TrxR inhibition and antiproliferative activities of structurally diverse gold N-heterocyclic carbene complexes

Gold compounds with N-heterocyclic carbene (NHC) ligands have been widely described as potent thioredoxin reductase (TrxR) inhibitors and effective anticancer agents. However, despite these promising aspects structure-activity-relationship (SAR) studies still remain limited. In this study a structurally diverse library of gold(I) and gold(III) NHC complexes was investigated for inhibitory capacity against TrxR and for antiproliferative activity in HT-29 human colon adenocarcinoma cells with the aim of identifying a valid SAR. Overall results indicated that the bioactivity, carried by the gold center, is intimately linked to the chemical properties of the residues at the NHC scaffold as well as other ligands coordinated to the gold atom. Although a direct correlation between IC50 values for cytotoxicity and enzyme inhibition could not be established, the inhibition of TrxR represents an important parameter to achieve a good cytotoxic activity.