Vitamin E recycling. The tocopheroxyl radical, formed during oxidation of ~-tocopherol (shown in the membrane), may
be reduced back to a-tocopherol by a number of compounds, including ubiquinol, cytochrome c, and ascorbate. Ascorbate can
be regenerated through reaction with thiols such as glutathione or lipoic acid. These can be returned to their reduced forms by
various mechanisms, drawing on the reducing power of NADH or NADPH. Adapted from Scientific American.