Human Metabolism of L-Ascorbic Acid and Erythorbic Acid

Abstract

Human subjects were partially depleted of ascorbic acid and then were given supplements of either L-ascorbic acid or erythorbic acid. At the end of supplementation, subjects who had received erythorbic acid were given a 300-mg load dose of this isomer. White cell and plasma concentrations and urinary excretion of total ascorbic acid were followed. The plasma was first to deplete in progressive ascorbic acid deficiency and with L-ascorbic acid supplementation plasma concentrations remained low until white cells were repleted. Plasma concentrations near 0.2 mg/100 ml were associated with white cell concentrations ranging from 9 to 23 mg/100 g. Results with erythorbic acid supplementation show that the uptake or “tissue fixation” of L-ascorbic acid is structurally specific for the L-configuration about carbon 5. The rejection of erythorbic acid by the white cells explains the high urinary excretion of this isomer and its apparent lack of anti-scorbutic activity. Maximal total body ascorbic acid, based on the assumption that white cell concentrations are proportional to body tissues in general, was calculated to be 4 g.