Dehydroascorbate, ascorbic acid biosynthesis

Ascorbic acid is a vitamin in primates. In most other animals, it can be synthesized by a branch of the glucoronic acid pathway (Chapter 18). It is apparently not changed into any coenzyme in the human being and participates as a vitamin in a reducing capacity in several biochemical reactions. These include the post-translational hydroxylation of proline in collagen biosynthesis (Chapter 8) and in tyrosine metabolism (Chapter 20). Ascorbic acid is oxidized to dehydroascorbic acid, a diketo derivative of ascorbate. Scurvy is a deficiency disease caused by a shortage of dietary ascorbic acid. In children, this results in defective bone formation in adults, extensive bleeding occurs in a number of locations. Scurvy is to be suspected if serum ascorbic acid levels fall below 1 jug/mL. 

Biosynthesis of ascorbic acid and its conversion into dehydroascorbic acid. See Oxalic acid (Fig. 2.). 

Otsuka et al. (1986) used TLC to isolate and partially characterize degradation products of 2,3-diketo-L-gulonic acid (intermediates in the biosynthesis of ascorbic acid) the products were characterized by different spectrometric methods. Mandrou et al. (1988) devised a TLC procedure to determine ascorbic and dehydroascorbic acids in fruit juices and wine the sample was reacted with 2,4-dinitrophenylhydrazine to form the osazones the osazones were spotted on the TLC plate and quantified by. in situ densitometry at 494 nm. 

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