New N-Benzoylthiourea-pyrrolidine-based Copper(II) complexes as anticancer agents

• Four novel N-benzoylthiourea–pyrrolidine-based Cu(II) complexes were synthesized and characterized. • Crystal structures of L2-Cu and L4-Cu were confirmed by single-crystal X-ray diffraction analysis. • The L3-Cu complex exhibited the strongest cytotoxicity, especially against A549 lung cancer cells (IC₅₀ = 4.46 µM). • Molecular docking studies supported the biological findings and revealed binding interactions at the target sites. • Ligand-to-complex conversion significantly enhanced anticancer activity in L1 and L3 derivatives. • The stability constants of the Cu(II) complexes were determined potentiometrically and modeled using the HYPERQUAD program. New copper(II) complexes derived from N -benzoylthiourea–pyrrolidine ligands were synthesized and characterized using infrared spectroscopy (IR), high-resolution mass spectrometry (HRMS), and single-crystal X-ray diffraction for the L2 – Cu and L4 – Cu complexes. The cytotoxic and in vitro anticancer activities of the ligands and their copper(II) complexes were evaluated against MCF-7 (human breast adenocarcinoma), A549 (non-small cell lung carcinoma), and HCT116 (human colon carcinoma) cell lines, with BEAS-2B normal lung epithelial cells as a control. Among the tested compounds, the L3 – Cu complex exhibited the strongest cytotoxicity, particularly against A549 cells (IC 50 : 4.46 µM), surpassing cisplatin (>100 µM for A549) and showing lower toxicity toward BEAS-2B cells (15.4 µM). L1, L3 , and L1 – Cu were the most active against HCT116 cells (IC 50 : 11.29–8.86 µM). Molecular docking simulations revealed strong binding interactions with phosphoinositide 3-kinase (PI3K) and histone deacetylase 6 (HDAC6) in A549 cells, c-Jun N-terminal kinase 1 (JNK1) in HCT116 cells, and estrogen receptor alpha (ERα) in MCF-7 cells. The stability constants of the copper(II) complexes were determined by potentiometric titration and analyzed using the HYPERQUAD program. Overall, N -benzoylthiourea–based copper(II) complexes, particularly L3 – Cu , demonstrate potent and selective anticancer activity supported by both experimental and computational findings.