Spectroscopic and electrochemical characterization of gold(I) and gold(III) complexes with glyoxaldehyde bis(thiosemicarbazones): cytotoxicity against human tumor cell lines and inhibition of thioredoxin reductase activity

Complexes Au(2)(H(2)Gy3DH)(2)]Cl(2) (1), Au(H(2)Gy3Me)]Cl(3) (2) and Au(H(2)Gy3Et)]Cl(3) (3) were obtained with glyoxaldehyde bis(thiosemicarbazone) (H(2)Gy3DH) and its N(3)-methyl (H(2)Gy3Me) and N(3)-ethyl (H(2)Gy3Et) derivatives. The bis(thiosemicarbazones) and their gold(I) and gold(III) complexes exhibited anti-proliferative activity against HL-60, Jurkat (leukemia) and MCF-7 (breast cancer) cells at 10 μmol L(-1). Complex (2) was able to in vitro inhibit thioredoxin reductase (TrxR) activity, which suggests that inhibition of TrxR could be part of its mechanism of action.