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.