A Spectroscopic Study of Interaction of Auricyanide with N-Acetylcysteine

Abstract

Interaction of auricyanide, an important metabolite of anti-arthritic gold-based drug auranofin, was studied in vitro with a pharmacologically active ligand Nacetylcysteine with a view to understand reactivity of gold in vivo. Formation of reduction product aurocyanide occurred through mono- and di-N-acetylcysteine-substituted intermediates. The product and intermediates were identified and monitored spectrophotometrically and by electrospray ionization mass spectrometry. This study suggests successive substitution with N-acetylcysteine through trans effect. At equimolar concentrations of auricyanide and N-acetylcysteine, only mono-substituted mixed-ligand complex was formed. Substitution of the data obtained to various kinetic models suggested that the reaction orders are 0.6 in terms of Nacetylcysteine, 1.5 in terms of auricyanide, and 2 overall. The intermediates detected in this work may help to synthesize more effective and less toxic gold drugs.