Transformation And Residual Determination Of Non-steroidal Anti-inflammatory Drugs

Nowadays,non-steroidal anti-inflammatory drugs(NSAIDs)are one of the most frequently-used human and veterinary medicines.Due to their huge consumption,human and animal excretion,the limitations of sewage treatment technology and improper disposition of discarded drugs and other factors,NSAIDs and even their metabolites eventually enter the environment continuously in a variety of ways.They may accumulate in the body through the food chain amplification upon long-term exposure and thus cause serious consequences to the ecological system and human health.In view of the threat of residual NSAIDs in environment to ecosystems and human safety,its migration,transformation and toxicity assessment in the environment has attracted increasing attention in the field of environmental science and engineering.Several methods,including membrane treatment,chlorination,ultraviolet(UV)disinfection,ozone oxidation and so on,are commonly used during water treatment.There are significant differences in the migration and transformation behavior of NSAIDs during the wastewater treatment(from complete removal to almost no removal).Additionally,a variety of transformation products(TPs)are inevitably formed during water treatment,some of which may be more toxic than the parent compounds.Therefore,it is necessary to assess the potential environmental risks of the various TPs during the water treatment process.In addition,due to the reasonable and non-therapeutic purposes in animals,the residual NSAIDs in animal-related foods were universal.Long-term consumption of food that contains residual NSAIDs could cause gastrointestinal,liver,kidney,cardiovascular,blood and nervous system damage and other adverse effects.Moreover,these hazards are often hidden and difficult to reverse.At present,it is normal for various food safety standards to require the detection of the residual NSAIDs,but rarely involving the metabolites of them.Although the concentrations of metabolites are even lower than their parent compound,the potential effects of the metabolites could not be ignored,owing to their potentially more toxicity than the parent forms.Therefore,in order to ensure food safety and protect public health,it is urgent to understand the metabolism of NSAIDs and toxicity of their metabolites in animals,especially for those metabolites whose toxicity was higher than that of the parent drugs.Based on the above analysis,this thesis primarily focuses on the following aspects of NSAIDs:1.The chlorination kinetics of three fenamic acids,i.e.mefenamic acid(MEF),tolfenamic acid(TOL)and clofenamic acid(CLO),was examined at different pHs,which followed second-order reaction under studied conditions.The transformation products(TPs)were identified by liquid chromatography-mass spectrometer(LC-MS)and gas chromatography-mass spectrometer(GC-MS).Chlorine substitution,oxidation and the joint oxidation with chlorine substitution were mainly reactions involved in chlorination.Moreover,the total toxicity of the TPs was assayed based on luminescent bacteria.Under different pHs,the different types of TPs might form,resulting in the varied total toxicity.The toxicity of all three fenamic acids chlorinated at pH of 8 was greater than those at pHs of 6 and 7.2.The photodegradation of ketoprofen(KET),carprofen(CAR)and diclofenac acid(DIC)was conducted under UV irradiation.The kinetic results show that the studied three pharmaceuticals obeyed first-order reaction with the decreasing rate order of CAR,KET and DIC.Moreover,eight,three and six TPs for KET,CAR and DIC were respectively identified by GC-MS and LC-MS.Decarboxylation,de-chlorination,oxidation,demethylation,esterification and cyclization were proposed to be associated with the transformation of the three pharmaceuticals.Toxicity prediction of the TPs was carried out based on quantitative structure-activity relationship models(QSARs)and the results indicate that some of the TPs turned out to be more toxic than the parent compounds.3.The biotransformation of five NSAIDs by pig liver microsomes(PLMs)was studied.Firstly,PLMs were prepared by calcium sedimentation method.The protein content was determined to be 10.63 ± 0.81 mg mL-1 by Bradford assay.Next,the pseudo-first-order kinetics mode was obtained for the metabolism of MEF,TOL,CLO,flufenamic acid and flurbiprofen(FBP)by PLMs in vitro.The metabolites were identified by LC-MS and the hydroxylation of benzene was the dominating metabolic pathway.Finally,the toxicity was predicted based on QSARs.Decreased toxicity was observed for almost all the metabolites of the studied NSAIDs except for FBP,whose main metabolite exhibited slightly more toxic for some species.The present study provided a preliminary foundation to understand the biotranformation of NSAIDs and the toxicity of their metabolites,which was of great significance in animal food safety.4.A novel magnetic nanoparicle(Fe3O4-SiO2-S-N+)was initially synthesized by"thiol-ene" click chemistry reaction.As a magnetic solid-phase extraction(MSPE)sorbent,Fe3O4-SiO2-S-N+ was utilized to analyze eight NSAIDs spiked in water samples.Some factors that affected the extraction efficiency,including the pH value and ionic strength of the sample solution,type and composition of desorption solution,extraction time as well as desorption time,were systematically optimized.Under the optimal conditions,the developed method exhibited wide linearity ranges and low limits of detection.No NSAIDs residues were detected in Yangtze river water samples using the developed method.The novel material possessed the advantages of simple preparation,effectiveness and good batch-to-batch reproducibility.It shows high analytical potential for NSAIDs determination in environmental water samples.5.In this chapter,bovine serum albumin(BSA)was immobilized onto penetrable SiO2 via Schiff base method.The obtained BSA-SiO2 was employed as the HPLC stationary phase.Firstly,D-and L-tryptophan were used as probes to systematically investigate the chiral chromatographic performance of the BSA-SiO2.The excellent enantioseparation ability and acceptable stability were obtained.Then,the BSA-SiO2 stationary phase was applied to study the interaction between imatinib mesylate(IM)and BSA by frontal affinity chromatography.A single type of binding site was found for IM with the immobilized BSA,and the hydrogen-bonding and van der Waals interactions were supposed to be contributing interactions.Compared to the traditional SiO2 for HPLC stationary phase,the proposed penetrable SiO2 simultaneously contained macropores and mesopores,thus possessed larger capacity to bond more BSA,minimizing column overloading effects and enhancing enantioseparation ability.In addition,the lower running column back pressure and fast mass transfer were meaningful for the column stability and lifetime.It was a good substrate to immobilize biomolecules for fast chiral resolution and screening the drug-protein interactions.6.The results of the above five chapters were summarized.The shortcomings of the current research and the prospects of future study were also generalized.7.The determination of the residual NSAIDs in environmental samples and animal origin foodstuffs during the past ten years was reviewed.Several commonly used sample pretreatment methods and detection techniques were summarized.