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Melatonin and its metabolites: new findings regarding their production and their radical scavenging actions

100%

Reiter R. J., Tan D.-x., Pilar Terron M., Flores L. J., Czarnocki Z.

2007

vol. 54

issue 1

1-9

This review summarizes some of the recent findings concerning the long-held tenet that the enzyme, N-acetyltransferase, which is involved in the production of N-acetylserotonin, the immediate precursor of melatonin, may in fact not always control the quantity of melatonin generated. New evidence from several different laboratories indicates that hydroxyindole-O-methyltransferase, which O-methylates N-acetylserotonin to melatonin may be rate-limiting in some cases. Also, the review makes the point that melatonin's actions are uncommonly widespread in organs due to the fact that it works via membrane receptors, nuclear receptors/binding sites and receptor-independent mechanisms, i.e., the direct scavenging of free radicals. Finally, the review briefly summarizes the actions of melatonin and its metabolites in the detoxification of oxygen and nitrogen-based free radicals and related non-radical products. Via these multiple processes, melatonin is capable of influencing the metabolism of every cell in the organism.

Melatonin as an antioxidant: biochemical mechanisms and pathophysiological implications in humans.

86%

Reiter R. J., Tan D.-x., Mayo J. C., Sainz R. M., Leon J., Czarnocki Z.

2003

vol. 50

issue 4

1129-1146

This brief resume enumerates the multiple actions of melatonin as an antioxidant. This indoleamine is produced in the vertebrate pineal gland, the retina and possibly some other organs. Additionally, however, it is found in invertebrates, bacteria, unicellular organisms as well as in plants, all of which do not have a pineal gland. Melatonin's functions as an antioxidant include: a), direct free radical scavenging, b), stimulation of antioxidative enzymes, c), increasing the efficiency of mitochondrial oxidative phosphorylation and reducing electron leakage (thereby lowering free radical generation), and 3), augmenting the efficiency of other antioxidants. There may be other functions of melatonin, yet undiscovered, which enhance its ability to protect against molecular damage by oxygen and nitrogen-based toxic reactants. Numerous in vitro and in vivo studies have documented the ability of both physiological and pharmacological concentrations to melatonin to protect against free radical destruction. Furthermore, clinical tests utilizing melatonin have proven highly successful; because of the positive outcomes of these studies, melatonin's use in disease states and processes where free radical damage is involved should be increased.

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2 Acta Biochimica Polonica

1 2007

1 2003

2 Czarnocki Z.

2 Reiter R. J.

2 Tan D.-x.

1 Flores L. J.

1 Leon J.

1 Mayo J. C.

1 Pilar Terron M.

1 Sainz R. M.

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Melatonin and its metabolites: new findings regarding their production and their radical scavenging actions

Melatonin as an antioxidant: biochemical mechanisms and pathophysiological implications in humans.