Comparison of the degradation mechanisms of diclofenac in the presence of iron octacarboxyphthalocyanine and myeloperoxidase

Abstract

The degradation process of diclofenac (DCF) by hematoprotein myeloperoxidase (MPO) and iron octacarboxyphthalocyanine (FePcOC) in the presence of hydrogen peroxide was compared. During the oxidation of diclofenac, in the presence of iron octacarboxyphthalocyanine (FePcOC) and hydroxyl radicals (HO•) (from H2O2), an intermediate product (dimer with an m/z value of 587) with the characteristic yellow colouration and an intense band at λmax = 451 nm is formed. Iron octacarboxyphthalocyanine oxidises in the presence of hydrogen peroxide, following the first-order reaction kinetics for FePcOC and H2O2. The concentration of diclofenac does not affect the initial reaction rate. For comparison, the oxidation of DCF in the presence of myeloperoxidase and hydrogen peroxide also provided yellow-coloured solutions with an absorption maximum at λmax = 451 nm. However, LC-MS/MS analysis indicates the presence of at least seven main products of the diclofenac oxidation process in the final reaction mixture, including two dimers with the ion mass [M−H]¯ = 587.01. The mechanism of the diclofenac degradation with hematoprotein myeloperoxidase is more complex than with iron octacarboxyphthalocyanine. Furthermore, the biological activity of diclofenac and DCF dimer (iron octacarboxyphthalocyanine and hydroxyl radicals degradation product) was tested. In this case, the long-term assayed in vitro against E. coli, colorectal HCT116 and melanoma Me45 cancer cells were performed.