Bacteria often show resistance against
antibiotics due to various mechanisms such as the expression of efflux pumps, biofilm formation, or bacterial quorum sensing (QS) controls. For successful therapy, the discovery of alternative agents is crucial. The objective of this study was to evaluate the efflux pump, anti-biofilm, and QS inhibiting, as well as antibacterial effects of
2-trifluoroacetonylbenzoxazole ligands (1-3) and their
metal complexes (4-12) in bacteria. The
ligand 2 and its Zn(II) complex 5, and furthermore the Cu(II) complex 7 of
ligand 1, exerted remarkable antibacterial activity on the Staphylococcus aureus 272123 (MRSA) strain. In the minimum inhibitory concentration (MIC) reduction assay the
ligand 3, the Zn(II) complex 5 of
ligand 2, and the Cu(II), Ni(II), Mg(II), Fe(III) complexes (7, 8, 9, 12) of
ligand 1 enhanced the antibacterial activity of
ciprofloxacin in MRSA. An increased
ethidium bromide accumulation was detected for
ligand 3 in MRSA while the Fe(III) complex 12 of
ligand 1 decreased the biofilm formation of the reference S. aureus ATCC 25923 strain. The Zn(II) and Ag(II) complexes (3 and 4) of
ligand 1 and
ligand 3 inhibited the QS. Based on our results, the
ligands and their
metal complexes could be potential alternative drugs in the treatment of
infectious diseases.