Significance of melatonin in antioxidative defense system

Reactions and products

Dun Xian Tan, Lucien C. Manchester, Russel J Reiter, Wen Bo Qi, Malgorzata Karbownik, Juan R. Calvo

Research output: Contribution to journalArticle

403 Citations (Scopus)

Abstract

Melatonin is a potent endogenous free radical scavenger, actions that are independent of its many receptor-mediated effects. In the last several years, hundreds of publications have confirmed that melatonin is a broad-spectrum antioxidant. Melatonin has been reported to scavenge hydrogen peroxide (H2O2), hydroxyl radical (HO·), nitric oxide (NO·), peroxynitrite anion (ONOO-), hypochlorous acid (HOCl), singlet oxygen (1O2), superoxide anion (O2-) and peroxyl radical (LOO·), although the validity of its ability to scavenge O2- and LOO· is debatable. Regardless of the radicals scavenged, melatonin prevents oxidative damage at the level of cells, tissues, organs and organisms. The antioxidative mechanisms of melatonin seem different from classical antioxidants such as vitamin C, vitamin E and glutathione. As electron donors, classical antioxidants undergo redox cycling; thus, they have the potential to promote oxidation as well as prevent it. Melatonin, as an electron-rich molecule, may interact with free radicals via an additive reaction to form several stable end-products which are excreted in the urine. Melatonin does not undergo redox cycling and, thus, does not promote oxidation as shown under a variety of experimental conditions. From this point of view, melatonin can be considered a suicidal or terminal antioxidant which distinguishes it from the opportunistic antioxidants. Interestingly, the ability of melatonin to scavenge free radicals is not in a ratio of mole to mole. Indeed, one melatonin molecule scavenges two HO·. Also, its secondary and tertiary metabolites, for example, N1-acetyl-N2-formyl-5-methoxykynuramine, N-acetyl-5-methoxykynuramine and 6- hydroxymelatonin, which are believed to be generated when melatonin interacts with free radicals, are also regarded as effective free radical scavengers. The continuous free radical scavenging potential of the original molecule (melatonin) and its metabolites may be defined as a scavenging cascade reaction. Melatonin also synergizes with vitamin C, vitamin E and glutathione in the scavenging of free radicals. Melatonin has been detected in vegetables, fruits and variety of herbs. In some plants, especially in flowers and seeds (the reproductive organs which are most vulnerable to oxidative insults), melatonin concentrations are several orders of magnitude higher than measured in the blood of vertebrates. Melatonin in plants not only provides an alternative exogenous source of melatonin may be an important antioxidant in plants which protects them from a hostile environment that includes extreme heat, cold and pollution, all of which generate free radicals. Copyright (C) 2000 S. Karger AG, Basel.

Original languageEnglish (US)
Pages (from-to)137-159
Number of pages23
JournalBiological Signals and Receptors
Volume9
Issue number3-4
StatePublished - 2000

Fingerprint

Melatonin
Free Radicals
Antioxidants
Scavenging
Free Radical Scavengers
Metabolites
Vitamin E
Hydroxyl Radical
Ascorbic Acid
Molecules
Oxidation-Reduction
Glutathione
Extreme Cold
Extreme Heat
Electrons
Hypochlorous Acid
Oxidation
Singlet Oxygen
Peroxynitrous Acid
Vegetables

Keywords

  • Antioxidants
  • Free radicals
  • Melatonin
  • Metabolite
  • Plants
  • Reactive oxygen species

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

Cite this

Tan, D. X., Manchester, L. C., Reiter, R. J., Qi, W. B., Karbownik, M., & Calvo, J. R. (2000). Significance of melatonin in antioxidative defense system: Reactions and products. Biological Signals and Receptors, 9(3-4), 137-159.

Significance of melatonin in antioxidative defense system : Reactions and products. / Tan, Dun Xian; Manchester, Lucien C.; Reiter, Russel J; Qi, Wen Bo; Karbownik, Malgorzata; Calvo, Juan R.

In: Biological Signals and Receptors, Vol. 9, No. 3-4, 2000, p. 137-159.

Research output: Contribution to journalArticle

Tan, DX, Manchester, LC, Reiter, RJ, Qi, WB, Karbownik, M & Calvo, JR 2000, 'Significance of melatonin in antioxidative defense system: Reactions and products', Biological Signals and Receptors, vol. 9, no. 3-4, pp. 137-159.
Tan, Dun Xian ; Manchester, Lucien C. ; Reiter, Russel J ; Qi, Wen Bo ; Karbownik, Malgorzata ; Calvo, Juan R. / Significance of melatonin in antioxidative defense system : Reactions and products. In: Biological Signals and Receptors. 2000 ; Vol. 9, No. 3-4. pp. 137-159.
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