Synthesis, X-ray structures and anticancer activity of gold(I)-carbene complexes with selenones as co-ligands and their molecular docking studies with thioredoxin reductase

Five new gold(I) complexes of carbene and selenone ligands (1–5) having the general formula, [Au(IPr)(selenone)]PF₆ were synthesized by the reaction of [Au(IPr)Cl] (0) with selenones (IPr = 1,3-Bis(2,6-di-isopropylphenyl)imidazol-2-ylidene and selenone = 1,3-imidazolidine-2-selenone, N-ethyl-1,3-imidazolidine-2-selenone, N-propyl-1,3-imidazolidine-2-selenone, N,N′-dimethyl-1,3-imidazolidine-2-selenone and N,N′-diethyl-1,3-imidiazolidine-2-selenone for 1–5 respectively). The complexes were characterized by elemental analysis, IR and NMR (¹H, ¹³C, ⁷⁷Se) spectroscopy, and two of them by X-ray crystallography. The X-ray diffraction analysis of complexes 2 and 4 revealed that they were composed of [Au(IPr)(Selenone)]⁺ and PF₆⁻ ions. In the complex ions, gold(I) atom adopts a linear geometry. In vitro cytotoxicity was appraised for all complexes against HCT15, A549 and MCF7 cancer cell lines. The IC₅₀ values showed that the complexes exhibited poor activity as compared to cisplatin. However, the complex 1 showed a promising anticancer activity (IC₅₀ = 33 ± 1 μM) similar to that exhibited by cisplatin (32 ± 2 μM) against HCT15 (human colon cancer) cell line. The molecular docking analysis showed the potential inhibitory capacity of the gold complexes with thioredoxin reductase with complex 4 having the highest binding affinity with a score of −34.45. The interactions of the gold complexes with tryptophan and lysozyme were studied electrochemically using Cyclic and Square Wave Voltammetry.