Design, Synthesis and Antiproliferative Activities of Oxidative Stress Inducers Based on 2-Styryl-3,5-dihydro-4H-imidazol-4-one Scaffold

The 2-styryl-3,5-dihydro-4H-imidazol-4-one might be considered as a system with isosteric properties similar to trans-cinnamaldehyde (styrylaldehyde), a safe natural compound that exhibited interesting activities against various cancers. We synthesized a series of compounds that differ structurally in having different alkyl, aryl and heterocyclic substituents at the N3 position of the 2-styryl-4-imidaolone pharmacophore. The compounds were assayed for their cytotoxicity against both cancer and normal cell lines. In addition, their cellular mechanism of action as reactive oxygen species (ROS) inducers were investigated. Many of the synthesized compounds showed higher activities on colon, breast and hepatic cancer cell lines than the parent trans-cinnamaldehyde. Compounds 3a and 3e showed selective antiproliferative activity against cancer cell lines at low micromolar to sub-micromolar IC50 value. Compounds were extremely less toxic on normal cell lines baby hamster kidney fibroblasts (BHK) and human lung tissue fibroblast (WI-38). Similar to trans-cinnamaldehyde, the colon cancer cell cycle analysis indicated cell cycle changes consistent with increased oxidative stress leading to apoptosis. Compound 3e caused elevation of all cell oxidative indicators of ROS such as a decrease in reduced glutathione, increased malondialdehyde and suppression of catalase and superoxide dismutase activities. Dihydroethidium staining, nuclear fragmentation and increased caspase-3 further confirmed extensive apoptotic induction due to ROS accumulation upon treatment of human colon adenocarcinoma (HCT116) cells with compounds 3a and 3e. Changes in human breast adenocarcinoma (MCF7) cells were less revealing for ROS induction and increased oxidative stress. Conclusion: The compounds represent an example of efficient rescaffolding of a natural compound to a highly potent drug-like analogues.