The effect of UVA light on the anaerobic oxidation of ascorbic acid and the glycation of lens proteins.

Purpose: To determine whether UVA-excited human lens chromophores can cause the oxidation of ascorbic acid in the absence of oxygen, and whether these oxidation products are capable of glycating lens proteins.

Methods: The oxidation of ascorbic acid, mediated by UVA irradiation in the presence of aged human lens proteins, was measured in the absence of oxygen by the decrease in absorbance at 265 nm in vitro. An action spectrum from 320 to 400 nm was determined for both ascorbate oxidation and the photobleaching of the lens yellow pigments at lambda = 350 nm.

Isolation and characterization of a new advanced glycation endproduct of dehydroascorbic acid and lysine.

Proteins are subject of posttranslational modification by sugars and their degradation products in vivo. The process is often referred as glycation. L-Dehydroascorbic acid (DHA), an oxidation product of L-ascorbic acid (vitamin C), is known as a potent glycation agent.