Synthesis of new N,N′-Pd(Pt) complexes based on sulfanyl pyrazoles, and investigation of their in vitro anticancer activity

Incorporating Alkylthio Groups Provides Potent In Vitro Anticancer Activity to Water Soluble and Aqueous Stable Diiron(I) Bis-Cyclopentadienyl Complexes

We synthesized five novel diiron(I) complexes with a varying S-functionalized vinyliminium ligand, 3a-e, which were structurally characterized by IR and NMR spectroscopy, and single crystal X-ray diffraction in one representative case. Based on NMR and UV-Vis methods, these complexes show adequate water solubility (3 - 19 mM), balanced amphiphilicity (Log Pow values ranging from -0.46 to 0.16), and substantial stability in physiological-like solutions (> 90% unchanged after 24 h in DMEM cell culture medium). The cytotoxicity of the N-cyclohexyl complexes 3a-d was determined on human (A2780, A375, MCF-7) and murine cancer (B16F10, 4T1) cell lines. The leading compound 3d, featuring methylthio-group, N-cyclohexyl and 4-methoxyphenyl substituents, exhibited IC50 values in the low micromolar range and demonstrated remarkable selectivity for malignant phenotypes. Several in-depth experiments were conducted to elucidate the biochemistry of 3d, including evaluation of cell death induction, proliferation rate and cellular redox status. Spectroelectrochemical and binding studies with DNA and bovine serum albumin (BSA) were also conducted. Despite its similarity to cisplatin in inducing apoptosis, the redox signature of 3d is distinct, characterized by a strong scavenging potential of reactive oxygen and nitrogen species (ROS and RNS).

Anticancer diiron aminocarbyne complexes with labile N-donor ligands

The novel diiron amine complexes [Fe2Cp2(CO)(NH2R')(μ-CO){μ-CN(Me)(Cy)}]CF3SO3 [R' = H, 3; Cy, 4; CH2CH2NH2, 5; CH2CH2NMe2, 6; CH2CH2(4-C6H4OMe), 7; CH2CH2(4-C6H4OH), 8; Cp = η5-C5H5, Cy = C6H11 = cyclohexyl] were synthesized in 49-92 % yields from [Fe2Cp2(CO)2(μ-CO){μ-CN(Me)(Cy)}]CF3SO3, 1a, using a straightforward two-step procedure. They were characterized by IR and multinuclear NMR spectroscopy, and the structure of 7 was confirmed through X-ray diffraction analysis. Complexes 3-8 and the acetonitrile adducts [Fe2Cp2(CO)(NCMe)(μ-CO){μ-CN(Me)(R)}]CF3SO3 (R = Cy, 2a; Me, 2b; Xyl = 2,6-C6H3Me2, 2c) were assessed for their water solubility, octanol-water partition coefficient and stability in physiological-like solutions. The in vitro antiproliferative activity of 2a-c and 3-8 was tested on seven human cancer cell lines (A2780, A2780R, PC3, A549, MCF7, HOS and HT-29), while the selectivity was evaluated using normal MRC-5 cells. Overall, the complexes exhibited variable cytotoxicity, with IC50 values reaching the low micromolar range for 3, 7 and 8 in A2780 and A2780R cells, along with significant selectivity. Targeted experiments covered cell cycle modification, induction of cell death, mitochondrial membrane potential, ROS production and interaction with DNA and bovine serum albumin (BSA) as a model protein. The interaction of 3 with BSA was further investigated through computational studies. Results showed a negligible increase in intracellular ROS levels (except for 2b) and insignificant changes in mitochondrial membrane potential.

The effect of a varying pyridine ligand on the anticancer activity of Diiron(I) bis-cyclopentadienyl complexes

The new diiron complexes [Fe2Cp2(CO)(L)(μ-CO){μ-CN(Me)(Cy)}]CF3SO3 (L = pyridine, 3a; 4-aminopyridine, 3b; 4-dimethylaminopyridine, 3c; 4-trifluoromethylpyridine, 3d; nicotinic acid, 4; Cp = η5-C5H5, Cy = C6H11 = cyclohexyl) were synthesized in moderate to high yields using two distinct synthetic routes from the precursors 1 (L = CO, for 4) and 2 (L = NCMe, for 3a-d), respectively. All products were characterized by IR and multinuclear NMR spectroscopy, and the structures of 3b and 3d were ascertained by X-ray diffraction studies. The behavior of the complexes in aqueous solutions (solubility, Log Pow, stability) was assessed using NMR and UV-Vis methods. The in vitro antiproliferative activity of 3a-c and 4 was evaluated against seven human cancer cell lines (A2780, A2780R, A549, MCF-7, PC3, HOS and HT-29) and one normal cell line (MRC-5), following 24 h of incubation (MTT test). Overall, 3-4 demonstrated stronger cytotoxicity than cisplatin, with 3c emerging as the most potent compound. The activity seems primarily linked to the inhibition of metabolic processes in the cancer cells, including depletion of reactive oxygen species (ROS) levels. However, subtle differences have been observed between the complexes, with 4 exerting its cytotoxicity through a distinct multimodal mechanism.

1,3,5-Triaza-7-phosphaadamantane and Cyclohexyl Groups Impart to Di-Iron(I) Complex Aqueous Solubility and Stability, and Prominent Anticancer Activity in Cellular and Animal Models

Using a multigram-scalable synthesis, we obtained nine dinuclear complexes based on nonendogenous iron(I) centers and featuring variable aminocarbyne and P-ligands. One compound from the series (FEACYP) emerged for its strong cytotoxicity in vitro against four human cancer cell lines, surpassing the activity of cisplatin by 3-6 times in three cell lines, with an average selectivity index of 6.2 compared to noncancerous HEK293 cells. FEACYP demonstrated outstanding water solubility (15 g/L) and stability in physiological-like solutions. It confirmed its superior antiproliferative activity when tested in 3D spheroids of human pancreatic cancer cells and showed a capacity to inhibit thioredoxin reductase (TrxR) similar to auranofin. In vivo treatment of murine LLC carcinoma with FEACYP (8 mg kg-1 dose) led to excellent tumor growth suppression (88%) on day 15, with no signs of systemic toxicity and only limited body weight loss.

Novel binuclear copper(II) complexes with sulfanylpyrazole ligands: synthesis, crystal structure, fungicidal, cytostatic, and cytotoxic activity

New binuclear copper(II) [Cu(II)] tetraligand complexes (six examples) with sulfanylpyrazole ligands were synthesized. Electron spin resonance (ESR) studies have shown that in solution the complexes are transformed to the mononuclear one. Fungicidal properties against Candida albicans were found for the Cu complexes with benzyl and phenyl substituents. An in vitro evaluation of the cytotoxic properties of Cu chelates against HEK293, Jurkat, MCF-7, and THP-1 cells identified the Cu complex with the cyclohexylsulfanyl substituent in the pyrazole core as the lead compound, whereas the Cu complex without a sulfur atom in the pyrazole ligand had virtually no cytotoxic or fungicidal activity. The lead Cu(II) complex was more active than cisplatin. Effect of the S-containing Cu complex on apoptosis and cell cycle distribution has been investigated as well.

Ligand and Linkage Isomers of Bis(ethylthiocarbamato) Copper Complexes with Cyclic C6H8 Backbone Substituents: Synthesis, Characterization, and Antiproliferation Activity

A series of isomeric bis(alkylthiocarbamate) copper complexes have been synthesized, characterized, and evaluated for antiproliferation activity. The complexes were derived from ligand isomers with 3-methylpentyl (H2L2) and cyclohexyl (H2L3) backbone substituents, which each yield a pair of linkage isomers. The thermodynamic products CuL2a/3a have two imino N and two S donors resulting in three five-member chelate rings (555 isomers). The kinetic isomers CuL2b/3b have one imino and one hydrazino N donor and two S donors resulting in four-, six-, and five-member rings (465 isomers). The 555 isomers have more accessible CuII/I potentials (E1/2 = -811/-768 mV vs. ferrocenium/ferrocene) and lower energy charge transfer bands than their 465 counterparts (E1/2 = -923/-854 mV). Antiproliferation activities were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR-90) using the MTT assay. CuL2a was potent (A549EC50 = 0.080 μM) and selective (IMR-90EC50/A549EC50 = 25) for A549. Its linkage isomer CuL2b had equivalent A549 activity, but lower selectivity (IMR-90EC50/A549EC50 = 12.5). The isomers CuL3a and CuL3b were less potent with A549EC50 values of 1.9 and 0.19 μM and less selective with IMR-90EC50/A549EC50 ratios of 2.3 and 2.65, respectively. There was no correlation between reduction potential and A549 antiproliferation activity/selectivity.

Recent Advances in the Development of Pyrazole Derivatives as Anticancer Agents

Pyrazole derivatives, as a class of heterocyclic compounds, possess unique chemical structures that confer them with a broad spectrum of pharmacological activities. They have been extensively explored for designing potent and selective anticancer agents. In recent years, numerous pyrazole derivatives have been synthesized and evaluated for their anticancer potential against various cancer cell lines. Structure-activity relationship studies have shown that appropriate substitution on different positions of the pyrazole ring can significantly enhance anticancer efficacy and tumor selectivity. It is noteworthy that many pyrazole derivatives have demonstrated multiple mechanisms of anticancer action by interacting with various targets including tubulin, EGFR, CDK, BTK, and DNA. Therefore, this review summarizes the current understanding on the structural features of pyrazole derivatives and their structure-activity relationships with different targets, aiming to facilitate the development of potential pyrazole-based anticancer drugs. We focus on the latest research advances in anticancer activities of pyrazole compounds reported from 2018 to present.

Cytotoxic Effects of New Palladium(II) Complexes with Thiazine or Thiazoline Derivative Ligands in Tumor Cell Lines

The synthesis of analogs of cisplatin, which is a widely used chemotherapeutic agent, using other metal centers could be an alternative for cancer treatment. Pd(II) could be a substitute for Pt(II) due to its coordination chemistry similarity. For that reason, six squared-planar Pd(II) complexes with thiazine and thiazoline ligands and formula [PdCl2(L)] were synthesized and characterized in this work. The potential anticarcinogenic ability of the compounds was studied via cytotoxicity assay in three different human tumor cell lines, i.e., epithelial cervix carcinoma (HeLa), promyelocytic leukemia (HL-60), and histiocytic lymphoma (U-937). Data obtained showed that complexes with methyl substitutions did not modify cell viability, while no-methyl substituted compounds had a moderate cytotoxic effect on all three cell lines. The complexes with phenyl substitutions displayed the lowest IC50 values, which ranged between 46.39 ± 3.99 μM and 62.74 ± 6.45 μM. Moreover, Pd accumulation inside the cell was observed after incubation with any of the four complexes mentioned, and the two complexes with phenyl rings were found to induce an increase in the percentage of apoptotic cells. These results suggested that the presence of bulky substitutions on the ligands such as phenyl groups may influence the cytotoxicity of the chemotherapeutic agents synthesized.

Modeling the structure and reactivity landscapes of a pyrazole-ammonium ionic derivative using wavefunction-dependent characteristics and screening for potential anti-inflammatory activity

Spectroscopic investigations of 1-phenyl -2,3-dimethyl-5-oxo-1,2-dihydro-1H-pyrazol-4-ammonium 2[(2-carboxyphenyl) disulfanyl]benzoate (PACB) reported experimentally and theoretically. NH-O interaction is observed and there is a very large downshift for NH-O stretching frequency. Reactive sites are identified from the chemical and electronic properties. For PACB the maximum repulsion was around H33, H55 and H57 atom. LOL shows red regions between C-C and blue around C atoms are surrounded by a delocalized electron cloud. The red ring is a hallmark of electron density depletion from the NCI plot due to electrostatic repulsion and its existences suggests that coordination sphere for PACB is minimally strained around the central ion. Atomic contact energy values and high score of the docking results obtained propose that, PACB may have inhibitory properties and have a significant function in pharmacological chemistry. Molecular dynamics simulation was performed to validate the stability of the title compound with the Bovine thrombin-activatable fibrinolysis inhibitor protein.Communicated by Ramaswamy H. Sarma.

Ruthenium(II)-Tris-pyrazolylmethane Complexes Inhibit Cancer Cell Growth by Disrupting Mitochondrial Calcium Homeostasis

While ruthenium arene complexes have been widely investigated for their medicinal potential, studies on homologous compounds containing a tridentate tris(1-pyrazolyl)methane ligand are almost absent in the literature. Ruthenium(II) complex 1 was obtained by a modified reported procedure; then, the reactions with a series of organic molecules (L) in boiling alcohol afforded novel complexes 2–9 in 77–99% yields. Products 2–9 were fully structurally characterized. They are appreciably soluble in water, where they undergo partial chloride/water exchange. The antiproliferative activity was determined using a panel of human cancer cell lines and a noncancerous one, evidencing promising potency of 1, 7, and 8 and significant selectivity toward cancer cells. The tested compounds effectively accumulate in cancer cells, and mitochondria represent a significant target of biological action. Most notably, data provide convincing evidence that the mechanism of biological action is mediated by the inhibiting of mitochondrial calcium intake.

Synthesis, crystal structure, and in vitro evaluation of the anticancer activity of new Pt (Pd) complexes with 1-[(dimethylamino)methyl]-2-naphthol ligand

The synthesis of new Pt(II) and Pd(II) complexes with 1-aminomethyl-2-naphtol ligands has been first performed. The adducts of [PtCl4]2- and [PdCl4]2- anions with the 1-aminomethyl-2-naphtol NH cation were synthesized. The structure for four Pt (Pd)-containing compounds was investigated using X-ray diffraction. The obtained compounds were examined for in vitro cytotoxic activity against Jurkat and K562 human leukemia cells, lymphoma U937cells, A2780 and the cisplatin-resistant A2780cis lines of human ovarian cancer, and normal fibroblasts. Study of induction of apoptosis and the effect of new palladium and platinum complexes on the cell cycle was carried out. The cells showed a higher sensitivity to Pt(II) compounds than to Pd(II) ones. All the synthesized metal complexes show much more antitumor activity compared with a platinum-containing cisplatin drug.

Anticancer Diiron Vinyliminium Complexes: A Structure-Activity Relationship Study

A series of 16 novel diiron complexes of general formula [Fe2Cp2(CO)(μ-CO){μ-η1:η3-C(R')C(R″)CN(R)(Y)}]CF3SO3 (2-7), bearing different substituents on the bridging vinyliminium ligand, was synthesized in 69-95% yields from the reactions of diiron μ-aminocarbyne precursors with various alkynes. The products were characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy; moreover the X-ray structures of 2c (R = Y = CH2Ph, R' = R″ = Me) and 3a (R = CH2CH=CH2, Y = R' = Me, R″ = H) were ascertained by single-crystal X-ray diffraction studies. NMR and UV-Vis methods were used to assess the D2O solubility, the stability in aqueous solution at 37 °C and the octanol-water partition coefficients of the complexes. A screening study evidenced a potent cytotoxicity of 2-7 against the A2780 cancer cell line, with a remarkable selectivity compared to the nontumoral Balb/3T3 cell line; complex 4c (R = Cy, Y = R' = R″ = Me) revealed as the most performant of the series. The antiproliferative activity of a selection of complexes was also assessed on the cisplatin-resistant A2780cisR cancer cell line, and these complexes were capable of inducing a significant ROS production. Moreover, ESI-MS experiments indicated the absence of interaction of selected complexes with cytochrome c and the potentiality to inhibit the thioredoxin reductase enzyme (TrxR).

Anticancer and antibacterial potential of robust Ruthenium(II) arene complexes regulated by choice of α-diimine and halide ligands

Several complexes of general formula [Ru(halide)(η⁶-p-cymene)(α-diimine)]⁺, in the form of nitrate, triflate and hexafluorophosphate salts, including a newly synthesized iodide compound, were investigated as potential anticancer drugs and bactericides. NMR and UV-Vis studies evidenced remarkable stability of the complexes in water and cell culture medium. In general, the complexes displayed strong cytotoxicity against A2780 and A549 cancer cell lines with IC₅₀ values in the low micromolar range, and one complex (RUCYN) emerged as the most promising one, with a significant selectivity compared to the non-cancerous HEK293 cell line. A variable affinity of the complexes for BSA and DNA binding was ascertained by spectrophotometry/fluorimetry, circular dichroism, electrophoresis and viscometry. The performance of RUCYN appears associated to enhanced cell internalization, favored by two cyclohexyl substituents, rather than to specific interaction with the evaluated biomolecules. The chloride/iodide replacement, in one case, led to increased cellular uptake and cytotoxicity at the expense of selectivity, and tuned DNA binding towards intercalation. Complexes with iodide or a valproate bioactive fragment exhibited the best antimicrobial profiles.