Benzoxazole-Based Metal Complexes to Reverse Multidrug Resistance in Bacteria.

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.

In Vitro Evaluation of the Multidrug Resistance Reversing Activity of Novel Imidazo[4,5-b]pyridine Derivatives.

BACKGROUND/AIM: Malignant diseases present a significant public health burden worldwide and their treatment is further complicated by the phenomenon of multidrug resistance. Derivatives of imidazopyridine exhibit several remarkable pharmacological activities and they could reverse the multidrug resistance of cancer cells due to overexpressing P-glycoprotein. MATERIALS AND METHODS: A series of novel imidazo[4,5-b]pyridine derivatives were synthesized and their biological activities were evaluated in vitro using parental (PAR) and multidrug resistant (MDR; ABCB1-overexpressing) mouse T-lymphoma cells. The cytotoxic activity and selectivity of the tested compounds were assessed by the thiazolyl blue tetrazolium bromide (MTT) assay, the ABCB1 modulating activity was measured by rhodamine 123 accumulation assay using flow cytometry. RESULTS: Six compounds (b, c, d, f, h and i) showed moderate-to-high cytotoxic activity on the tested cell lines, while derivative i presented with promising selectivity towards the MDR cell line. Derivatives a, d, f, g and i were proven to be effective modulators of the ABCB1 multidrug efflux pump, with two compounds showing efflux pump modulatory activity at 2 µM concentration. CONCLUSION: Based on our experimental results, compounds that showed potent activity are those with a short carbon side chain; a methoxy group on the benzene ring; a heterocyclic (triazole) side chain and the presence of an alkylated N-atom at position 4.