Urinary metabolites and antioxidant products of exogenous melatonin in the mouse

Xiaochao Ma, Jeffrey R. Idle, Kristopher W. Krausz, Dun Xian Tan, Leopoldo Ceraulo, Frank J. Gonzalez

Research output: Contribution to journalArticlepeer-review

51 Scopus citations


Exogenous melatonin is widely used for sleep disorders and has potential value in neuroprotection, cardioprotection and as an antioxidant. Here, a novel method is described for the determination of melatonin and six metabolites in mouse urine by use of q1LC-MS/MS and GC-MS. LC-MS/MS is used for the measurement of melatonin, N1-acetyl-5-methoxykynuramine (AMK), N 1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and 6-hydroxymelatonin (6-HMEL), while GC/MS is used for the determination of N-[2-(5-methoxy-2-oxo-2,3-dihydro-1H-indol-3-yl)-ethyl]-acetamide (2-OMEL) and cyclic 3-hydroxymelatonin (3-HMEL) with detection limits on column of 0.02-0.5 pmol, depending on the metabolite. Following oral administration of melatonin to mice, a 0-24 hr urine collection revealed the presence of melatonin (0.2% dose), 6-HMEL (37.1%) and NAS (3.1%) comprising >90% of the total metabolites; AMK and AFMK were also detected at 0.01% each; 2-OMEL was found at 2.2% of the dose, which is >100 times more than the AMK/AFMK pathway, and comprises >5% of the melatonin-related material detected in mouse urine. 3-HMEL was largely found as a sulfate conjugate. These studies establish sensitive assays for determination of six melatonin metabolites in mouse urine and confirm the potential for antioxidant activity of melatonin through the identification in vivo of AMK and AFMK, ring-opened metabolites with a high capacity for scavenging reactive oxygen species.

Original languageEnglish (US)
Pages (from-to)343-349
Number of pages7
JournalJournal of pineal research
Issue number4
StatePublished - May 2006
Externally publishedYes


  • Antioxidants
  • Melatonin
  • Mouse
  • Urine

ASJC Scopus subject areas

  • Endocrinology


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