Formation of diastereoisomeric 3a-hydroxypyrroloindoles from a tryptophan residue analog mediated by iron(II)-EDTA and l-ascorbate

Uchida, Koji; Enomoto, Nobuo; Itakura, Koichi; Kawakishi, Shunrô

doi:10.1016/0003-9861(90)90456-9

Cited by 16 publications

(14 citation statements)

References 39 publications

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“…These results are consistent with two previous studies showing that 5-hydroxytryptophan reduced lipid peroxidation and reversed membrane rigidity in hepatic cells and microsomal membranes treated with iron [23,25]. It has been proposed that the indole nucleus of tryptophan is the moiety of the molecule responsible for the antioxidant function [33]. Although our study did not address the chemical mechanism of the antioxidant activity, according to our results it seems reasonable to consider that hydroxylation of the amino acid activates its antioxidant behavior, which may be related to its ability to transfer electrons to free radicals.…”

Section: Resultssupporting

confidence: 92%

Melatonin and Structurally-Related Compounds Protect Synaptosomal Membranes from Free Radical Damage

Millán-Plano

Piedrafita

Miana-Mena

et al. 2010

IJMS

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Since biological membranes are composed of lipids and proteins we tested the in vitro antioxidant properties of several indoleamines from the tryptophan metabolic pathway in the pineal gland against oxidative damage to lipids and proteins of synaptosomes isolated from the rat brain. Free radicals were generated by incubation with 0.1 mM FeCl3, and 0.1 mM ascorbic acid. Levels of malondialdehyde (MDA) plus 4-hydroxyalkenal (4-HDA), and carbonyl content in the proteins were measured as indices of oxidative damage to lipids and proteins, respectively. Pinoline was the most powerful antioxidant evaluated, with melatonin, N-acetylserotonin, 5-hydroxytryptophan, 5-methoxytryptamine, 5-methoxytryptophol, and tryptoline also acting as antioxidants.

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Section: Resultssupporting

confidence: 92%

Melatonin and Structurally-Related Compounds Protect Synaptosomal Membranes from Free Radical Damage

Millán-Plano

Piedrafita

Miana-Mena

et al. 2010

IJMS

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“…In this process, one melatonin molecule has a capacity to scavenge two HO W . This model is supported by previously published research which showed that a similar reaction occurred between tryptophan (a precursor of melatonin) and HO W [66,67]. Since the most reactive site in the indole ring is position 3, even though there is a side chain, it is certainly reasonable that the nucleophilic addition interaction between melatonin and HO W would be more favorable at position 3 than at other positions.…”

Section: Proposed Mechanisms Of Melatonin Scavenging Free Radicalssupporting

confidence: 71%

Significance of Melatonin in Antioxidative Defense System: Reactions and Products

et al. 2000

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Melatonin is a potent endogenous free radical scavenger, actions that are independent of its many receptor-mediated effects. In the last several years, hundreds of publications have confirmed that melatonin is a broad-spectrum antioxidant. Melatonin has been reported to scavenge hydrogen peroxide (H₂O₂), hydroxyl radical (HO·), nitric oxide (NO·), peroxynitrite anion (ONOO^–), hypochlorous acid (HOCl), singlet oxygen (¹O₂), superoxide anion (O₂^–·) and peroxyl radical (LOO·), although the validity of its ability to scavenge O₂^–· and LOO· is debatable. Regardless of the radicals scavenged, melatonin prevents oxidative damage at the level of cells, tissues, organs and organisms. The antioxidative mechanisms of melatonin seem different from classical antioxidants such as vitamin C, vitamin E and glutathione. As electron donors, classical antioxidants undergo redox cycling; thus, they have the potential to promote oxidation as well as prevent it. Melatonin, as an electron-rich molecule, may interact with free radicals via an additive reaction to form several stable end-products which are excreted in the urine. Melatonin does not undergo redox cycling and, thus, does not promote oxidation as shown under a variety of experimental conditions. From this point of view, melatonin can be considered a suicidal or terminal antioxidant which distinguishes it from the opportunistic antioxidants. Interestingly, the ability of melatonin to scavenge free radicals is not in a ratio of mole to mole. Indeed, one melatonin molecule scavenges two HO·. Also, its secondary and tertiary metabolites, for example, N¹-acetyl-N²-formyl-5-methoxykynuramine, N-acetyl-5-methoxykynuramine and 6-hydroxymelatonin, which are believed to be generated when melatonin interacts with free radicals, are also regarded as effective free radical scavengers. The continuous free radical scavenging potential of the original molecule (melatonin) and its metabolites may be defined as a scavenging cascade reaction. Melatonin also synergizes with vitamin C, vitamin E and glutathione in the scavenging of free radicals. Melatonin has been detected in vegetables, fruits and a variety of herbs. In some plants, especially in flowers and seeds (the reproductive organs which are most vulnerable to oxidative insults), melatonin concentrations are several orders of magnitude higher than measured in the blood of vertebrates. Melatonin in plants not only provides an alternative exogenous source of melatonin for herbivores but also suggests that melatonin may be an important antioxidant in plants which protects them from a hostile environment that includes extreme heat, cold and pollution, all of which generate free radicals.

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“…Interestingly, in this process one molecule of melatonin scavenges two ḃ OH [18]. This model is supported by previously published research showing that similar reactions occur between tryptophan (a precursor of melatonin) and ḃ OH [19, 20]. Cyclic 3‐hydroxymelatonin has been therefore claimed as one of the stable products of melatonin's scavenging ḃ OH, and it is a footprint product that results when one molecule of indoleamine scavenges two ḃ OH [18].…”

Section: Hydroxyl Radicalmentioning

confidence: 55%

The chemistry of melatonin's interaction with reactive species

Allegra

Reíter

Tan

et al. 2002

Journal of Pineal Research

654

524

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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.

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Formation of diastereoisomeric 3a-hydroxypyrroloindoles from a tryptophan residue analog mediated by iron(II)-EDTA and l-ascorbate

Cited by 16 publications

References 39 publications

Melatonin and Structurally-Related Compounds Protect Synaptosomal Membranes from Free Radical Damage

Melatonin and Structurally-Related Compounds Protect Synaptosomal Membranes from Free Radical Damage

Significance of Melatonin in Antioxidative Defense System: Reactions and Products

The chemistry of melatonin's interaction with reactive species

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