title: Melatonin does not react rapidly with hydrogen peroxide.
abstract: It has been claimed that melatonin reacts directly with hydrogen peroxide with a very high rate constant (2.5 x 10(5)-2.3 x 10(6) M(-1) s(-1)) Both these values were derived from inhibition by melatonin of peroxidase-catalyzed oxidation of Phenol Red by hydrogen peroxide, assuming that this inhibition is due to direct scavenging of hydrogen peroxide by melatonin. In this study, we show that this reasoning is illegitimate and melatonin decreases the yield of oxidation of Phenol Red as a competitive substrate. Monitoring changes of concentration of hydrogen peroxide incubated with melatonin using Xylenol Orange points to poor reactivity of melatonin with H2O2.
authors.affiliation: Department of Molecular Biophysics, University of Łódź, Banacha 12/16, 90-237 Łódź, Poland. agrzelak@biol.uni.lodz.pl
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Grzelak
authors.forename: Ewa
authors.initials: E
authors.lastname: Macierzyńska
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Bartosz
mesh_terms: D002839:Chromans / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008550:Melatonin / Q000737:chemistry* / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D010636:Phenols; D010637:Phenolsulfonphthalein / Q000737:chemistry; D013454:Sulfoxides; D013997:Time Factors; D014364:Tryptophan / Q000494:pharmacology; D014443:Tyrosine / Q000494:pharmacology; D014992:Xylenes / Q000737:chemistry
chemical_list: D002839:Chromans; D010636:Phenols; D013454:Sulfoxides; D014992:Xylenes; D014443:Tyrosine; D014364:Tryptophan; D006861:Hydrogen Peroxide; D010637:Phenolsulfonphthalein; D008550:Melatonin; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; C016833:xylenol orange