A convenient synthesis, characterization and biological evaluation of novel schiff base heterocycles as potential antimicrobial, antitubercular agents and their structural activity relationship

A series of (E)-1-methyl-3-((substituted phenylimino)methyl)quinolin-2(1H)-one schiff bases (3a-j) bearing quinoline moiety synthesized successfully in ethanol by condensation of starting material 1-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde (1) with various substituted anilines (2a-j). The structure of the newly synthesized compounds was confirmed by proton (1H) and carbon (13C) nuclear magnetic resonance spectroscopy, Fourier transformation infrared (FT-IR), Mass spectroscopic study and elemental analysis. The in-vitro antimicrobial activity of the synthesized compounds was undertaken by agar well diffusion method against gram positive bacteria (Bacillus licheniformis and Bacillus cereus) gram negative bacteria (Escherichia coli and Acetobactor sp.) and antifungal activity against (Aspergillus Flavus and Pichnanomala). Further the compounds which shows good activity (3b, 3c, 3d, 3f, 3g and 3j) are screened for in-vitro antitubercular activity by Micro-plate alamar blue assay (MABA) method against mycobacterium tuberculosis H37Rv strain provided important information about activity against these strains. The structure activities of the synthesized compounds were also discussed. Compounds 3a, 3c, 3d, 3f and 3g show good argument with the different substituent attached to the phenyl ring.