Melatonin directly scavenges free radicals generated in red blood cells and a cell-free system: Chemiluminescence measurements and theoretical calculations

I. B. Zavodnik, A. V. Domanski, E. A. Lapshina, M. Bryszewska, R. J. Reiter

Research output: Contribution to journalArticle

73 Scopus citations

Abstract

Melatonin, a pineal secretory product, has properties of both direct and indirect powerful antioxidant. The aim of the present study was to compare the radical-scavenging, structural and electronic properties of melatonin and tryptophan, precursor of melatonin. Using the alkoxyl- and peroxyl radical-generating systems [the organic peroxide-treated human erythrocytes and a cell-free system containing the azo-initiator 2,2′-azobis(2-amidinopropane)dihydrochloride], we evaluated the radical-scavenging effects of melatonin and tryptophan. Melatonin rather than tryptophan at concentrations of 100-2000 μM markedly inhibited membrane lipid peroxidation in human erythrocytes treated with organic hydroperoxide as well as radical-induced generation of luminol-dependent chemiluminescence. The apparent Stern-Volmer constants for inhibition of membrane lipid peroxidation by melatonin and tryptophan were estimated to be (0.23 ± 0.05) × 104 M- 1 and (0.02 ± 0.005) × 104 M- 1, respectively. The apparent Stern-Volmer constants for inhibition of azo-initiator-derived peroxyl radical generation by melatonin and tryptophan were determined to be (0.42 ± 0.05) × 104 M- 1 and (0.04 ± 0.01) × 104 M- 1, respectively. The structural and electronic properties of melatonin and its precursor, tryptophan, were determined theoretically by performing semi-empirical and ab initio calculations. The high radical-scavenging properties of melatonin may be explained by the high surface area value and high dipole moment value. From the thermodynamic standpoint, based on our calculations, N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK), was the most stable end oxidative product of melatonin.

Original languageEnglish (US)
Pages (from-to)391-400
Number of pages10
JournalLife Sciences
Volume79
Issue number4
DOIs
StatePublished - Jun 20 2006

Keywords

  • Free radicals
  • Melatonin
  • Molecular structure
  • tert-Butyl hydroperoxide

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)

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