Synthesis of new steroidal imidazo [1,2-a] pyridines: DNA binding studies, cleavage activity and in vitro cytotoxicity

Abstract A one-pot strategy for the catalytic synthesis of series of new 5α-cholestan-6- spiro -5′-phenylamino-2H-imidazo [1′,2′-a] pyridines ( 4 – 14 ) has been investigated. The synthesized products were obtained in good yields (85–90%) and the protocol uses Multi-component Reaction (MCR) involving steroidal ketones, 2-aminopyridines, isocyanides and propylphosphonic anhydride (®T3P) as a catalyst. After characterization by spectral and analytical data, the interaction studies of compounds ( 4 – 6 ) with DNA were studied by UV–vis, fluorescence spectroscopy, gel electrophoresis and molecular docking. The compounds bind to DNA preferentially through electrostatic and hydrophobic interactions with K b ; 2.35 × 10 4 , 3.71 × 10 4 and 3.24 × 10 4  M −1 , respectively, indicating the higher binding affinity of compound 5 towards DNA. Gel electrophoresis showed the concentration dependent cleavage activity of compounds 4 – 6 with DNA. Molecular docking studies suggested that compounds bind through minor groove to DNA. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay depicted promising anti-proliferative activity of compound 4 – 9 against different given cancer cells. In Western blotting, the expressions of relevant apoptotic markers depicted an apoptosis by steroidal imidazopyridines in A549 cells. Annexin V-FITC/PI staining data indicated that compounds could effectively induce apoptosis in A549 cells in a dose-dependent manner. FACS analysis shows that the compound 6 bring about cell cycle arrest at 2.62 μM concentration.