Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/8/2003
Publication Date: 7/31/2003
Citation: Horne, E., Coyle, T., Okeeffe, M., Alvinerie, M., Galtier, P., Brandon, D.L. 2003. Release of protein-bound residues of thiabendazole from liver. Journal of Agricultural and Food Chemistry. 51:5552-5555. Interpretive Summary: In order to evaluate fully the safety of veterinary drugs used in food animals, it is important to characterize the residues which may ultimately enter the human food chain. Thiabendazole, used both as a fungicide and as a veterinary anti-worm compound, was used to treat cultures of rabbit liver cells, a model system which mimicks the formation of residues in food animals. Three methods were tested for releasing residues which are tightly bound to proteins within the cell. The most efficient procedure combined use of acidic conditions and enzyme treatment. The residues were isolated using column chromatography on immobilized monoclonal antibodies. The only molecule definitely identified was thiabendazole itself. The mechanism of its attachment to protein and the structures of additional residues not bound by the antibody columns may be revealed by further studies.
Technical Abstract: Tissue-bound residues of thiabendazole (TBZ), a veterinary anthelmintic and post-harvest fungicide, are formed when this compound is incubated with rabbit hepatocytes or administered to mice or pigs. Several pretreatment steps were investigated for removing free TBZ and metabolites prior to the release of bound residues, and three procedures were evaluated for the release of bound residues from solvent-extracted rabbit hepatocytes: incubation under acidic conditions, enzymatic action using cystathionine b-lyase, and Raney nickel desulphurisation. Immunoaffinity chromatography utilising monoclonal antibodies capable of binding TBZ or its 5-hydroxy metabolite enabled isolation of crossreactive residue fractions. Residues released from incurred pig liver and isolated by immunoaffinity included TBZ, as determined by HPLC with photodiode - array detection. The methodology described should facilitate food safety assessments of TBZ.