Ascorbate radical and ascorbic acid level in human serum and age.

Free radical in human serum was observed by an electron spin resonance (ESR) technique and was assigned to ascorbate radical. Quantitative estimation revealed that the ESR intensity could be used as an expedient mean. The ESR intensity of ascorbate radical, the concentrations of total ascorbic acid and oxidized form of ascorbic acid were determined on sera of 200 healthy individuals whose ages ranged from 12 to 96 years. The ESR intensity as well as the concentrations of total and oxidized form of ascorbic acid declined with age. There were significant correlations between the ESR intensity and the concentrations of total and oxidized form of ascorbic acid. From these results, the clinical significance of the concentrations of total ascorbic acid, ascorbate radical and the oxidized form was discussed in relation to age.