The chemistry of melatonin's interaction with reactive species

Abstract

Melatonin has been shown to be an effective antioxidant in a number of experimental models both in vitro and in vivo. Considering the data available, it is now clear that the indoleamine is involved in antioxidative mechanisms more complex than originally envisaged. These range from the direct radical scavenging of a variety of radicals and reactive species to the control and/or modulation of a number of processes which may trigger a redox imbalance between antioxidant and prooxidant species. This review focuses on the direct radical scavenging activity of melatonin and provides a summary of the mechanisms of the reactions between the indoleamine and reactive species in pure chemical solutions. These actions likely account for at least some of the protective actions of melatonin under conditions of high oxidative stress.

Does Melatonin Ameliorate Neurological Changes Associated With Alzheimer’s Disease in Ovariectomized Rat Model?

“…Melatonin has a powerful scavenging activity for hydroxyl and peroxyl radicals over that of both glutathione and vitamin E. Melatonin also conserves the activities of the antioxidant enzymes via enhancing gene expression of these enzymes [29]. Melatonin has a phenol group that provides a proton to detoxify hydroxyl or lipid peroxy radicals and thus can reduce lipid peroxidation induced by Al in Alzheimer's patients [30]. Also, melatonin has the ability to serve as a metal chelator to reduce metal toxicity [31].…”

Melatonin ameliorates experimental hepatic fibrosis induced by carbon tetrachloride in rats

“…Pathologic grading showed that the fibrogenesis was much less severe in CCl 4 Moreover, treatment with melatonin (5, 10 mg/kg) significantly reduced the MDA content and increased the GPx activity in liver homogenates compared with model control group (MDA: 7.89 ± 1.49 noml/mg prot vs 6.29 ± 1.42 noml/mg prot and 6.25 ± 2.27 noml/mg prot, respectively, P = 0.015, P = 0.015; GPx: 49.13 ± 8.72 U/mg prot vs 57.38 ± 7.65 U/mg prot and 61.39 ± 13.15 U/mg prot, respectively, P = 0.035, P = 0.003).…”

“…Melatonin (N-acetyl-5-metyoxytr yptamine), a secretory product of the pineal gland, is a powerful endogenous antioxidant, regulates circadian rhythms, sleep and immune system activity, behaves as a free radical scavenger [4] , eliminates oxygen free radicals and reactive intermediates [5][6][7][8][9] . Both in vitro and in vivo experiments have shown that melatonin can protect cells, tissues, and organs against oxidative damage induced by a variety of free-radical-generating agents and processes, such as safrole, lipopolysaccharide (LPS), carbon tetrachloride (CCl 4 ), ischemia-reperfusion, amyloid-protein, and ionizing radiation [10][11][12] .…”

Therapeutic Effect of Melatonin in Experimental Uveitis

“…24 It was demonstrated that melatonin has an important immunomodulatory role and it may provide neuroprotection in different systems. 25 Although the full range of physiological actions of melatonin is still not completely known, it has been demonstrated that melatonin possesses widespread free radical scavenging and antioxidant activities, 26,27 and that some of its scavenging actions are likely due to its metabolites, cyclic 3-hydroxymelatonin, N1-acetyl-N2-formyl-5-methoxykynuramine, and N-acetyl-5-methoxykynuramine. 28,29 Several lines of evidence suggest that melatonin may act as a protective agent in ocular conditions such as photokeratitis, cataract, glaucoma, retinopathy of prematurity, and ischemia/reperfusion injury (for a review see 30 ).…”