Organic Acids as Potent Inhibitors of Myoglobin Pseudo-Peroxidase Activity and Myoglobin-Dependent Protein Tyrosine Nitration

The pseudo-peroxidase activity of myoglobin plays a significant role in tissue damage during oxidative stress either within tissues or in its free form. Effective inhibitors could protect tissues from damage caused by oxidative stress. Eight organic acids found in plants were selected, and their inhibitory effects against the peroxidase activity of myoglobin were tested. IC₅₀ values were determined and compared. All organic acids reduce myoglobin's peroxynitrite-independent chlorination activity to varying degrees. Ascorbic acid, malic acid, and oxalic acid can be classified as strong inhibitors, whereas succinic acid, citric acid, acetic acid, fumaric acid, and l-(+)-tartaric acid are considered weak inhibitors. Ascorbic acid is the most potent and acetic acid is the least effective inhibitor. The results suggest that organic acids significantly inhibit myoglobin peroxidase activity. Due to their natural and nontoxic origin, they can be considered as easily accessible and nontoxic alternatives to peroxidase activity inhibitors of myoglobin.