The Action of Hypochlorous Acid on Polymeric Components of Cartilage

The action of sodium hypochlorite on N-acetylglucosamine, N-acetylgalactosamine, chondroitinsulfate and hyaluronic acid was studied by 1H-nuclear magnetic resonance (1H-NMR) in order to model some aspects of degradation processes caused by neutrophils on carbohydrate polymers of cartilage in rheumatoid arthritis. N-Acetyl side groups of carbohydrate monomers and chondroitinsulfate yield a resonance at 2.01-2.04 ppm in proton NMR-spectra. This resonance is observed in hyaluronic acid solutions only after a prolonged incubation to yield shorter polymeric chains. Sodium hypochlorite causes a continuous decrease of the line for N-acetyl groups. Two new resonances appear in the 1H-NMR spectra. An intermediate product, assumed as a chlorinated product of N-acetyl side chains, shows a chemical shift of about 2.35 ppm. This intermediate is hydrolyzed to a carbohydrate ring and acetate (1.90 ppm). Sodium hypochlorite acts in all systems investigated mainly on N-acetyl groups. Only small effects on the carbohydrate ring were found under our experimental conditions.