The mass spectrometric analysis of the urinary metabolites of melatonin and its deuterated analogues, confirming their identity as N-acetylserotonin and 6-hydroxymelatonin.

In a recent study, we showed that melatonin could be metabolized to N-acetylserotonin and 6-hydroxymelatonin. To confirm this finding rats were administered three different forms of deuterated melatonin intraperitoneally. Their urines were analysed by gas chromatography/mass spectrometry and the results showed, in each case, that the appropriate deuterated (or non-deuterated) metabolite had been formed. From these data it is clear that N-acetylserotonin is a urinary metabolite of melatonin.