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A series of 5,7-dibromo-2-benzoylbenzofurans were synthesized by the Rap–Stoermer condensation of 5,7-dibromosalicylaldehyde with diverse phenacyl bromides and evaluated for in-vitro antibacterial activities against methicillin-sensitive Staphylococcus aureus (MSSA) ATCC 29213, methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, and MRSA ATCC 33591 by agar dilution method. The synergistic effects were determined by using the agar dilution checkerboard assay. The derivatives bearing carboxylic acid functional groups exhibited reasonable activity against MRSA strains with the best MIC = 32 µg/mL (9b, 9d). Moreover, the additive or synergistic interactions against MRSA strains was observed in six combinations (1b + cefuroxime/gentamicin, 1c + ciprofloxacin/gentamicin, 9b + gentamicin, and 9c + ciprofloxacin) with the fractional inhibitory concentration index (FICI) values in the range of 0.375–1.0. Significantly, the MICs of these antibiotics were reduced 2–4-fold. The results of the MTT assay illustrated the low mammalian cell cytotoxicity of these potent compounds. [ABSTRACT FROM AUTHOR]

In order to discover new antibacterial agents, series of 2-salicyloylbenzofuran derivatives were designed, synthesized and evaluated for their antibacterial activities against three Gram-(+) strains (methicillin-sensitive Staphylococcus aureus (MSSA) ATCC 29213, methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, and Streptococcus faecalis (S. faecalis) ATCC 29212) and one Gram-(-) strain (Escherichia coli (E. coli) ATCC 25922). The 2-salicyloylbenzofuran heterocycles were generated by Rap-Stoermer condensation of salicylaldehydes with phenacyl bromides and then converted to diverse O-ether derivatives by Williamson synthesis. The targeted products were screened for in vitro qualitative (zone of inhibition) and quantitative (MIC) antibacterial activities by agar well diffusion assay and agar dilution method. Amongst the compounds, those bearing carboxylic acid functional group were found to exhibit reasonable activity against Gram-(+) bacterial strains including S. faecalis, MSSA and MRSA with the most potent antibacterial agent 8h (MICs = 0.06-0.12 mM). Besides, the 2-salicyloylbenzofurans partly displayed inhibitory activity against MRSA with the best MICs = 0.14 mM (8f) and 0.12 mM (8h). Finally, the antibacterial results preliminarily suggested that the substituent bearing carboxylic acid group at salicyloyl-C2 and the bromine atoms on the benzofuran moiety seem to be the functionality necessary for antibacterial activities. [ABSTRACT FROM AUTHOR]