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Oxidation of melatonin by taurine chloramine.
J Pineal Res. 2010 Sep; 49(2):115-22.JP

Abstract

Melatonin is widely known for its antioxidant, immunomodulatory, and anti-inflammatory effects. Hypochlorous acid (HOCl) is one example of an endogenous oxidant that is promptly neutralized by melatonin. Melatonin also inhibits myeloperoxidase, the enzyme that catalyzes the oxidation of chloride to HOCl. Taurine is the most abundant free amino acid in leukocytes. In activated neutrophils, taurine is converted to taurine chloramine (Tau-NHCl) through a reaction with HOCl. In addition, the related compound taurine bromamine (Tau-NHBr) can be released by neutrophils and eosinophils. The aim of this study was to investigate the reactivity of Tau-NHCl and Tau-NHBr with melatonin. We found that melatonin can react with either Tau-NHCl or Tau-NHBr, leading to the production of 2-hydroxymelatonin and N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK). The reaction was pH-dependent, and it occurs more rapidly at a slightly acidic pH. Tau-NHBr was significantly more reactive than Tau-NHCl. Using Tau-NHBr as the oxidizing agent, 1 mm melatonin was oxidized in less than 1 min. The pH dependence of the reaction with Tau-NHCl and the increased reactivity of Tau-NHBr can be explained by a mechanism based on the initial attack of chloronium (Cl(+)) or bromonium (Br(+)) ions on melatonin. We also found that the addition of iodide to the reaction medium increased the yield of AFMK. These findings could contribute to the establishment of new functions for melatonin in inflammatory and parasitic diseases, where the role of this indoleamine has been extensively investigated.

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Authors+Show Affiliations

Ximenes VF
Departamento de Química, Faculdade de Ciências, Unesp - Univ Estadual Paulista, Bauru, SP, Brasil. vfximenes@fc.unesp.br
Padovan CZ
No affiliation info available
Carvalho DA
No affiliation info available
Fernandes JR
No affiliation info available

MeSH

Chromatography, High Pressure LiquidHydrogen-Ion ConcentrationHypochlorous AcidIodidesKineticsKynuramineMelatoninOxidation-ReductionTaurine

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

20545824

Citation

Ximenes, Valdecir F., et al. "Oxidation of Melatonin By Taurine Chloramine." Journal of Pineal Research, vol. 49, no. 2, 2010, pp. 115-22.
Ximenes VF, Padovan CZ, Carvalho DA, et al. Oxidation of melatonin by taurine chloramine. J Pineal Res. 2010;49(2):115-22.
Ximenes, V. F., Padovan, C. Z., Carvalho, D. A., & Fernandes, J. R. (2010). Oxidation of melatonin by taurine chloramine. Journal of Pineal Research, 49(2), 115-22. https://doi.org/10.1111/j.1600-079X.2010.00772.x
Ximenes VF, et al. Oxidation of Melatonin By Taurine Chloramine. J Pineal Res. 2010;49(2):115-22. PubMed PMID: 20545824.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Oxidation of melatonin by taurine chloramine. AU - Ximenes,Valdecir F, AU - Padovan,Camila Z, AU - Carvalho,Danielle A, AU - Fernandes,João Roberto, Y1 - 2010/05/27/ PY - 2010/6/16/entrez PY - 2010/6/16/pubmed PY - 2010/12/18/medline SP - 115 EP - 22 JF - Journal of pineal research JO - J Pineal Res VL - 49 IS - 2 N2 - Melatonin is widely known for its antioxidant, immunomodulatory, and anti-inflammatory effects. Hypochlorous acid (HOCl) is one example of an endogenous oxidant that is promptly neutralized by melatonin. Melatonin also inhibits myeloperoxidase, the enzyme that catalyzes the oxidation of chloride to HOCl. Taurine is the most abundant free amino acid in leukocytes. In activated neutrophils, taurine is converted to taurine chloramine (Tau-NHCl) through a reaction with HOCl. In addition, the related compound taurine bromamine (Tau-NHBr) can be released by neutrophils and eosinophils. The aim of this study was to investigate the reactivity of Tau-NHCl and Tau-NHBr with melatonin. We found that melatonin can react with either Tau-NHCl or Tau-NHBr, leading to the production of 2-hydroxymelatonin and N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK). The reaction was pH-dependent, and it occurs more rapidly at a slightly acidic pH. Tau-NHBr was significantly more reactive than Tau-NHCl. Using Tau-NHBr as the oxidizing agent, 1 mm melatonin was oxidized in less than 1 min. The pH dependence of the reaction with Tau-NHCl and the increased reactivity of Tau-NHBr can be explained by a mechanism based on the initial attack of chloronium (Cl(+)) or bromonium (Br(+)) ions on melatonin. We also found that the addition of iodide to the reaction medium increased the yield of AFMK. These findings could contribute to the establishment of new functions for melatonin in inflammatory and parasitic diseases, where the role of this indoleamine has been extensively investigated. SN - 1600-079X UR - https://www.unboundmedicine.com/medline/citation/20545824/Oxidation_of_melatonin_by_taurine_chloramine_ L2 - https://doi.org/10.1111/j.1600-079X.2010.00772.x DB - PRIME DP - Unbound Medicine ER -