Synthesis, Characterization and Antibacterial Activities of New Fluorinated Chalcones

Abstract

A series of five fluorinated chalcones (E)-3-(2′-ethoxyphenyl)-1-(4-Fluoro-2-hydroxyphenyl)prop-2-en-1-one(4),(E)-3-(3′,4′-diethoxyphenyl)-1-(4-fluoro-2-hydroxyl-phenyl)prop-2-en-1-one(5),(E)-3-(2′,3′-dihydrobenzofuran-5-yl)-1-(4-Fluoro-2-hydroxylphenyl)prop-2-en-1-one(6),(E)-3-(3′,5′-Bis[trifluoromethyl]phenyl)-1-(4-Fluoro-2-hydroxylphenyl)prop-2-en-1-one(7) and (E)-3-(4′-diethylaminophenyl)-1-(4-Fluoro-2-hydroxylphenyl)prop-2-en-1-one(8) were synthesized by a modified Claisen-Schmidt condensation of 4-fluoro-2-hydroxyacetophenone with the appropriate aromatic aldehydes. The compounds were characterized by spectroscopic methods and evaluated for their antibacterial activity against Gram-positive (Methicillin-resistant S. aureus, Vancomycin-resistant enterococci, S. aureus, S. pyrogenes, S. faecalis) and Gram-negative (E. coli, S. typhi, C. ulcerans, P. mirabilis, P. aeruginosa) pathogenic bacteria strains using the agar diffusion method. The compounds exhibited broad spectrum activity against eight of these pathogens with compounds (4), (5) and (8) found to be the most potent in the series with zones of inhibition ranging from 23 to 28 mm and MIC between 25 and 50 µg/mL. All the compounds except (7) containing 3-(3′,5′-bis[trifluoromethyl]phenyl) moiety, showed a remarkable activity against MRSA [MIC = 25–50 µg/mL]. Compound (8) exhibited good activity against P. aeruginosa [MIC = 50 µg/mL]. Compounds (4), (5) and (8) were active against C. ulcerans [MIC = 50 µg/mL]. The broad-spectrum standard drug, ciprofloxacin, was inactive against MRSA, P. aeruginosa and C. ulcerans.