New Iminodiacetate-Thiosemicarbazone Hybrids and Their Copper(II) Complexes Are Potential Ribonucleotide Reductase R2 Inhibitors with High Antiproliferative Activity

Copper(II) Complexes with Isomeric Morpholine-Substituted 2-Formylpyridine Thiosemicarbazone Hybrids as Potential Anticancer Drugs Inhibiting Both Ribonucleotide Reductase and Tubulin Polymerization: The Morpholine Position Matters

The development of copper(II) thiosemicarbazone complexes as potential anticancer agents, possessing dual functionality as inhibitors of R2 ribonucleotide reductase (RNR) and tubulin polymerization by binding at the colchicine site, presents a promising avenue for enhancing therapeutic effectiveness. Herein, we describe the syntheses and physicochemical characterization of four isomeric proligands H2L3-H2L6, with the methylmorpholine substituent at pertinent positions of the pyridine ring, along with their corresponding Cu(II) complexes 3-6. Evidently, the position of the morpholine moiety and the copper(II) complex formation have marked effects on the in vitro antiproliferative activity in human uterine sarcoma MES-SA cells and the multidrug-resistant derivative MES-SA/Dx5 cells. Activity correlated strongly with quenching of the tyrosyl radical (Y•) of mouse R2 RNR protein, inhibition of RNR activity in the cancer cells, and inhibition of tubulin polymerization. Insights into the mechanism of antiproliferative activity, supported by experimental results and molecular modeling calculations, are presented.

Schiff bases and their metal complexes to target and overcome (multidrug) resistance in cancer

Overcoming multidrug resistance (MDR) is one of the major challenges in cancer therapy. In this respect, Schiff base-related compounds (bearing a R1R2CNR3 bond) gained high interest during the past decades. Schiff bases are considered privileged ligands for various reasons, including the easiness of their preparation and the possibility to form complexes with almost all transition metal ions. Schiff bases and their metal complexes exhibit many types of biological activities and are used for the treatment and diagnosis of various diseases. Until now, 13 Schiff bases have been investigated in clinical trials for cancer treatment and hypoxia imaging. This review represents the first collection of Schiff bases and their complexes which demonstrated MDR-reversal activity. The areas of drug resistance covered in this article involve: 1) Modulation of ABC transporter function, 2) Targeting lysosomal ABCB1 overexpression, 3) Circumvention of ABC transporter-mediated drug efflux by alternative routes of drug uptake, 4) Selective activity against MDR cancer models (collateral sensitivity), 5) Targeting GSH-detoxifying systems, 6) Overcoming apoptosis resistance by inducing necrosis and paraptosis, 7) Reactivation of mutated p53, 8) Restoration of sensitivity to DNA-damaging anticancer therapy, and 9) Overcoming drug resistance through modulation of the immune system. Through this approach, we would like to draw attention to Schiff bases and their metal complexes representing highly interesting anticancer drug candidates with the ability to overcome MDR.

Evaluation the cytotoxic effect of Fe3O4@Glu-Gingerol on lung adenocarcinoma cell line (A549) with biological mechanisms

The use of nanotechnology products with supermagnetic properties for targeted delivery of drugs has gained attention recently. Due to the anticancer features of Gingerol, the major phenolic compound from Ginger, this study aims to prepare Fe3O4@Glucose-Gingerol nanoparticles (NPs) and investigate their anticancer potential in a lung adenocarcinoma cell line. The physical and chemical features of the nanoparticles were investigated by FT-IR, XRD, zeta potential, DLS, EDS mapping, VSM, and electron microscope imaging. Cytotoxic effects of the nanoparticles for the A549 (lung adenocarcinoma) and MRC-5 (normal) cell lines was investigated by MTT assay. Furthermore, the effects of Fe3O4@Glucose-Gingerol nanoparticles on the expression of the CASP8, BAX, and BCL2 genes and the activity of Caspase 3 were characterized. The flow cytometry assay (annexin V/PI) was employed to find out the percentage of apoptotic cells. The Fe3O4@Glu-Gingerol NPs were spherical (42-67 nm), without elemental impurity, and with surface charge, DLS size, and magnetic saturation of -47.7 mV, 154 nm, and 35 emu/g, respectively. Fe3O4@Glu-Gingerol NPs showed a remarkable greater toxicity in the A549 cells than normal cell line with the 50 % inhibition concentration (IC50) of 190 and 554 μg/mL, respectively. Treatment of lung adenocarcinoma cells with the Fe3O4@Glu-Gingerol NPs led to an increase in cell apoptosis from 4.6 to 39.48 %. Also, the CASP8 and BAX genes were upregulated by 2.49 and 2.8 folds, respectively, while a downregulation by 0.75 folds was noticed for the BCL2. Moreover, apoptotic features were observed in Fe3O4@Glu-Gingerol NPs treated cells by Hoechst staining, and activation of Caspase 3 by 2.8 folds. This study revealed that the Fe3O4@Glu-Gingerol NPs have antiproliferative effects on the lung adenocarcinoma cell line by activation of intrinsic and extrinsic apoptosis that is a promising feature in cancer treatment.

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.

Physical structure of constitutional isomers influences antiproliferation activity of thiosemicarbazone-alkylthiocarbamate copper complexes

A series of hybrid thiosemicarbazone-alkylthiocarbamate copper complexes with similar electronic environments but distinct physical structures have been prepared, characterized, and evaluated for antiproliferation activity. The complexes include the constitutional isomers (1-phenylpropane-1-imine-(O-ethylthiocarbamato)-2-one-(N-methylthiosemicarbazonato))copper(II) (CuL1) and (1-phenylpropane-1-one-(N-methylthiosemicarbazonato)-2-imine-(O-ethylthiocarbamato))copper(II) (CuL2) along with (1-propane-1-imine-(O-ethylthiocarbamato)-2-one-(N-methylthiosemicarbazonato))copper(II) (CuL3). Complexes CuL1 and CuL2 differ in the positions of the pendent thiosemicarbazone (TSC) and alkylthiocarbamate (ATC) moieties on the 1-phenylpropane backbone. Complex CuL3 employs a propane backbone with the TSC in the 2-position as in CuL1. The isomer pair CuL1 and CuL2 have equivalent electronic environments with indistinguishable CuII/I potentials (E1/2 = -0.86 V vs. ferrocenium/ferrocene) and electron paramagnetic resonance (EPR) spectra (g∥ = 2.26, g⊥ = 2.08). The electronic structure of CuL3 has a similar E1/2 of -0.84 V and identical EPR parameters to CuL1, 2. Single crystal X-ray diffraction studies confirm a consistent donor environment with no substantial variation in the CuN or CuS bond distances and angles between the complexes. The antiproliferation activities of the CuL1-3 were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR-90) using the MTT assay. CuL1 had the highest A549 activity (A549EC50 = 0.065 μM) and selectivity (IMR-90EC50/A549EC50 = 20). The constitutional isomer CuL2 displayed decreased A549 activity (0.18 μM) and selectivity (10.6). The complex CuL3 displayed activity (0.009 μM) similar to CuL1 but with a lack of selectivity (1.0). Cellular copper loading determined by ICP-MS was consistent with the activity and selectivity trends. The complexes CuL1-3 did not induce reactive oxygen species (ROS) generation.

Trigger of apoptosis in human liver cancer cell line (HepG2) by titanium dioxide nanoparticles functionalized by glutamine and conjugated with thiosemicarbazone

The incidence of liver cancer, the third cause of cancer-associated death, has been growing, worldwide. The increasing trend of liver cancer incidence and mortality indicates the inefficiency of current therapeutic approaches, especially anticancer chemotherapy. Owing to the promising anticancer potential of Thiosemicarbazone (TSC) complexes, this work was conducted to synthesize titanium oxide nanoparticles conjugated with TSC through glutamine functionalization (TiO2@Gln-TSC NPs) and characterize their anticancer mechanism in HepG2 liver cancer cells. Physicochemical analyses of the synthesized particles, including FT-IR, XRD, SEM, TEM, Zeta potential and DLS, and EDS-mapping confirmed the proper synthesis and conjugation of TiO2@Gln-TSC NPs. The synthesized NPs were almost spherical, with a size range of 10-80 nm, a zeta potential of - 57.8 mV, a hydrodynamic size of 127 nm, and without impurities. Investigation of the cytotoxic effect of TiO2@Gln-TSC in HepG2 and HEK293 human normal cells indicated significantly higher toxicity in cancer cells (IC50 = 75 µg/mL) than normal cells (IC50 = 210 µg/mL). Flow cytometry analysis of TiO2@Gln-TSC treated and control cells showed that the population of apoptotic cells considerably increased from 2.8 to 27.3% after treatment with the NPs. Moreover, 34.1% of the TiO2@Gln-TSC treated cells were mainly arrested at the sub-G1 phase of the cell cycle, which was significantly greater than control cells (8.4%). The Hoechst staining assay showed considerable nuclear damage, including chromatin fragmentation and the appearance of apoptotic bodies. This work introduced TiO2@Gln-TSC NPs as a promising anticancer compound that could combat liver cancer cells through apoptosis induction.

Comparative evaluation of the structure and antitumor mechanism of mononuclear and trinucleated thiosemicarbazone Cu(II) complexes

The ratio of ligand to Cu(II) ions has an essential effect on the geometrical configuration and anti-tumour activity of metal-based complexes. In this work, we synthesised two Cu(II) thiosemicarbazone complexes, namely, [Cu(L)(Cl)] (C1) and [Cu₃(L)₂(Cl)₄] (C2), by controlling the ratio of Cu(II) ion to ligand, to evaluate their anti-tumour activity. The ability of C1 to catalyze hydrogen peroxide to produce reactive oxygen species (ROS) was significantly higher than that of Cu(II) ion. Moreover, the bridge of Cu(II) and two molecules generated a new complex (C2), which, in contrast to C1, enhanced the generation of Fenton-like-triggered ROS. Consequently, the produced ROS depleted reduced glutathione, caused oxidative cell stress and promoted apoptosis through mitochondrial apoptotic pathways. In addition, C2 exhibited better tumour suppression than C1 in a nude mouse tumour xenograft model.

Discovery of Small Molecule COX-1 and Akt Inhibitors as Anti-NSCLC Agents Endowed with Anti-Inflammatory Action

Targeted therapies have come into prominence in the ongoing battle against non-small cell lung cancer (NSCLC) because of the shortcomings of traditional chemotherapy. In this context, indole-based small molecules, which were synthesized efficiently, were subjected to an in vitro colorimetric assay to evaluate their cyclooxygenase (COX) inhibitory profiles. Compounds 3b and 4a were found to be the most selective COX-1 inhibitors in this series with IC₅₀ values of 8.90 µM and 10.00 µM, respectively. In vitro and in vivo assays were performed to evaluate their anti-NSCLC and anti-inflammatory action, respectively. 2-(1H-Indol-3-yl)-N'-(4-morpholinobenzylidene)acetohydrazide (3b) showed selective cytotoxic activity against A549 human lung adenocarcinoma cells through apoptosis induction and Akt inhibition. The in vivo experimental data revealed that compound 3b decreased the serum myeloperoxidase and nitric oxide levels, pointing out its anti-inflammatory action. Moreover, compound 3b diminished the serum aminotransferase (particularly aspartate aminotransferase) levels. Based on the in vitro and in vivo experimental data, compound 3b stands out as a lead anti-NSCLC agent endowed with in vivo anti-inflammatory action, acting as a dual COX-1 and Akt inhibitor.

Switching of the Polarity-Sensitive Aggregation Pattern of a Thiosemicarbazone-Based Anticancer Luminophore and Its Involvement in Cellular Apoptosis of the Human Lung Cancer Cell Line

Elucidation of the photophysical and biochemical properties of small molecules can facilitate their applications as prospective therapeutic imaging (theragnostic) agents. Herein, we demonstrate the luminescence behavior of a strategically designed potential therapeutic thiosemicarbazone derivative, (E)-1-(4-(diethylamino)-2-hydroxybenzylidene)-4,4-dimethylthiosemicarbazide (DAHTS), accompanied by the illustration of its solvation and solvation dynamics using spectroscopic techniques and exploring its promising antitumor activities by adopting the necessary biochemical assays. Solvent-dependent photophysical properties, namely UV-vis absorption, fluorescence emission, and excitation profiles, concentration-dependent studies, and time-resolved fluorescence decays, serve as footprints to explain the existence of DAHTS monomers, its excited-state intramolecular proton transfer (ESIPT) product, and dimeric and aggregated forms. The emission intensity progressively intensifies with increasing polarity and proticity of the solvents up to MeOH, but in water, a sudden dip is seen. Solvent polarity and H-bonding modulate the fluorescence behavior of the primary emission peak and significantly influence the formation of the dimer and DAHTS aggregates. The designed luminophore (DAHTS) exhibits significant antiproliferative activity against the human lung cancer (A549) cell lines with inhibitory concentrations (IC₅₀) of 16.88 and 11.92 μM for 24 and 48 h, respectively. DAHTS effectively reduces the cell viability and induces cytotoxicity with extensive morphological changes in A549 cells in the form of spikes when compared to the normal HEK cell lines. More importantly, it increases the p53 expression at the mRNA level that consolidates its potential therapeutic activity. The effect of DAHTS on apoptotic pathways against the A549 cell line has been investigated to determine its probable mechanism of cell death. Thus, the all-inclusive understanding of the photophysical properties and the necessary biochemical assays put forward important steps toward tailoring the thiosemicarbazone core structure for favorable cancer theragnostic applications in academic and pharmaceutical research.

Synthesize of Bi2O3/Gln-TSC nanoparticles and evaluation of their toxicity on prostate cancer cells and expression of CASP8, BAX, and Bcl-2 genes

Due to the high prevalence and considerable increase of prostate cancer, finding novel therapeutic compounds for the treatment of prostatic cancer has been the goal of many researches. In this study, we aimed to fabricate the Bismuth oxide (Bi₂O₃) NPs, functionalized with glutamine (Gln) and conjugated with Thiosemicarbazide (TSC). Then, the anticancer mechanism of the synthesized NPs was investigated using the cellular and molecular tests including MTT assay, Flow cytometry, Caspase-3 activity assay, Hoechst staining and Real Time PCR. The FT-IR and XRD assays confirmed the identity of the synthesized Bi₂O₃/Gln-TSC NPs. The size range of the synthesized spherical particles was 10-60 nm and the zeta potential was - 23.8 mV. The purity of the NPs was confirmed by EDX-mapping analysis. The Bi₂O₃/Gln-TSC was considerably more toxic for prostate cancer cells than normal human cells and the IC₅₀ was calculated 35.4 and 305 µg/mL, respectively. The exposure to the NPs significantly increased the frequency of apoptotic cells from 4.7 to 75.3%. Moreover, the expression of the CASP8, BAX, and Bcl-2 genes after exposure to the NPs increased by 2.8, 2.3, and 1.39 folds. Treating the cancer cells with Bi₂O₃/Gln-TSC increased the activity of the Caspase-3 protein and apoptotic morphological features were observed by Hoechst staining in the treated cells. This work showed that Bi₂O₃/Gln-TSC has considerable cytotoxicity for prostate cancer cells and could inducing both intrinsic and extrinsic pathways of apoptosis.

Developing a Copper(II) Agent Based on His-146 and His-242 Residues of Human Serum Albumin Nanoparticles: Integration To Overcome Cisplatin Resistance and Inhibit the Metastasis of Nonsmall Cell Lung Cancer

To overcome the resistance of nonsmall cell lung cancer (NSCLC) cells to cisplatin and inhibit their metastasis, we proposed to develop a Cu(II) agent based on the specific residue(s) of HSA nanoparticles (NPs) for multitargeting the tumor microenvironment (TME). To this end, we not only synthesized four Cu(II) 2-hydroxy-3-methoxybenzaldehyde thiosemicarbazone compounds (C1-C4), obtaining a Cu compound (C4) with significant cytotoxicity by studying their structure-activity relationships, but also revealed the binding mechanism of C4 to HSA through X-ray crystallography and confirmed the successful construction of a new HSA-C4 NPs delivery system. C4 and HSA-C4 NPs inhibited the A549cisR tumor growth and metastasis, and HSA NPs optimized the anticancer behavior of C4. We further confirmed the anticancer mechanism of the C4/HSA-C4 NP multitargeting TME to overcome cisplatin resistance: killing tumor cells by acting on the mtDNA and inducing apoptosis, polarizing M2-type macrophages to the M1-type, and inhibiting angiogenesis.

Unsymmetrical Trifluoromethyl Methoxyphenyl β-Diketones: Effect of the Position of Methoxy Group and Coordination at Cu(II) on Biological Activity

Copper(II) complexes with 1,1,1-trifluoro-4-(4-methoxyphenyl)butan-2,4-dione (HL1) were synthesized and characterized by elemental analysis, FT-IR spectroscopy, and single crystal X-ray diffraction. The biological properties of HL1 and cis-[Cu(L1)₂(DMSO)] (3) were examined against Gram-positive and Gram-negative bacteria and opportunistic unicellular fungi. The cytotoxicity was estimated towards the HeLa and Vero cell lines. Complex 3 demonstrated antibacterial activity towards S. aureus comparable to that of streptomycin, lower antifungal activity than the ligand HL1 and moderate cytotoxicity. The bioactivity was compared with the activity of compounds of similar structures. The effect of changing the position of the methoxy group at the aromatic ring in the ligand moiety of the complexes on their antimicrobial and cytotoxic activity was explored. We propose that complex 3 has lower bioavailability and reduced bioactivity than expected due to strong intermolecular contacts. In addition, molecular docking studies provided theoretical information on the interactions of tested compounds with ribonucleotide reductase subunit R2, as well as the chaperones Hsp70 and Hsp90, which are important biomolecular targets for antitumor and antimicrobial drug search and design. The obtained results revealed that the complexes displayed enhanced affinity over organic ligands. Taken together, the copper(II) complexes with the trifluoromethyl methoxyphenyl-substituted β-diketones could be considered as promising anticancer agents with antibacterial properties.

Triapine Analogues and Their Copper(II) Complexes: Synthesis, Characterization, Solution Speciation, Redox Activity, Cytotoxicity, and mR2 RNR Inhibition

Three new thiosemicarbazones (TSCs) HL¹–HL³ as triapine analogues bearing a redox-active phenolic moiety at the terminal nitrogen atom were prepared. Reactions of HL¹–HL³ with CuCl₂·2H₂O in anoxic methanol afforded three copper(II) complexes, namely, Cu(HL¹)Cl₂ (1), [Cu(L²)Cl] (2′), and Cu(HL³)Cl₂ (3), in good yields. Solution speciation studies revealed that the metal-free ligands are stable as HL¹–HL³ at pH 7.4, while being air-sensitive in the basic pH range. In dimethyl sulfoxide they exist as a mixture of E and Z isomers. A mechanism of the E/Z isomerization with an inversion at the nitrogen atom of the Schiff base imine bond is proposed. The monocationic complexes [Cu(L^1–3)]⁺ are the most abundant species in aqueous solutions at pH 7.4. Electrochemical and spectroelectrochemical studies of 1, 2′, and 3 confirmed their redox activity in both the cathodic and the anodic region of potentials. The one-electron reduction was identified as metal-centered by electron paramagnetic resonance spectroelectrochemistry. An electrochemical oxidation pointed out the ligand-centered oxidation, while chemical oxidations of HL¹ and HL² as well as 1 and 2′ afforded several two-electron and four-electron oxidation products, which were isolated and comprehensively characterized. Complexes 1 and 2′ showed an antiproliferative activity in Colo205 and Colo320 cancer cell lines with half-maximal inhibitory concentration values in the low micromolar concentration range, while 3 with the most closely related ligand to triapine displayed the best selectivity for cancer cells versus normal fibroblast cells (MRC-5). HL¹ and 1 in the presence of 1,4-dithiothreitol are as potent inhibitors of mR2 ribonucleotide reductase as triapine.

Three triapine analogues HL¹−HL³ bearing a phenolic redox-active moiety showed moderate antiproliferative activity, while one of the oxidation products HL^2c′·CH3COOH revealed high cytotoxicity in Colo205 and Colo320 cancer cell lines. Coordination of HL¹−HL³ to copper(II) increased strongly the cytotoxicity, with complex 2′ showing IC₅₀ values of 0.181 and 0.159, respectively. The highest cytotoxicity of 2′ is likely due to the highest thermodynamic stability, more negative reduction potential, and the lowest rate of reduction by GSH.

The Synthesis of a Bis(thiosemicarbazone) Macrocyclic Ligand and the Mn(II), Co(II), Zn(II) and 68Ga(III) Complexes

A 1,4,7,10-tetraazacyclododecane (cyclen) variant bearing two thiosemicarbazone pendant groups has been prepared. The ligand forms complexes with Mn2+, Co2+ and Zn2+. X-ray crystallography of the Mn2+, Co2+ and Zn2+ complexes showed that the ligand provides a six-coordinate environment for the metal ions. The Mn2+ and Zn2+ complexes exist in the solid state as racemic mixtures of the Δ(δ,δ,δ,δ)/Λ(λ,λ,λ,λ) and Δ(λ,λ,λ,λ)/Λ(δ,δ,δ,δ) diastereomers, and the Co2+ complex exists as the Δ(δ,δ,δ,δ)/Λ(λ,λ,λ,λ) and Δ(λ,λ,λ,δ)/Λ(δ,δ,δ,λ) diastereomers. Density functional theory calculations indicated that the relative energies of the diastereomers are within 10 kJ mol-1. Magnetic susceptibility of the complexes indicated that both the Mn2+ and Co2+ ions are high spin. The ligand was radiolabelled with gallium-68, in the interest of developing new positron emission tomography imaging agents, which produced a single species in high radiochemical purity (>95%) at 90 °C for 10 min.

Coumarin-Based Triapine Derivatives and Their Copper(II) Complexes: Synthesis, Cytotoxicity and mR2 RNR Inhibition Activity

A series of thiosemicarbazone-coumarin hybrids (HL¹-HL³ and H₂L⁴) has been synthesised in 12 steps and used for the preparation of mono- and dinuclear copper(II) complexes, namely Cu(HL¹)Cl₂ (1), Cu(HL²)Cl₂ (2), Cu(HL³)Cl₂ (3) and Cu₂(H₂L⁴)Cl₄ (4), isolated in hydrated or solvated forms. Both the organic hybrids and their copper(II) and dicopper(II) complexes were comprehensively characterised by analytical and spectroscopic techniques, i.e., elemental analysis, ESI mass spectrometry, 1D and 2D NMR, IR and UV–vis spectroscopies, cyclic voltammetry (CV) and spectroelectrochemistry (SEC). Re-crystallisation of 1 from methanol afforded single crystals of copper(II) complex with monoanionic ligand Cu(L¹)Cl, which could be studied by single crystal X-ray diffraction (SC-XRD). The prepared copper(II) complexes and their metal-free ligands revealed antiproliferative activity against highly resistant cancer cell lines, including triple negative breast cancer cells MDA-MB-231, sensitive COLO-205 and multidrug resistant COLO-320 colorectal adenocarcinoma cell lines, as well as in healthy human lung fibroblasts MRC-5 and compared to those for triapine and doxorubicin. In addition, their ability to reduce the tyrosyl radical in mouse R2 protein of ribonucleotide reductase has been ascertained by EPR spectroscopy and the results were compared with those for triapine.

Anti-glycemic potential of benzophenone thio/semicarbazone derivatives: synthesis, enzyme inhibition and ligand docking studies

Inhibition of dipeptidyl peptidase-IV (DPP-IV) has been identified as a promising approach for the treatment of type 2 diabetes mellitus (T2DM). Therefore, development of DPP-IV inhibitors with new chemical scaffold is of utmost importance to medicinal chemistry. In the present study, we identified benzophenone thio- and semicarbazone scaffolds as novel DPP-IV inhibitors. For that purpose, benzophenone thio- and semicarbazone were synthesized through a 2-step reaction. These newly synthetic derivatives were characterized by different spectroscopic techniques, including HREI-MS and NMR. whereas stereochemistry of the iminic bond was predicted by NOESY experiments. Thio- and semicarbazones derivatives were evaluated for their DPP-IV inhibitory potential and found to exhibit a good to moderate enzyme inhibitory activity. Most active and non-cytotoxic derivatives were further evaluated for their DPP-IV inhibitory potential in in cellulo model. The binding sites as well as affinity of active compounds for DPP- IV enzyme were predicted by in silico studies, and compared to a standard drug, sitagliptin. Pharmacophore studies of thio- and semicarbazones derivatives 1-29 suggest that substitution of aryl group, particularly a lipophilic substituents at C-4″ of benzene ring, and a hydroxyl at C-4' strongly influenced the DPP-IV inhibitory activity. Compound 9 showed the highest inhibitory activity (IC₅₀ = 15.0 ± 0.6 µM), whereas compounds 10, 17, 12, 14 and 23 showed a moderate activity with IC₅₀ values in the range of 28.9-39.2 µM. This study identifies thio- and semicarbazones as new classes of DPP-IV inhibitors which may translate into safe and effective therapeutics for a better management of type 2 diabetes.Communicated by Ramaswamy H. Sarma.

Insight into the Anticancer Activity of Copper(II) 5-Methylenetrimethylammonium-Thiosemicarbazonates and Their Interaction with Organic Cation Transporters

A series of four water-soluble salicylaldehyde thiosemicarbazones with a positively charged trimethylammonium moiety ([H2LR]Cl, R = H, Me, Et, Ph) and four copper(II) complexes [Cu(HLR)Cl]Cl (1-4) were synthesised with the aim to study (i) their antiproliferative activity in cancer cells and, (ii) for the first time for thiosemicarbazones, the interaction with membrane transport proteins, specifically organic cation transporters OCT1-3. The compounds were comprehensively characterised by analytical, spectroscopic and X-ray diffraction methods. The highest cytotoxic effect was observed in the neuroblastoma cell line SH-5YSY after 24 h exposure and follows the rank order: 3 > 2 > 4 > cisplatin > 1 >>[H2LR]Cl. The copper(II) complexes showed marked interaction with OCT1-3, comparable to that of well-known OCT inhibitors (decynium 22, prazosin and corticosterone) in the cell-based radiotracer uptake assays. The work paves the way for the development of more potent and selective anticancer drugs and/or OCT inhibitors.

Synthesis and toxicity assessment of Fe3O4 NPs grafted by ∼ NH2-Schiff base as anticancer drug: modeling and proposed molecular mechanism through docking and molecular dynamic simulation

Superparamagnetic iron oxide nanoparticles have been synthesized using chain length of (3-aminopropyl) triethoxysilane for cancer therapy. First, we have developed a layer by layer functionalized with grafting 2,4-toluene diisocyanate as a bi-functional covalent linker onto a nano-Fe₃O₄ support. Then, they were characterized by Fourier transform infrared, X-ray powder diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and VSM techniques. Finally, all nanoparticles with positive or negative surface charges were tested against K562 (myelogenous leukemia cancer) cell lines to demonstrate their therapeutic efficacy by MTT assay test. We found that the higher toxicity of Fe₃O₄@SiO₂@APTS ∼ Schiff base-Cu(II) (IC₅₀: 1000 μg/mL) is due to their stronger in situ degradation, with larger intracellular release of iron ions, as compared to surface passivated NPs. For first time, the molecular dynamic simulations of all compounds were carried out afterwards optimizing using MM+, Semi-empirical (AM1) and Ab-initio (STO-3G), Forcite Gemo Opt, Forcite Dynamics, Forcite Energy and CASTEP in Materials studio 2017. The energy (eV), space group, lattice parameters (Å), unit cell parameters (Å), and electron density of the predicted structures were taken from the CASTEP module of Materials Studio. The docking methods were used to predict the DNA binding affinity, ribonucleotide reductase, and topoisomerase II.

Bioactive Salen-type Schiff Base Transition Metal Complexes as Possible Anticancer Agents

Although metal-based anticancer drugs have been recognized as the most effective agents over the organic compounds, non-selectivity and high toxic effects have limited their applications in a way that only three Pt-analogues have progressed into clinical use. These problems have spurred chemists to develop different strategies based on alternative targets. This work focuses on predicting potency and mode of interactions of a series of salen type Schiff base transition metal complexes derived from meso-1,2-diphenyl-1,2-ethylenediamine, over some proteins (HDAC7, HDAC2, CatB, B-RAF kinase, TopII, RNR, TS, and rHA) using computational docking method, to be later considered as possible anticancer agents. The obtained results showed that all complexes exhibited higher affinity for HDAC7 than the other targets. Moreover, the bromo-derivatives of the copper compounds were more active on HDAC7 than the other derivatives. Such bromo compounds showed considerable interactions with Kinase, RNR, TS, and CatB. Contrary to Histone deacetylase (HAD)C7; HDAC2 was predicted to be relatively poor target. As expected, formation of the hydrophobic interactions between the metal complexes and the protein targets were essential for activity of the metal compounds. This study provides some more information for further optimizations and development of new metallodrugs as enzyme inhibitors for potential therapeutic agents.

Isoquinoline thiosemicarbazone displays potent anticancer activity with in vivo efficacy against aggressive leukemias

A potent class of isoquinoline-based α-N-heterocyclic carboxaldehyde thiosemicarbazone (HCT) compounds has been rediscovered; based upon this scaffold, three series of antiproliferative agents were synthesized through iterative rounds of methylation and fluorination modifications, with anticancer activities being potentiated by physiologically relevant levels of copper. The lead compound, HCT-13, was highly potent against a panel of pancreatic, small cell lung carcinoma, prostate cancer, and leukemia models, with IC₅₀ values in the low-to-mid nanomolar range. Density functional theory (DFT) calculations showed that fluorination at the 6-position of HCT-13 was beneficial for ligand-copper complex formation, stability, and ease of metal-center reduction. Through a chemical genomics screen, we identify DNA damage response/replication stress response (DDR/RSR) pathways, specifically those mediated by ataxia-telangiectasia and Rad3-related protein kinase (ATR), as potential compensatory mechanism(s) of action following HCT-13 treatment. We further show that the cytotoxicity of HCT-13 is copper-dependent, that it promotes mitochondrial electron transport chain (mtETC) dysfunction, induces production of reactive oxygen species (ROS), and selectively depletes guanosine nucleotide pools. Lastly, we identify metabolic hallmarks for therapeutic target stratification and demonstrate the in vivo efficacy of HCT-13 against aggressive models of acute leukemias in mice.

Thiosemicarbazone-metal complexes exhibiting cytotoxicity in colon cancer cell lines through oxidative stress

Colorectal cancer is the third most common type of cancer and has a high incidence in developed countries. At present, specific treatments are being required to allow individualized therapy depending on the molecular alteration on which the drug may act. The aim of this project is to evaluate whether HPTSC and HPTSC* thiosemicarbazones (HPTSC = pyridine-2-carbaldehyde thiosemicarbazone and HPTSC* = pyridine-2-carbaldehyde 4N-methylthiosemicarbazone), and their complexes with different transition metal ions as Cu(II), Fe(III) and Co(III), have antitumor activity in colon cancer cells (HT-29 and SW-480), that have different oncogenic characteristics. Cytotoxicity was evaluated and the involvement of oxidative stress in its mechanism of action was analyzed by quantifying the superoxide dismutase activity, redox state by quantification of the thioredoxin levels and reduced/oxidized glutathione rate and biomolecules damage. The apoptotic effect was evaluated by measurements of the levels of caspase 9 and 3 and the index of histones. All the metal-thiosemicarbazones have antitumor activity mediated by oxidative stress. The HPTSC*-Cu was the compound that showed the best antitumor and apoptotic characteristics for the cell line SW480, that is KRAS gene mutated.

Organoruthenated Nitroxoline Derivatives Impair Tumor Cell Invasion through Inhibition of Cathepsin B Activity

Lysosomal cysteine peptidase cathepsin B (catB) is an important tumor-promoting factor involved in tumor progression and metastasis representing a relevant target for the development of new antitumor agents. In the present study, we synthesized 11 ruthenium compounds bearing either the clinical agent nitroxoline that was previously identified as potent selective reversible inhibitor of catB activity or its derivatives. We demonstrated that organoruthenation is a viable strategy for obtaining highly effective and specific inhibitors of catB endo- and exopeptidase activity, as shown using enzyme kinetics and microscale thermophoresis. Furthermore, we showed that the novel metallodrugs by catB inhibition significantly impair processes of tumor progression in in vitro cell based functional assays at low noncytotoxic concentrations. Generally, by using metallodrugs we observed an improvement in catB inhibition, a reduction of extracellular matrix degradation and tumor cell invasion in comparison to free ligands, and a correlation with the reactivity of the monodentate halide leaving ligand.

Eleven ruthenium compounds bearing either the clinical agent nitroxoline or its potent cathepsin B (catB) inhibiting derivatives were evaluated as antimetastatic agents. We demonstrated that organoruthenation is a viable strategy for obtaining highly effective and specific inhibitors of catB activities, as shown using enzyme kinetics and microscale thermophoresis. Furthermore, we showed that the novel metallodrugs significantly impair processes of tumor progression in in vitro cell based functional assays at low noncytotoxic concentrations.

Chemical biology suggests pleiotropic effects for a novel hexanuclear copper(ii) complex inducing apoptosis in hepatocellular carcinoma cells

A new hexanuclear copper(ii) complex proved potential chemotherapeutic applicability in inducing apoptosis in cancer calls by acting on multiple targets and signaling pathways.

New Water-Soluble Copper(II) Complexes with Morpholine-Thiosemicarbazone Hybrids: Insights into the Anticancer and Antibacterial Mode of Action

Six morpholine-(iso)thiosemicarbazone hybrids HL¹–HL⁶ and their Cu(II) complexes with good-to-moderate solubility and stability in water were synthesized and characterized. Cu(II) complexes [Cu(L^1–6)Cl] (1–6) formed weak dimeric associates in the solid state, which did not remain intact in solution as evidenced by ESI-MS. The lead proligands and Cu(II) complexes displayed higher antiproliferative activity in cancer cells than triapine. In addition, complexes 2–5 were found to specifically inhibit the growth of Gram-positive bacteria Staphylococcus aureus with MIC₅₀ values at 2–5 μg/mL. Insights into the processes controlling intracellular accumulation and mechanism of action were investigated for 2 and 5, including the role of ribonucleotide reductase (RNR) inhibition, endoplasmic reticulum stress induction, and regulation of other cancer signaling pathways. Their ability to moderately inhibit R2 RNR protein in the presence of dithiothreitol is likely related to Fe chelating properties of the proligands liberated upon reduction.

Binding Specificities of Nanobody•Membrane Protein Complexes Obtained from Chemical Cross-Linking and High-Mass MALDI Mass Spectrometry

The application of nanobodies as binding partners for structure stabilization in protein X-ray crystallography is taking an increasingly important role in structural biology. However, the addition of nanobodies to the crystallization matrices might complicate the optimization of the crystallization process, which is why analytical techniques to screen and characterize suitable nanobodies are useful. Here, we show how chemical cross-linking combined with high-mass matrix-assisted laser/desorption ionization mass spectrometry can be employed as a fast screening technique to determine binding specificities of intact nanobody•membrane protein complexes. Titration series were performed to rank the binding affinity of the interacting nanobodies. To validate the mass spectrometry data, microscale thermophoresis was used, which showed binding affinities of the stronger binding nanobodies, in the low μM range. In addition, mass spectrometry provides access to the stoichiometry of the complexes formed, which enables the definition of conditions under which homogeneous complex states are present in solution. Conformational changes of the membrane protein were investigated and competitive binding experiments were used to delimit the interaction sites of the nanobodies, which is in agreement with crystal structures obtained. The results show the diversity of specifically binding nanobodies in terms of binding affinity, stoichiometry, and binding site, which illustrates the need for an analytical screening approach.

Copper(II) Thiosemicarbazone Complexes and Their Proligands upon UVA Irradiation: An EPR and Spectrophotometric Steady-State Study

X- and Q-band electron paramagnetic resonance (EPR) spectroscopy was used to characterize polycrystalline Cu(II) complexes that contained sodium 5-sulfonate salicylaldehyde thiosemicarbazones possessing a hydrogen, methyl, ethyl, or phenyl substituent at the terminal nitrogen. The ability of thiosemicarbazone proligands to generate superoxide radical anions and hydroxyl radicals upon their exposure to UVA irradiation in aerated aqueous solutions was evidenced by the EPR spin trapping technique. The UVA irradiation of proligands in neutral or alkaline solutions and dimethylsulfoxide (DMSO) caused a significant decrease in the absorption bands of aldimine and phenolic chromophores. Mixing of proligand solutions with the equimolar amount of copper(II) ions resulted in the formation of 1:1 Cu(II)-to-ligand complex, with the EPR and UV-Vis spectra fully compatible with those obtained for the dissolved Cu(II) thiosemicarbazone complexes. The formation of the complexes fully inhibited the photoinduced generation of reactive oxygen species, and only subtle changes were found in the electronic absorption spectra of the complexes in aqueous and DMSO solutions upon UVA steady-state irradiation. The dark redox activity of copper(II) complexes and proligand/Cu(II) aqueous solutions towards hydrogen peroxide which resulted in the generation of hydroxyl radicals, was confirmed by spin trapping experiments.

Thermophoresis for characterizing biomolecular interaction

The study of biomolecular interactions is crucial to get more insight into the biological system. The interactions of protein-protein, protein-nucleic acids, protein-sugars, nucleic acid-nucleic acids and protein-small molecules are supporting therapeutics and technological developments. Recently, the development in a large number of analytical techniques for characterizing biomolecular interactions reflect the promising research investments in this field. In this review, microscale thermophoresis technology (MST) is presented as an analytical technique for characterizing biomolecular interactions. Recent years have seen much progress and several applications established. MST is a powerful technique in quantitation of binding events based on the movement of molecules in microscopic temperature gradient. Simplicity, free solutions analysis, low sample volume, short analysis time, and immobilization free are the MST advantages over other competitive techniques. A wide range of studies in biomolecular interactions have been successfully carried out using MST, which tend to the versatility of the technique to use in screening binding events in order to save time, cost and obtained high data quality.

Isomerism and reactivity of nickel(ii) acetylacetonate bis(thiosemicarbazone) complexes

The formation of asymmetric and symmetric nickel(ii) bis-thiosemicarbazone complexes has been investigated by NMR and UV-Vis spectroscopy which shed new light on the complexation mechanism and reactivity of these unusual isomers.

Copper complexes as prospective anticancer agents: in vitro and in vivo evaluation, selective targeting of cancer cells by DNA damage and S phase arrest

A series of six new bis(thiosemicarbazone)copper(i) complexes of the type [Cu(L^1–6)₂Cl] (1–6) have been synthesized and characterized. The molecular structure of the ligand L⁴ was determined by the single crystal XRD method. All the complexes adopted trigonal planar (Y-shaped) geometry. All the complexes strongly bind with CT-DNA via intercalative mode, which was further supported by molecular docking studies. Further, the complexes were effectively bind with BSA as observed by UV-Vis and fluorescence spectra. All the complexes effectively cleave pBR322 DNA through hydrolytic pathway as evidenced from T4 ligase experiments. All the complexes interact with the anticancer receptor focal adhesion kinase (FAK) via electrostatic, van der Waals, hydrogen bonding, σ–π and π–π interactions. In vitro cytotoxicity of the complexes were assessed by MTT assay against four cancer cell lines such as human breast adenocarcinoma (MCF-7), cervical (HeLa), epithelioma (Hep-2) and Ehrlich ascites carcinoma (EAC), and two normal cell lines namely normal human dermal fibroblasts (NHDF) and L6 myotubes with respect to the commercially used anticancer drug cisplatin. All the complexes induce apoptosis in EAC cells, which was confirmed by AO/EB, Hoechst 33258 and PI staining methods. The complexes block cell cycle progression of EAC cells in S phase (DNA synthesis). The cellular uptake studies confirmed the ability of the complexes to go into the cytoplasm and accumulation in the cell nuclei. In the in vivo anticancer studies, the complexes significantly reduce the tumour volume in female Swiss albino mice. Overall, our results ensure the role of thiosemicarbazone-based copper(i) complexes as prospective anticancer agents, induction of apoptosis and S phase arrest with the mitochondrial controlled pathway.

The thiosemicarbazone-based copper(i) complexes causing S phase arrest and apoptosis involving the mitochondrial controlled pathway has been investigated.

Gly–Gly–His tripeptide- and silver nanoparticle-assisted electrochemical evaluation of copper(ii) ions in aqueous environment

A sensitive and selective electrochemical sensor for Cu²⁺ assay is developed using tripeptide-based recognition and silver nanoparticle-modified electrode.

Tetranuclear and dinuclear phenoxido bridged copper complexes based on unsymmetrical thiosemicarbazone ligands

Dinuclear and tetranuclear copper(ii) complexes based on N,S ligand systems in the solid state and in solution are described.

Synthesis, anticancer activity and mechanism of action of new thiazole derivatives

Thiazole derivatives are recognized to possess various biological activities as antiparasitic, antifungal, antimicrobial and antiproliferative. The present work reports the synthesis of 22 new substances belonging to two classes of compounds: thiosemicarbazones and thiazoles, with the purpose of developing new drugs that present high specificity for tumor cells and low toxicity to the organism. A cytotoxic screening was performed to evaluate the performance of the new derivatives in five tumor cell lines. Eight compounds were shown to be promising in at least three tumor cell lines. These compounds had their IC₅₀ determined within 72 h and the activity structure ratio was assessed. The effect of the best compounds on PBMC and hemolytic activity assay was then evaluated. The compound 1d was considered the most promising among the samples tested and its influence on cell cycle, DNA fragmentation and mitochondrial depolarization was evaluated.