Antitumor Effect of Organometallic Half-Sandwich Ru(II)–Arene Complexes Bearing a Glutathione S‑Transferase Inhibitor

The facile modification of the ligands in organometallic Ru­(II)–arene complexes offers more opportunities to optimize their pharmacological profiles. Herein, three Ru­(II)–arene complexes containing a glutathione S-transferase (GST) inhibitor (NBDHEX) in chelate ligand have been designed and synthesized in this study. In vitro results indicated that the ligation with NBDHEX significantly increased the activities and selectivities of the organometallic Ru­(II)–arene complexes against tumor cells, especially complex 3, which was the most active compound among the tested compounds. DFT calculations and hydrolysis results demonstrated that complex 3 with more alkyl groups in the arene ligand has increased electron density at the Ru­(II) center as compared with complexes 1 and 2, thus resulting in the improved hydrolysis rate, which may be responsible for its higher anticancer activity. Further studies showed that complexes 1–3 can cause the loss of the mitochondrial membrane potential and upregulate the expression of Bcl-2 and Bax in A549 cells, suggesting that complexes 1–3-induced cell death may be mediated via the mitochondrial apoptotic pathway. Thus, these findings suggested that simultaneous modification of the chelate ligands and arene rings in the organometallic Ru­(II)–arene complexes is an effective way to improve their pharmacological properties.