Assessment of antioxidant activity, redox behavior, and human serum albumin binding of pyrogallol-coumarin hybrids

The antioxidant activity of the compounds, two pyrogallol-coumarin hybrids (PCH-1 and PCH-2), was evaluated using DPPH, ABTS, and FRAP assays. The obtained results indicate the excellent antioxidant potential of both compounds. Quantitative evaluation showed that PCH-2 exhibits antioxidant capacity comparable to or better than standard compounds (NDGA, gallic acid, and trolox). In addition, PCH-1 and PCH-2 showed significant cytotoxic activity against HCT-116 colon cancer cells, and the cytotoxicity was achieved by their pro-oxidant activity. UV–Vis and fluorescence spectroscopy show that strong and specific interactions between HSA and the synthesized compounds result in ground-state complex formation and temperature-dependent binding. Thermodynamic analysis showed that PCH-1 binding is primarily driven by hydrophobic interactions, while PCH-2 associates with HSA mainly through hydrogen bonding and van der Waals interactions. Molecular binding studies revealed a strong binding affinity of PCH for HSA, especially at site I. Rigid docking of PCHs gave negative binding free energies (ΔG ≈ −27.9 to −35.9 kJ/mol) and binding constants (Kb = 0.5–12.6 μmol/L), indicating enhanced ligand-protein interactions via hydrogen bonds and hydrophobic contacts. These results suggest stable HSA-ligand complexes and support the potential of HSA as a carrier for the compounds under study.