Chain-Breaking Phenolic 2,3-Dihydrobenzo[b]selenophene Antioxidants: Proximity Effects and Regeneration Studies

Vijay P. Singh*, Jiajie Yan, Jia Fei Poon, Paul J. Gates, Ray J. Butcher, Lars Engman

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

5 Citations (Scopus)
284 Downloads (Pure)

Abstract

Phenolic 2,3-dihydrobenzo[b]selenophene antioxidants bearing an OH-group ortho (9), meta (10, 11) and para (8) to the Se were prepared by seleno-Claisen rearrangement/intramolecular hydroselenation. meta-Isomer (11) was studied by X-ray crystallography. The radical-trapping activity and regenerability of compounds 8–11 were evaluated using a two-phase system in which linoleic acid was undergoing peroxidation in the lipid phase while regeneration of the antioxidant by co-antioxidants (N-acetylcysteine, glutathione, dithiothreitol, ascorbic acid, tris(carboxyethyl)phosphine hydrochloride) was ongoing in the aqueous layer. Compound 9 quenched peroxyl radicals more efficiently than α-tocopherol. It also provided the most long-lasting antioxidant protection. With thiol co-antioxidants it could inhibit peroxidation for more than five-fold longer than the natural product. Regeneration was more efficient when the aqueous phase pH was slightly acidic. Since calculated O−H bond dissociation energies for 8–11 were substantially larger than for α-tocopherol, an antioxidant mechanism involving O-atom transfer from peroxyl to selenium was proposed. The resulting phenolic selenoxide/alkoxyl radical would then exchange a hydrogen atom in a solvent cage before antioxidant regeneration at the aqueous lipid interphase.

Original languageEnglish
Pages (from-to)15080-15088
Number of pages9
JournalChemistry - A European Journal
Volume23
Issue number60
Early online date9 Oct 2017
DOIs
Publication statusPublished - 26 Oct 2017

Keywords

  • antioxidants
  • Claisen rearrangement
  • lipid peroxidation
  • phenols
  • selenium

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