Multitarget evaluation of 4-substituted 7-hydroxycoumarin derivatives: anticancer activity, topoisomerase I inhibition, and interaction with human serum albumin

Coumarins are known to provide promising scaffolds for the development of new anticancer drugs, yet their multitarget biological profiles remain insufficiently explored. This study presents a comprehensive evaluation of four newly synthesized 4-substituted 7-hydroxycoumarin derivatives C1-C4, highlighting their combined antiproliferative, enzyme-inhibitory, and pharmacokinetic properties. The compounds were tested for their cytotoxic effects on A549 lung carcinoma cells and CCD-18Co fibroblasts, inhibition of topoisomerase I (Topo I), and binding interactions with human serum albumin (HSA). Derivatives C1, C2, and C4 showed selective suppression of A549 metabolic activity and proliferation, while exhibiting minimal toxicity toward non-cancerous fibroblasts. All compounds inhibited Topo I to varying degrees, with C1 displaying the highest potency, indicating that specific hydroxyl group arrangements are crucial for enzyme inhibition. Fluorescence spectroscopy and molecular docking revealed moderate to high HSA affinity (10⁴-10⁶ M^-1) and predominantly single-site binding, supporting their favorable plasma transport potential. Thermodynamic analysis showed distinct interaction patterns: C1 and C2 formed complexes stabilized primarily by hydrogen bonds and van der Waals forces, whereas C3 and C4 interacted mainly through hydrophobic forces. Competitive displacement assays identified Sudlow site I as the principal binding region, although molecular docking studies also suggested the possible involvement of site III. Overall, this work introduces a novel series of coumarin derivatives with a clearly defined multitarget anticancer profile which combines selective cytotoxicity, effective Topo I inhibition, and strong pharmacokinetic characteristics, thereby underscoring the potential of these derivatives as lead structures for further anticancer drug development.