N-(4-Hydroxyphenyl)acetamide against diiodine towards polyiodide dianion

Abstract

The direct reaction of N-(4-hydroxyphenyl)acetamide or paracetamol (C₈H₉NO₂, PACET), a widely used Non Steroidal Anti-Inflammatory Drug (NSAID), with diiodine forms an ionic salt with the formula {[(PACET)₂H⁺]₂·(I₈)²⁻} (1) with the simultaneous reduction of iodine to iodide. The compound was characterized by X-ray diffraction analysis. Compound 1 contains the polyiodide (I₈)²⁻ counter dianions, in a z-shape conformation. By taking into account secondary I⋯I interaction the shape turns out to be rectangular. Moreover, N-(4-hydroxyphenyl)acetamide inhibits the catalytic activity of horse radish peroxidase (HRP) (a model of thyroid peroxidase (TPO)) on the oxidation of iodides to diiodine by hydrogen peroxide, as evidence of the kinetic and computational studies. The inhibition activity of PACET against the catalytic oxidation of iodides by H₂O₂ in the presence of FeTPPCl (a model of the active site of TPO) is measured as a result of the yield of I₃⁻.