Article · Wikipedia archive · Last revised Jul 21, 2026

6-Hydroxymelatonin

6-Hydroxymelatonin (6-OHM) is a naturally occurring, endogenous, major active metabolite of melatonin. 6-Hydroxymelatonin is produced as a result of the enzymatic conversion of melatonin through hydroxylation. Similar to melatonin, 6-OHM is a full agonist of the MT1 and MT2 receptors. It is also an antioxidant and neuroprotective, and is even more potent in this regard relative to melatonin.

Last revised
Jul 21, 2026
Read time
≈ 2 min
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Wikipedia ↗
6-Hydroxymelatonin
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Names
Preferred IUPAC name
N-[2-(6-Hydroxy-5-methoxy-1H-indol-3-yl)ethyl]acetamide
Other names
6-Oxymelatonin
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.164.426
KEGG
UNII
  • InChI=1S/C13H16N2O3/c1-8(16)14-4-3-9-7-15-11-6-12(17)13(18-2)5-10(9)11/h5-7,15,17H,3-4H2,1-2H3,(H,14,16)
    Key: OMYMRCXOJJZYKE-UHFFFAOYSA-N
  • InChI=1/C13H16N2O3/c1-8(16)14-4-3-9-7-15-11-6-12(17)13(18-2)5-10(9)11/h5-7,15,17H,3-4H2,1-2H3,(H,14,16)
    Key: OMYMRCXOJJZYKE-UHFFFAOYAK
  • CC(=O)NCCC1=CNC2=CC(=C(C=C21)OC)O
Properties
C13H16N2O3
Molar mass 248.282 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

6-Hydroxymelatonin (6-OHM) is a naturally occurring, endogenous, major active metabolite of melatonin.1 6-Hydroxymelatonin is produced as a result of the enzymatic conversion of melatonin through hydroxylation.2 Similar to melatonin, 6-OHM is a full agonist of the MT1 and MT2 receptors.34 It is also an antioxidant and neuroprotective, and is even more potent in this regard relative to melatonin.56

Role in metabolism

The determination of 6-OHM in human urine has been used to track the metabolism and excretion of melatonin using LC-MS/MS, providing quantifiable insights into circadian rhythm regulation and its oxidative role as a biomarker.7 6-OHM is one of four of the primary metabolic products of melatonin in the liver and is also a byproduct of its breakdown due to exposure to light. It is known to be very effective in protecting cells from oxidative damage caused by ultraviolet (UV) radiation.8 Based on comparisons with other melatonin-related compounds, it is suggested that the protective effects of 6-OHM in mitigating oxidative stress are primarily attributed to their ability to scavenge free radicals.9

See also

See also

References

References

  1. Hardeland R (2010). "Melatonin metabolism in the central nervous system". Curr Neuropharmacol. 8 (3): 168–81. doi:10.2174/157015910792246164. PMC 3001211. PMID 21358968.
  2. Magliocco, G.; Le Bloc'h, F.; Thomas, A.; Desmeules, J.; Daali, Y. (2021-09-01). "Simultaneous determination of melatonin and 6-hydroxymelatonin in human overnight urine by LC-MS/MS". Journal of Chromatography. 1181 122938. doi:10.1016/j.jchromb.2021.122938. PMID 34521018.
  3. Dubocovich ML (1988). "Pharmacology and function of melatonin receptors". FASEB J. 2 (12): 2765–73. doi:10.1096/fasebj.2.12.2842214. PMID 2842214. S2CID 45788574.
  4. Browning, Christopher; Beresford, Isabel; Fraser, Neil; Giles, Heather (2000). "Pharmacological characterization of human recombinant melatonin mt1and MT2receptors". British Journal of Pharmacology. 129 (5): 877–886. doi:10.1038/sj.bjp.0703130. ISSN 0007-1188. PMC 1571913. PMID 10696085.
  5. Maharaj DS, Glass BD, Daya S (2007). "Melatonin: new places in therapy". Biosci. Rep. 27 (6): 299–320. doi:10.1007/s10540-007-9052-1. PMID 17828452. S2CID 32437175.
  6. Álvarez-Diduk R, Galano A, Tan DX, Reiter RJ (2015). "N-Acetylserotonin and 6-Hydroxymelatonin against Oxidative Stress: Implications for the Overall Protection Exerted by Melatonin". J Phys Chem B. 119 (27): 8535–43. doi:10.1021/acs.jpcb.5b04920. PMID 26079042.
  7. Magliocco, G.; Le Bloc'h, F.; Thomas, A.; Desmeules, J.; Daali, Y. (2021-09-01). "Simultaneous determination of melatonin and 6-hydroxymelatonin in human overnight urine by LC-MS/MS". Journal of Chromatography B. 1181 122938. doi:10.1016/j.jchromb.2021.122938. PMID 34521018.
  8. Maharaj, Deepa S.; Anoopkumar-Dukie, Shailendra; Glass, Beverley D.; Antunes, Edith M.; Lack, Barbara; Walker, Roderick B.; Daya, Santy (2002-04-30). "The identification of the UV degradants of melatonin and their ability to scavenge free radicals". Journal of Pineal Research. 32 (4): 257–261. doi:10.1034/j.1600-079x.2002.01866.x. ISSN 0742-3098. PMID 11982796.
  9. Álvarez-Diduk, Ruslán; Galano, Annia; Tan, Dun Xian; Reiter, Russel J. (2015-07-09). "N -Acetylserotonin and 6-Hydroxymelatonin against Oxidative Stress: Implications for the Overall Protection Exerted by Melatonin". The Journal of Physical Chemistry B. 119 (27): 8535–8543. doi:10.1021/acs.jpcb.5b04920. ISSN 1520-6106. PMID 26079042.