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Phenolic and indolic free-radical scavengers as luminophores Janine Wendler; Sabine Holst; Ruediger Hardeland*; Beata K. Zsizsik; Burkhard Poeggeler Institute of Zoology and Anthropology, University of Goettingen, Berliner Str. 28, Goettingen, D-37073, Germany      *(rhardel@gwdg.de) During oxidation of various phenolic (sinapinic and caffeic acids, curcumin, resveratrol) and indolic (indole-3-pyruvic and -propionic acids; 5-methoxyindoles) free-radical scavengers, light is emitted. Studies were carried out in moderately alkaline (pH 8), hemin-catalyzed hydrogen peroxide systems, in which luminescence was used for analyzing interactions with different types of free radicals. In most cases, light emission was only partially inhibited by DMSO, but almost totally suppressed by Tiron, indicating that emitter formation can take place by different mechanisms, (a) by sequential interactions with hydroxyl radicals and superoxide anions and (b) by iron-catalyzed addition of oxygen from superoxide anions. Emitter formation from caffeic acid required the initial interaction with hydroxyl radicals, leading to a pink-colored compound (also partially quenching luminescence); addition of DMSO at the start of reaction both suppressed formation of this compound and luminescence, whereas later additions of DMSO were only partially inhibitory. [Poster: hardelan.ruedig.40942]

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