Anti-AOZ polyclonal antibody

1. The major metabolite resulting from the biotransformation of furaltadone (5-morpholinomethyl- 3-[5-nitrofurfurylidene-amino]-2-oxazolidinone) by pig hepatocytes was shown to result from the N-oxidation of the tertiary nitrogen in the morpholino-ring, leaving the nitrofuran ring unchanged. 2. No evidence could be obtained for the formation of an open-chain cyano-metabolite, a minor metabolite in the case of the related nitrofuran drug furazolidone (N-(5-nitro-2-furfurylidene)-3-amino-2-oxazolidinone). This metabolite was the major metabolite, following incubation of furaltadone and furazolidone with Salmonella typhimurium bacteria. 3. The N-oxide was not further metabolized by pig hepatocytes or bacteria, and gave negative test results in the Ames-test (TA 100, no S9-mix) at the highest tested dose of 1 mu g/plate. Furaltadone gave a positive result at 10 ng/plate. 4. The biotransformation of both drugs by pig hepatocytes and bacteria resulted in the formation of protein-bound metabolites, with no clear quantitative differences between the two drugs. The intact 3-amino-2-oxazolidinone (AOZ) and 5-morpholinomethyl-3-amino-2-oxazolidinone (AMOZ) side-chains of furazolidone and furaltadone, respectively, could be released from these metabolites by mild acid treatment. 5. Hepatocytes incubated with the AMOZ side-chain of furaltadone showed a decreased monoamine oxidase activity at high dose levels (IC50 3.7 mM), whereas exposure to the AOZ side-chain of furazolidone resulted in a clear inhibition at 10 000-fold lower concentrations (IC50 0.5 mu M). In the presence of 1% dimethylsulphoxide (DMSO), the MAO-inhibition by AMOZ and especially AOZ was remarkably reduced. 6. It is concluded that protein-bound metabolites containing an intact and releasable side-chain might be present in tissues of animals treated with furaltadone. However, these residues might be of less toxicological concern than those of furazolidone.

Nitrofuran antibiotics cannot be used in food production within the European Union because of their potential health risks to consumers. The recent discovery of their widespread use in global food industries and the finding of semicarbazide in baby food as a result of packaging contamination have focused attention on the toxicity and stability of these drugs and their metabolites. The stability of the nitrofuran marker residues 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidone (AMOZ), 1-aminohydantoin (AHD) and semicarbazide (SEM) were tested. Muscle and liver of nitrofuran treated pigs were cooked by frying, grilling, roasting and microwaving. Between 67 and 100% of the residues remained after cooking, demonstrating that these metabolites are largely resistant to conventional cooking techniques and will continue to pose a health risk. The concentration of metabolites in pig muscle and liver did not drop significantly during 8 months of storage at -20 degrees C. Metabolite stock and working standard solutions in methanol were also stable for 10 months at 4 degrees C. Only a 10 ng ml(-1) solution of SEM showed a small drop in concentration over this extended storage period.