Antimicrobial activity and DNA/BSA binding affinities of silver(I) and gold(III) complexes with 1,6-naphthyridine

Silver(I) and gold(III) complexes with aromatic nitrogen-containing heterocycles have shown an effective and wide-spectrum antimicrobial activity. The possible mechanism of their antimicrobial activity can be attributed to the interactions of these complexes with biomolecules, including DNA and proteins. In the present study, new silver(I) complex with 1,6-naphthyridine (1,6-naph), {[Ag(1,6-naph)(H₂O)](BF₄)}_n (1) was synthesized and characterized by NMR, IR and UV-Vis spectroscopy, and its crystal structure was determined by single-crystal X-ray diffraction analysis. The complex 1 and the previously reported analogue gold(III) complex [1], [AuCl₃(1,6-naph)], were evaluated for antimicrobial activity against the panel of representative microorganisms, while their cytotoxicity was tested against normal human lung fibroblast cell line (MRC-5). The binding affinity of these complexes with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied to clarify the mode of their antimicrobial activity.