Antioxidant Activities of Hydroxylated Naphthalenes: The Role of Aryloxyl Radicals. Issue 1 (20th January 2023)

• Record Type: Journal Article
• Authors: Lino, Valeria; Manini, Paola; Galeotti, Marco; Salamone, Michela; Bietti, Massimo; Crescenzi, Orlando; Napolitano, Alessandra; d'Ischia, Marco
• Is Part Of: ChemPlusChem. Volume 88:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-20
• Subjects: antioxidants -- dihydroxynaphthalenes -- electron transfer -- hydrogen atom transfer -- laser flash photolysis -- radicals; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/cplu.202200449
• Languages: English
• ISSNs: 2192-6506

Abstract

Abstract: Herein is delineated a first systematic framework for the definition of structure‐antioxidant property relationships in the dihydroxynaphthalene (DHN) series. The results obtained by a combined experimental and theoretical approach revealed that 1, 8‐DHN is the best performing antioxidant platform, with its unique hydrogen‐bonded peri ‐hydroxylation pattern contributing to a fast H atom transfer process. Moreover, the comparative analysis of the antioxidant properties of DHNs carried out by performing DPPH and FRAP assays and laser flash photolysis experiments, revealed the higher antioxidant power associated with an α‐substitution pattern (i. e. in 1, 8‐ and 1, 6‐DHN) with respect to DHNs exhibiting a β‐substitution pattern (i. e. in 2, 6‐ and 2, 7‐DHN). DFT calculations and isolation and characterization of the main oligomer intermediates formed during the oxidative polymerization of DHNs supported this evidence by providing unprecedented insight into the generation and fate of the intermediate naphthoxyl radicals, which emerged as the main factor governing the antioxidant activity of DHNs. Abstract : A systematic framework for the definition of structure‐antioxidant property relationships in the dihydroxynaphthalene (DHN) series is discussed in this work. The results obtained by a combined experimental and theoretical approach confirmed and supported the highest antioxidant power of 1, 8‐DHN due to the unique hydrogen‐bonded peri ‐hydroxylation pattern contributing to the high stabilization of the corresponding naphthoxyl radical, and pointed out for the first time the enhanced antioxidant activity associated with the α‐hydroxynaphthalene ring system (e. g. 1, 8‐DHN, 1, 6‐DHN and 1‐HN) due to faster HAT processes.