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Is 5-HTP an Antioxidant?
by Erowid
November 22, 2001

5-HTP appears to work as an antioxidant, as well as being a precursor to serotonin. 5-HTP's hydroxy (OH) group differentiates it from L-Tryptophan, an essential amino acid. Oxidation of 5-HTP would likely lead to the OH group being severed and the molecule becoming L-Tryptophan, thus the immediate oxidative product of 5-HTP is likely also not toxic.

There is some direct evidence from laboratory research showing 5-HTP functions as an antioxidant. Researchers have demonstrated that 5-HTP can scavenge Nitrc Oxide (NO), peroxide radicals, and other oxidative radicals directly.

  • "Inhibition of free radical processes by antioxidants--tryptophan and 5-hydroxytryptophan."
    Simic MG, al-Sheikhly M, Jovanovic SV. Bibl Nutr Dieta 1989;(43):288-96
    Pub Med - No Abstract

  • "Melatonin and its precursors scavenge nitric oxide."
    Noda Y, Mori A, Liburdy R, Packer L. J Pineal Res 1999 Oct;27(3):159-63
    Pub Med Abstract
    "Serotonin, N-acetyl-5-hydroxytryptamine, and 5-hydroxytryptophan, respectively, showed moderate scavenging activity compared to melatonin. Tryptophan, which has neither a methoxy nor a hydroxyl group in the 5-position, exhibited the least NO scavenging activity."

  • "Serotonin protects NK cells against oxidatively induced functional inhibition and apoptosis."
    Betten A, Dahlgren C, Hermodsson S, Hellstrand K. J Leukoc Biol 2001 Jul;70(1):65-72
    Pub Med Abstract
    "A detailed analysis of these protective effects revealed that serotonin scavenged reactive oxygen species (ROS) derived from the H(2)O(2)-myeloperoxidase (-MPO) system. Serotonin shared this scavenger activity with its precursor, 5-hydroxytryptophan (5-HTP); however, serotonin was >10-fold more potent than 5-HTP in protecting NK cells against functional inhibition and apoptosis.