Synthesis of alpha-tocopherolquinone by the rat and its reduction by mitochondria.

The combination of alpha-tocopherolquinone and alpha-tocopherolquinol varied in tissues of the rat from 20 nmol/g of adipose tissue to 215 nmol/g of liver. In each tissue except the brain, the alpha-tocopherolquinone and alpha-tocopherolquinol were about equal. In the brain, the level of the hydroquinone was more than 5 times the level of the quinone. Neither compound was detected in blood. Both [2-14C5mevalonic acid and L-[14C]tyrosine were incorporated into alpha-tocopherolquinone but not into alpha-tocopherol. This indicates that alpha-tocopherol is not the precursor of alpha-tocopherolquinone. In the presence of beta-hydroxybutyrate, pyruvate, succinate, and NADH, alpha-tocopherolquinone was reduced to alpha-tocopherolquinol by liver mitochondria. Since the reduction was not inhibited by rotenone or antimycin A, it is likely that the reduction of alpha-tocopherolquinone is not part of the classical mitochondrial electron transport system.