Distribution, metabolism, and excretion of musk xylene in rats

Distribution, metabolism and excretion of musk xylene (MX) were investigated in male Wistar rats. Urinary and fecal excretion accounted for 10 and 75% of the dose (70 mg/kg), respectively, on day 7 after orally administration of 3H-MX to rats. Total residue of radioactivity in tissues on day 7 was less than 2.0% of the administered dose. The highest concentration was found in adipose tissue and the second was in liver. Some metabolites of MX were identified using GC-MS and NMR after purification by column or thin layer chromatography of feces, bile and urine extracts. MX, 2-NH2-MX, 2-Ac-MX, 2-NH2-3-CH2OH-MX, and 2-NH2-5-tert-BuOH-MX were found in feces, bile and urine. 4-NH2-MX and metabolite X were found in feces and urine. 4-NH2-3-CH2OH-MX was found in urine. HO-MX was found in bile. The major route of excretion for MX was the feces via bile. The reduction of the 2-nitro group of MX to the amino group was a key step in metabolism. Further metabolism of 2-NH2-MX may proceed by decreased steric hindrance of functional group.