and hydroxylated enrofloxacins (M3-1 and M3-2) were found. The quantitative analysis revealed that the concentrations of enrofloxacin and its primary metabolite ciprofloxacin were 0.2780 mg/kg and 0.0064 mg/kg respectively. These results suggested that enrofloxacin could be converted into a variety of metabolites through distinct metabolic pathways in different organisms. This is probably due to diverse living environments, fish figures, drug metabolic enzymes, and other factors in different species.