A new palladium(II) complex containing ethylenediamine and 2-thioxo-4-thiazolidinone exhibits high activity against resistant Campylobacter jejuni strains

This manuscript describes the synthesis and spectroscopic characterization of two new Pt²⁺ and Pd²⁺ complexes containing ethylenediamine (en) and 2-thioxo-4-thiazolidinone (L1) as ligands. Infrared and NMR data suggest that L1 coordinates to the metal ions in a monodentate manner by the sulfur atom (S⁻). The coordination sphere of the metals is completed by an ethylenediamine molecule coordinated by the two nitrogen atoms. The metal complexes were evaluated against six resistant strains of Campylobacter jejuni. The Pd²⁺ complex (1) was more active than the Pt²⁺ complex (2) and the free ligand (L1), exhibiting high to moderate activity (MBC between 1.56 and 100 μg/mL) against the strains tested. Thereafter, the Pd²⁺ complex was evaluated in a tumoral cell line (B16-F10, murine melanoma) and in two non-tumoral cell lines (NIH/3 T3, mouse fibroblast, and C2C12, mouse myoblast), but no significant activity was observed (IC₅₀ values ≥137.3 μM), suggesting that it does not exhibit considerable toxicity. Thus, the biological data reported here indicate that the Pd²⁺ complex is a promising antibacterial agent which deserves further investigation, since there is a strong need to produce new drugs that are active against multidrug-resistant pathogens.