Catalytic role of copper and iron ions in the depolymerization of hyaluronic acid by ascorbic acid

Copper and iron ions at physiological concentrations catalyzed the decrease of viscosity of hyaluronic acid solutions brought about by ascorbic acid. This reaction required the presence of oxygen as did the reaction with ascorbic acid alone. The ascorbic acid was converted by iron and copper ions to products more active than itself. Dehydroascorbic acid and dihydroxymaleic acid were also active autoxidants. Ethylenediaminetetraacetic acid (EDTA) had no effect on the reaction with ascorbic acid alone. However, EDTA abolished the catalytic effect of copper ions but enhanced the effect of iron ions in the presence of ascorbic acid. Catalase was a strong inhibitor of the ascorbic acid system with and without iron or copper ions but was not as effective for ferrous ions in the absence of ascorbic acid.