Copper(II) complexes with different diamines as inhibitors of bacterial quorum sensing activity

Abstract

Three copper(II) complexes, trans-[Cu(1,3-pd)2Cl2]?H2O (Cu1; 1,3-pd is 1,3-propanediamine), trans-[Cu(2,2-diMe-1,3-pd)2Cl2] (Cu2; 2,2-diMe- -1,3-pd is 2,2-dimethyl-1,3-propanediamine) and trans-[Cu(1,3-pnd)2Cl2]?H2O (Cu3; 1,3-pnd is (?)-1,3-pentanediamine), were synthesized and structurally characterized by elemental microanalyses, IR, electronic absorption and reflectance spectroscopy and molar conductivity measurements. The antimicrobial efficiency of the complexes against four clinically relevant microorganisms and their antiproliferative effect on the normal human lung fibroblast cell line MRC-5 were evaluated. Since in many bacteria, pathogenicity is regulated by an intercellular communication process called quorum sensing (QS), the effect of the copper(II) complexes Cu1?3 on bacterial QS was examined. The obtained results showed that these complexes inhibited violacein production in Chromobacterium violaceum CV026, indicating their anti-QS activity via the homoserine lactone (HSL) pathway. Two biosensor strains were used to determine which pathway, C4-HSL (N-butanoylhomoserine lactone) or 3OC12-HSL (N-(3-oxododecanoyl)homoserine lactone), was affected by the copper(II) complexes. The biological activities of the copper(II) complexes were compared with those for the nickel(II) complexes of the general formula trans- -[Ni(L)2(H2O)2]Cl2 (L = 1,3-pd, 2,2-diMe-1,3-pd and 1,3-pnd).