ESR studies of ascorbic acid-dependent recycling of the vitamin Ehomologue Trolox by coenzyme Q₀ in murine skin homogenates

Abstract

The recycling of Trolox, a water-soluble vitamin E homologue, by coenzyme Q₀ (CoQ₀) during Cu²⁺-initiated oxidation of ascorbate in mouse skin homogenates was investigated using electron spin resonance (ESR) spectroscopy. In a mixture containing CoQ₀, Cu²⁺ and mouse skin homogenates, the ESR signal of CoQ₀ semiquinone radical (CoQ₀^.-) appeared and declined with time; addition of Trolox accelerated the CoQ₀^.- signal decay. Only after the disappearance of the CoQ₀^.- signal was the appearance of the Trolox phenoxyl radical signal observed. In addition, the lifetime of the CoQ₀^.- signal and the length of the lag period during which the Trolox radical ESR signal could not be detected were dependent on the presence of Trolox, CoQ₀ or Cu²⁺. The resultsm suggest that CoQ₀^.-, formed by the interaction between CoQ₀ and endogenous ascorbic acid (AscH^-) in skin homogenates, regenerates Trolox from its phenoxyl radical.