Metabolite residues

Cefon, J.J., Gutierrez-Panizo, C., Barba, A., and Camara, M.A.Endosulfan isomers and metabolite residue degradation incarnation (Dianthus caryophyllu by-product under different environmental conditions, / Environ. Sci. Health, B30(2) 221-232, 1995. 

Holt, R.F. Determination of hexazinone and metabolite residues using nitrogen-selective gas chromatography, J. Agric. Food CAem.,29(l) 165-172, 1981. 

Because of its widespread therapeutic use and because the question of residues in food producing animals, SDM was selected for a study between species to compare its metabolism, the pharmacokinetics of the parent drug as well as its metabolites. Residue depletion studies were performed in edible tissues of calves, pigs and in the eggs of laying-hens. 

Table 27.3 Estimated dietary exposure to atrazine and corresponding chloro-metabolite residues (Tier I versus Tier III)a...

Metabolite/residue analysis. Milk, urine and plasma samples were first analyzed by a microbiological cylinder/plate procedure against M.luteus which has a limit of detection of 0.02 ppm. A sub-sample of the milk was prepared for this assay by a centrifugation step followed by a pH adjustment to 8.5. In addition, an HPLC/RAM analysis was conducted after treating another sub-sample with FTSH (10% formic acid, 30% trifluoroacetic acid, 2% sodium chloride, 2N hydrochloric acid) followed by centrifugation to precipitate the proteins. The supernatant was basified and concentrated by C-18 solid phase extraction (SPE) techniques. The HPLC conditions were Column - 20 cm x 4.8 mm C-8 Mobile-phase -linear gradient at 5%/minute from 90 10 O.IM pH 7 phosphate buffer methanol to 20 80 Detectors - UV operated at 214 nm and a radioactivity flow detector operated in the DPM mode. 

Ceftiofur is known to rapidly metabolize after intramuscular administration, resulting in metabolite residues found in milk and tissue. Reported metabolites include desfuroylceftlofur (DEC), desfuroylceftlofur cysteine disulfide (DCCD), protein-bound DEC, and ceftiofur thiolactone. " Because these metabolites are all micro-biologically active, the EU MRL was defined as the sum of all residues retaining the f)-lactam structure, expressed as DEC, " whereas the Codex Alimentarius Commission (CAC) defined DEC as the only marker residue, simplifying the analysis. This approach is also used in the United States of America. 

This discussion will be related to the fate of pesticides in animals and plants where humans may be exposed to intake of metabolite residues. This area of pesticide biochemical research still has problems that involve identification of metabolites, recognizing the significance of major and minor metabolites, interpretation of data, and the significance of the results as they relate to the toxicity of the compound. 

Tissue blood partition coefficients were developed for the parent pyrethroids and their metabolites, by using a published mechanistic model introduced by Poulin and Thiele (2002a b) and log Dpn 7 4 values. The estimated coefficients, especially those of adipose tissue, were too high and had to be corrected by using a procedure in which the proportion of parent or metabolite residues that are unbound to plasma albumin is considered, as described in the GastroPlus model (SimulationsPlus, Inc., Lancaster, CA). The literature suggested that values be adjusted by multiplying... 

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