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Synthesis, antioxidant activity and structure–activity relationships for a new series of 2‐( N ‐acylaminoethyl)indoles with melatonin‐like cytoprotective activity
Author(s) -
Spadoni Gilberto,
Diamantini Giuseppe,
Bedini Annalida,
Tarzia Giorgio,
Vacondio Federica,
Silva Claudia,
Rivara Mirko,
Mor Marco,
Plazzi Pier Vincenzo,
Zusso Morena,
Franceschini Davide,
Giusti Pietro
Publication year - 2006
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.2005.00309.x
Subject(s) - melatonin , cytoprotection , indole test , antioxidant , chemistry , luzindole , free radical scavenger , lipid peroxidation , structure–activity relationship , stereochemistry , lipophilicity , biochemistry , pharmacology , receptor , antagonist , in vitro , biology , oxidative stress , endocrinology
5‐Methoxy‐2‐( N ‐acetylaminoethyl)indole ( 5d ), a melatonin analogue derived from the transposition of the acetylaminoethyl side chain from C 3 to C 2 of the indole nucleus, had been previously characterized as a low affinity antagonist at MT 1 and MT 2 membrane receptors; this molecule is endowed with good in vitro antioxidant and cytoprotective potency in rat cerebellar cell cultures, comparable to or better than those of melatonin. In order to further investigate the role of structure–antioxidant activity relationships in cytoprotection, the structure of 5d was systematically modulated to design a new series of compounds. The 5‐methoxy group was replaced by substituents with different electronic and lipophilic properties and it was moved to a different position on the indole ring. Other modifications of the lead structure involved the methylation of the indole nitrogen or its replacement by a sulfur atom. The side chain was also modified either increasing its lipophilicity or introducing an ionisable acid group. The antioxidant activity of this set of compounds was evaluated by the ABTS and conjugated dienes (CD) assays, while their cytoprotection was evaluated against kainate‐induced cytotoxicity in cultured cerebellar neurons. In both antioxidant assays, the shift of the 5‐methoxy group to the 4‐position of the indole nucleus led to the most active radical scavenger ( 9 ), more potent than the parent compound and melatonin in the antioxidant tests, but much less effective as a cytoprotectant. Sharp structure–activity relationships were registered for cytoprotection, where the maintenance of the 5‐alkoxy‐2‐( N ‐acylaminoethyl)indole scaffold appeared as the key feature to confer both antioxidant and cytoprotective activity to the structure. Some derivatives of the set, however, together with the most potent 5d , maintained a significant antioxidant and cytoprotective effect and could be employed as tools for in vivo pharmacological investigations on neuroprotective efficacy of melatonin‐related indoles.