The chemical behaviour of dehydro-l-ascorbic acid in vitro and in vivo

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Abstract
Diketogulonic acid in the presence of HC1 forms a derivative with dinitrophenylhydrazine. When ascorbic and dehydroascorbic acids are present they are first converted to diketogulonic acid which then reacts with the reagent. The rate of conversion of dehydroascorbic acid is independent of the initial conc., proceeds as a first order reaction, the temp. coefficient at 25[degree]-35[degree] being 22; it also depends on the pH, the rate being high at pH 7.4. In in vivo expts. with scorbutic guinea pigs, diketogulonic acid was destroyed or excreted. When dehydroascorbic acid was injected it was partly converted into diketogulonic acid and partly reduced to ascorbic acid, the latter mainly in the liver. Administered per os it was gradually absorbed, but much remained unchanged in the stomach for 15-30 mins. In the small intestine, owing to alkalinity, it was converted into diketogulonic acid. When 120 mg. diketogulonic acid were injected, about 25 mg. were excreted in the urine in 25 hrs., most of it in the first 4 hrs. Injected dehydro-ascorbic acid was similarly excreted as diketogulonic acid.