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

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 results suggest that CoQ0*-, formed by the interaction between CoQ0 and endogenous ascorbic acid (AscH-) in skin homogenates, regenerates Trolox from its phenoxyl radical.