Comprehensive experimental and computational evaluation of novel linagliptin-analogues: Synthesis, DFT calculations,...

Recent evidence suggests that linagliptin and its structural derivatives exhibit biological activities beyond glycemic control, highlighting the linagliptin scaffold as a promising platform for multifunctional drug design. In this study, eight novel linagliptin-based azo-imine derivatives (3a-h) were designed, synthesized, and structurally characterized, with the stereochemistry of representative compound 3e confirmed by 2D NMR. Computational analyses (DFT, molecular docking, and molecular dynamics simulations) were employed to support electronic structure elucidation and ligand-protein interaction stability. Specifically, 250 ns molecular dynamics simulations confirmed that the 6XFP-3h complex maintains high structural stability and thermodynamic equilibration throughout the trajectory. All derivatives displayed moderate antioxidant activity (TEAC = 0.46-0.84). Antiproliferative effects were evaluated against A549 and DLD1 cancer cell lines, with WI-38 fibroblasts used to assess selectivity. Compound 3h exhibited the highest potency, with IC₅₀ values of 0.66 µM (A549) and 0.29 µM (DLD1), while compounds 3d and 3e showed cytotoxicity comparable to cisplatin. Selectivity index analysis revealed moderate but discernible cancer cell preference, with compound 3h demonstrating the most favorable selectivity toward DLD1 cells (SI = 3.62). These results suggest that compound 3h represents a prioritized candidate within this series and support linagliptin-based azo-imine derivatives as a tractable framework for further structure-activity relationship optimization.