Characterization of the antioxidant effects of melatonin and related indoleamines in vitro

Abstract

The antioxidant and possible pro-oxidant effects of melatonin and related indoleamines (tryptophan, serotonin, N-acetylserotonin, and 5-methoxytryptamine) were studied in vitro. In two model membrane systems, i.e., phospholipid liposomes and rat erythrocytes, lipid peroxidation induced by Fe2+ and H2O2, respectively, were reduced by the tested indoleamines except for tryptophan. The 5-hydroxy-indoleamines, serotonin, and N-acetylserotonin exhibited pro-oxidant actions in the bleomycin assay by reducing Fe3+ to Fe2+, which leads to DNA damage. The 5-methoxy-indoleamines, melatonin and 5-methoxytryptamine, were devoid of any pro-oxidant actions in this assay. Serotonin, but not N-acetylserotonin, scavenged the superoxide anion. None of the indoleamines tested had any reactivity towards H2O2. All the indoleamines, including tryptophan, were, however, shown to react with hypochlorous acid. These findings support an antiperoxidative and antioxidant action of melatonin which is devoid of pro-oxidant effect on non-lipid substrates.

Protective Effect of Selenoarginine against Oxidative Stress inD-Galactose-Induced Aging Mice

“…Thus SOD and GPx are two important indicators in aging assessment. 25,26) Our results suggest that the level of MDA increased and that SOD and GPx activities decreased in the liver, serum, kidney, and brain in D-gal-induced aging mice as compared with the normal group, in accordance with previously reported data. 27) The results showed that oxidative stress in mice tissues was induced by D-gal with the formation of lipid peroxide.…”

Potent Neuroprotective Properties against the Alzheimer β-Amyloid by an Endogenous Melatonin-related Indole Structure, Indole-3-propionic Acid

“…IPA is produced by deamination of L-tryptophan by commensal bacteria in human and animal intestines (45), although its production by other tissues has not been systematically investigated. The lack of pro-oxidant effects is perhaps the most important feature of IPA, which, as mentioned, is shared only by melatonin (28,38). In contrast, significant enhancement of iron-mediated formation of hydroxyl radicals was found when we explored the reactions catalyzed by glutathione, trolox, ascorbic acid, and selected indoles, in agreement with a previous study (34).…”

Interactions of melatonin with mammalian mitochondria. Reducer of energy capacity and amplifier of permeability transition

“…Subsequently, the reaction of the radical with molecular oxygen would produce superoxide anion. One proposal is that this ROS, which cannot be scavenged by melatonin (Chan and Tang 1996), oxidises the critical sulfydryl groups responsible for pore opening (McStay et al 2002). It is also assumed that H 2 O 2 is generated in small amounts in the absence of Ca 2?…”

“…In the first case melatonin scavenges both the hydroxyl and peroxyl radicals generated by tBOOH, without involving the electron flux triggered by pyruvate/malate. In the later, melatonin favors the generation of superoxide anion, a ROS that is not scavenged by melatonin itself (Chan and Tang 1996). In this case the electron flux is triggered by succinate and directly affected by the interaction with melatonin, which generates the ROS.…”