Studies on the metabolic conversion of ascorbate
Schmidt, K.; Oberritter, H.; Bruchelt, G.; Hagmaier, V.; Hornig, D.
International Journal for Vitamin and Nutrition Research. Internationale Zeitschrift für Vitamin- und Ernahrungsforschung. Journal International de Vitaminologie et de Nutrition 53(1): 77-85
1983
ISSN/ISBN: 0300-9831 PMID: 6406384 Document Number: 210213
Guineapigs metabolized [1-14C]ascorbic acid faster to [14C]carbon dioxide (peak exhalation at 30 min) than rats (peak exhalation at 2 to 3 h) following single oral administration, but total excretion was comparable. This finding might be related to the differences in the absorption mechanism of ascorbic acid in these species. The large difference in retention capacity of ascorbic acid in the liver is suggested to be due to multiple recirculation of ascorbic acid in the guineapig. Homogenate preparations of rat stomach, small intestine or liver as well as cultured intestinal microbial flora did not cause metabolic degradation on incubation with [1-14C]ascorbic acid to 14CO2. It is therefore suggested that the observed excretion of 14CO2 is due to spontaneous non-enzymical reaction in liver and other tissues. Analysis of ascorbic acid metabolites formed on incubation by analytical isotachophoresis suggests that ascorbic acid is a rather stable substrate whereas dehydroascorbate and 2,3-diketogulonic acid are rapidly degraded. This allows the assumption that metabolism of ascorbic acid in vivo might not involve dehydroascorbic acid. The results do not support the hypothesis that ascorbic acid undergoes presystemic metabolism to CO2 in the intestinal wall.