We report a novel coantioxidant system based on TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) that, in biologically relevant model systems, rapidly converts chain-carrying alkylperoxyl radicals to HOO·. Extremely efficient quenching of HOO· by TEMPO blocks the oxidative chain. Rate constants in chlorobenzene were measured to be 1.1 × 109 M-1 s-1 for the reductive reaction TEMPO + HOO· → TEMPOH + O2 and 5.0 × 107 M-1 s-1 for the oxidative reaction TEMPOH + HOO· → TEMPO + H2O2. These rate constants are significantly higher than that associated with the reaction of HOO· with α-tocopherol, Nature's best lipid soluble antioxidant (k = 1.6 × 106 M-1 s-1). These data show that in the presence of ROO·-to-HOO· chain-transfer agents, which are common in lipophilic environments, the TEMPO/TEMPOH couple protects organic molecules from oxidation by establishing an efficient reductive catalytic cycle. This catalytic cycle provides a new understanding of the efficacy of the antioxidant capability of TEMPO in nonaqueous systems and its potential to act as a chemoprotective against radical damage.

Baschieri, A., Valgimigli, L., Gabbanini, S., Dilabio, G.A., Romero-Montalvo, E., Amorati, R. (2018). Extremely Fast Hydrogen Atom Transfer between Nitroxides and HOO · Radicals and Implication for Catalytic Coantioxidant Systems. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140(32), 10354-10362 [10.1021/jacs.8b06336].

Extremely Fast Hydrogen Atom Transfer between Nitroxides and HOO · Radicals and Implication for Catalytic Coantioxidant Systems

Baschieri, Andrea;Valgimigli, Luca
;
Amorati, Riccardo
2018

Abstract

We report a novel coantioxidant system based on TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) that, in biologically relevant model systems, rapidly converts chain-carrying alkylperoxyl radicals to HOO·. Extremely efficient quenching of HOO· by TEMPO blocks the oxidative chain. Rate constants in chlorobenzene were measured to be 1.1 × 109 M-1 s-1 for the reductive reaction TEMPO + HOO· → TEMPOH + O2 and 5.0 × 107 M-1 s-1 for the oxidative reaction TEMPOH + HOO· → TEMPO + H2O2. These rate constants are significantly higher than that associated with the reaction of HOO· with α-tocopherol, Nature's best lipid soluble antioxidant (k = 1.6 × 106 M-1 s-1). These data show that in the presence of ROO·-to-HOO· chain-transfer agents, which are common in lipophilic environments, the TEMPO/TEMPOH couple protects organic molecules from oxidation by establishing an efficient reductive catalytic cycle. This catalytic cycle provides a new understanding of the efficacy of the antioxidant capability of TEMPO in nonaqueous systems and its potential to act as a chemoprotective against radical damage.
2018
Baschieri, A., Valgimigli, L., Gabbanini, S., Dilabio, G.A., Romero-Montalvo, E., Amorati, R. (2018). Extremely Fast Hydrogen Atom Transfer between Nitroxides and HOO · Radicals and Implication for Catalytic Coantioxidant Systems. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 140(32), 10354-10362 [10.1021/jacs.8b06336].
Baschieri, Andrea; Valgimigli, Luca*; Gabbanini, Simone; Dilabio, Gino A.; Romero-Montalvo, Eduardo; Amorati, Riccardo
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/659439
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