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On the free radical scavenging activities of melatonin's metabolites, AFMK and AMK
Author(s) -
Galano Annia,
Tan Dun Xian,
Reiter Russel J.
Publication year - 2013
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/jpi.12010
Subject(s) - melatonin , chemistry , scavenger , scavenging , radical , free radical scavenger , reactive oxygen species , metabolite , antioxidant , hydroxyl radical , photochemistry , biochemistry , biology , neuroscience
The reactions of N 1 ‐acetyl‐ N 2 ‐formyl‐5‐methoxykynuramine ( AFMK ) and N 1 ‐acetyl‐5‐methoxykynuramine ( AMK ) with • OH , • OOH , and • OOCC l 3 radicals have been studied using the density functional theory. Three mechanisms of reaction have been considered: radical adduct formation ( RAF ), hydrogen transfer ( HT ), and single electron transfer ( SET ). Their relative importance for the free radical scavenging activity of AFMK and AMK has been assessed. It was found that AFMK and AMK react with • OH at diffusion‐limited rates, regardless of the polarity of the environment, which supports their excellent • OH radical scavenging activity. Both compounds were found to be also very efficient for scavenging • OOCC l 3 , but rather ineffective for scavenging • OOH . Regarding their relative activity, it was found that AFMK systematically is a poorer scavenger than AMK and melatonin. In aqueous solution, AMK was found to react faster than melatonin with all the studied free radicals, while in nonpolar environments, the relative efficiency of AMK and melatonin as free radical scavengers depends on the radical with which they are reacting. Under such conditions, melatonin is predicted to be a better • OOH and • OOCC l 3 scavenger than AMK , while AMK is predicted to be slightly better than melatonin for scavenging • OH . Accordingly it seems that melatonin and its metabolite AMK constitute an efficient team of scavengers able of deactivating a wide variety of reactive oxygen species, under different conditions. Thus, the presented results support the continuous protection exerted by melatonin, through the free radical scavenging cascade.