Metabolism of D-ascorbic acid-1-C14 in guinea pigs and rats.

The availability of L-ascorbic acid labeled with Cl4 had made possible studies on the metabolism of the vitamin in man (l), guinea pig (2,3), and rat (4, 5). In the present investigation the metabolic fate of carboxyllabeled n-ascorbic acid and carboxyl-labeled L-ascorbic acid was compared in guinea pigs and rats. This study is of interest, since little is known of the biological fate of D-ascorbic acid. In addition, it was thought that information might be obtained which would explain why the D isomer is reported to have no vitamin C activity in guinea pigs (6, 7). The tracer technique was required in this investigation, since it is not possible to distinguish by chemical methods small amounts of n-ascorbic acid from normally occurring n-ascorbic acid in biological material. The results to be presented show that the carboxyl carbon of D-ascorbic acid, like that of L-ascorbic acid, is extensively oxidized to COZ. Because of the rapid metabolism and excretion of n-ascorbic acid, it is retained in the body to a considerably lesser extent than L-ascorbic acid, which may be an important factor in explaining why D-ascorbic acid has virtually no vitamin C activity in guinea pigs.’