Abstract
Melatonin is being increasingly promoted as a treatment for 'jet lag' and insomnia and has been suggested to act as an antioxidant in vivo. The antioxidant and potential pro-oxidant activities of melatonin were investigated in vitro. Melatonin was able to scavenge hypochlorous acid (HOCl) at a rate sufficient to protect catalase against inactivation by this molecule. Melatonin could also prevent the oxidation of 5-thio-2- nitrobenzoic acid by HOCl. Melatonin decreased the peroxidation of ox-brain phospholipids with a calculated IC50 of (210 ± 2.3) μM. In contrast, serotonin which also scavenged HOCl, was much more effective in decreasing phospholipid peroxidation (IC50 15 ± 5 μM). Both compounds reacted with trichloromethylperoxyl radical (CCl3O2) with rate constants of (2.7 ± 0.2) x 108 and (1.2 ± 0.1) x 108 M-1 s-1 respectively. Melatonin did not scavenge superoxide radical and weakly protected DNA against damage by the ferric bleomycin system. By contrast serotonin was weakly pro-oxidant in the ferric-bleomycin system and strongly pro-oxidant in the Fe3+- EDTA/H2O2-deoxyribose system. Solubility restrictions precluded examination of melatonin in this system. Our data show that melatonin exerts only limited direct antioxidant activities.
Original language | English (US) |
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Pages (from-to) | 307-315 |
Number of pages | 9 |
Journal | Free Radical Biology and Medicine |
Volume | 21 |
Issue number | 3 |
DOIs | |
State | Published - 1996 |
Keywords
- Melatonin
- antioxidants
- free radicals
- lipid peroxidation
- peroxyl radicals
ASJC Scopus subject areas
- Biochemistry
- Physiology (medical)