Synthesis and antimicrobial activity of N-alkyl substituted p-methyl (E)-3- and 4-azachalconium bromides

Authors: NURETTİN YAYLI, GÜLBİN MISIR, NURAN YAYLI, AHMET YAŞAR, EMİNE DEMİR, ZİHNİ DEMİRBAĞ

Abstract: Twenty new N-alkyl substituted p-methyl (E)-3- and 4-azachalcones (1a-j, 2a-j){3-[(1E)-3-(4-methylp-henyl)-3- oxoprop-1-en-1-yl]-1-alkyl (C_{5-12,_{14-15) pyridinium bromides (1a-j) and 4-[(1E)-3-(4-methylp-henyl)-3-oxoprop-1-en-1-yl]-1-alkyl (C_{5-12,_{14-15) pyridinium bromides (2a-j)} were synthesized and tested for antimicrobial activities against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Enterococcus faecalis, Proteus vulgaris, and Escherichia coli. They showed good antimicrobial activity especially against the gram-positive bacteria tested with minimal inhibitory concentration (MIC) values less than 4.7 \mu g/mL in most cases. The optimum length of the alkyl chain for better and broader activity is situated in the range of 8-12 carbon atoms in the series of compounds 1a-j, 2a-j. The non-alkylated compounds 1-2 were not effective as were the ones alkylated with 14 or 15 C alkyl groups (1i, 1j, 2i, 2j). N-Alkyl derivatives of p-methyl (E)-3-azachalcone (1a-h) showed better activity in comparison to those of p-methyl (E)-4-azachalcone (2a-h). The antimicrobial activity increased as the length of the alkyl substitution increased from 5 to 12 carbons.

Keywords: N-Alkyl p-Methyl-(E)-3-, 4-azachalconium bromides; antimicrobial activity.

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