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In our continuing efforts to develop therapeutically active coumarin‐based compounds, a series of new C4–C4′ biscoumarin–pyrimidine conjugates (1a–l) was synthesized via SN2 reaction of substituted 4‐bromomethyl coumarin with thymine. All compounds were characterized using spectroscopic techniques, that is, attenuated total reflection infrared (ATR‐IR), CHN elemental analysis, and 1H and 13C NMR (nuclear magnetic resonance). In addition, the structure of compound 1d (1,3‐bis[(7‐chloro‐2‐oxo‐2H‐chromen‐4‐yl)methyl]‐5‐methylpyrimidine‐2,4(1H,3H)‐dione) was established through X‐ray crystallography. Compounds 1a–l were screened for in vitro anticancer activity against C6 rat glioma cells. Among the screened compounds, 1,3‐bis[(6‐chloro‐2‐oxo‐2H‐chromen‐4‐yl)methyl]‐5‐methylpyrimidine‐2,4(1H,3H)‐dione (1c) was identified as the best antiproliferative candidate, exhibiting an IC50 value of 4.85 μM. All the compounds (1a–l) were found to be nontoxic toward healthy human embryonic kidney cells (HEK293), indicating their selective nature. In addition, the most active compound (1c) displayed strong binding interactions with the drug carrier protein, human serum albumin, and exhibited good solution stability at biological pH conditions. Fluorescence, UV–visible spectrophotometry and molecular modeling methodologies were employed for studying the interaction mechanism of compound 1c with protein.

To get an idea about the pharmacokinetics and pharmacodynamics, it is important to study the drug‐protein interaction. Therefore, herein, we studied the interaction of diclofenac sodium (DIC) with human hemoglobin. The binding study of nonsteroidal antiinflammatory drug, DIC with human hemoglobin (HHB) was done by utilizing fluorescence, UV–visible, time‐resolved fluorescence and far‐UV circular dichroism spectroscopy (CD). Various thermodynamic parameters such as enthalpy change (ΔH), entropy change (ΔS), and Gibbs free energy change (ΔG) were also calculated. CD results showed that DIC induces secondary structure change in HHB. Fluorescence resonance energy transfer was also performed. Additionally, it was also observed that DIC inhibits the esterase‐like enzymatic activity of HHB via competitive inhibition.