Evaluation of in-vitro antimicrobial activity of some newly synthesized 7-hydroxy 4-methyl coumarin congeners

A series of substituted 8-arylazo 7-hydroxy 4-methyl coumarin (4a-4g) were synthesized and in-vitro evaluation for their preliminary antibacterial activities against E.coli, Staphylococcus aurous, Bacillus subtilis and Pseudomonas aeroginosa were carried out by agar-well diffusion method. Initially, the diazotized primary aryl amines, 3a-3g were synthesized and followed by coupling with 7-hydroxy 4-methyl coumarin. The synthesized compounds were structurally elucidated by UV, IR, HNMR and Mass spectroscopy. These compounds mainly existed in azo and hydrazone tautomeric equilibrium. Solvatochromic behavior of the compounds was also investigated by studying their UV-visible spectra of different organic solvents. Zone of inhibition results revealed that the product 4g exhibited greater antibacterial potential against all bacterial strains and other compounds (4a-4f) showed moderate activity and compared to standard antibiotic, Ampicillin. Finally, it was concluded that the compounds having coumarin nucleus bearing sulfonamide and -N=Nfunctional groups in same molecular structural frame, the compound 4g had tremendous zone of inhibition against Staphylococcus aurous and Bacillus subtilis while other compounds were responsible for moderate antibacterial activity due to structural presence of nitro, methoxy and methyl group in phenyl ring. The change in the maximum absorbance of the synthesized compounds in different solvents was determined and the solvatochromic property of the compound showed a medium red shift and showed moderate solvent dependency over the bathochromic shift.