Synthesis, Structure-Activity Relationship and Antibacterial Activity of Some Simple (E)-Chalcones

Abstract

In present work, 14 simple (E)-chalcones (1-14), synthesized via the Claisen-Schmidt condensation between arylmethyl ketone and aromatic aldehyde in the presence of either in NaOH or H3BO3, were tested for in vitro antibacterial activity against two Gram-positive (Staphylococcus aureus and Bacillus subtilis) and three Gram-negative (Escherichia coli, Enterobacter cloacae and Klebsiella pneumoniae) bacterial strains. Among them, (E)-3-(4-hydroxy-3-methoxyphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (8) was found most efficient, while (E)-3-(4-(dimethylamino)phenyl)-1-phenylprop-2-en-1-one (4) and (E)-1-(2,4-dihydroxyphenyl)-3-(4-(dimethylamino)-phenyl)prop-2en-1-one (14) were completely ineffective. The rest of the (E)-chalcones have displayed moderate to good antibacterial activity, particularly against Gram-positive bacteria, while E. coli was found resistant. From the structure-activity relationship (SAR) analysis, it is revealed that the presence of a strong electron-withdrawing group (NO2) in ring A and the presence of electron-donating group in ring B of (E)-chalcones could enhance the antibacterial activity. The presence of hydroxyl and/or alkoxyl substituents in both 3 and 4 positions of ring B proved beneficial.