Failure to find bound ascorbic acid in plasma.

The fact that in experimental scurvy the concentration of ascorbic acid in the cellular elements of blood decreases more slowly than does the concentration in plasma (24) has led to the hypothesis that ascorbic acid might be bound’ to cellular protein (5, 6). There is, however, little direct evidence to support such a hypothesis. Saha, Majumdar, and Guha (7, 8) demonstrated the presence of bound ascorbic acid (ascorbigen) in trichloroacetic acid filtrates of laked whole blood. Ghosh and Guha (9) identified a similar substance in extracts of cabbage, which would not dialyze through parchment or cellophane membranes. If these two substances are similar, then ascorbic acid is bound to a relatively small nondialyzable molecule. Guha et al. did not, however, indicate whether bound ascorbic acid was located in the cellular elements, in the plasma, or in both. Investigators disagree on the question of whether or not bound ascorbic acid occurs in plasma. Use of such physical methods as ultrafiltration (lo), ultracentrifugation (ll), refractometry (12), and electrophoresis (13) has led to conflicting results. Consequently, we undertook a systematic study of the physicochemical behavior of ascorbic acid in plasma, utilizing several of the physical methods previously tried in an effort to explore further this problem.