Study on crystallographic structure and antiproliferative effect of mixed-ligand strontium(II) complex and N, Nˊ–bis(2-hydroxy-5-methylphenyl) pyridine-2,6-dicarboxamide ligand

The novel amide ligand, N,Nˊ–bis(2-hydroxy-5-methylphenyl) pyridine-2,6-dicarboxamide (L) was synthesized through the condensation reaction of pyridine-2,6-dicarbonylchloride with 2-amino-4-methylphenol (1:2). The new mixed-ligand complex [Sr(pydcH)2(H2O)3][Sr(pydcH2)(pydcH)(pydc)]2.[Sr(pydcH2)2(H2O)3].2H2O (C) (where pydc is pyridine-2,6-dicarboxylate) was prepared from the reaction of L with Sr(NO3)2·4H2O metal salt. The structures were characterized by single-crystal X-ray diffraction. A study on the antiproliferative effect of compounds was done by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay against two cancer cell lines including A375 (a human melanoma) and HT29 (a human colon adenocarcinoma), and also a normal HFF (a human foreskin fibroblast) cell line. A potent and selective cytotoxicity effect was exhibited for the complex toward A375 (IC50= 2.42 μM, MAE= 73.91%) cells. Further evaluations confirmed that ROS (Reactive oxygen species) level has increased by 307.7% in A375 cells following treatment with the complex compared to the control. Also, the decrease of MMP (Mitochondrial membrane potential) in the mentioned cell line was significant. Finally, the apoptotic cell death and the cell cycle arrest in the S-phase were recognized in A375 cells treated with the complex.