The metabolism of benzyl isothiocyanate and its cysteine conjugate in guinea-pigs and rabbits

1. Following oral administration of benzyl isothiocyanate or its cysteine conjugate the major metabolite isolated from urine of guinea-pigs and rabbits was a cyclic mercaptopyruvate conjugate, 4-hydroxy-4-carboxy-3-benzylthiazolidin-2-thione.2. Renal excretion of the metabolite after oral administration of benzyl isothiocyanate or its cysteine conjugate to guinea-pigs amounted to 23% and 33% respectively.The corresponding N-acetylcysteine conjugate of benzyl isothiocyanate (a mercapturic acid) was present as a minor metabolite.3. After oral or i.v. administration of the glutathione, cysteinylglycine, cysteine or N-acetylcysteine conjugates of benzyl isothiocyanate to guinea-pigs, the major metabolite in urine was 4-hydroxy-4-carboxy-3-benzylthiazolidin-2-thione, with the N-acetylcysteine conjugate of benzyl isothiocyanate present in traces only.4. It is concluded that during formation of the cyclic mercaptopyruvate conjugate, the cysteine conjugate predominantly undergoes transamination, and only a small ...