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.
In an attempt to search for new and efficient antifungal agents, five chalcones namely (E)-3-(4′-diethylaminophenyl), (E)-3-(2′-ethoxyphenyl), (E)-3-(3′,4′-diethoxyphenyl), (E)-3-(2′,3′-dihydrobenzofuran-5-yl) and (E)-3-(3′,5′-bis[trifluoromethyl] phenyl)-1-(2-hydroxyphenyl) prop-2-en-1-one were synthesized from 2-hydroxyacetophenone with the corresponding substituted benzaldehydes. The synthesized chalcones were characterized by GC-MS, FTIR, 1 H NMR and 13 C NMR spectra analysis. The antifungal activities of these chalcone derivatives were evaluated against five candida species using the agar diffusion method. All the compounds showed varying degrees of activity against the fungi with the compounds containing the 4′-(diethylamino)phenyl and 2′-ethoxyphenyl moieties being the most potent in the series against the pathogens with MIC between 25 and 50 µg mL −1. Results clearly revealed the electronic effect of substituents on the Bring of the chalcone on its antimicrobial activity with the compound containing the 4′-(diethylamino) substituent which is a strong electron releasing substituent, showing the highest activity while the compound containing the 3′,5′-bis[trifluoromethyl] substituent, which is a strong electron withdrawing substituent, showing a lower potency against the tested candida species.
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