Study of the Interaction of Some Potential Anticancer Gold(III) Complexes with Biologically Important Thiols Using NMR, UV–Vis, and Electrochemistry

Abstract

ABSTRACTThe interaction of gold(III) complexes [Au(en)Cl2]Cl, [Au(en)2]Cl3, [Au(cis‐DACH)Cl2]Cl, and [Au(cis‐DACH)2]Cl3 (en = ethylenediamine, DACH = cis‐1,2‐diaminocyclohexane) with biologically important thiols, such as glutathione (GSH), dl‐penicillamine (PSH), mercaptoacetic acid (MAA), and N‐(2‐mercaptopropionyl)glycine (MPG), has been studied using 1H, 13C NMR, UV–vis spectroscopy and electrochemistry in aqueous solution. Kinetic data revealed that the reactivity of their substitution reaction followed the order: [Au(en)Cl2]+ > [Au(en)2]3+ > [Au(cis‐DACH)Cl2]+ > [Au(cis‐DACH)2]3+. The thiol reactivity increased with decreasing its size, viz. MAA ≫ MPG > PSH > GSH. Square wave stripping voltammetry displayed peaks for Au(III) and Au(I) at +0.875 V and +1.4 V respectively. The interaction of the complexes with thiols resulted in reduction of gold(III) to gold(I) and thiol ligands (RSH) were oxidized to disulfide (RSSR).