Melatonin contaminants

Williamson BL, Tomlinson AJ, Naylor S, et al. Contaminants in commercial preparations of melatonin [Letter]. Mayo Clin Proc 1997 72 1094-1095. 

It is unclear whether this was a direct hepatotoxic effect of melatonin (or a contaminant), or if hepatitis was caused indirectly by an immunomodulatory mechanism. 

The reliability and consistency of commercial melatonin has been questioned (3). One group analysed three commercial melatonin formulations and identified analogues of the contaminant of L-tryptophan compounds implicated in an epidemic of eosinophilia-myalgia syndrome in the 1980s (27). There have been no reports of this condition associated with melatonin consumption, but food supplements are not required to comply with the same manufacturing and monitoring quality control standards as drugs. 

Drugs that are not regulated by the FDA are more likely to be contaminated with impurities. They may also be inaccurately labeled and not contain the amount of melatonin listed on the label. According to the National Sleep Foundation, a batch of melatonin was examined and found to contain much more of the hormone than was listed on the label. According to another study, one third of the medications that supposedly contained melatonin did not contain any melatonin, while an additional 40% contained much less than was stated on the label. 

Williamson, B. L. Tomlinson, A. I Mishra, P. K. Gleich, G. J. Naylor, S. 1998. Structural characterization of contaminants found in commercial preparations of melatonin similarities to case-related compounds from L-tryptophan associated with eosinophilia-myalgia syndrome. Chem. Res. Toxicol., 11,234-240. 

Published analysis of three commercial melatonin preparations revealed the presence of seven contaminants, shown to be present at 0.1-0.5% in all products. Four of the contaminants were identified as... 

Naylor S, Johnson KL, Williamson BL, Klarskov K, and Gleich GJ (1999) Structural characterization of contaminants in commercial preparations of melatonin by on-line HPLG-electrospray ionization-tandem mass spectrometry. Advances in Experimental Medicine and Biology 467 769-777. 

Abdel-Wahhab, M.A., Abdel-Galil, M.M. El Lithey, M. (2005) Melatonin counteracts oxidative stress in rats ted an ochratoxin A contaminated diet. J. Pineal Res. 38, 130-135. 

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