Ruthenium(II)‐Dithiocarbazates as Anticancer Agents: Synthesis, Solution Behavior, and Mitochondria‐Targeted Apoptotic Cell Death

Abstract

The reaction of the Ru(PPh 3 ) 3 Cl 2 with HL 1À 3 À OH (À OH stands for the oxime hydroxyl group; HL 1 À OH = diacetylmonoxime-S-benzyldithiocarbazonate; HL 2 À OH = diacetylmonoxime-S-(4-methyl)benzyldithiocarbazonate; andgives three new ruthenium complexes [Ru II (L 1À 3 À H)(PPh 3 ) 2 Cl] (1-3) (À H stands for imine hydrogen) coordinated with dithiocarbazate imine as the final products. All ruthenium(II) complexes (1-3) have been characterized by elemental (CHNS) analyses, IR, UV-vis, NMR ( 1 H, 13 C, and 31 P) spectroscopy, HR-ESI-MS spectrometry and also, the structure of 1-2 was further confirmed by single crystal X-ray crystallography. The solution/aqueous stability, hydrophobicity, DNA interactions, and cell viability studies of 1-3 against HeLa, HT-29, and NIH-3T3 cell lines were performed. Cell viability results suggested 3 being the most cytotoxic of the series with IC 50 6.9 � 0.2 μM against HeLa cells. Further, an apoptotic mechanism of cell death was confirmed by cell cycle analysis and Annexin V-FITC/PI double staining techniques. In this regard, the live cell confocal microscopy results revealed that compounds primarily target the mitochondria against HeLa, and HT-29 cell lines. Moreover, these ruthenium complexes elevate the ROS level by inducing mitochondria targeting apoptotic cell death.

LVVO-Ethyl Maltol-Based Metallodrugs (L2– = Tridentate ONO Ligands): Hydrophobicity, Hydrolytic Stability, and Cytotoxicity via ROS-Mediated Apoptosis

“…Also, in the case of A549 cells, the PCC values were found to be 0.77, 0.83, 0.83, and 0.82 for 1 – 4 , respectively, suggesting the high selectivity of the compounds toward the mitochondria. Thus, compounds with higher hydrophobic behavior have a higher tendency to gather in the lipid organelles like mitochondria owing to their negative potential difference across the membrane. ,, …”

“…In order to determine whether complex-induced cell death occurs by apoptosis or necrosis, a biparametric flow cytometric analysis using annexin V-FITC and PI double staining assays was performed. , As shown in Figure , after the treatment of 2 (0.5 × IC 50 , 1.0 × IC 50 , and 2.0 × IC 50 ), the percentage of apoptotic cells increases significantly (88.5%) compared to the control (10.0%) at higher concentrations. However, the necrotic cell contents were also observed, i.e., 50.8% at 0.5 × IC 50 concentration, but a steady decrease in the cell number was observed with an increase in the concentration of 2 .…”

“…To get further insights, apoptosis produced by 2 was examined in the presence of the ROS scavenger Nacetylcysteine (NAC) before being treated with the complex. 47 In Figure 10c, an around 60% drop in apoptotic and necrotic cells demonstrates the significance of ROS in the process of cell death. However, there still remains a 30.6% cell content in the apoptotic and necrotic region in the presence of the ROS scavenger, further indicating that other cell death mechanism is also taking part, which is probably due to the DNA binding results.…”

“…However, there still remains a 30.6% cell content in the apoptotic and necrotic region in the presence of the ROS scavenger, further indicating that other cell death mechanism is also taking part, which is probably due to the DNA binding results. 47,126,127 Live, Apoptotic, and Necrotic Cell Analysis by AO/EB Staining Methods. As observed from annexin V-FITC/PI assays, the vanadium complex induces apoptosis as well as necrosis based upon the concentrations of 2 against the HT-29 cells.…”

“…Therefore, O– and N– atom donor ligands with these active bioimportant moieties will provide new chemical as well as biological features to the complexes regarding their structure and biological applications. In addition to the primary ligand, the combination of an ancillary organic ligand that can increase lipophilicity with extended cellular uptake and intracellular distribution leading to better anticancer potential is another fascinating strategy for the design of potential metallodrugs. , In this sense, ethyl maltol (Hema, derived from a natural product maltol), with known biological activities, can provide the desired biological suitability to vanadium metal complexes. , In many works in the literature, ethyl maltol is reported to enhance the membrane permeability and overall in vitro anticancer activity of the different transition metal complexes. ,, Also, different vanadium complexes with ethyl maltol-like coligands, i.e., “flavanoid-like”, “catecholato-like”, and “curcumin-like” modes, are reported to enhance the cytotoxicity results of the vanadium metal complexes significantly by improving hydrophobicity and membrane permeability.…”