Chemical modification of medicines from natural product-based molecules has become of interest in recent years. In this study, a series of halogenated azo derivatives 1a-d were synthesised via coupling reaction, followed by Steglich esterification with aspirin (a natural product derivative) to form azo derivatives 2a-d. While, halogenated azo-aspirin 3a-d were synthesised via direct coupling reaction of aspirin and diazonium salt. Bacteriostatic activity was demonstrated against E. coli and S. aureus via turbidimetric kinetic method. Compound 3a-d showed excellent antibacterial activities against E. coli (MIC 75-94 ppm) and S. aureus (MIC 64-89 ppm) compared to ampicillin (MIC 93 and 124 ppm respectively), followed by 1a-d and 2a-d. The presence of reactive groups of -OH, N=N, C=O and halogens significantly contribute excellent interaction towards E. coli and S. aureus. Molecular dockings analysis of 3a against MIaC protein showed binding free energy of -7.2 kcal/mol (E. coli) and -6.6 kcal/mol (S. aureus).
In this study, a series of chalcone derivatives (1a-c) were synthesized via Claisen-Schmidt condensation, followed by aza-Michael addition to form pyrazoline derivatives (2a-c and 3a-c). The reaction was performed via microwave radiation to give excellent yields (77-93%) in 1-3.5 min. Microwave-assisted reaction of Fischer esterification of pyrazolines (2a-c and 3a-c) afforded heteroaromatic pyrazoline esters (4a-c) in high yield (83-96% in <2 min) compared to conventional reflux (55-79% in 30 min). Compounds 1a-c and 3a-c demonstrated excellent antibacterial activity against Staphylococcus aureus via disc diffusion assay with inhibition zone with 13 and 19 mm compared to a standard drug, ampicillin (11 mm). Structure activity relationship of 1b and 3b were visualized via molecular docking interaction against 4pql protein of S. aureus with binding free energy −7.0 and −8.0 kcal/mol, respectively. This study is significant in drug discovery process particularly for pharmaceutical industries.
The rise of antimicrobial resistance for infectious bacteria has become an alarming issue to human health. New antimicrobial drugs are in dire need and pivotal to overcome this issue. In this study, aspirinate azo ligands bearing different halogens L1-5 has been prepared via diazo-coupling reaction. The ligands L1-5 were coordinated with silver, Ag (I) metal to produce Ag (I) aspirin-azo complexes C1-5. The antibacterial properties of L1-5 and C1-5 were evaluated against Staphylococcus aureus and Escherichia coli using turbidimetric kinetic method. The complexes C1-5 showed comparable growth inhibition activity towards E. coli (MIC 82-105 ppm) and S. aureus (MIC 80-105 ppm) compared to ligands L1-5 with E. coli (MIC 83-200 ppm), S. aureus (80-131 ppm) and ampicillin (MIC 93 and 124 ppm, respectively). The excellent bacterial resistance of both L1-5 and C1-5 indicates the potential of aspirinate azo and their complexes as new antibacterial agents, which significantly benefit to the pharmaceutical industries.
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