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  • Indole-3-pyruvic and -propionic acids, kynurenic acid, and related metabolites as luminophores and free-radical scavengers.

Indole-3-pyruvic and -propionic acids, kynurenic acid, and related metabolites as luminophores and free-radical scavengers.

Advances in experimental medicine and biology (2000-03-18)
R Hardeland, B K Zsizsik, B Poeggeler, B Fuhrberg, S Holst, A Coto-Montes
ABSTRACT

Chemiluminescence associated with oxidation by free radicals was investigated in an alkaline, hemin-catalysed hydrogen peroxide system, using the following tryptophan metabolites as radical scavengers: indole-3-pyruvic, indole-3-propionic, kynurenic, xanthurenic and quinaldic acids and 4-hydroxy-quinoline. Light emission from oxidation of the indolic compounds was only partially inhibited by the hydroxyl-radical scavenger DMSO, but strongly suppressed by the superoxide-anion scavenger Tiron, whereas chemi-luminescence generated from kynurenic acid was strongly inhibited by either of these compounds. Light emission from oxidation of kynurenic acid lasts for a surprisingly long period of time: At 0.4 mM and 20 degrees C, luminescence increased for 5 hours and continued at a high rate for more than a day. Comparison of structural analogues indicated that the 4-hydroxyl and carboxyl groups of kynurenic acid are essential for effective light emission, and that an additional 8-hydroxyl residue leading to an intramolecular hydrogen bond diminishes the reaction rate.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Indole-3-pyruvic acid, ≥97%
Sigma-Aldrich
3-Indolepropionic acid, ReagentPlus®, 99%
Sigma-Aldrich
Indole-3-propionic acid, ≥99.0% (T)
Sigma-Aldrich
Indole-3-propionic acid, ≥97.0% (T)