Palladium(II) Complexes of 4-Phenyl-3-thiosemicarbazone Ligands: Insights Into Cytotoxic Properties And Mode of Cell Death

Reactions between sodium tetrachloropalladate and 2- (or 4-) substituted 4-phenyl-3-thiosemicarbazone ligands (HLR), with various electron-donating and electron-withdrawing substituents (R = OCH3, NO2, and Cl), afford square-planar complexes of the general formula [Pd(LR)2]. Ground-state geometry optimization and the vibrational analysis of cis- and trans-isomers of the complexes were carried out to get an insight into the stereochemistry of the complexes. Natural bond orbital analysis was used to analyze how the nature of the substituent affects the natural charge of the metal center, the type of hybridization, and the strength of the M-N and M-S bonds. Using spectrophotometry, the stability of the complexes, and their DNA binding abilities were assessed. The Pd(II) complexes showed moderate cytotoxicity against MCF-7 and Caco-2 cell lines, two of the assessed malignant cell lines, resulting in all known cell death types, including early apoptotic bodies and late apoptotic vacuoles as well as evident necrotic bodies.

A Comparison of In Vitro Studies between Cobalt(III) and Copper(II) Complexes with Thiosemicarbazone Ligands to Treat Triple Negative Breast Cancer

Metal complexes have gained significant attention as potential anti-cancer agents. The anti-cancer activity of [Co(phen)2(MeATSC)](NO3)3•1.5H2O•C2H5OH 1 (where phen = 1,10-phenanthroline and MeATSC = 9-anthraldehyde-N(4)-methylthiosemicarbazone) and [Cu(acetylethTSC)Cl]Cl•0.25C2H5OH 2 (where acetylethTSC = (E)-N-ethyl-2-[1-(thiazol-2-yl)ethylidene]hydrazinecarbothioamide) was investigated by analyzing DNA cleavage activity. The cytotoxic effect was analyzed using CCK-8 viability assay. The activities of caspase 3/7, 9, and 1, reactive oxygen species (ROS) production, cell cycle arrest, and mitochondrial function were further analyzed to study the cell death mechanisms. Complex 2 induced a significant increase in nicked DNA. The IC50 values of complex 1 were 17.59 μM and 61.26 μM in cancer and non-cancer cells, respectively. The IC50 values of complex 2 were 5.63 and 12.19 μM for cancer and non-cancer cells, respectively. Complex 1 induced an increase in ROS levels, mitochondrial dysfunction, and activated caspases 3/7, 9, and 1, which indicated the induction of intrinsic apoptotic pathway and pyroptosis. Complex 2 induced cell cycle arrest in the S phase, ROS generation, and caspase 3/7 activation. Thus, complex 1 induced cell death in the breast cancer cell line via activation of oxidative stress which induced apoptosis and pyroptosis while complex 2 induced cell cycle arrest through the induction of DNA cleavage.

New Stable Gallium(III) and Indium(III) Complexes with Thiosemicarbazone Ligands: A Biological Evaluation

The aim of this work is to explore a new library of coordination compounds for medicinal applications. Gallium is known for its various applications in this field. Presently, indium is not particularly important in medicine, but it shares a lot of chemical traits with its above-mentioned lighter companion, gallium, and is also used in radio imaging. These metals are combined with thiosemicarbazones, ligating compounds increasingly known for their biological and pharmaceutical applications. In particular, the few ligands chosen to interact with these hard metal ions share the ideal affinity for a high charge density. Therefore, in this work we describe the synthesis and the characterization of the resulting coordination compounds. The yields of the reactions vary from a minimum of 21% to a maximum of 82%, using a fast and easy procedure. Nuclear Magnetic Resonance (NMR) and Infra Red (IR) spectroscopy, mass spectrometry, elemental analysis, and X-ray Diffraction (XRD) confirm the formation of stable compounds in all cases and a ligand-to-metal 2:1 stoichiometry with both cations. In addition, we further investigated their chemical and biological characteristics, via UV-visible titrations, stability tests, and cytotoxicity and antibiotic assays. The results confirm a strong stability in all explored conditions, which suggests that these compounds are more suitable for radio imaging applications rather than for antitumoral or antimicrobic ones.

Ternary Phenolate-Based Thiosemicarbazone Complexes of Copper(II): Magnetostructural Properties, Spectroscopic Features and Marked Selective Antiproliferative Activity against Cancer Cells

The new diprotic ligand 3,5-di-tert-butylsalicylaldehyde 4-ethyl-3-thiosemicarbazone, abbreviated H2(3,5-t-Bu2)-sal4eT, exists as the thio-keto tautomer and adopts the E-configuration with respect to the imine double bond, as evidenced by single-crystal X-ray analysis and corroborated by spectroscopic characterisation. Upon treatment with Cu(OAc)2·H2O in the presence of either 2,9-dimethyl-1,10-phenanthroline (2,9-Me2-phen) or 1,10-phenanthroline (phen) as a co-ligand in MeOH, this thiosemicarbazone undergoes conformational transformation (relative donor-atom orientations: syn,anti → syn,syn) concomitantly with tautomerisation and double deprotonation to afford the ternary copper(II) complexes [Cu{(3,5-t-Bu2)-sal4eT}(2,9-Me2-phen)] (1) and [Cu2{3,5-t-Bu2)-sal4eT}2(phen)] (2). Crystallographic elucidation has revealed that complex 1 is a centrosymmetric dimer of mononuclear copper(II) complex molecules brought about by intermolecular H-bonding. The coordination geometry at the copper(II) centre is best described as distorted square pyramidal in accordance with the trigonality index (τ = 0.14). The co-ligand adopts an axial-equatorial coordination mode; hence, there is a disparity between its two Cu-N coordinate bonds arising from weakening of the apical one as a consequence of the tetragonal distortion. The axial X-band ESR spectrum of complex 1 is consistent with retention of this structure in solution. Complex 2 is a centrosymmetric dimer of dinuclear copper(II) complex molecules exhibiting intermolecular H-bonding and π-π-stacking interactions. The two copper(II) centres, which are 4.8067(18) Å apart and bridged by the thio-enolate nitrogen of the quadridentate thiosemicarbazonate ligand, display two different coordination geometries, one distorted square planar (τ4 = 0.082) and the other distorted square pyramidal (τ5 = 0.33). Such dinuclear copper(II) thiosemicarbazone complexes, which are crystallographically characterised, are extremely rare. In vitro, complexes 1 and 2 outperform cisplatin as antiproliferative agents in terms of potency and selectivity towards HeLa and MCF-7 cancer cell lines.

Human Serum Albumin-Platinum(II) Agent Nanoparticles Inhibit Tumor Growth Through Multimodal Action Against the Tumor Microenvironment

To overcome the limitations of traditional platinum (Pt)-based drugs and further improve the targeting ability and therapeutic efficacy in vivo, we proposed to design a human serum albumin (HSA)-Pt agent complex nanoparticle (NP) for cancer treatment by multimodal action against the tumor microenvironment. We not only synthesized a series of Pt(II) di-2-pyridone thiosemicarbazone compounds and obtained a Pt(II) agent [Pt(Dp44mT)Cl] with significant anticancer activity but also successfully constructed a novel HSA-Pt(Dp44mT) complex nanoparticle delivery system. The structure of the HSA-Pt(Dp44mT) complex revealed that Pt(Dp44mT)Cl binds to the IIA subdomain of HSA and coordinates with His-242. The HSA-His242-Pt-Dp44mT NPs had an obvious effect on the inhibition of tumor growth, which was superior to that of Dp44mT and Pt(Dp44mT)Cl, and they had almost no toxicity. In addition, the HSA-His242-Pt-Dp44mT NPs were found to kill cancer cells by inducing apoptosis, autophagy, and inhibiting angiogenesis.

Combined In Silico and In Vitro Analyses to Assess the Anticancer Potential of Thiazolidinedione-Thiosemicarbazone Hybrid Molecules

The number of people affected by cancer and antibiotic-resistant bacterial infections has increased, such that both diseases are already seen as current and future leading causes of death globally. To address this issue, based on a combined in silico and in vitro approach, we explored the anticancer potential of known antibacterials with a thiazolidinedione-thiosemicarbazone (TZD-TSC) core structure. A cytotoxicity assessment showed encouraging results for compounds 2-4, with IC50 values against T98G and HepG2 cells in the low micromolar range. TZD-TSC 3 proved to be most toxic to cancer cell lines, with IC50 values of 2.97 ± 0.39 µM against human hepatoma HepG2 cells and IC50 values of 28.34 ± 2.21 µM against human glioblastoma T98G cells. Additionally, compound 3 induced apoptosis and showed no specific hemolytic activity. Furthermore, treatment using 3 on cancer cell lines alters these cells' morphology and further suppresses migratory activity. Molecular docking, in turn, suggests that 3 would have the capacity to simultaneously target HDACs and PPARγ, by the activation of PPARγ and the inhibition of both HDAC4 and HDAC8. Thus, the promising preliminary results obtained with TZD-TSC 3 represent an encouraging starting point for the rational design of novel chemotherapeutics with dual antibacterial and anticancer activities.

Design, synthesis, biological activities, and evaluation of molecular docking-dynamics studies of new thiosemicarbazones that may be effective against Alzheimer's disease

Donepezil is one of the most used drugs in the treatment of Alzheimer's disease. Its activity as an AChE inhibitor makes new studies with these enzyme inhibitors attractive. For this purpose, in this study, 12 compounds including thiosemicarbazone pharmacophore, have been synthesized for the treatment of the Alzheimer's disease. 3,4-Dimethoxybenzene or 1,3-benzodioxolone rings were used for the PAS region. The substituted piperazine benzene structure is preferred for the CAS region. At the same time, the thiosemicarbazone pharmacophore structure with known ChE enzyme inhibition potential was used as a bridge connecting the CAS and PAS regions. Structure determination of compounds 3a-3l were revealed using 13 C-NMR, 1 H-NMR, and HRMS spectroscopic methods. The inhibition profile of obtained compounds (3a-3l) against ChE was evaluated using in vitro modified Ellman method. Compounds 3a, 3b, 3f, 3g and 3i exhibited inhibitory activity against the AChE enzyme. Compound 3a showed the highest inhibitory potential with an IC50  = 0.030 ± 0.001 μM. As a result of molecular docking studies, compound 3a displayed important interactions compared to other active derivatives. Molecular dynamics studies are important to see the stability of the complex formed by ligand and protein. RMSD, RMSF ang Rg parameters were calculated via dynamic studies. In conclusion, compound 3a may be a potential AChE enzyme inhibitor with its strong inhibitory potential and behavior in silico.

Discovery of novel thiosemicarbazone derivatives with potent and selective anti-Candida glabrata activity

A series of 21 novel compounds containing a thiosemicarbazone moiety were designed and synthesised based on hit compound 1 from our in-house compound library screening. Most compounds showed potent antifungal activity in vitro against seven common pathogenic fungi. Notably, all compounds showed high potency against Candida glabrata 537 (MIC = ≤0.0156-2 µg/mL). Of note, compounds 5j and 5r displayed excellent antifungal activity against Candida krusei 4946 and Candida auris 922. Additionally, compounds 5j and 5r also showed high potency against 15 C. glabrata isolates with MIC values ranging from 0.0625 µg/mL to 4 µg/mL, with compound 5r being slightly superior to 5j. Moreover, compound 5r has certain effect against biofilm formation of C. glabrata. Furthermore, compound 5r has minimal cytotoxicity against HUVECs with an IC₅₀ value of 15.89 µg/mL and no haemolysis at 64 µg/mL. Taken together, these results suggest that promising lead compound 5r deserves further investigation.

Synthesis, biological evaluation, and molecular docking study of xanthene-linked thiosemicarbazones as cholinesterase inhibitors

This study delineates the design and synthesis of a series of xanthene-based thiosemicarbazones that show low μM inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), crucial enzymes associated with, among others, Alzheimer's Disease (AD) pathology. Despite FDA-approved AChE inhibitors being frontline treatments for AD, there remains a need for agents exhibiting improved efficacy and selectivity. Our synthesized series demonstrate meaningful inhibition against AChE (IC50 ranging from 4.2 to 62 μM). These compounds exhibit comparatively lower potency against BChE (IC50 values between 64 and 315 μM), showcasing a pronounced AChE selectivity compared to physostigmine. The selectivity index for the compounds between the two targets does vary between 0.02 and 0.75 highlighting that even minor structural differences can have drastic effects on protein interactions. Molecular docking insights further substantiated these observations, revealing the importance of the xanthene scaffold for AChE-binding and the aryl R2 moiety for BChE interactions. Notably, some compounds demonstrated dual enzyme targeting, emphasizing their interactions could be exploited for developing monotherapies against cholinesterase-associated neurodegenerative afflictions like AD. Collectively, these findings suggest that xanthene-based thiosemicarbazones are a promising and highly accessible scaffold that deserve further investigative exploration in the cholinesterase inhibitor therapeutic landscape.Communicated by Ramaswamy H. Sarma.

2-Oxoquinoline-based-thiosemicarbazones as multitargeting neurotherapeutics against Alzheimer's disease: In vitro and in silico studies of MAO and ChE inhibitors

Alzheimer's disease (AD) presents a multifactorial neurological disorder with multiple enzyme involvement in its onset. Conventional monotherapies fall short in providing long-term relief, necessitating the exploration of alternative multitargeting approaches to address the complexity of AD. Therefore, the design, synthesis, and in vitro and in silico evaluation of 2-oxoquinoline-based thiosemicarbazones 9a-r as multipotent analogs, able to simultaneously inhibit the cholinesterase (ChE) and monoamine oxidase (MAO) enzymes for the potential treatment of AD, are reported. In the in vitro experimental evaluation of MAO and ChE inhibition, all tested compounds demonstrated remarkable potency exhibiting nonselective inhibition of both MAO-A and MAO-B, and selective inhibition of acetylcholinesterase (AChE) over butyrylcholinesterase (BChE), with 9d, 9j, and 9m evolving as lead compounds for MAO-A, MAO-B, and AChE, displaying IC50 values of 0.35 ± 0.92, 0.50 ± 0.02, and 0.25 ± 0.13 μM, respectively. Moreover, the kinetic studies revealed that all tested compounds inhibited all three enzymes through a competitive mode of inhibition. Furthermore, the molecular docking studies of the most active compounds revealed several crucial interactions, particularly hydrogen bonding interactions. These interactions were observed between the nitrogen and sulfur atoms of thiosemicarbazone and the nitrogen and oxygen atoms of the quinoline ring with various amino acids, suggesting the strong interactions of these compounds with the enzymes.

Microwave-assisted solvent-free synthesis of some novel thiazole-substituted thiosemicarbazone analogues: antimicrobial and anticancer studies

The increased resistance to antibiotics has compelled researchers to devise novel active compounds targeting multidrug-resistant pathogenic microorganisms. A series of thiosemicarbazone derivatives was synthesized by reacting thiosemicarbazide with 2-aryl-4-formylthiazole, 2-aryl-5-formyl-4-methylthiazole, and/or 5-acetyl-2-aryl-4-methylthiazole compounds. These thiosemicarbazone-based thiazole adducts were evaluated for their inhibitory activities against tuberculosis H37Ra and Bovis BCG mycobacteria. Their cytotoxicity was assessed against two cancer cell lines: colonic carcinoma (HCT-116) and cervical cancer (HeLa). Notably, these thiosemicarbazones exhibited minimal cytotoxic effects on these cell lines even at their highest concentrations. Furthermore, the prepared thiosemicarbazone derivatives demonstrated significant antimicrobial efficacy against Bacillus subtilis and Staphylococcus aureus (Gram-positive bacterial pathogens) as well as Escherichia coli and Pseudomonas fluorescens (Gram-negative bacterial pathogens). While most of the prepared thiosemicarbazone derivatives exhibited moderate activity against Candida albicans (a fungal strain), their performance was notable. The thiosemicarbazone-based thiazole adducts were also successfully synthesized using a solvent-free approach under microwave irradiation. Compared with conventional reflux methods, the microwave-assisted technique yielded high thiazole yields within just 5 min, obviating the need for catalysis. This study signifies significant strides toward the rational design of more potent antimycobacterial agents.

New Amino Acid-Based Thiosemicarbazones and Hydrazones: Synthesis and Evaluation as Fluorimetric Chemosensors in Aqueous Mixtures

Bearing in mind the interest in the development and application of amino acids/peptides as bioinspired systems for sensing, a series of new phenylalanine derivatives bearing thiosemicarbazone and hydrazone units at the side chain were synthesised and evaluated as fluorimetric chemosensors for ions. Thiosemicarbazone and hydrazone moieties were chosen because they are considered both proton-donor and proton-acceptor, which is an interesting feature in the design of chemosensors. The obtained compounds were tested for the recognition of organic and inorganic anions (such as AcO-, F-, Cl-, Br-, I-, ClO4-, CN-, NO3-, BzO-, OH-, H2PO4- and HSO4-) and of alkaline, alkaline-earth, and transition metal cations, (such as Na+, K+, Cs+, Ag+, Cu+, Cu2+, Ca2+, Cd2+, Co2+, Pb2+, Pd2+, Ni2+, Hg2+, Zn2+, Fe2+, Fe3+ and Cr3+) in acetonitrile and its aqueous mixtures in varying ratios via spectrofluorimetric titrations. The results indicate that there is a strong interaction via the donor N, O and S atoms at the side chain of the various phenylalanines, with higher sensitivity for Cu2+, Fe3+ and F- in a 1:2 ligand-ion stoichiometry. The photophysical and metal ion-sensing properties of these phenylalanines suggest that they might be suitable for incorporation into peptide chemosensory frameworks.

Synthesis and Biological Activity of Piperidinothiosemicarbazones Derived from Aminoazinecarbonitriles

To investigate how structural modifications affect tuberculostatic potency, we synthesized seven new piperidinothiosemicrabazone derivatives 8-14, in which three of them had a pyrazine ring replacing the pyridine ring. Derivatives 8-9 and 13-14 exhibited significant activity against the standard strain (minimum inhibitory concentration (MIC) 2-4 μg/mL) and even greater activity against the resistant M. tuberculosis strain (MIC 0.5-4 μg/mL). Additionally, the effects of compounds 8-9 were entirely selective (MIC toward other microorganisms ≥ 1000 μg/mL) and non-toxic (IC50 to HaCaT cells 5.8 to >50 μg/mL). The antimycobacterial activity of pyrazine derivatives 11-12 was negligible (MIC 256 to >500 μg/mL), indicating that replacing the aromatic ring was generally not a promising line of research in this case. The zwitterionic structure of compound 11 was determined using X-ray crystallography. Absorption, distribution, metabolism, and excretion (ADME) calculations showed that all compounds, except 11, could be considered for testing as future drugs. An analysis of the structure-activity relationship was carried out, indicating that the higher basicity of the substituent located at the heteroaromatic ring might be of particular importance for the antituberculous activity of the tested groups of compounds.

Inhibition of Topoisomerases by Metal Thiosemicarbazone Complexes

Topoisomerases, common targets for anti-cancer therapeutics, are crucial enzymes for DNA replication, transcription, and many other aspects of DNA metabolism. The potential anti-cancer effects of thiosemicarbazones (TSC) and metal-TSC complexes have been demonstrated to target several biological processes, including DNA metabolism. Human topoisomerases were discovered among the molecular targets for TSCs, and metal-chelated TSCs specifically displayed significant inhibition of topoisomerase II. The processes by which metal-TSCs or TSCs inhibit topoisomerases are still being studied. In this brief review, we summarize the TSCs and metal-TSCs that inhibit various types of human topoisomerases, and we note some of the key unanswered questions regarding this interesting class of diverse compounds.

Crystal Design, Antitumor Activity and Molecular Docking of Novel Palladium(II) and Gold(III) Complexes with a Thiosemicarbazone Ligand

The current research describes the synthesis and characterization of 2-acetylpyridine N(4)-cyclohexyl-thiosemicarbazone ligand (HL) and their two metal complexes, [Au(L)Cl][AuCl₂] (1) and [Pd(L)Cl]·DMF (2). The molecular structures of the compounds were determined by physicochemical and spectroscopic methods. Single crystal X-ray diffraction was employed in the structural elucidation of the new complexes. The complexes showed a square planar geometry to the metal center Au(III) and Pd(II), coordinated with a thiosemicarbazone molecule by the NNS-donor system and a chloride ion. Complex (1) also shows the [AuCl₂]^- counter-ion in the asymmetric unit, and complex (2) has one DMF solvent molecule. These molecules play a key role in the formation of supramolecular structures due to different interactions. Noncovalent interactions were investigated through the 3D Hirshfeld surface by the d_norm function and the 2D fingerprint plots. The biological activity of the compounds was evaluated in vitro against the human glioma U251 cells. The cytotoxicity results revealed great antitumor activity in complex (1) compared with complex (2) and the free ligand. Molecular docking simulations were used to predict interactions and properties with selected proteins and DNA of the synthesized compounds.

Synthesis, structure, ADME and biological activity of three 2,6-disubstituted thiosemicarbazone derivatives

Three new 2,6-disubstituted thiosemicarbazone derivatives of pyridine, namely, 2-{amino[6-(pyrrolidin-1-yl)pyridin-2-yl]methylidene}-N,N-dimethylhydrazine-1-carbothioamide, C₁₃H₂₀N₆S, 2-{amino[6-(piperidin-1-yl)pyridin-2-yl]methylidene}-N,N-dimethylhydrazine-1-carbothioamide, C₁₄H₂₂N₆S, and 2-[amino(6-phenoxypyridin-2-yl)methylidene]-N,N-dimethylhydrazine-1-carbothioamide monohydrate, C₁₅H₁₇N₅OS·H₂O, have been synthesized and characterized by NMR spectroscopy and low-temperature single-crystal X-ray diffraction. In addition, their antibacterial and anti-yeast activities have been determined. The ability of the tested compounds to inhibit bacterial growth was comparable to vancomycin as a reference drug. Compared to isoniazid (MIC 0.125 and 8 µg ml^-1), the compounds showed the ability to inhibit the growth of Mycobacterium tuberculosis to a moderate degree for the standard strain and at the same level or higher (MIC 4-8 µg ml^-1) for the resistant strain. All three compounds adopt the zwitterionic form in the crystal structure regardless of the presence or absence of solvent molecules.

TZD-Based Hybrid Molecules Act as Dual Anti-Mycobacterium tuberculosis and Anti-Toxoplasma gondii Agents

Two distinct intracellular pathogens, namely Mycobacterium tuberculosis (Mtb) and Toxoplasma gondii (Tg), cause major public health problems worldwide. In addition, serious and challenging health problems of co-infections of Tg with Mtb have been recorded, especially in developing countries. Due to this fact, as well as the frequent cases of resistance to the current drugs, novel anti-infectious therapeutics, especially those with dual (anti-Tg and anti-Mtb) modes of action, are needed. To address this issue, we explored the anti-Tg potential of thiazolidinedione-based (TZD-based) hybrid molecules with proven anti-Mtb potency. Several TZD hybrids with pyridine-4-carbohydrazone (PCH) or thiosemicarbazone (TSC) structural scaffolds were more effective and more selective than sulfadiazine (SDZ) and trimethoprim (TRI). Furthermore, all of these molecules were more selective than pyrimethamine (PYR). Further studies for the most potent TZD-TSC hybrids 7, 8 and 10 and TZD-PCH hybrid molecule 2 proved that these compounds are non-cytotoxic, non-genotoxic and non-hemolytic. Moreover, they could cross the blood-brain barrier (BBB), which is a critical factor linked with ideal anti-Tg drug development. Finally, since a possible link between Tg infection and the risk of glioblastoma has recently been reported, the cytotoxic potential of TZD hybrids against human glioblastoma cells was also evaluated. TZD-PCH hybrid molecule 2 was found to be the most effective, with an IC₅₀ of 19.36 ± 1.13 µg/mL against T98G cells.

Synthesis and Structure-Activity Relationship of 2,6-Disubstituted Thiosemicarbazone Derivatives of Pyridine as Potential Antituberculosis Agents

In this study, six new 2,6-disubstituted thiosemicarbazone derivatives of pyridine were synthesized (4−9), and their tuberculostatic activity was evaluated. All of them showed two- to eightfold higher activity (minimum inhibitory concentration (MIC) 0.5−4 µg/mL) against the resistant strain compared with the reference drug. Compounds 5 and 7, which contained the most basic substituents—pyrrolidine and piperidine—in their structure, strongly inhibited the growth of the standard strain (MIC 2 µg/mL). Furthermore, the same derivatives exhibited activity comparable to that of the reference drugs against some types of Gram-positive bacteria (MIC 0.49 µg/mL) and showed no cytotoxicity (IC50 > 50 µg/mL) in HaCaT cells. The zwitterionic structure of each compound was determined using X-ray crystallography. Absorption, distribution, metabolism, and excretion analyses showed that all compounds are good drug candidates. Thus, compounds 5 and 7 were identified as leading structures for further research on antituberculosis drugs with extended effects.

FeIII in the high-spin state in dimethylammonium bis[3-ethoxysalicylaldehyde thiosemicarbazonato(2-)-κ3O2,N1,S]ferrate(III)

The synthesis and crystal structure (100 K) of the title compound, [(CH₃)₂NH₂][Fe(C₁₀H₁₁O₂N₃S)₂], are reported. The asymmetric unit consists of an octahedral [Fe^III(L)₂]^- fragment, where L^2- is 3-ethoxysalicylaldehyde thiosemicarbazonate(2-), and a dimethylammonium cation. Each L^2- ligand binds with the thiolate S, the imine N and the phenolate O atoms as donors, resulting in an Fe^IIIS₂N₂O₂ chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis positions, and mutually trans N atoms. The Fe^III ion is in the high-spin state at 100 K. The variable-temperature magnetic susceptibility measurements (5-320 K) are consistent with the presence of a high-spin Fe^III ion with D = 0.83 (1) cm^-1 and g = 2.

Phenotypic and in silico studies for a series of synthetic thiosemicarbazones as New Delhi metallo-beta-lactamase carbapenemase inhibitors

The past two decades have been marked by a global spread of bacterial resistance to β-lactam drugs and carbapenems derivatives are the ultimate treatment against multidrug-resistant bacteria. β-lactamase expression is related to resistance which demands the development of bacterial resistance blockers. Drug inhibitor combinations of serine-β-lactamase and β-lactam were successful employed in therapy despite their inactivity against New Delhi metallo-beta-lactamase (NDM). Until now, few compounds are active against NDM-producing bacteria and no specific inhibitors are available yet. The rational strategy for NDM inhibitors development starts with in vitro assays aiming to seek compounds that could act synergistically with β-lactam antibiotics. Thus, eight thiosemicarbazone derivatives were synthesized and investigated for their ability to reverse the resistant phenotype in NDM in Enterobacter cloacae. Phenotypic screening indicated that four isatin-beta-thiosemicarbazones showed Fractional Inhibitory Concentration (FIC) ≤ 250 µM in the presence of meropenem (4 µg/mL). The most promising compound (FIC= 31.25 µM) also presented synergistic effect (FICI = 0.34). Docking and molecular dynamics studies on NDM-thiosemicarbazone complex suggested that 2,3-dihydro-1H-indol-2-one subunit interacts with catalytic zinc and interacted through hydrogen bonds with Asp124 acting like a carboxylic acid bioisostere. Additionally, thiosemicarbazone tautomer with oxidized sulfur (thione) seems to act as a spacer rather than zinc chelator, and the aromatic moieties are stabilized by pi-pi and cation-pi interactions with His189 and Lys221 residues. Our results addressed some thiosemicarbazone structural changes to increase its biological activity against NDM and highlight its scaffold as promising alternatives to treat bacterial resistance.Communicated by Ramaswamy H. Sarma.

QSAR Studies, Molecular Docking, Molecular Dynamics, Synthesis, and Biological Evaluation of Novel Quinolinone-Based Thiosemicarbazones against Mycobacterium tuberculosis

In this study, a series of novel quinolinone-based thiosemicarbazones were designed in silico and their activities tested in vitro against Mycobacterium tuberculosis (M. tuberculosis). Quantitative structure-activity relationship (QSAR) studies were performed using quinolinone and thiosemicarbazide as pharmacophoric nuclei; the best model showed statistical parameters of R² = 0.83; F = 47.96; s = 0.31, and was validated by several different methods. The van der Waals volume, electron density, and electronegativity model results suggested a pivotal role in antituberculosis (anti-TB) activity. Subsequently, from this model a new series of quinolinone-thiosemicarbazone 11a-e was designed and docked against two tuberculosis protein targets: enoyl-acyl carrier protein reductase (InhA) and decaprenylphosphoryl-β-D-ribose-2'-oxidase (DprE1). Molecular dynamics simulation over 200 ns showed a binding energy of -71.3 to -12.7 Kcal/mol, suggesting likely inhibition. In vitro antimycobacterial activity of quinolinone-thiosemicarbazone for 11a-e was evaluated against M. bovis, M. tuberculosis H37Rv, and six different strains of drug-resistant M. tuberculosis. All compounds exhibited good to excellent activity against all the families of M. tuberculosis. Several of the here synthesized compounds were more effective than the standard drugs (isoniazid, oxafloxacin), 11d and 11e being the most active products. The results suggest that these compounds may contribute as lead compounds in the research of new potential antimycobacterial agents.

Introducing N-Heteroaromatic Bases into Copper(II) Thiosemicarbazon Complexes: A Way to Change their Biological Activity

Three new copper(II) complexes, [Cu(1,10-Phen)(L)] (1), [Cu(2,2'-Bpy)(L)] (2) and [Cu(3,4-Lut)(L)] (3), where H₂ L=2-[(2,4-dihydroxyphenyl)methylidene]-N-(prop-2-en-1-yl)hydrazine-1-carbothioamide, 1,10-Phen=1,10-phenanthroline, 2,2'-Bpy=2,2'-bipyridine, 3,4-Lut=3,4-lutidine, have been synthesized and characterized by elemental analysis, FTIR spectroscopy and single crystal X-ray crystallography (1, 2). All compounds are mononuclear. The introduction of a monodentate N-heteroaromatic base (3,4-dimethylpyridine) has led to a significant increase of antimicrobial activity against Gram-negative Escherichia coli and antifungal activity against Candida albicans compared to the pro-ligand and the precursor complex [Cu(L)H₂ O]. The introduction of bidentate N-heteroaromatic bases did not lead to such increase of antimicrobial and antifungal activities. Moreover, complex 3 surpasses the inhibitory activity of tetracycline toward Enterobacter cloacae and the inhibitory activity of fluconazole toward Candida parapsilosis and Cryptococcus neoformans. The study of antioxidant activity against cation radicals ABTS⋅⁺ showed that complexes 1-3 are more active than Trolox, but only introduction of the monodentate N-heteroaromatic base (3,4-dimethylpyridine) led to the increase of antioxidant properties compared to the precursor complex.

Synthesis of New Triazole-Based Thiosemicarbazone Derivatives as Anti-Alzheimer's Disease Candidates: Evidence-Based In Vitro Study

Triazole-based thiosemicarbazone derivatives (6a-u) were synthesized then characterized by spectroscopic techniques, such as 1HNMR and 13CNMR and HRMS (ESI). Newly synthesized derivatives were screened in vitro for inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. All derivatives (except 6c and 6d, which were found to be completely inactive) demonstrated moderate to good inhibitory effects ranging from 0.10 ± 0.050 to 12.20 ± 0.30 µM (for AChE) and 0.20 ± 0.10 to 14.10 ± 0.40 µM (for BuChE). The analogue 6i (IC₅₀ = 0.10 ± 0.050 for AChE and IC₅₀ = 0.20 ± 0.050 µM for BuChE), which had di-substitutions (2-nitro, 3-hydroxy groups) at ring B and tri-substitutions (2-nitro, 4,5-dichloro groups) at ring C, and analogue 6b (IC₅₀ = 0.20 ± 0.10 µM for AChE and IC₅₀ = 0.30 ± 0.10 µM for BuChE), which had di-Cl at 4,5, -NO₂ groups at 2-position of phenyl ring B and hydroxy group at ortho-position of phenyl ring C, emerged as the most potent inhibitors of both targeted enzymes (AChE and BuChE) among the current series. A structure-activity relationship (SAR) was developed based on nature, position, number, electron donating/withdrawing effects of substitution/s on phenyl rings. Molecular docking studies were used to describe binding interactions of the most active inhibitors with active sites of AChE and BuChE.

A Thiosemicarbazone Derivative as a Booster in Photodynamic Therapy-A Way to Improve the Therapeutic Effect

Photodynamic therapy is one of the most patient friendly and promising anticancer therapies. The active ingredient is irradiated protoporphyrin IX, which is produced in the body that transfers energy to the oxygen-triggering phototoxic reaction. This effect could be enhanced by using iron chelators, which inhibit the final step of heme biosynthesis, thereby increasing the protoporphyrin IX concentration. In the presented work, we studied thiosemicarbazone derivative, which is a universal enhancer of the phototoxic effect. We examined several genes that are involved in the transport of the heme substrates and heme itself. The results indicate that despite an elevated level of ABCG2, which is responsible for the PpIX efflux, its concentration in a cell is sufficient to trigger a photodynamic reaction. This effect was not observed for 5-ALA alone. The analyzed cell lines differed in the scale of the effect and a correlation with the PpIX accumulation was observed. Additionally, an increased activation of the iron transporter MFNR1 was also detected, which indicated that the regulation of iron transport is essential in PDT.

Synthesis of novel thiosemicarbazone derivatives and investigation of their dual AChE and MAO-B inhibitor effects

In this study, 15 thiosemicarbazone derivatives were synthesized. Analysis of the obtained compounds was performed by means of ¹ H-NMR, ¹³ C-NMR and high resolution mass spectroscopy (HRMS) spectroscopic methods. The inhibition effect of the obtained compounds on cholinesterase and monoaminoxidase (MAO) enzymes were investigated with in vitro methods. None of the compounds showed significant activity on the butyrylcholinesterase enzyme. On the other hand, compounds 3b, 3c, 3e, 3k, 3l, 3m, 3n and 3o displayed significant activity on acetylcholinesterase (AChE) while compounds 3f, 3i, 3k, 3l, 3m, 3n, 3o also showed remarkable effects on monoamine oxidase-B (MAO-B) enzymes. For the selected compounds, docking studies were performed and the enzyme active site and binding modes were determined. It was revealed that the strongest interaction with AChE and MAO-B enzyme active sites was observed with the compound 3k. Another important factor in the treatment of diseases affecting the central nervous system such as Alzheimer's is the ability of the compounds to cross the blood-brain barrier (BBB). Additionally, the agents planned for the treatment of these diseases must also pass the blood-brain barrier. Therefore, in silico BBB penetration properties of active compounds were investigated.

Synthesis, Characterization, and Cytotoxicity Studies of N-(4-Methoxybenzyl) Thiosemicarbazone Derivatives and Their Ruthenium(II)-p-cymene Complexes

The reaction of [Ru₂Cl₂(μ-Cl)₂(η⁶-p-cymene)₂] with two thiosemicarbazones obtained by the condensation of N-(4-methoxybenzyl) thiosemicarbazide and 1,4-hydroxy-3-methoxyphenyl)ethan-1-one (HL¹) or 2-fluoro-4-hydroxybenzaldehyde (HL²) was studied. The cationic complexes of formula [RuCl(η⁶-p-cymene)(HL)]⁺ were isolated as solid chloride and trifluoromethylsulfate (TfO) salts. A study of the solid state and NMR spectra suggests the presence in the material of two isomers that differ in the configuration in the iminic bond, C2=N3, of the coordinated thiosemicarbazone in the triflate salts and only the E isomer in the chloride. An X-ray study of single crystals of the complexes supports this hypothesis. The thiosemicarbazone ligand coordinates with the ruthenium center through the iminic and sulfur atoms to form a five-membered chelate ring. Furthermore, the isolation of single crystals containing the thiosemicarbazonate complex [Ru₂(μ-L²)₂(η⁶-p-cymene)₂]²⁺ suggests the easy labilization of the coordinated chloride in the complex. The redox behavior of the ligands and complexes was evaluated by cyclic voltammetry. It seems to be more difficult to oxidize the complex derived from HL¹ than HL². The ability of the complexes to inhibit cell growth against the NCI-H460, A549 and MDA-MB-231 lines was evaluated. The complexes did not show greater potency than cisplatin, although they did have greater efficacy, especially for the complex derived from HL¹.

Biomolecular Interactions of Cytotoxic Ruthenium Compounds with Thiosemicarbazone or Benzothiazole Schiff Base Chelates

Herein we illustrate the formation and characterization of new paramagnetic ruthenium compounds, trans-P-[RuCl(PPh₃ )₂ (pmt)]Cl (1) (Hpmt=1-((pyridin-2-yl)methylene)thiosemicarbazide), trans-P-[RuCl(PPh₃ )₂ (tmc)]Cl (2) (Htmc=1-((thiophen-2-yl)methylene)thiosemicarbazide) and a diamagnetic ruthenium complex, cis-Cl, trans-P-[RuCl₂ (PPh₃ )₂ (btm)] (3) (btm=2-((5-hydroxypentylimino)methyl)benzothiazole). Agarose gel electrophoresis experiments of the metal compounds illustrated dose-dependent binding to gDNA by 1-3, while methylene blue competition assays suggested that 1 and 2 are also DNA intercalators. Assessment of the effects of the compounds on topoisomerase function indicated that 1-3 are capable of inhibiting topoisomerase I activity in terms of the ability to nick supercoiled plasmid DNA. The cytotoxic activities of the metal complexes were determined against a range of cancer cell lines versus a non-tumorigenic control cell line, and the complexes were, in general, more cytotoxic towards the cancer cells, displaying IC₅₀ values in the low micromolar range. Time-dependent stability studies showed that in the presence of strong nucleophilic species (such as DMSO), the chloride co-ligands of 1-3 are rapidly substituted by the former as proven by the suppression of the substitution reactions in the presence of an excess amount of chloride ions. The metal complexes are significantly stable in both DCM and an aqueous phosphate buffer containing 2 % DMSO.

Benzimidazole Bearing Thiosemicarbazone Derivatives Act as Potent α-Amylase and α-Glucosidase Inhibitors; Synthesis, Bioactivity Screening and Molecular Docking Study

Diabetes mellitus is one of the most chronic metabolic diseases. In the past few years, our research group has synthesized and evaluated libraries of heterocyclic analogs against α-glucosidase and α-amylase enzymes and found encouraging results. The current study comprises the evaluation of benzimidazole-bearing thiosemicarbazone as antidiabetic agents. A library of fifteen derivatives (7-21) was synthesized, characterized via different spectroscopic techniques such as HREI-MS, NMR, and screened against α-glucosidase and α-amylase enzymes. All derivatives exhibited excellent to good biological inhibitory potentials. Derivatives 19 (IC₅₀ = 1.30 ± 0.20 µM and 1.20 ± 0.20 µM) and 20 (IC₅₀ = 1.60 ± 0.20 µM and 1.10 ± 0.01 µM) were found to be the most potent among the series when compared with standard drug acarbose (IC₅₀ = 11.29 ± 0.07 and 11.12 ± 0.15 µM, respectively). These derivatives may potentially serve as the lead candidates for the development of new therapeutic representatives. The structure-activity relationship was carried out for all molecules which are mainly based upon the pattern of substituent/s on phenyl rings. Moreover, in silico docking studies were carried out to investigate the active binding mode of selected derivatives with the target enzymes.

Gallium(III)-Pyridoxal Thiosemicarbazone Derivatives as Nontoxic Agents against Gram Negative Bacteria

Many bacterial strains are developing mechanism of resistance to antibiotics, rendering last-resort antibiotics inactive. Therefore, new drugs are needed and in particular metal-based compounds represent a valid starting point to explore new antibiotic classes. In this study we have chosen to investigate gallium(III) complexes for their potential antimicrobial activity against different strains of Klebsiella pneumoniae, Escherichia coli and Pseudomonas aeruginosa which have developed different type of resistance mechanism, including the expression of β-lactamases (NDM-1, ESβL or AmpC) or the production of biofilm. We studied a series of thiosemicarbabazones derived from pyridoxal, their related Ga(III) complexes, and the speciation in solution of the Ga(III)/ligand systems as a function of the pH. Proton dissociation constants and conditional stability constants of Ga(III) complexes were evaluated by UV/Vis spectroscopy, and the most relevant species at physiological pH were identified. The compounds are active against resistant Gram negative strain with minimal inhibitory concentration in the μM range, while no cytotoxicity was detected in eukaryotic cells.

Half-Sandwich Arene Ruthenium(II) Thiosemicarbazone Complexes: Evaluation of Anticancer Effect on Primary and Metastatic Ovarian Cancer Cell Lines

In this study, we describe the synthesis, characterization and antiproliferative activity of three organo-ruthenium(II) half-sandwich complexes [RuCl(η⁶-p-cym)(N,S-L)]Cl (I, II, and III). To form these complexes, three thiosemicarbazone ligands (TSCs) were synthesized; L = 5-nitro-2-carboxyaldehyde-thiophen-N-methyl-thiosemicarbazone, (L1); 2-acetyl-5-bromo-thiophen-N-methyl-thiosemicarbazone, (L2) and 2-acetyl-5-bromo-thiophen-N,N-dimethyl-thiosemicarbazone, (L3). The isolated compounds were analyzed using spectroscopic techniques such as elemental analysis, conductance measurements, FT-IR, ¹H NMR spectroscopy, MALDI-TOF mass spectrometry, and single-crystal XRD. Our results demonstrated that the synthesized thiosemicarbazone ligands (TSCs) are bound to the metal ion as a bidentate ligand that coordinates through the thiocarbonyl sulfur and azomethine nitrogen atoms in all complexes (I, II, and III). The X-ray crystal structures of L1 and L2 revealed that both compounds are crystallized in the triclinic crystal system with space group P-1. The biological potency of newly synthesized TSC ligands (L1, L2, and L3) and their corresponding ruthenium complexes (I, II, and III) were investigated on human primary ovarian (A2780) and human metastatic ovarian (OVCAR-3) cell lines. To get detailed information respecting antitumor properties, cytotoxicity, DNA/BSA binding affinity, cellular uptake, DNA binding competition, and trans-epithelial resistance measurement assays were performed. Our results demonstrate that newly synthesized ruthenium(II) complexes possess potential biological activity. Moreover, we observe that the ruthenium complexes reported here show anticancer activity on primary (A2780) and metastatic (OVCAR-3) ovarian cancer cells.

A new series of thiosemicarbazone-based anti-inflammatory agents exerting their action through cyclooxygenase inhibition

In an endeavor to identify potent anti-inflammatory agents, new thiosemicarbazones (TSCs) incorporated into a diaryl ether framework (2a-2l) were prepared and screened for their in vitro inhibitory effects on cyclooxygenases (COXs). 4-[4-(Piperidin-1-ylsulfonyl)phenyl]-1-[4-(4-cyanophenoxy)benzylidene]thiosemicarbazide (2c) was the most potent and selective COX-1 inhibitor in this series, with an IC₅₀ value of 1.89 ± 0.04 µM. On the other hand, 4-[4-(piperidin-1-ylsulfonyl)phenyl]-1-[4-(4-nitrophenoxy)benzylidene]thiosemicarbazide (2b) was identified as a nonselective COX inhibitor (COX-1 IC₅₀  = 13.44 ± 0.65 µM, COX-2 IC₅₀  = 12.60 ± 0.78 µM). Based on molecular docking studies, the diaryl ether and the TSC groups serve as crucial moieties for interactions with pivotal amino acid residues in the active sites of COXs. According to MTT test, compounds 2b and 2c showed low cytotoxic activity toward NIH/3T3 cells. Their in vivo anti-inflammatory and antioxidant potencies were also assessed using the lipopolysaccharide-induced sepsis model. Compounds 2b and 2c diminished high-sensitivity C-reactive protein, myeloperoxidase, nitric oxide, and malondialdehyde levels. Both compounds also caused a significant decrease in aspartate aminotransferase levels as well as alanine aminotransferase levels. In silico pharmacokinetic studies suggest that compounds 2b and 2c possess favorable drug-likeness and oral bioavailability. It can be concluded that these compounds may act as orally bioavailable anti-inflammatory and antioxidant agents.

Design, synthesis, cytotoxicity, and molecular docking studies of novel thiazolyl-hydrazone derivatives as histone lysine acetyl-transferase inhibitors and apoptosis inducers

Compounds containing both thiazole and arylsulfone moieties are recognized for their high biological activity and ability to fight a variety of ailments. Thus, in this context, new derivatives of (thiazol-2-yl)hydrazone with an arylsulfone moiety were synthesized as CPTH2 analogs with potent anti-histone lysine acetyl-transferase activity. Compounds 3, 4, 10b, and 11b showed an excellent inhibitory effect on P300 (E1A-associated protein p300), compared to CPTH2. Among all the tested derivatives, compound 10b revealed the highest activity against both P300 and pCAF. In addition, the new hits were tested for anticancer efficacy against two leukemia cell lines. Most of them showed a moderate to potent antitumor effect on the k562 and CCRF-CEM cell lines. Interestingly, the activity of compound 10b against the k562 cell line was found to be higher than that of CPTH2. Furthermore, it showed a good safety profile, better than CPTH2 on normal cells. Molecular docking analysis was carried out to reveal the crucial binding contacts in the inhibition of the P300 and pCAF enzymes.

Solution Equilibrium Studies on Salicylidene Aminoguanidine Schiff Base Metal Complexes: Impact of the Hybridization with L-Proline on Stability, Redox Activity and Cytotoxicity

The proton dissociation processes of two tridentate salicylidene aminoguanidine Schiff bases (SISC, Pro-SISC-Me), the solution stability and electrochemical properties of their Cu(II), Fe(II) and Fe(III) complexes were characterized using pH-potentiometry, cyclic voltammetry and UV-visible, ¹H NMR and electron paramagnetic resonance spectroscopic methods. The structure of the proline derivative (Pro-SISC-Me) was determined by X-ray crystallography. The conjugation of L-proline to the simplest salicylidene aminoguanidine Schiff base (SISC) increased the water solubility due to its zwitterionic structure in a wide pH range. The formation of mono complexes with both ligands was found in the case of Cu(II) and Fe(II), while bis complexes were also formed with Fe(III). In the complexes these tridentate ligands coordinate via the phenolato O, azomethine N and the amidine N, except the complex [Fe(III)L₂]⁺ of Pro-SISC-Me in which the (O,N) donor atoms of the proline moiety are coordinated beside the phenolato O, confirmed by single crystal X-ray crystallographic analysis. This binding mode yielded a stronger Fe(III) preference for Pro-SISC-Me over Fe(II) in comparison to SISC. This finding is also reflected in the lower redox potential value of the iron-Pro-SISC-Me complexes. The ligands alone were not cytotoxic against human colon cancer cell lines, while complexation of SISC with Cu(II) resulted in moderate activity, unlike the case of its more hydrophilic counterpart.

Potential thiosemicarbazone-based enzyme inhibitors: Assessment of antiproliferative activity, metabolic enzyme inhibition properties, and molecular docking calculations

A new series of thiosemicarbazone derivatives (1-11) were prepared from various aldehydes and isocyanates with high yields and practical methods. The structures of these compounds were elucidated by Fourier transform infrared, ¹ H-nuclear magnetic resonance (NMR), ¹³ C-NMR spectroscopic methods and elemental analysis. Cytotoxic effects of target compounds were determined by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide assay and compound 1 showed significant cytotoxic activity against both MCF-7 and MDA-MB-231 cells, with half-maximal inhibitory concentration values of 2.97 μM and 6.57 μM, respectively. Moreover, in this study, the anticholinergic and antidiabetic potentials of these compounds were investigated. To this aim, the effect of the newly synthesized thiosemicarbazone derivatives on the activities of acetylcholinesterase (AChE) and αglycosidase (α-Gly) was evaluated spectrophotometrically. The title compounds demonstrated high inhibitory activities compared to standard inhibitors with K_i values in the range of 122.15-333.61 nM for α-Gly (K_i value for standard inhibitor = 75.48 nM), 1.93-12.36 nM for AChE (K_i value for standard inhibitor = 17.45 nM). Antiproliferative activity and enzyme inhibition at the molecular level were performed molecular docking studies for thiosemicarbazone derivatives. 1M17, 5FI2, and 4EY6, 4J5T target proteins with protein data bank identification with (1-11) compounds were docked for anticancer and enzyme inhibition, respectively.

Crystal structures of 3/4-pyridyl-based thiosemicarbazones and related Cu and Ni coordination compounds

In this investigation, the crystal structures of the thio-ligands 3-formylpyridine 4-phenylthiosemicarbazone (C₁₃H₁₂N₄S, 1) and 4-benzoylpyridine 4-ethylthiosemicarbazone (C₁₅H₁₆N₄S, 2), and of two new coordination compounds, chlorido(3-formylpyridine 4-phenylthiosemicarbazone-κS)bis(triphenylphosphane-κP)copper(I) acetonitrile monosolvate, [CuCl(C₁₃H₁₂N₄S)(C₁₈H₁₅P)₂]·CH₃CN, 3, and bis(3-formylpyridine 4-ethylthiosemicarbazonato-κ²N¹,S)nickel(II), [Ni(C₉H₁₁N₄S)₂], 4, are reported. In complex 3, the thio-ligand coordinates in a neutral form to the Cu atom through its S-donor atom, and in complex 4, the anionic thio-ligand chelates to the Ni atom through N- and S-donor atoms. The geometry of complex 3 is distorted tetrahedral [bond angles 99.70 (5)-123.23 (5)°], with the P-Cu-P bond angle being the largest, while that of complex 4 is square planar, with trans-S-Ni-S and N-Ni-N bond angles of 180°.

Iron-Chelation Treatment by Novel Thiosemicarbazone Targets Major Signaling Pathways in Neuroblastoma

Despite constant advances in the field of pediatric oncology, the survival rate of high-risk neuroblastoma patients remains poor. The molecular and genetic features of neuroblastoma, such as MYCN amplification and stemness status, have established themselves not only as potent prognostic and predictive factors but also as intriguing targets for personalized therapy. Novel thiosemicarbazones target both total level and activity of a number of proteins involved in some of the most important signaling pathways in neuroblastoma. In this study, we found that di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) potently decreases N-MYC in MYCN-amplified and c-MYC in MYCN-nonamplified neuroblastoma cell lines. Furthermore, DpC succeeded in downregulating total EGFR and phosphorylation of its most prominent tyrosine residues through the involvement of NDRG1, a positive prognostic marker in neuroblastoma, which was markedly upregulated after thiosemicarbazone treatment. These findings could provide useful knowledge for the treatment of MYC-driven neuroblastomas that are unresponsive to conventional therapies.

Assessment of the In Vitro and In Vivo Antifungal Activity of NSC319726 against Candida auris

Candida auris is an emerging yeast pathogen of candidemia with the ability to develop resistance to all current antifungal drug classes. Novel antifungal therapies against C. auris are warranted. NSC319726 is a thiosemicarbazone with an inhibitory effect on fungal ribosome biogenesis that has demonstrated some antifungal activity. In this study, we assessed the in vitro activity and in vivo efficacy of NSC319726 against C. auris. NSC319726 was active in vitro against 22 C. auris isolates from different clades, with MICs ranging from 0.125 to 0.25 mg/liter. Despite complete visual growth inhibition, the effect was described as fungistatic in time-kill curves. Interactions with fluconazole, amphotericin B, and micafungin, as tested by the checkerboard dilution method, were described as indifferent. NSC319726 demonstrated significant effects in rescuing G. mellonella larvae infected with two distinct C. auris isolates, compared to the untreated group. In conclusion, NSC319726 demonstrated in vitro activity against C. auris and in vivo efficacy in an invertebrate model of infection. Its potential role as a novel antifungal therapy in humans should be further investigated. IMPORTANCE Candida auris is emerging as a major public health threat because of its ability to cause nosocomial outbreaks of severe invasive candidiasis. Management of C. auris infection is difficult because of its frequent multidrug-resistant profile for currently licensed antifungals. Here, we show that the thiosemicarbazone NSC319726 was active in vitro against a large collection of C. auris isolates from different clades. Moreover, the drug was well tolerated and effective for the treatment of C. auris infection in an invertebrate model of Galleria mellonella. We conclude that NSC319726 might represent an interesting drug candidate for the treatment of C. auris infection.

Novel Thiosemicarbazone Derivatives: In Vitro and In Silico Evaluation as Potential MAO-B Inhibitors

MAO-B inhibitors are frequently used in the treatment of neurodegenerative diseases such as Parkinson’s and Alzheimer’s. Due to the limited number of compounds available in this field, there is a need to develop new compounds. In the recent works, it was shown that various thiosemicarbazone derivatives show hMAO inhibitory activity in the range of micromolar concentration. It is thought that benzofuran and benzothiophene structures may mimic structures such as indane and indanone, which are frequently found in the structures of such inhibitors. Based on this view, new benzofuran/benzothiophene and thiosemicarbazone hybrid compounds were synthesized, characterized and screened for their hMAO-A and hMAO-B inhibitory activity by an in vitro fluorometric method. The compounds including methoxyethyl substituent (2b and 2h) were found to be the most effective agents in the series against MAO-B enzyme with the IC₅₀ value of 0.042 ± 0.002 µM and 0.056 ± 0.002 µM, respectively. The mechanism of hMAO-B inhibition of compounds 2b and 2h was investigated by Lineweaver–Burk graphics. Compounds 2b and 2h were reversible and non-competitive inhibitors with similar inhibition features as the substrates. The K_i values of compounds 2b and 2h were calculated as 0.035 µM and 0.046 µM, respectively, with the help of secondary plots. The docking study of compound 2b and 2h revealed that there is a strong interaction between the active sites of hMAO-B and analyzed compound.

Hybrid Quinoline-Thiosemicarbazone Therapeutics as a New Treatment Opportunity for Alzheimer's Disease‒Synthesis, In Vitro Cholinesterase Inhibitory Potential and Computational Modeling Analysis

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and the leading cause of dementia worldwide. The limited pharmacological approaches based on cholinesterase inhibitors only provide symptomatic relief to AD patients. Moreover, the adverse side effects such as nausea, vomiting, loss of appetite, muscle cramps, and headaches associated with these drugs and numerous clinical trial failures present substantial limitations on the use of medications and call for a detailed insight of disease heterogeneity and development of preventive and multifactorial therapeutic strategies on urgent basis. In this context, we herein report a series of quinoline-thiosemicarbazone hybrid therapeutics as selective and potent inhibitors of cholinesterases. A facile multistep synthetic approach was utilized to generate target structures bearing multiple sites for chemical modifications and establishing drug-receptor interactions. The structures of all the synthesized compounds were fully established using readily available spectroscopic techniques (FTIR, ¹H- and ¹³C-NMR). In vitro inhibitory results revealed compound 5b as a promising and lead inhibitor with an IC₅₀ value of 0.12 ± 0.02 μM, a 5-fold higher potency than standard drug (galantamine; IC₅₀ = 0.62 ± 0.01 μM). The synergistic effect of electron-rich (methoxy) group and ethylmorpholine moiety in quinoline-thiosemicarbazone conjugates contributes significantly in improving the inhibition level. Molecular docking analysis revealed various vital interactions of potent compounds with amino acid residues and reinforced the in vitro results. Kinetics experiments revealed the competitive mode of inhibition while ADME properties favored the translation of identified inhibitors into safe and promising drug candidates for pre-clinical testing. Collectively, inhibitory activity data and results from key physicochemical properties merit further research to ensure the design and development of safe and high-quality drug candidates for Alzheimer’s disease.

Design, Synthesis, Cytotoxic Screening and Molecular Docking Studies of Novel Hybrid Thiosemicarbazone Derivatives as Anticancer Agents

Thiosemicarbazones have been the focus of scientists owing to their broad clinical anticancer range. Herein, A Series of new thiosemicarbazone derivatives 5-9 were synthesized and confirmed through the use of different spectroscopic techniques along with elemental analysis. The in vitro cytotoxic activity of compounds 5-9 against MCF-7 and A549 cell lines and normal breast cells were assessed. Several compounds were found to be active. The most active compound 7 caused MCF-7 cell cycle arrest at G1/ S phases; and induced apoptosis at the pre-G1 phase. The apoptosis-inducing activity of compound 7 was proofed by the elevation of caspase 3/7 activity and also by up-regulation of the expression of Bax and p53 proteins together with the down-regulation of the expression of the Bcl-2 protein. It also had a strong inhibitory effect topoisomerase IIβ enzyme. Molecular Docking study revealed that the synthesized compounds had good docking scores compared to the standard drug Etoposide towards the topoisomerase IIβ protein (3QX3). Overall, these findings confirmed that the new thiosemicarbazone derivatives could aid in the development of promising cancer drug candidates.

Design and Synthesis of Novel Betulin Derivatives Containing Thio-/Semicarbazone Moieties as Apoptotic Inducers through Mitochindria-Related Pathways

Two new series of betulin derivatives with semicarbazone (7a-g) or thiosemicarbazone (8a-g) groups at the C-28 position were synthesized. All compounds were evaluated for their in vitro cytotoxicities in human hepatocellular carcinoma cells (HepG2), human breast carcinoma cells (MCF-7), human lung carcinoma cells (A549), human colorectal cells (HCT-116) and normal human gastric epithelial cells (GES-1). Among these compounds, 8f displayed the most potent cytotoxicity with an IC₅₀ value of 5.86 ± 0.61 μM against MCF-7 cells. Furthermore, the preliminary mechanism studies in MCF-7 cells showed that compound 8f could trigger the intracellular mitochondrial-mediated apoptosis pathway by losing MMP level, which was related with the upregulation of Bax, P53 and cytochrome c expression; the downregulation of Bcl-2 expression; activation of the expression levels of caspase-3, caspase-9, cleaved caspase-3 and cleaved caspase-9; and an increase in the amounts of intracellular reactive oxygen species. These results indicated that compound 8f may be used as a valuable skeleton structure for developing novel antitumor agents.

Molecular Docking, DFT Calculations, Effect of High Energetic Ionizing Radiation, and Biological Evaluation of Some Novel Metal (II) Heteroleptic Complexes Bearing the Thiosemicarbazone Ligand

New Pb(II), Mn(II), Hg(II), and Zn(II) complexes, derived from 4-(4-chlorophenyl)-1-(2-(phenylamino)acetyl)thiosemicarbazone, were synthesized. The compounds with general formulas, [Pb(H₂L)₂(OAc)₂]ETOH.H₂O, [Mn(H₂L)(HL)]Cl, [Hg₂(H₂L)(OH)SO₄], and [Zn(H₂L)(HL)]Cl, were characterized by physicochemical and theoretical studies. X-ray diffraction studies showed a decrease in the crystalline size of compounds that were exposed to gamma irradiation (γ-irradiation). Thermal studies of the synthesized complexes showed thermal stability of the Mn(II) and Pb(II) complexes after γ-irradiation compared to those before γ–irradiation, while no changes in the Zn(II) and Hg(II) complexes were observed. The optimized geometric structures of the ligand and metal complexes are discussed regarding density functional theory calculations (DFT). The antimicrobial activities of the ligand and metal complexes against several bacterial and fungal stains were screened before and after irradiation. The Hg(II) complex has shown excellent antibacterial activity before and after γ-irradiation. In vitro cytotoxicity screening of the ligand and the Mn(II) and Zn(II) complexes before and after γ-irradiation disclosed that both the ligand and Mn(II) complex exhibited higher activity against human liver (Hep-G2) than Zn(II). Molecular docking was performed on the active site of MK-2 and showed good results.

Albumin Conjugates of Thiosemicarbazone and Imidazole-2-thione Prochelators: Iron Coordination and Antiproliferative Activity

The central role of iron in tumor progression and metastasis motivates the development of iron-binding approaches in cancer chemotherapy. Disulfide-based prochelators are reductively activated upon cellular uptake to liberate thiol chelators responsible for iron sequestration. Herein, a trimethyl thiosemicarbazone moiety and the imidazole-2-thione heterocycle are incorporated in this prochelator design. Iron binding of the corresponding tridentate chelators leads to the stabilization of a low-spin ferric center in 2 : 1 ligand-to-metal complexes. Native mass spectrometry experiments show that the prochelators form stable disulfide conjugates with bovine serum albumin, thus affording novel bioconjugate prochelator systems. Antiproliferative activities at sub-micromolar levels are recorded in a panel of breast, ovarian and colorectal cancer cells, along with significantly lower activity in normal fibroblasts.

The Oncogenic Signaling Disruptor, NDRG1: Molecular and Cellular Mechanisms of Activity

NDRG1 is an oncogenic signaling disruptor that plays a key role in multiple cancers, including aggressive pancreatic tumors. Recent studies have indicated a role for NDRG1 in the inhibition of multiple tyrosine kinases, including EGFR, c-Met, HER2 and HER3, etc. The mechanism of activity of NDRG1 remains unclear, but to impart some of its functions, NDRG1 binds directly to key effector molecules that play roles in tumor suppression, e.g., MIG6. More recent studies indicate that NDRG1s-inducing drugs, such as novel di-2-pyridylketone thiosemicarbazones, not only inhibit tumor growth and metastasis but also fibrous desmoplasia, which leads to chemotherapeutic resistance. The Casitas B-lineage lymphoma (c-Cbl) protein may be regulated by NDRG1, and is a crucial E3 ligase that regulates various protein tyrosine and receptor tyrosine kinases, primarily via ubiquitination. The c-Cbl protein can act as a tumor suppressor by promoting the degradation of receptor tyrosine kinases. In contrast, c-Cbl can also promote tumor development by acting as a docking protein to mediate the oncogenic c-Met/Crk/JNK and PI3K/AKT pathways. This review hypothesizes that NDRG1 could inhibit the oncogenic function of c-Cbl, which may be another mechanism of its tumor-suppressive effects.

Synthesis of indole-substituted thiosemicarbazones as an aldose reductase inhibitor: an in vitro, selectivity and in silico study

Aim: Indole is an important component of many drug molecules, and its conjugation with thiosemicarbazone moiety would be advantageous in finding lead compounds for the development of diabetic complications. Methodology: We have designed, synthesized and evaluated a series of 17 indole-thiosemicarbazones (3a-q) as aldose reductase (ALR2) and aldehyde reductase (ALR1) inhibitors. Results: After in vitro evaluation, all indole-thiosemicarbazones showed significant inhibition against both enzyme ALR1 and ALR2 with IC₅₀ in range of 0.42-20.7 and 1.02-19.1 μM, respectively. The docking study was also carried out to consider the putative binding of molecules with the target enzymes. Conclusion: Compound 3f was found to be most active and selective for ALR2. The indole-thiosemicarbazones series described here has selective hits for diabetes-mellitus-associated complications.

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.

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.

Influence of Complexation of Thiosemicarbazone Derivatives with Cu (II) Ions on Their Antitumor Activity against Melanoma Cells

A series of thiosemicarbazone derivatives was prepared and their anti-tumor activity in vitro was tested. The X-ray investigation performed for compounds T2, T3 and T5 confirmed the synthesis pathway and assumed molecular structures of analyzed thiosemicarbazones. The conformational preferences of the thiosemicarbazone system were characterized using theoretical calculations by AM1 method. Selected compounds were converted into complexes of Cu (II) ions. The effect of complexing on anti-tumor activity has been investigated. The copper(II) complexes, with Schiff bases T1, T10, T12, T13, and T16 have been synthesized and characterized by chemical and elemental analysis, FTIR spectroscopy and TGA method. Thermal properties of coordination compounds were studied using TG-DTG techniques under dry air atmosphere. G361, A375, and SK-MEL-28 human melanoma cells and BJ human normal fibroblast cells were treated with tested compounds and their cytotoxicity was evaluated with MTT test. The compounds with the most promising anti-tumour activity were then selected and their cytotoxicity was verified with cell cycle analysis and apoptosis/necrosis detection. Additionally, DNA damages in the form of a basic sites presence and the expression of oxidative stress and DNA damage response genes were evaluated. The obtained results indicate that complexation of thiosemicarbazone derivatives with Cu (II) ions improves their antitumor activity against melanoma cells. The observed cytotoxic effect is associated with DNA damage and G2/M phase of cell cycle arrest as well as disorders of the antioxidant enzymes expression.

Selective Cytotoxic Effects of 5-Trifluoromethoxy-1H-indole-2,3-dione 3-Thiosemicarbazone Derivatives on Lymphoid-originated Cells

AIM

The present study aims to identify the anticancer effect of novel 1H-indole-2,3-dione 3-thiosemicarbazone derivatives. These compounds could be promissing anticancer agents in leukemia treatment.

BACKGROUND

Conventional chemotherapeutic agents accumulate in both normal and tumor cells due to non-specificity. For effective cancer treatment, new drugs need to be developed to make chemotherapeutics selective for cancer cells. The ultimate goal of cancer treatment is to reduce systemic toxicity and improve the quality of life.

METHOD

In this study, the anticancer effects of 5-trifluoromethoxy-1H-indole-2,3-dione 3-thiosemicarbazone derivatives (A-L) were investigated in chronic myelogenous leukemia K562, Burkitt's lymphoma P3HR1, acute promyelocytic leukemia HL60 cells and vincristine-resistant sublines of K562 and P3HR1 cells. Additionally, the compounds were tested on lymphoid derived cells from ALL patients. In order to investigate the particular mechanism of death caused by the cytotoxic effects of the compounds, immunohistochemical caspase 3 staining was performed in P3HR1 cells, and resulting apoptotic activities were demonstrated.

RESULT

All compounds tested have been found to have cytotoxic effects against lymphoma cells at submicromolar concentrations (IC50= 0.89-1.80 µM). Most compounds show significant selectivity for the P3HR1 and P3HR1 Vin resistant. The most effective and selective compound is 4-bromophenyl substituted compound I (IC50=0.96 and 0.89 µM). Cyclohexyl and benzyl substituted compounds D and E have also been found to have cytotoxic effects against K562 cell lines (IC50=2.38 µM), while the allyl substituted compound C is effective on all cell lines (IC50=1.13-2.21 µM). 4-Fluorophenyl substituted F compound has been observed to be effective on all cells (IC50=1.00-2.41 µM) except K562 cell. Compound C is the only compound that shows inhibition of HL-60 cells (IC50= 1.13 µM). Additionally, all compounds exhibited cytotoxic effects on lymphoid-derived cells at 1µM concentration. These results are in accordance with the results obtained in lymphoma cells.

CONCLUSION

All compounds tested have submicromolar concentrations of cytotoxic effects on cells. These compounds hold promise for the future treatment of leukemia cancer.

Mixed Ligand-metal Complexes of 2-(butan-2-ylidene) Hydrazinecarbothioamide- Synthesis, Characterization, Computer-Aided Drug Character Evaluation and in vitro Biological Activity Assessment

BACKGROUND

Mixed ligand-metal complexes are efficient chelating agents because of their flexible donor ability. Mixed ligand complexes containing hetero atoms sulphur, nitrogen and oxygen have been probed for their biological significance.

METHODS

Nine mixed ligand-metal complexes of 2-(butan-2-ylidene) hydrazinecarbothioamide (2- butanone thiosemicarbazone) with pyridine, bipyridine and 2-picoline as co-ligands were synthesized with Cu, Co and Zn salts. The complexes were tested against MDA-MB231 (MDA) and A549 cell lines. Antibacterial activity was tested against Staphylococcus aureus and Escherichia coli. The drug character of the complexes was evaluated on parameters viz. physicochemical properties, bioactivity scores, toxicity assessment and Absorption, Distribution, Metabolism, Excretion and Toxicity (ADMET) profile using various automated softwares. Molecular docking was performed against Ribonucleotide Reductase (RR) and topoisomerase II (topo II).

RESULTS

The mixed ligand-metal complexes were synthesized by condensation reaction for 4-5 h. The characterization was done by elemental analysis, 1H-NMR, FT-IR, molar conductance and UV spectroscopic techniques. Molecular docking results showed that [Cu(C₅H₁₁N₃S)(py)2(CH3COO)2], [Zn(C₅H₁₁N₃S)(bpy)(SO₄)] and [Zn(C₅H₁₁N₃S)(2-pic)2(SO4)] displayed the lowest binding energies with respect to RR. Against topo II [Cu(C₅H₁₁N₃S)(py)2(CH3COO)2], [Cu(C₅H₁₁N₃S)(bpy)(CH3COO)2] and [Zn(C₅H₁₁N₃S)(2-pic)2(SO₄)] had the lowest energies. The druglikness assessment was done using Leadlikeness and Lipinski's rules. Not more than two violations were obtained in case of each filtering rule showing drug-like character of the mixed ligand complexes. Some of the complexes exhibited positive bioactivity scores and almost all the complexes were predicted to be safe with no hazardous effects as predicted by the toxicity assessment. Ames test predicted the non-mutagenic nature of the complexes.

CONCLUSION

In vitro activity evaluation showed that [Zn(C₅H₁₁N₃S)(py)2(SO₄)], [Co(C₅H₁₁N₃S(bpy) (Cl)2] and [Cu(C₅H₁₁N₃S)(2-pic)2(CH3COO)2] were active against MDA. Against A549 [Co(C₅H₁₁N₃S)(py)2(Cl)2], [Cu(C₅H₁₁N₃S)(py)2(CH3COO)2] and [Co(C₅H₁₁N₃S(bpy)(Cl)2] were active. Antibacterial evaluation showed that [Co(C₅H₁₁N₃S)(bpy)(Cl)2], [Zn(C₅H₁₁N₃S)(2-pic)2(SO₄)] and [Cu(C₅H₁₁N₃S)(2-pic)2(CH3COO)2] were active against S. aureus. Against E. coli, [Zn(C₅H₁₁N₃S)(2- pic)2(SO₄)] showed activity at 18-20 mg dose range.