Use of K Value of Ascorbic Acid as a Clinical Index of Attack by Oxygen Radicals

The K value=[AFR]2/[RAsA] [DAsA ] (RAsA, reduced form of ascorbic acid; DAsA, oxidized form of ascorbic acid; AFR, ascorbate free radical), and changes in AFR concentration in human serum were examined after exposure to oxygen radicals. After the exposure, RAsA decreased, DAsA increased, and K value increased. Since the K value is constant in healthy subjects, it is regarded to be a clinical index to indicate the attack of oxygen radicals in living system. Whereas changes in AFR concentration in ascorbate solutions showed a one-way decrease after an initial increase, changes in serum were those of a persistent pattern with slight fluctuation after the initial increase. The difference was found to be attributable to the presence of a serum factor that inhibits ascorbate oxidation.