Assessment of safety and quality aspects of boiling treatment of quail eggs.

A total of 300 quail eggs were collected randomly from different markets in Cairo and Giza Governorates. Five eggs were represented as one egg sample. Shell and content of each egg were examined for their microbiological contents, sensory evaluation and study of Escherichia coli O157 survival in artificially contaminated eggs. Moreover, qualitative detection of antimicrobial residues by seven plates microbiologically bioassay and confirmed by validated high-performance liquid chromatography (HPLC) methods for positively reacted antimicrobials in raw and boiled samples. There was a significant difference (P < 0·05) between the grading score of eggs after the boiling at 2-, 4-, 5- and 7-min. Based on the survival results, the refrigeration storage and boiling for 5 min of quail eggs was confirmed that such eggs are without E. coli O157. After the boil, the concentrations of oxytetracycline (OTC) and 4-Epi-OTC residues were significantly reduced, and there was no effect on the concentration of sulphadimidine (SDD), amoxicillin (AMO) and Diketo residues. Samples that exceeded the maximum residual limits (MRLs) were 17·0%, 12·0%, 10·0%, 16·0% and 14·0% for SDD, OTC, 4-Epi-OTC, AMO and Diketo, respectively. After boiling, no significant change was noted for SDD, AMO and Diketo, but all OTC and 4-Epi-OTC were completely below MRLs. Therefore, SDD and AMO with their metabolite (Diketo) are heat-stable antimicrobial residues with multiple human health hazards.

Simple method for the determination of anthelmintic drugs in milk intended for human consumption using liquid chromatography-tandem mass spectrometry.

BACKGROUND: Helminth infections in animals to be consumed by humans are an important medical and public health problem. Pharmaceutical research has focused on developing new anthelmintic drugs for parasite control in these animals. However, the incorrect use of anthelmintics can leave residues in animal products intended for human consumption. Their determination is therefore crucial in terms of food safety. RESULTS: In this work, a simple and sensitive method has been developed for the analysis of anthelmintic drugs in milk. The method involves extraction of the analytes using a QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, and separation and determination by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The use of a core-shell column significantly reduced the analysis time compared with conventional columns. The method was validated and applied to the analysis of different commercial milk samples: whole, semi-skimmed and skimmed cows' milk, and goats' milk. None of the benzimidazoles studied was found in the samples analyzed, so these were spiked with the analytes at three concentration levels (10, 50, and 100 µg kg-1 ). CONCLUSIONS: The proposed method provided high sensitivity compared with other methods for the determination of anthelmintics in milk samples, at concentration levels well below the established maximum residue limit (MRLs) values. The proposed method is simple, easy, precise, accurate, and leads to good recovery levels. It can be used successfully for the routine analysis. © 2021 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Determination of Methylene Blue and Its Metabolite Residues in Aquatic Products by High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

A sensitive and reliable method was developed to determine methylene blue (MB) and its metabolite residues, including azure A (AZA), azure B (AZB), and azure C (AZC) in aquatic products by HPLC-MS/MS. The samples were extracted by acetonitrile and cleaned up by alumina-neutral (ALN) cartridges. The analytes were separated on a Sunfire C18 column (150 mm × 2.1 mm, 5 µm). The method was validated according to the European criteria of Commission Decision 2002/657/CE. Good linearity between 1-500 µg/L was obtained with correlation coefficients (R2) greater than 0.99. The limit of quantification (LOQ) was 1.0 µg/kg. The average recoveries at three levels of each compound (1, 5, and 10 µg/kg) were demonstrated to be in the range of 71.8-97.5%, with relative standard deviations (RSDs) from 1.05% to 8.63%. This method was suitable for the detection of methylene blue and its metabolite residues in aquatic products.

A novel tool to screen for treatments with clenbuterol in bovine: Identification of two hepatic markers by metabolomics investigation.

Surveillance of illegal use of growth promoters such as ß2-agonists in food producing animals rely on the detection of drug residues by LC-MS/MS. Screening strategies focusing on indirect physiological responses following administration of active compounds are promising approaches to strengthen existing targeted methods and ensure food safety. A metabolomics analysis based on LC-HRMS was carried out on liver extracts from bulls experimentally treated with clenbuterol combined with dexamethasone (n = 8) to mimic a potential anabolic practice, and control animals (n = 8). Nicotinic acid and 5'-deoxy-5'-methylthioadenosine were identified as biomarkers of treatment. Ratio values of such markers to others of the same metabolic pathways (nicotinamide or methionine) were used to develop a classification model to assign animals as treated with clenbuterol or non-treated. The classification model was tested on an external validation set comprising 74 animals either treated with different anabolic compounds (ß2-agonists, sexual steroids, corticosteroid), or non-treated, showing 100% sensitivity and specificity.

Monitoring the behavior of imazalil and its metabolite in grapes, apples, and the processing of fruit wine at enantiomeric level.

BACKGROUND: Imazalil is widely used in agriculture, which may pose a threat to food safety. This study aimed to investigate the fate of imazalil and its main metabolite, R14821 (imazalil-M), in field grapes and apples, and in the processing of fruit wine at the enantiomeric level. RESULTS: Analysis method was established to determine imazalil and imazalil-M enantiomers in grape, apple, fruit wine and pomace. The method showed acceptable recoveries of 71.6-99.9% and precision with relative standard deviation of 0.3-11.7%. Processing factors (PFs) were 0.15-0.40 (for imazalil enantiomers) and <0.13-0.83 (for imazalil-M enantiomers) during the wine-making process. The PFs after individual steps including washing, peeling, fermentation, and clarification were all less than 1. No enantioselective dissipation of imazalil was found in grapes under field conditions with half-lives of 23.82-24.49 days. R-(-)-imazalil degraded slightly faster than S-(+)-imazalil in apples under field conditions with half-lives of 9.82-10.09 days. S-(+)-imazalil-M preferentially degraded in field grapes and apple. No significant enantioselectivity of imazalil and imazalil-M was observed during the wine-making process. The enantiomeric fraction (EF) values of imazalil were 0.484-0.511 and 0.509-0.522 in grape wine and cider, respectively. The EFs were 0.484-0.501(in grape wine) and 0.484-0.504 (in cider) for imazalil-M. CONCLUSION: The results showed that the wine-making process could reduce imazalil and imazalil-M residues in grapes and apples. The finding of non-enantioselectivity of imazalil during the processing of fruit wine was useful for accurate risk assessment for imazalil in raw and processing fruits. © 2021 Society of Chemical Industry.

Terminal residue and dietary intake risk assessment of prothioconazole-desthio and fluoxastrobin in wheat field ecosystem.

BACKGROUND: Wheat is one of the most important cereal crops worldwide, and use of fungicides is an essential part of wheat production. Both prothioconazole and fluoxastrobin give excellent control of important seed and soilborne pathogens. The combination of these two fungicides shows a complementary mode of action and has a wide usage around the world. But the residue levels of these fungicides in the wheat matrix are still unknown. RESULTS: In the current study, a simple, low-cost and highly sensitive method using modified QuECHERS procedure combined with high-performance liquid chromatography-tandem mass spectrometry was developed to simultaneously quantify E- and Z-fluoxastrobin and the main metabolite prothioconazole-desthio of prothioconazole in the wheat matrix. The recoveries of prothioconazole-desthio, E-fluoxastrobin and Z-fluoxastrobin ranged from 84% to 101%, with relative standard deviation of less than 13.2%. The terminal residues of prothioconazole-desthio and E- and Z-fluoxastrobin were studied in wheat grain and straw under field conditions. The results showed that the terminal residue of the target compounds ranged from <0.01 to 0.029 mg kg-1 and <0.05 to 7.6 mg kg-1 in wheat grain and straw (expressed as dry weight), respectively. The risk quotients of prothioconazole-desthio and fluoxastrobin were 0.2% and 3.2%. CONCLUSIONS: The residue levels of the target analytes in wheat grain were lower than the maximum residue limits recommended by the Chinese Ministry of Agriculture. And the calculated risk quotient values were far below 100%, indicating a low dietary intake health risk to consumers. © 2021 Society of Chemical Industry.

Transmission of Zearalenone, Deoxynivalenol, and Their Derivatives from Sows to Piglets during Lactation.

Sows were fed naturally contaminated diets containing: (i) 100 ppb zearalenone (ZEN) one week before farrowing and during the lactation period (at 26 days), (ii) 100 ppb ZEN one week before farrowing and 300 ppb ZEN during the lactation period, or (iii) 300 ppb ZEN one week before farrowing and during the lactation period. All diets contained 250 ppb deoxynivalenol (DON). The highest levels of ZEN, α-ZEL, or ß-ZEL were observed in the serum of sows fed 300 ppb ZEN before farrowing and during lactation. However, only α-ZEL was significantly increased in the colostrum and milk of these sows. Sows fed the 300 ppb ZEN during the complete trial presented a significant decrease in backfat thickness before farrowing. This effect was accompanied by a decrease in serum leptin levels. These sows also presented a decrease in estradiol levels and this effect was observed in their piglets exposed during lactation, which presented increased glucagon-like peptide 1, but no changes in serum levels of ZEN, α-ZEL, or ß-ZEL. Although all sows were fed the same levels of DON, the serum levels of DON and de-epoxy-DON were increased only in the serum of piglets from the sows fed a diet with the highest ZEN levels during the whole experimental period. Moreover, these piglets presented gut inflammation, as indicated by significantly increased calprotectin levels in their serum.

A Dissipation Pattern of Gibberellic Acid and Its Metabolite, Isogibberellic Acid, during Tea Planting, Manufacturing, and Brewing.

As a widely used plant growth regulator, the gibberellic acid (GA3) residue in tea has potential risk for human health. Herein, the degradation of GA3 and its conversion into main metabolites were investigated during tea planting, manufacturing, and brewing using ultrahigh-performance liquid chromatography tandem mass spectrometry. The metabolite iso-GA3 was first discovered during the tea production chain and identified using Q-Exactive Orbitrap mass spectrometry. GA3 dissipated following first-order kinetics in tea shoots with half-lives ranging from 2.46 to 2.74 days. It was degraded into iso-GA3 in tea shoots, which had a longer residual period than GA3. Meanwhile, external application of GA3 could increase the proportion of growth-promoting endogenous phytohormones and lead to rapid growth of tea plants. During tea manufacturing, iso-GA3 was quickly and massively converted from GA3. Fixing (heat at 220-230 °C) played an important role in the dissipation of GA3 and iso-GA3 during green tea manufacturing, but there were high residues of iso-GA3 in black tea. High transfer rates (77.3 to 94.5%) of GA3 and iso-GA3 were observed during tea brewing. These results could provide a practical reference for food safety in tea and other agricultural products and the guidance for scientific application of GA3 in tea planting.

Cloning and in vivo metabolizing activity study of CYP3A4 on amiodarone drug residues: A possible probiotic and therapeutic option.

BACKGROUND: Amiodarone represents a principal antiarrhythmic pharmaceutical drug available in the market for the treatment of ventricular arrhythmias. However, despite its better efficacy, the usage of amiodarone is associated with extracardiac toxicity. The human body evolved a system of cytochrome P450 enzymes which play an essential role in the metabolism of harmful foreign substances. Therefore, CYP enzymes may either lead to the elimination or degradation of the leftover drug residues. OBJECTIVE: The present study focused on successful utilization of Saccharomyces cerevisiae strain OBS2 with probiotic- cum- therapeutic potential and expressing in silico enhanced human cytochrome P4503A4 for the degradation of leftover drug residues of amiodarone in vitro and in vivo. METHODOLOGY: In this study, cytochrome P4503A4 (1W0E) was taken as a template and the predicted 3D model of mutant CYP3A4 was developed using different bioinformatics tools. Selected mutant (Glu165Asp) protein was reverse translated and transcribed into cDNA sequence. The cDNA of CYP3A4 was synthesized, cloned into p427TEF construct and transformed into Saccharomyces cerevisiae OBS2. The degradation of leftover drug residues of amiodarone in vitro and in vivo using recombinant Saccharomyces cerevisiae OBS2 expressing CYP3A4 was evaluated. RESULT: The CYP3A4 activity in recombinant probiotic yeast was observed as 108 IU/mL and in vitro degradation of leftover drug residues of amiodarone was observed as 66.32 %. Whereas, in vivo degradation of leftover drug residues of amiodarone was observed as 72.61 % along with recovery of organ damage in histopathological studies of the animal model. CONCLUSION: Saccharomyces cerevisiae OBS2 expressing CYP3A4 can be used for probiotic and therapeutic applications.

A physiologically based pharmacokinetic model of doxycycline for predicting tissue residues and withdrawal intervals in grass carp (Ctenopharyngodon idella).

The extensive use of doxycycline in aquaculture results in drug residue violations that negatively impact human food safety. This study aimed to develop a physiologically based pharmacokinetic (PBPK) model for doxycycline to predict drug residues and withdrawal times (WTs) in grass carp (Ctenopharyngodon idella) after daily oral administration for 3 days. Physiological parameters including cardiac output and organ weights were measured experimentally. Chemical-specific parameters were obtained from the literature or estimated by fitting to the observed data. The model properly captured the observed kinetic profiles of doxycycline in tissues (i.e., liver, kidney, muscle + skin and gill). The predicted WT in muscle + skin by Monte Carlo analysis based on sensitive parameters identified at 24 h after drug administration was 41 d, which was similar to 43 d calculated using the tolerance limit method. Sensitivity analysis identified two additional sensitive parameters at 6 weeks: intestinal transit rate constant and urinary elimination rate constant. The predicted WT in muscle + skin based on sensitive parameters identified at 6 weeks was 54 d. This model provides a useful tool to estimate tissue residues and withdrawal times for doxycycline in grass carp and also serves a foundation for extrapolation to other fish species and other tetracyclines.

Surface plasmon resonance biosensor for the determination of 3-methyl-quinoxaline-2-carboxylic acid, the marker residue of olaquindox, in swine tissues.

To monitor the illegal use of olaquindox in animals, a monoclonal antibody-based surface plasmon resonance (SPR) biosensor method has been developed to detect 3-methyl-quinoxaline-2-carboxylic acid, the marker residues of olaquindox, in swine tissues. The limit of detection was 1.4 µg kg-1 in swine muscle and 2.7 µg kg-1 in swine liver, which are lower than the EU recommended concentration (10 µg kg-1). The recoveries were from 82% to 104.6%, with coefficients of variation of less than 12.2%. Good correlations between SPR and HPLC results (r = 0.9806, muscle; r = 0.9698, liver) and between SPR and ic-ELISA results (r = 0.9918, muscle; r = 0.9873, liver) were observed in the affected tissues, which demonstrated the reliability of the SPR method. This method would be a rapid and reliable tool for the screening of the residues of olaquindox in the edible tissues of animals.

Gold Immunochromatography Assay for the Rapid Detection of Spiramycin in Milk and Beef Samples Based on a Monoclonal Antibody.

Spiramycin (SP) residues in food do harm to human health. It is necessary to establish rapid detection method for SP. In this work, a monoclonal antibody (mAb)-based gold immunochromatography assay (GICA) is developed for the rapid detection of SP. Under optimum conditions, the half-maximal inhibitory concentration of SP-mAb is 0.43 ng mL-1 . The subtype of SP-mAb is IgG2b. This antibody has no cross-reactivity with other analogues and has high affinity (4.52 × 1010 L mol-1 ). Qualitative results can be visualized with the naked eye, with a visual detection limit of 1.0 ng mL-1 and cut-off value of 10 ng mL-1 . A hand-held strip scanner is used for the quantitative analysis, with LOD 0.43 ng mL-1 in assay buffer. The recoveries of SP ranged from 72.3% to 112% in milk and 98.5% to 115% in beef, with variable coefficient ranging from 9.4% to 11.7% in milk and 8.14% to 15.4% in beef. Besides, the proposed GICA method for SP is confirmed by LC-MS/MS in SP-spiked milk and beef samples. Overall, the developed GICA can be a useful tool for SP residues on-site screening in milk and beef samples.

High-efficiency biodegradation of chloramphenicol by enriched bacterial consortia: Kinetics study and bacterial community characterization.

The risk of environmental pollution caused by chloramphenicol has necessitated special attention. Biodegradation has tremendous potential for chloramphenicol removal in the environment. Six chloramphenicol-degrading consortia were acclimated under different culture conditions to investigate their chloramphenicol biodegradation behaviors, and the bacterial community structures were comprehensively characterized. The enriched consortia CL and CH which utilized chloramphenicol as their sole carbon and energy source could thoroughly degrade 120 mg/L chloramphenicol within 5 days, and the mineralization rate reached up to 90%. Chloramphenicol biodegradation kinetics by different enriched consortia fit the modified Gompertz model or the first-order decay model (R2≥0.97). Consortia CL could almost completely degrade 1-500 mg/L CAP with a final mineralization rate of 87.8-91.7%. Chloramphenicol 3-acetate was identified to be a major intermediate of CAP biodegradation by metabolite analysis and enzyme activity assay. 16S rRNA sequencing analysis revealed that the diversities and abundances of the main genera in the enriched consortia were distinct from each other. Forty-one core OTUs belonging to 18 genera were the core bacteria which might be related to chloramphenicol biodegradation. Among them, the genera Sphingomonas, Chryseobacterium, Cupriavidus, Bradyrhizobium, Burkholderia, and Afipia with high abundance may play potential roles for chloramphenicol biodegradation.

Comparison of data acquisition modes with Orbitrap high-resolution mass spectrometry for targeted and non-targeted residue screening in aquacultured eel.

RATIONALE: A current trend in monitoring chemical contaminants in animal products is to use high-resolution mass spectrometry (HRMS). In this study, several HRMS data acquistion modes using Orbitrap MS for simultaneous full-scan MS in combination with MS2 analysis were evaulated for their effectiveness in detecting and identifying both targeted and non-targeted veterinary drug residues in aquacultured eel samples. METHODS: Sample preparation consisted of an acidic acetonitrile extraction with solid-phase extraction cleanup for analysis using LC/HRMS. Different data acquisition methods, including full-scan MS with non-targeted all ion fragmentation (AIF), multiplexed or variable data-independent analysis (mDIA or vDIA), targeted data-dependent MS2 (DDMS2), and parallel reaction monitoring (PRM) acquisition, were explored. The methods were evaluated with fortified eel tissue and imported eel samples to determine how many analytes could be detected and identified. RESULTS: For non-targeted data acquisition, the number of analytes detected using DIA methods matched the results obtained by AIF, but the resulting product ion scans were more diagnostic because characteristic ions were predominant in the DIA MS2 spectra. In targeted analysis for a limited list of 68 compounds, full-scan MS followed by PRM was advantageous compared with DDMS2 because high-quality MS2 spectra were generated for almost all the analytes at target testing levels. CONCLUSIONS: For residue screening, AIF has fast MS1 scan speed with adequate detection of product ions but may lead to false positive findings. DIA methods are better suited to monitor for both targeted and non-targeted compounds because they generate more characteristic MS2 spectra for retrospective library searching. For follow-up targeted analysis, PRM is prefered over DDMS2 when searching for a limited set of compounds.

Tissue Distribution, Accumulation, and Metabolism of Chiral Flufiprole in Loach (Misgurnus anguillicaudatus).

Flufiprole is an insecticide used in the rice field and may pose a potential threat to aquatic organisms including loach. To investigate the transformation products of flufiprole in loach, the accumulation, elimination, and tissue distribution in vivo as well as the metabolism in vitro at the enantiomeric level were studied. Flufiprole enantiomers rapidly accumulated and were metabolized to flufiprole sulfone, fipronil, and flufiprole amide in the tissues. Enantiomeric fractions showed the preferential accumulation and degradation of S-flufiprole. The residue of the chiral metabolite flufiprole amide was also enantioselective. The individual enantiomer treatment indicated that S-flufiprole was preferentially metabolized to flufiprole sulfone and R-flufiprole to fipronil. The metabolites were more persistent than flufiprole with longer half-lives. The metabolism in liver microsomes also reached consistent conclusions. The dietary risk assessment indicated that flufiprole would not cause unacceptable threats to human health. However, the metabolites of flufiprole should be considered in the risk evaluation.

Multiresidue Determination of 27 Sulfonamides in Poultry Feathers and Its Application to a Sulfamethazine Pharmacokinetics Study on Laying Hen Feathers and Sulfonamide Residue Monitoring on Poultry Feathers.

A method for the simultaneous determination of 27 sulfonamides in poultry feathers using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established in this study. The samples were extracted using 0.1 mol/L HCl solutions in a 60 °C water bath for 2 h, purified using hydrophilic-lipophilic balance solid-phase extraction, nitrogen-dried, and then reconstituted for UPLC-MS/MS analysis, which was performed with a CSH-C18 column. Linearity, limit of detection, limit of quantification, recovery, and precision were calculated in accordance with Commission Decision 2002/657/EC. For linearity, all standard curves showed a standard coefficient greater than 0.99, and the recoveries and coefficient of variation were 89-115% and <20%, respectively. The limit of detection and limit of quantification were 0.2-5 and 0.5-20 ng/g, respectively. The method was successfully applied to sulfamethazine (SMZ) residue accumulation monitoring in laying hen feathers and sulfonamide residue monitoring on poultry feathers. SMZ residue accumulation in the laying hen feathers was studied after administration with 100 mg/kg of SMZ for 21 consecutive days. SMZ residues were still detected in feathers 14 days after drug administration and persisted for up to 85 days. Results from 42 poultry feather samples showed that the feather is a suitable medium to monitor the illegal use of sulfonamides in poultry production.

Detection of p-Nitroaniline Released from Degradation of 4,4'-Dinitrocarbanilide in Chicken Breast during Thermal Processing.

The diphenylurea 4,4'-dinitrocarbanilide (DNC) is the residue of concern left in edible tissues of broilers fed diets containing the anticoccidial nicarbazin. When chicken meat is submitted to thermal processing, p-nitroaniline (p-NA) is expected from DNC degradation. This work aimed at evaluating whether thermal processing of DNC-containing chicken meat induces p-NA appearance. First, a hydrolysis assay was performed in aqueous solutions at 100 °C in different pH, confirming that DNC cleavage yields p-NA. Then a novel LC-MS/MS method was used to detect traces of this aromatic amine in DNC-containing chicken breast fillets subjected to cooking methods. Our evidence showed p-NA occurrence in such chicken meat samples, which corroborated results from hydrolysis assay. The p-NA appearance in fillets was rather discrete during boiling treatment, but its concentration became pronounced over time for grilling, frying, and roasting, achieving respectively 326.3, 640.0, and 456.9 µg/kg. As far as we are concerned, no other research identified degradation products from DNC residue in heat-processed chicken fillets. Therefore, this study leads to additional approaches to assess impacts on food safety.

Residue behaviours, dissipation kinetics and dietary risk assessment of pyaclostrobin, cyazofamid and its metabolite in grape.

BACKGROUND: Grape is an important fruit consumed either fresh or processed, therefore, fungicide misuse of grape has become an issue of global food safety and human health. Pyraclostrobin, and cyazofamid have been applied to grape frequently. RESULTS: Here a simple QuEChERS (quick, easy, cheap, effective, rugged, and safe) liquid chromatography mass spectrometry technique has been developed and validated for the determination of pyraclostrobin, cyazofamid and its metabolite CCIM in open field grape samples. The recoveries of these three in the range of 0.01 to 5 mg kg-1 (n = 5) ranged from 73.1% to 97.9%. The relative standard deviations (RSDs) were below 12% for all cases. The limits of quantitation of each analyte was 0.005 mg kg-1 , which was lower than maximum residue limits of not only pyraclostrobin but also cyazofamid. Not only dissipation kinetics but also residue determination was obtained in grape for those three pesticides. Furthermore, their half-lives in grapes were 10.7-30.1 days, recommending the pre-harvest intervals for these three of 14 days. The calculated hazard quotient and acute hazard index lower than 100% illustrated the safety of intake of grape for the Chinese population for not only long-term but also short-term dietary risk assessment. CONSLUSIONS: The less than 30 day half-life illustrated that pyraclostrobin and cyazofamid could degrade relatively easily in the environment. The long-term and short-term dietary risk assessment also illustrated the intake safety of these three. Thus, a 14 day pre-harvest interval was safe and recommended. The results of this study contributed to environmental protection, food safety and human health. © 2019 Society of Chemical Industry.

Discovery of the Marker Residue of Olaquindox in Pigs, Broilers, and Carp.

The excretion, metabolism, distribution, and residue depletion of olaquindox (OLA), an antibacterial and growth-promoting agent used in food-producing animals for decades without a clear understanding of metabolic fate, was completely studied in pigs, broilers, carp, and rats using a radio-tracing approach combined with liquid chromatography-ion trap/time-of-flight mass spectroscopy to define the scientific marker residue (MR). After a single gavage of [3H]OLA, over 92% of the dose was excreted via urine. OLA was transformed into eight metabolites (O1-O8) in pigs and broilers, four metabolites (O1, O2, O4, and O7) in carp, and nine metabolites (O1-O9) in rats. O2 was the major residue in edible tissues of four species and persisted for the longest time in the kidneys with the longest half-life of 3.52-4.6 d. Bisdesoxyolaquindox (O2) is designated to be the MR, and the kidneys are considered to be the target tissue for OLA in food producing animals. Monitoring for this metabolite would improve the food safety evaluation and residue control of this drug.

Development and application of a population physiologically based pharmacokinetic model for florfenicol and its metabolite florfenicol amine in cattle.

Florfenicol (FF) is used in cattle to treat respiratory diseases but could result in tissue residues. This study aimed to develop a population physiologically based pharmacokinetic (PBPK) model to predict the concentrations of FF and its metabolite, florfenicol amine (FFA), in cattle after four different routes of administration, and to calculate and compare the withdrawal intervals (WDIs) with approved withdrawal times based on different marker residues and their MRLs or tolerances. A flow-limited PBPK model including both FF and FFA sub-models were developed with published data using acslXtreme. This model predicted FF and FFA concentrations in tissues and plasma/serum after intramuscular or subcutaneous administration. Based on the model, the WDIs of 46 and 58 days were calculated to ensure that total residue concentrations (FF + FFA) in 95th percentile of the population after intramuscular and subcutaneous administration were below the MRL, respectively. WDIs were calculated as 44 and 47 days to ensure that FFA concentrations after intramuscular and subcutaneous administration fell below tolerances in 99th percentile of the population, respectively. WDIs were longer than the corresponding label in China, US, and EU. This model provides a useful tool to predict tissue residues of FF and FFA in cattle to improve food safety.