Premium
The melatonin metabolite N 1 ‐acetyl‐5‐methoxykynuramine is a potent singlet oxygen scavenger
Author(s) -
Schaefer Meike,
Hardeland Rüdiger
Publication year - 2009
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.2008.00614.x
Subject(s) - singlet oxygen , dabco , rose bengal , chemistry , photochemistry , melatonin , metabolite , oxygen , reactive oxygen species , octane , medicinal chemistry , stereochemistry , biochemistry , biology , organic chemistry , neuroscience
Singlet oxygen was generated by means of rose bengal under irradiation by visible light. N 1 ‐acetyl‐5‐methoxykynuramine (AMK) was rapidly destroyed by this reactive oxygen species, whereas its formylated precursor, N 1 ‐acetyl‐ N 2 ‐formyl‐5‐methoxykynuramine (AFMK), was remarkably inert. At photon fluence rates of 1400 μ mol photons/m 2 s, and using 20 μ m rose bengal, most of initially 0.2 m m AMK was destroyed within 2 min, whereas AFMK remained practically unchanged for much longer periods of time. Competition experiments with other scavengers revealed the following order of reactivity towards singlet oxygen: diazabicyclo‐[2,2,2]‐octane (DABCO) << imidazole < 4‐ethylphenol < N α ‐acetylhistidine < histidine < melatonin < AMK, the last one being about 150 times more effective than DABCO. Contrary to the oxidation in free radical‐generating systems, AMK did not form adducts with the tyrosine side chain fragment, 4‐ethylphenol, under the influence of singlet oxygen. In UV‐exposed cells (keratinocytes, plant cells) it is likely to be more rapidly destroyed by singlet oxygen than formed from AFMK.