Characterization of the Reaction between Sialic Acid (N-Acetylneuraminic Acid) and Hydrogen Peroxide

Abstract

In a previous report, we had demonstrated the antioxidant activity of the sialic acid N-acetylneuraminic acid (Neu5Ac, NANA). This activity can counteract the cytotoxicity of hydrogen peroxide (H2O2), and the antitoxicity is a result of a direct chemical reaction, whereby NANA reduces H2O2 in the culture media. The influence of the potential of hydrogen (pH) and temperature in this reaction was investigated. The reaction velocity is remarkably less at low pH and/or low temperature, but it increases with these parameters. Furthermore, the reaction product generated in the slow reaction under acidic conditions (pH 3.1) was analyzed. We detected 4-(acetylamino)-2,4-dideoxy-D-glycero-D-galacto-octonic acid (ADOA) as the decarboxylation product of NANA; this is the same product we previously obtained in a faster reaction at neutral pH (pH 7.5). Furthermore, ADOA was generated not only from the reaction with the NANA monomer but also from that with alpha(2-->8) homodimer of NANA (DP2). Thus, it can be considered that the reaction between NANA and H2O2 can occur under various pH conditions and for NANA residues in a glycochain.