Antimicrobial salicylaldehyde schiff bases: synthesis, characterization and evaluation

ABSTRACT

As the pathogens soon develop resistance to the existing antibiotics, the demand for new and more effective anti-microbial agents is a continuous phenomenon. In this paper we are reporting synthesis and spectral data of eight Schiff bases of salicylaldehyde with different amines, and evaluation of their anti-microbial activities against different bacterial strains. The bases were synthesized by reflux method, and their structures were determined based FT-IR,[1]HNMR,[13]C-NMR and Mass spectrometric data. The Schiff bases synthesized included 2-[[[Z]-[2-hydroxyphenyl] methylidene] amino]benzoicacid [SB1], 4-[[[Z]-[2-hydroxyphenyl] methylidene] amino] benzoic acid [SB2],2- [[naphthalene-2-ylimino] methyl] phenol [SB3],2-2'-[benzene-1,4- iylbis [nitrilomethylylidene]] diphenol [SB4], 2-2'- [benzene-1,2-diylbis [nitrile-[E]-methylylidene]]diphenol [SB5], 2-[[2- phenylhydrazineylidene] methyl]phenol [SB6], 2- 2'-[ethene-1,2-diylbis[iminomethanediyl]]diphenol [SB7] and 2-[[Z]-[phenylimino] methyl]phenol [SB8]. The antimicrobial activities of synthesized Schiff bases were determined in terms of zones of inhibition and minimum inhibitory concentrations [MICs]. All the bases showed moderate to good activities against all the tested microorganisms. The MICs of most compounds were 100-200microg/mL against different microorganisms. However, it was 50micro g/mL for SB1 against P. aeruginosa [1], SB3 against P. aurantiaca, P. aeruginosa [1], E. coli [2], S. typhi [2] and C. freundii, SB4against E. coli [2], S. typhi [1] and S. maltophilia, SB5 against K. pneumoniae and S. typhi [2], SB6 against P. aeruginosa [3] and C. freundii, SB7 against E. cloacae and A. lipoferum, andSB8against E. coli [2]. Considerably active bases may prove to be potential candidates for future antibiotic drugs