Synthesis, characterization, antiproliferative and anti-metastatic properties of two ruthenium–DMSO complexes containing 2,2′-biimidazole

Enantiomeric Complexes Based on Ruthenium(III) and 2,2'-Biimidazole: X-ray Structure and Magnetic Properties

We have prepared and characterized two Ru(III) compounds based on the 2,2'-biimidazole (H2biim) ligand, namely, a single complex of formula cis-[RuCl2(H2biim)2]Cl·4H2O (1) and a racemic mixture of formula {cis-[RuCl2(H2biim)2]Cl}2·4H2O (2), which contains 50% of Ru(III) complex 1. Both compounds crystallize in the monoclinic system with space groups C2 and P21 for 1 and 2, respectively. These complexes exhibit the metal ion bonded to four nitrogen atoms from two H2biim molecules and two chloride ions, which balance part of the positive charges in a distorted octahedral geometry. Significant differences are observed in their crystal packing, which leads to the observation of differences in their respective magnetic behaviors. Despite having imidazole rings in both compounds, π-π stacking interactions occur only in the crystal structure of 2, and the shortest intermolecular Ru···Ru separation in 2 is consequently shorter than that in 1. Variable-temperature dc magnetic susceptibility measurements performed on polycrystalline samples of 1 and 2 reveal different magnetic behaviors at low temperatures: while 1 behaves pretty much as a magnetically isolated mononuclear Ru(III) complex with S = 1/2, 2 exhibits the behavior of an antiferromagnetically coupled system with S = 0 and a maximum in the magnetic susceptibility curve at approximately 3.0 K.

N-Iodosuccinimide-Mediated Synthesis of Benzo-Fused Bisimidazoles Enabled by a One-Pot Tandem Reaction of Fluorinated Propargyl Amidines

A N-iodosuccinimide (NIS)-mediated divergent and efficient tandem reaction between fluorinated propargyl amidines and aromatic o-diamines without any metal catalyst and additive under mild reaction conditions was developed for the synthesis of benzo-fused bisimidazoles in moderate to excellent yields. Preliminary mechanistic studies suggested that this reaction proceeded by an intermediate of secondary amine derived from 5-iodomethyl imidazole, and NIS played another role of oxidation reagent to promote the formation of a benzimidazole motif.

Recent development of imidazole derivatives as potential anticancer agents

Cancer, one of the key health problems globally, is a group of related diseases that share a number of characteristics primarily the uncontrolled growth and invasive to surrounding tissues. Chemotherapy is one of the ways for the treatment of cancer which uses one or more anticancer agents as per chemotherapy regimen. Limitations of most anticancer drugs due to a variety of reasons such as serious side effects, drug resistance, lack of sensitivity and efficacy etc. generate the necessity towards the designing of novel anticancer lead molecules. In this regard, the synthesis of biologically active heterocyclic molecules is an appealing research area. Among heterocyclic compounds, nitrogen containing heterocyclic molecules has fascinated tremendous consideration due to broad range of pharmaceutical activity. Imidazoles, extensively present in natural products as well as synthetic molecules, have two nitrogen atoms, and are five membered heterocyclic rings. Because of their countless physiological and pharmacological characteristics, medicinal chemists are enthused to design and synthesize new imidazole derivatives with improved pharmacodynamic and pharmacokinetic properties. The aim of this present chapter is to discuss the synthesis, chemistry, pharmacological activity, and scope of imidazole-based molecules in anticancer drug development. Finally, we have discussed the current challenges and future perspectives of imidazole-based derivatives in anticancer drug development.

Synthesis, Characterization, and Anticancer Activity of Benzothiazole Aniline Derivatives and Their Platinum (II) Complexes as New Chemotherapy Agents

We describe the synthesis, characterization, molecular modeling, and in vitro anticancer activity of three benzothiazole aniline (BTA) ligands and their corresponding platinum (II) complexes. We designed the compounds based on the selective antitumor properties of BTA, along with three types of metallic centers, aiming to take advantage of the distinctive and synergistic activity of the complexes to develop anticancer agents. The compounds were characterized using nuclear magnetic resonance spectrometry, Fourier transform infrared spectroscopy, mass spectrometry, elemental analysis, and tested for antiproliferative activity against multiple normal and cancerous cell lines. L1, L2, and L1Pt had better cytotoxicity in the liver, breast, lung, prostate, kidney, and brain cells than clinically used cisplatin. Especially, L1 and L1Pt demonstrated selective inhibitory activities against liver cancer cells. Therefore, these compounds can be a promising alternative to the present chemotherapy drugs.

Ruthenium(II)/(III) DMSO-Based Complexes of 2-Aminophenyl Benzimidazole with In Vitro and In Vivo Anticancer Activity

New anticancer ruthenium(II/III) complexes [RuCl₂(DMSO)₂(Hapbim)] (1) and [RuCl₃(DMSO) (Hapbim)] (2) (Hapbim = 2-aminophenyl benzimidazole) have been synthesized and characterized, and their chemotherapeutic potential evaluated. The interaction of the compounds with DNA was studied by both UV-Visible and fluorescence spectroscopies, revealing intercalation of both the Hapbim ligand and the Ru complexes. The in vitro cytotoxicity of the compounds was tested on human breast cancer (MCF7), human colorectal cancer (Caco2), and normal human liver cell lines (THLE-2), with compound (2) the most potent against cancer cells. The cytotoxic effect of (2) is shown to correlate with the ability of the Ru(III) complex to induce apoptosis and to cause cell-cycle arrest in the G2/M phase. Notably, both compounds were inactive in the noncancerous cell line. The anticancer effect of (2) has also been studied in an EAC (Ehrlich Ascites Carcinoma) mouse model. Significantly, the activity of the complex was more pronounced in vivo, with removal of the cancer burden at doses that resulted in only low levels of hepatotoxicity and nephrotoxicity. An apoptosis mechanism was determined by the observation of increased Bax and caspase 3 and decreased Bcl2 expression. Furthermore, (2) decreased oxidative stress and increased the levels of antioxidant enzymes, especially SOD, suggesting the enhancement of normal cell repair. Overall, compound (2) shows great potential as a chemotherapeutic candidate, with promising activity and low levels of side effects.

Evaluation of biomolecular interactions and cytotoxic activity of organometallic binuclear Ru(II) complexes of ferrocenyl thiosemicarbazones

Four new ferrocenyl substituted thiosemicarbazone ligands (L1-L4) and their corresponding binuclear ruthenium(II) arene complexes of the general type [(η⁶-p cym)(L)Ru(μ-im)Ru(L)(η⁶-p-cym)]Cl (C1-C4) and [(η⁶-p cym)(L)Ru(μ-azpy)Ru(L)(η⁶-p-cym)]Cl₂ (C5-C8) (cym = cymene, im = imidazole, azpy = 4,4'-azopyridine) have been synthesized and characterized. The structures of the complexes were established through DFT calculations and geometry optimization. The interactions of the binuclear complexes with DNA were investigated by absorption, emission and viscosity studies which indicated that the complexes bind to DNA via intercalation. Meanwhile, the interaction of complexes with the protein, bovine serum albumin (BSA), has also been studied using fluorescence emission spectroscopy. The experimental results show that the binuclear complexes exhibit good binding propensities to BSA. The complexes can quench the intrinsic fluorescence of BSA remarkably through a static or dynamic quenching process. In addition, the in vitro cytotoxicity of complexes C1-C8 against HeLa cell line was assayed which showed lower IC₅₀ values indicating their higher cytotoxicity and potency in killing the cancer cells at low concentrations.Communicated by Ramaswamy H. Sarma.

Synthesis, structural characterization, in vitro DNA binding, and antitumor activity properties of Ru(II) compounds containing 2(2,6-dimethoxypyridine-3-yl)-1H-imidazo(4,5-f)[1, 10]phenanthroline

The octahedral Ru(II) complexes containing the 2(2,6-dimethoxypyridine-3-yl)-1H-imidazo(4,5-f)[1, 10]phenanthroline ligand of type [Ru(N-N)₂(L)]²⁺, where N-N = phen (1,10-phenanthroline) (1), bpy (2,2^'-bipyridine) (2), and dmb (4,4^'-dimethyl-2,2^'-bipyridine) (3); L(dmpip) = (2(2,6-dimethoxypyridine-3-yl)1Himidazo(4,5-f)[1, 10]phenanthroline), have been synthesized and characterized by UV-visible absorption, molar conductivity, elemental analysis, mass, IR, and NMR spectroscopic techniques. The physicochemical properties of the Ru(II) complexes were determined by UV-Vis absorption spectroscopy. The DNA binding studies have been explored by UV-visible absorption, fluorescence titrations, and viscosity measurements. The supercoiled pBR322 DNA cleavage efficiency of Ru(II) complexes 1-3 was investigated. The antimicrobial activity of Ru(II) complexes was done against Gram-positive and Gram-negative microorganisms. The in vitro anticancer activities of all the complexes were investigated by cell viability assay, apoptosis, cellular uptake, mitochondrial membrane potential detection, and semi-quantitative PCR on HeLa cells. The result indicates that the synthesized Ru(II) complexes probably interact with DNA through an intercalation mode of binding with complex 1 having slightly stronger DNA binding affinity and anticancer activity than 2 and 3.

Synthesis, Characterisation and In Vitro Permeation, Dissolution and Cytotoxic Evaluation of Ruthenium(II)-Liganded Sulpiride and Amino Alcohol

Sulpiride (SPR) is a selective antagonist of central dopamine receptors but has limited clinical use due to its poor pharmacokinetics. The aim of this study was to investigate how metal ligation to SPR may improve its solubility, intestinal permeability and prolong its half-life. The synthesis and characterisation of ternary metal complexes [Ru(p -cymene)(L)(SPR)]PF6 (L1 = (R)-(+)-2-amino-3-phenyl-1-propanol, L2 = ethanolamine, L3 = (S)-(+)-2-amino-1-propanol, L4 = 3-amino-1-propanol, L5 = (S)-(+)-2-pyrrolidinemethanol) are described in this work. The stability constant of the [Ru(p -cymene)(SPR)] complex was determined using Job's method. The obtained value revealed higher stability of the metal complex in the physiological pH than in an acidic environment such as the stomach. The ternary metal complexes were characterised by elemental analysis, Fourier transform infrared spectroscopy (FT-IR), 1H and 13C nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermal analyses, Ultraviolet-Visible (UV-Vis). Solubility studies showed higher aqueous solubility for complexed SPR than the free drug. Dissolution profiles of SPR from the metal complexes exhibited slower dissolution rate of the drug. Permeation studies through the pig's intestine revealed enhanced membrane permeation of the complexed drug. In vitro methyl thiazolyl tetrazolium (MTT) assay showed no noticeable toxic effects of the ternary metal complexes on Caco-2 cell line.

Mitochondrial-targeted penetrating peptide delivery for cancer therapy

INTRODUCTION

Mitochondria are promising targeting organelles for anticancer strategies; however, mitochondria are difficult for antineoplastic drugs to recognize and bind. Mitochondria-penetrating peptides (MPPs) are unique tools to gain access to the cell interior and deliver a bioactive cargo into mitochondria. MPPs have combined or delivered a variety of antitumor cargoes and obviously inhibited the tumor growth in vivo and in vitro. MPPs create new opportunities to develop new treatments for cancer.

AREAS COVERED

We review the target sites of mitochondria and the target-penetration mechanism of MPPs, different strategies, and various additional strategies decorated MPPs for tumor cell mitochondria targeting, the decorating mattes including metabolism molecules, RNA, DNA, and protein, which exploited considered as therapeutic combined with MPPs and target in human cancer treatment.

EXPERT OPINION/COMMENTARY

Therapeutic selectivity that preferentially targets the mitochondrial abnormalities in cancer cells without toxic impact on normal cells still need to be deepen. Moreover, it needs appropriate study designs for a correct evaluation of the target delivery outcome and the degradation rate of the drug in the cell. Generally, it is optimistic that the advances in mitochondrial targeting drug delivery by MPPs plasticity outlined here will ultimately help to the discovery of new approaches for the prevention and treatment of cancers.

The effect of incorporating carboxylic acid functionalities into 2,2′-bipyridine on the biological activity of the complexes formed: synthesis, structure, DNA/protein interaction, antioxidant activity and cytotoxicity

Incorporation of carboxylic acid group in the bipyridine moiety has resulted in showing differences in DNA/protein binding affinity, efficiency in antioxidant activity and cytotoxicity.

Structure-activity relationship (SAR) study and design strategies of nitrogen-containing heterocyclic moieties for their anticancer activities

The present review article offers a detailed account of the design strategies employed for the synthesis of nitrogen-containing anticancer agents. The results of different studies describe the N-heterocyclic ring system is a core structure in many synthetic compounds exhibiting a broad range of biological activities. Benzimidazole, benzothiazole, indole, acridine, oxadiazole, imidazole, isoxazole, pyrazole, triazoles, quinolines and quinazolines including others drugs containing pyridazine, pyridine and pyrimidines are covered. The following studies of these compounds suggested that these compounds showed their antitumor activities through multiple mechanisms including inhibiting protein kinase (CDK, MK-2, PLK1, kinesin-like protein Eg5 and IKK), topoisomerase I and II, microtubule inhibition, and many others. Our concise representation exploits the design and anticancer potency of these compounds. The direct comparison of anticancer activities with the standard enables a systematic analysis of the structure-activity relationship among the series.

The biological effect of the nitroimidazole derivative of a polypyridyl ruthenium complex on cancer and endothelial cells

The ruthenium polypyridyl complexes [Ru(dip)2(bpy/bpy-2-nitroIm)](2+) (dip = 4,7-diphenyl-1,10-phenanthroline, bpy = 2,2'-bipyridine, bpy-2-nitroIm = 4-[3-(2-nitro-1H-imidazol-1-yl)propyl]) were found to be ca. ten times more cytotoxic against breast cancer (4T1) and human lung adenocarcinoma epithelial cells (A549) than a well-known anticancer drug, cisplatin. Even though the Ru complexes were quite cytotoxic towards FVB mouse lung microvascular endothelial cells (MLuMEC FVB) their efflux from these non transformed cells was much more efficient than from cancer ones. Both Ru complexes accumulated in cells. The cellular uptake of both Ru complexes occurs through passive diffusion while the nitroimidazole derivative is also endocytosed. They arrest cell growth in the S-phase and induce apoptosis. Such cell response can result from activation of oxidative stress by Ru complexes. The modulation of the mRNA expression profile for genes which might be involved in metastasis and angiogenesis processes by Ru complexes was analyzed for both cancer (4T1) and endothelial (MLuMEC FVB) cells. Ru complexes appeared to have a distinct impact on cell adhesion and migration as well as they affect endothelial cell vasculature. They are not only cytotoxic but are also potentially invasive and anti-metastatic agents. This work illustrates the putative future development of polypyridyl ruthenium.

Ruthenium complex Λ-WH0402 induces hepatocellular carcinoma LM6 (HCCLM6) cell death by triggering the Beclin-1-dependent autophagy pathway

To evaluate the anticancer mechanism of the new ruthenium complex-Λ-WH0402 at the cellular level, the in vitro cytotoxicity of Λ-WH0402 was investigated on 10 human tumor cell lines. Λ-WH0402 was found to have higher anticancer activity than cisplatin toward human liver cancer HCCLM6 cells that have high tumor metastatic characteristics. Meanwhile, Λ-WH0402 showed an antimetastatic effect on HCCLM6 cells in vitro, mostly through its effect on cell adhesion, invasion and migration. In addition, Λ-WH0402 significantly reduced tumor metastasis to the lungs in orthotopic mouse hepatocellular cancer (HCC) models induced by HCCLM6 cells. Furthermore, Λ-WH0402 exerted an inhibitory effect on tumor cell growth and proliferation and induced dose-dependent cell cycle arrest in the S phase in HCCLM6 cells. Immunoblotting analysis showed that Λ-WH0402 not only decreased the expression of antiapoptotic protein Bcl-2 and nutrient-deprivation autophagy factor-1 (NAF-1), but also significantly increased the expression of Beclin-1 in HCCLM6 cells. More importantly, we identified that Λ-WH0402 treatment reduced the interaction between Bcl-2 and Beclin-1, and increased the expression of autophagic activation marker LC3B-II in HCCLM6 cells. On the whole, our results suggested that the anitcancer activity of Λ-WH0402 is mediated through promoting the Beclin-1-dependent autophagy pathway in HCCLM6 cells.

Ruthenium complexes as inhibitors of human islet amyloid polypeptide aggregation, an effect that prevents beta cell apoptosis

Herein we show that ruthenium complexes could inhibit fibrosis of hIAPP and protect the hIAPP-induced cell damage by suppressing ROS generation, indicating the application potential of the complexes in treatment of T2DM by targeting hIAPP.

Multifaceted interplay between lipophilicity, protein interaction and luminescence parameters of non-intercalative ruthenium(II) polypyridyl complexes controlling cellular imaging and cytotoxic properties

Here, we examine the photophysical properties of five ruthenium(II) complexes comprising two 4,7-diphenyl-1,10-phenanthroline (dip) ligands and functionalized bipyridine (R₁bpy-R₂, where R₁ = H or CH₃, R₂ = H, CH₃, COO⁻,4-[3-(2-nitro-1H-imidazol-1-yl)propyl] or 1,3-dicyclohexyl-1-carbonyl-urea) towards development of luminescence probes for cellular imaging. These complexes have been shown to interact with albumin and the formed adducts exhibited up to eightfold increase in the luminescence quantum yield as well as the average lifetime of emission. It was demonstrated that they cannot bind to DNA through the intercalation mode and its luminescence in the presence of DNA is quenching. Cell viability experiments indicated that all complexes possess significant dose-dependent cytotoxicity (with IC₅₀ 5–19 μM) on 4T1 breast cancer cell line and their anti-proliferative activity correlates very well with their lipophilicity. Cellular uptake was studied by measuring the ruthenium content in cells using ICP-MS technique. As expected, the better uptake is directly related to higher lipophilicity of doubly charged ruthenium complexes while uptake of monocationic one is much lower in spite of the highest lipophilicity. Additionally staining properties were assessed using flow cytometry and fluorescence microscopy. These experiments showed that complex with 1,3-dicyclohexyl-1-carbonyl-urea substituent exhibits the best staining properties in spite of the lowest luminescence quantum yield in buffered solution (pH 7.4). Our results point out that both the imaging and cytotoxic properties of the studied ruthenium complexes are strongly influence by the level of internalization and protein interaction.

Recent developments of metal N-heterocyclic carbenes as anticancer agents

Metal based anticancer drugs have demonstrated their crucial role in preventing all types of cancers whereas their effectiveness is selective with respect to the cancer cells rather than the normal cells. Recently metal N-heterocyclic carbenes have established their selective performance for cancer cells excluding normal healthy cells based on which they are widely utilised for targeting cancer cells specifically which leads to cell death or cell growth inhibition. This is mainly due to their ionic character which helps them to localise in cancer cells with the help of enhanced expression of Organic Cation Transporters (OCT). Also their unique mechanism of action involving DNA binding, less recognizable by DNA repair machinery, mitochondria targeting gives them a new area for anticancer drug development. This review summarises the medicinal as well as pharmacological approach to the anticancer properties of metal NHC complexes.

Anticancer metallodrugs of glutamic acid sulphonamides: in silico, DNA binding, hemolysis and anticancer studies

In response to an increased demand for effective anticancer drugs, a series of disodium sulphonamides ofl-glutamic acid (L1–L3) was synthesized. Sulphonamides were complexed with copper(ii), nickel(ii) and ruthenium(iii) ions, separately and respectively.

Comprehensive review in current developments of imidazole-based medicinal chemistry

Imidazole ring is an important five-membered aromatic heterocycle widely present in natural products and synthetic molecules. The unique structural feature of imidazole ring with desirable electron-rich characteristic is beneficial for imidazole derivatives to readily bind with a variety of enzymes and receptors in biological systems through diverse weak interactions, thereby exhibiting broad bioactivities. The related research and developments of imidazole-based medicinal chemistry have become a rapidly developing and increasingly active topic. Particularly, numerous imidazole-based compounds as clinical drugs have been extensively used in the clinic to treat various types of diseases with high therapeutic potency, which have shown the enormous development value. This work systematically gives a comprehensive review in current developments of imidazole-based compounds in the whole range of medicinal chemistry as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents, together with their potential applications in diagnostics and pathology. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic imidazole-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes.

Targeting cancer cell mitochondria as a therapeutic approach

Mitochondria are double membrane-enveloped organelles that play a central role in cellular metabolism, calcium homeostasis, redox signaling and cell fates. They function as main generators of ATP, metabolites for the construction of macromolecules and reactive oxygen species. In many cancer cells, mitochondria seem dysfunctional, manifested by a shift of energy metabolism from oxidative phosphorylation to active glycolysis and an increase in reactive oxygen species generation. These metabolic changes are often associated with upregulation of NAD(P)H oxidase. Importantly, the metabolic reprogramming in a cancer cell is mechanistically linked to oncogenic signals. Targeting mitochondria as a cancer therapeutic strategy has attracted much attention in the recent years and multiple review articles in this area have been published. This article attempts to provide an update on recent progress in identification of mitochondria-associated molecules as potential anticancer targets and the respective targeting compounds.