Effect of different metal ions on the oxidative damage and antioxidant capacity of hyaluronic acid

Degradation and the antioxidative effect of Na–, Zn–, Co–, Cu–, and Mn–hyaluronic acid (HA) associates were studied. Our findings revealed the protective effect of certain counterions against ROS-induced HA degradation. We could also separate the antioxidative effect of certain counterions from that of the HA by examining the effect of the counterions in their free ionic forms. The result showed that metal ions with altering oxidative status (Co2+, Cu2+, Mn2+) proved to be effective in themselves or their effect added to that of HA when HA was also effective. Moreover, the effects of Co–HA against O2− and of Mn–HA against ONOO− as well as the synergic effect of Zn–HA associates where Zn2+ is of fixed oxidative status were attributed to the structure-stabilizing complex formed between certain counterions and HA. Our examination also concerned the influence of HA associates on the indirect antioxidation related to Fe2+ chelating. The individual effects of Zn2+, Co2+, and Cu2+ were only detectable, which could be explained by the competitive displacement of ferrous from its binding site.