The non-oxidative degradation of ascorbic acid at physiological conditions

The degradation of L-ascorbate (AsA) and its primary oxidation products, L-dehydroascorbate (DHA) and 3,3-L-diketogulonate (3,3-DKG) were studied under physiological conditions. Analysis determined that L-erythrulose (ERU) and oxalate were the primary degradation products of ASA regardless of which compound was used as the starting material. The identification of ERU was determined by proton decoupled C-13-nuclear magnetic resonance spectroscopy, and was quantified by high performance liquid chromatography, and enzymatic analysis. The molar yield of ERU from ?,3-DKG at pH 7.0 37 degrees C and limiting O-2, was > 97%. This novel ketose product of AsA degradation, was additionally qualitatively identified by gas-liquid chromatography, and by thin layer chromatography. ERU is an extremely reactive ketose, which rapidly glycates and crosslinks proteins, and therefore may mediate the AsA-dependent modification of protein (ascorbylation) seen in vitro, and also proposed to occur in vivo in human lens during diabetic and age-onset cataract formation. (C) 2000 Published by Elsevier Science B.V. All rights reserved.