Stabilization of L-ascorbic acid by superoxide dismutase and catalase.

The effects of superoxide dismutase (SOD) and catalase on the autoxidation rate of L-ascorbic acid (ASA) in the absence of metal ion catalysts were examined. The stabilization of ASA by SOD was confirmed, and the enzyme activity of SOD, which scavenges the superoxide anion formed during the autoxidation of ASA, contributed strongly to this stabilization. The stabilization of ASA by catalase was observed for the first time; however, the specific enzyme ability of catalase would not have been involved in the stabilization of ASA. Such proteins as bovine serum albumin (BSA) and ovalbumin also inhibited the autoxidation of ASA, therefore it seems that non-specific interaction between ASA and such proteins as catalase and BSA might stabilize ASA and that the non-enzymatic superoxide anion scavenging ability of proteins might be involved.