The non-oxidative degradation of ascorbic acid at physiological conditions

Abstract

The degradation of L-ascorbate (AsA) and its primary oxidation products, L-dehydroascorbate (DHA) and 2,3-L-diketogulonate (2, 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 (13)C-nuclear magnetic resonance spectroscopy, and was quantified by high performance liquid chromatography, and enzymatic analysis. The molar yield of ERU from 2,3-DKG at pH 7.0 37 degrees C and limiting O(2)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.

Browning and Decomposed Products of Model Orange Juice

“…2-Furoic acid 19) was also detected by another HPLC condition. Oxalic acid, which is one of decomposed products of AsA through 2,3-diketogulonic acid in physiological conditions, 26) was not detected in this stored solution. 3OH2P, furfural and 2-furoic acid were derived of AsA through dehydroascorbic acid, 27) while HMF and 5-hydroxymaltol were derived of fructose (data not shown).…”

2-Ammonio-6-(3-oxidopyridinium-1-yl)hexanoate (OP-lysine) Is a Newly Identified Advanced Glycation End Product in Cataractous and Aged Human Lenses

“…10) is also solid evidence that this post-translational modification of lysine exists in cataractous lenses. fructose, xylose, erythrulose, glyceraldehyde, glyceraldehyde 3-phosphate, methylglyoxal, 1,3-dihydroxyacetone, and glycolaldehyde are reactive carbonyl compounds known to be able to modify the ⑀ amino group of lysine residues in lens proteins (6,(15)(16)(17)(18)(19)(20)(21). The RP-HPLC analyses showed that none of the above carbonyl compounds was able to produce measurable amounts of OP-lysine when reacted with Boc-Lys at pH 7 for 5 days based on UV and fluorescence HPLC profiles of the reaction mixtures.…”

Mechanism of the antioxidant to pro-oxidant switch in the behavior of dehydroascorbate during LDL oxidation by copper(II) ions

“…Instead, it was proposed that the protection observed with ascorbate is due solely to its oxidation to dehydroascorbate and, perhaps, subsequent degradation to other products. As dehydroascorbate is extremely unstable in aqueous solution, undergoing facile delactonization to 2,3-diketo-L-gulonic acid, followed by transformation into a large number of products, which include ascorbic acid and erythroascorbic acid [43][44][45][46], it is possible that the effects of dehydroascorbate on LDL oxidation are indirect and are caused by its transformation products. [53] or in the plasma of smokers [54].…”