IR and NMR Studies on the Action of Hypochlorous Acid on Chondroitin Sulfate and Taurine

Although it has been recently shown by the use of1H nuclear magnetic resonance (1H NMR) spectroscopy that enzymatically formed hypochlorous acid (HOCl/Cl⊖) reacts with carbohydrates containingN-acetyl groups under the formation of acetate and presumably chloramines, mechanistical aspects of this reaction remain unknown. Since NMR spectroscopy suffers a lot from low sensitivity especially toward polymeric components giving less marked resonances, we used here infrared (IR) spectroscopy to characterize the products of the reaction between hypochlorite and chondroitin sulfate. NMR is used for means of comparison. The reaction of HOCl/Cl⊖with chondroitin sulfate does not change most regions of the IR spectrum of the polysaccharide markedly. Whereas most vibrational bands remain nearly unchanged toward their position and their relative intensities, an additional band at 975 cm−1is clearly detectable. This band is in good accordance with the proposed formation of a N-Cl-bond in chondroitin sulfate upon HOCl treatment. Additionally, NMR experiments clearly indicate that chloramine formation is accompanied by the formation of acetate. For comparison, taurine (2-amino-1-ethanesulfonic acid) was also investigated toward its reactivity with HOCl/Cl⊖. An analogous band at 975 cm−1was found which unequivocally indicates the formation of a chloramine. NMR also detects changes upon this reaction, but these changes cannot be exactly assigned to chloramine formation. Thus, we conclude that IR spectroscopy is most suitable for the detection of chloramines due to its relatively high sensitivity and the possibility to detect directly N-Cl-groups.