title: Melatonin does not "directly scavenge hydrogen peroxide": demise of another myth.
abstract: We have reexamined claims that melatonin directly scavenges hydrogen peroxide and shown them to be unfounded. Relative hydrogen peroxide concentrations were determined in the absence and presence of melatonin using both an isoluminol-based chemiluminescence assay (with measurements at circa 40 s, 6 h, and 24 h after mixing) and the phenol red/horseradish peroxidase assay employed by two earlier groups of workers (with measurements at 5 s, then every minute for the first 5 min, and then every hour to 5 h). Both assay procedures were in agreement. There was no significant change in the hydrogen peroxide concentrations over 24 h, and, furthermore, the concentrations of H(2)O(2) in the presence and absence of melatonin were the same within experimental error. Our results were obtained in metal ion-free systems. It therefore appears likely that the claims for a direct melatonin/H(2)O(2) reaction were due to contamination by traces of transition metal ions.
authors.affiliation: National Research Council of Canada, Ottawa, ON, Canada.
authors.forename: Grant
authors.initials: G
authors.lastname: Fowler
authors.forename: Malgosia
authors.initials: M
authors.lastname: Daroszewska
authors.forename: Keith U
authors.initials: KU
authors.lastname: Ingold
mesh_terms: D016166:Free Radical Scavengers / Q000494:pharmacology*; D006735:Horseradish Peroxidase / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry*; D008163:Luminescent Measurements; D008550:Melatonin / Q000494:pharmacology*; D010637:Phenolsulfonphthalein / Q000737:chemistry
chemical_list: D016166:Free Radical Scavengers; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D010637:Phenolsulfonphthalein; D008550:Melatonin