Rhodium(i) N-heterocyclic carbene complexes: synthesis and cytotoxic properties

Rhodium(i) complexes bearing N-heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of these types of complexes. A series of benzimidazolium salts and their [RhCl(NHC)(COD)] complexes were synthesized. The obtained complexes were synthesized and characterized by elemental analysis, FT-IR, H-1 and C-13 NMR. All compounds were screened for in vitro cytotoxic activities against a panel of human cancer cells (HT-29 colon, Ishikawa endometrial, and U-87 glioblastoma) using the MTT assay for 48 h of incubation time. Mouse fibroblast cells (L-929) were used as healthy cells. Complexes had exhibited significantly higher cytotoxic activity towards cancer cells than their ligands and complex 2b showed the most selective cytotoxic activity against HT-29 cancer cells (SI;7.05) and Ishikawa cancer cells (SI; more than 9.8). The complexes showed strong in vitro cytotoxic activity against cancer cells, with IC50 values of lower than 10 mu M (except 2a against HT-29 (12.8 mu M) and 2b against U-87 (11.1 mu M)). All complexes (2a-d) showed the highest in vitro cytotoxic activity against Ishikawa endometrial cancer cells with IC50 values of 2.93 +/- 0.06, <1, 2.60 +/- 0.05, and 2.85 +/- 0.06 mu M, respectively. Complexes were found to be highly cytotoxic against HT-29, Ishikawa, and U-87 cancer cells compared to the anticancer agents, cisplatin and 5-FU.

Automated summary

A series of rhodium(i) complexes with N-heterocyclic carbene ligands showed high in vitro cytotoxic activity against human cancer cells, with complex 2b exhibiting the most selective cytotoxic activity. These complexes demonstrated greater cytotoxicity against cancer cells compared to established anticancer agents cisplatin and 5-fluorouracil.