New compounds based on a benzimidazole nucleus : synthesis, characterization and cytotoxic activity against breast and colon cancer cell lines

Benzimidazolium salts and their Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation (PEPPSI) palladium N-heterocyclic carbene (Pd-NHC) based complexes have been synthesized and their structures characterized with a number of different instrumental techniques including NMR (H-1 and C-13), IR, EI-MS (for 2), X-ray (for 1, 2 and 4) and elemental analysis. The cytotoxicity of all the compounds was tested using the human embryonic kidney (HEK-293T), human breast epithelial adenocarcinoma (MDA-MB-231), and human colon epithelial colorectal adenocarcinoma (DLD-1) cell lines. The benzimidazolium salts (2-5) had more cytotoxic activity against cancerous cells compared with the metal complexes (6-9), which curiously exhibited no activity against any of the cell lines. Based on the IC50 values, compound 5 displayed the highest in vitro anticancer activity among compounds 2-9.