Inhibitory effect of organic acids on human neutrophil Myeloperoxidase’s peroxidation, chlorination, and nitration activities

Abstract Objectives Myeloperoxidase from polymorphonuclear leukocytes is an important enzyme in oxidative metabolism and has a key role in tissue injuries in oxidative stress and inflammatory conditions. Therefore, its inhibitors have become the focus of studies on new drug development in recent years. The aim of the study was to determine the inhibitory effect of organic acids on the peroxidation, chlorination, and nitration activities of myeloperoxidase. Methods Seven organic acids naturally abundant in plants were tested. Different activities of myeloperoxidase were measured in the presence of various amounts of organic acids, and inhibition rates and kinetic parameters were determined for each organic acid separately. Results All the organic acids examined had inhibitory effects on the different activities of myeloperoxidase. Comparison of the IC50 values obtained for peroxidation, chlorination, and nitration activities showed that oxalic acid was the strongest inhibitor of myeloperoxidase activity, while citric acid and succinic acid were the weakest. Conclusions The results suggested that all the organic acids examined are inhibitors of myeloperoxidase. In particular, oxalic acid and fumaric acid are popular candidates for drug development research. More studies are needed to determine the in vivo effects of organic acids and their effects in the treatment of disease.