Identification of the dimethylbenzyl mercapturic acid in urine of rats treated with 1,2,3-trimethylbenzene

The structure was investigated of the mercapturic acid excreted in urine of rats after the ip administration of 1,2,3-trimethylbenzene. Of the two regioisomeric mercapturic acids, ie N-acetyl-S-(2,3-dimethylbenzyl)-L-cysteine and N-acetyl-S-(2,6-dimethyl-benzyl)-L-cysteine, only the former was isolated by preparative HPLC and identified, by comparison with an authentic specimen. The excretion rate of the mercapturate was estimated to be 5% of dose, not a substantial metabolic route.