Coumarin‐Augmented Thiazole Hybrids as Dual Anticancer and Antibacterial Agents

Coumarins are a privileged scaffold in medicinal chemistry, renowned for diverse therapeutic activities including antiviral, anticancer, and neuroprotective effects. Building on our previous work with 3-substituted coumarins as inhibitors of tumor-associated carbonic anhydrases, we report a novel series of thiazol-hydrazono-coumarins targeting the ATP-binding domain of topoisomerase enzymes. Seventeen compounds were synthesized and evaluated for selective cytotoxicity against HeLa cells versus WI-38 fibroblasts and for antimicrobial activity against four ESKAPE pathogens, Escherichia coli, and Salmonella typhimurium. Several derivatives showed potent antibacterial activity, with MICs as low as 0.12 μg/mL against resistant Staphylococcus aureus strains and inhibition zones up to 33 mm against Gram-negative bacteria. Compound 13 exhibited strong selectivity, with an IC₅₀ of 26.8 μg/mL in HeLa cells and 220.7 μg/mL in WI-38 cells. The five most active compounds were studied via molecular docking and MM/GBSA to elucidate their binding to bacterial DNA gyrase, topoisomerase IV, and human topoisomerase IIα. A molecular dynamics simulation of the S. aureus DNA gyrase B-compound 13 complex revealed a novel hydrogen bond between the coumarin ring and serine-129. These findings highlight thiazol-hydrazono-coumarins as promising antibacterial leads with ancillary anticancer activity, supporting their potential in treating infections in immunocompromised cancer patients.