Differential inhibition of Maillard protein fluorescence by nitric oxide donors

The nitric oxide donors nitroprusside (NP) and S-nitroso-N-acetylpenicillamine (SNAP) were added repeatedly over a prolonged period into a protein fructation system of 0.05 M fructose and BSA. These additions inhibited Maillard reaction advanced-stage fluorescence generation in a dose-dependent manner without affecting initiation of glycation. NP caused 66% inhibition whereas SNAP caused only 30% inhibition at maximum dose. The lower inhibition by SNAP possibly reflects an interference caused by N-acetylpenicillamine and mediated by a metal-dependent enhanced free-radical generation. We propose, that the inhibition of fluorescence results from mutual annihilation between nitric oxide and free radicals, such as OH ., produced during fructation. In vivo generated nitric oxide may play a protective role in cells against the deleterious effect of free radicals that are associated with the augmented fructose autoxidation and fructation that occurs in diabetes. (C) 1998 Academic Press.