Synthesis, characterization, antimicrobial and biofilm inhibitory studies of new esterquats.

Novel esterquats (monoesterquats and diesterquats) were synthesized from 11-bromo undecanoic acid (11-BUA) and different alkyl amines. The prepared compounds were characterized by FT-IR, (1)H NMR, (13)C NMR and mass spectral analysis. 11-BUA was converted into methyl 11-bromo undecanoate which was further converted into amine ester (amine monoester and diester) by reacting with different aliphatic amines (hexyl, dodecyl, octadecyl, dioctyl and dicyclohexyl amine). Finally, the obtained amine esters were converted into esterquats (monoesterquat and diesterquat) by reacting with methyl iodide followed by ion exchange to afford chloride counter ion esterquats (5a-h). The synthesized esterquat products were studied for their antimicrobial and biofilm inhibitory activities. Among all the compounds, amine ester 3a and esterquat 5d showed potent antimicrobial activity towards pathogenic Gram-positive bacterial strains with minimum inhibitory concentration (MIC) values in the range of 3.9-15.6 μg mL(-1) and 1.9-7.8 μg mL(-1), respectively. The esterquat 5d also showed promising antifungal activity against Candida albicans MTCC 3017, Candida albicans MTCC 4748 and Candida aaseri MTCC 1962 strains with MIC value of 7.8 μg mL(-1) which was identical to standard Miconazole. The compounds which exhibited antimicrobial activity were also effective in anti-biofilm activity and it was found that compound 5d exhibited excellent biofilm inhibitory activity with IC50 value of 0.9 μg mL(-1) against Staphylococcus aureus MLS16 MTCC 2940.