A Structural Chemistry Perspective on the Antimalarial Properties of Thiosemicarbazone Metal Complexes

Thiosemicarbazone Mixed-Valence Cu(I/II) Complex against Lung Adenocarcinoma Cells through Multiple Pathways Involving Cuproptosis

Induction of cuproptosis and targeting of multiple signaling pathways show promising applications in tumor therapy. In this study, we synthesized two thiosemicarbazone-copper complexes ([CuII(L)Cl] 1 and [CuII2CuI(L)2Cl3] 2, where HL is the (E)-N-methyl-2-(phenyl(pyridin-2-yl)methylene ligand), to assess their antilung cancer activities. Both copper complexes showed better anticancer activity than cisplatin and exhibited hemolysis comparable to that of cisplatin. In vivo experiments showed that complex 2 retarded the A549 cell growth in a mouse xenograft model with low systemic toxicity. Primarily, complex 2 kills lung cancer cells in vitro and in vivo by triggering multiple pathways, including cuproptosis. Complex 2 is the first mixed-valent Cu(I/II) complex to induce cellular events consistent with cuproptosis in cancer cells, which may stimulate the development of mixed-valent copper complexes and provide effective cancer therapy.

Exploration of morpholine-thiophene hybrid thiosemicarbazones for the treatment of ureolytic bacterial infections via targeting urease enzyme: Synthesis, biochemical screening and computational analysis

An important component of the pathogenicity of potentially pathogenic bacteria in humans is the urease enzyme. In order to avoid the detrimental impact of ureolytic bacterial infections, the inhibition of urease enzyme appears to be an appealing approach. Therefore, in the current study, morpholine-thiophene hybrid thiosemicarbazone derivatives (5a-i) were designed, synthesized and characterized through FTIR, 1H NMR, 13C NMR spectroscopy and mass spectrometry. A range of substituents including electron-rich, electron-deficient and inductively electron-withdrawing groups on the thiophene ring was successfully tolerated. The synthesized derivatives were evaluated in vitro for their potential to inhibit urease enzyme using the indophenol method. The majority of compounds were noticeably more potent than the conventional inhibitor, thiourea. The lead inhibitor, 2-(1-(5-chlorothiophen-2-yl)ethylidene)-N-(2-morpholinoethyl)hydrazinecarbothioamide (5g) inhibited the urease in an uncompetitive manner with an IC50 value of 3.80 ± 1.9 µM. The findings of the docking studies demonstrated that compound 5g has a strong affinity for the urease active site. Significant docking scores and efficient binding free energies were displayed by the lead inhibitor. Finally, the ADME properties of lead inhibitor (5g) suggested the druglikeness behavior with zero violation.

Synthesis of novel coumarin-based thiosemicarbazones and their implications in diabetic management via in-vitro and in-silico approaches

Diabetes mellitus has a high prevalence rate and it has been deemed a severe chronic metabolic disorder with long-term complications. This research aimed to identify compounds that could potentially inhibit the vital metabolic enzyme α-glucosidase and thereby exert an anti-hyperglycemic effect. The main goal was to establish an effective approach to control diabetes. To proceed with this study, a series of novel coumarin-derived thiosemicarbazones 3a-3m was synthesized and examined using a variety of spectroscopic methods. Moreover, all the compounds were subjected to α-glucosidase inhibition bioassay to evaluate their antidiabetic potential. Fortunately, all the compounds exhibited several folds potent α-glucosidase inhibitory activities with IC50 values ranging from 2.33 to 22.11 µM, in comparison to the standard drug acarbose (IC50 = 873.34 ± 1.67 µM). The kinetic studies of compound 3c displayed concentration-dependent inhibition. Furthermore, the binding modes of these molecules were elucidated through a molecular docking strategy which depicted that the thiosemicarbazide moiety of these molecules plays a significant role in the interaction with different residues of the α-glucosidase enzyme. However, their conformational difference is responsible for their varied inhibitory potential. The molecular dynamics simulations suggested that the top-ranked compounds (3c, 3g and 3i) have a substantial effect on the protein dynamics which alter the protein function and have stable attachment in the protein active pocket. The findings suggest that these molecules have the potential to be investigated further as novel antidiabetic medications.

A new series of bioactive Mo(V)2O2S2-based thiosemicarbazone complexes: Solution and DFT studies, and antifungal and antioxidant activities

This paper deals with the synthesis, characterization, and studies of biological properties of a series of 5 coordination compounds based on binuclear core [Mo(V)2O2S2]2+ with thiosemicarbazones ligands bearing different substituents on the R1 position of the ligand. The complexes are first studied using MALDI-TOF mass spectrometry and NMR spectroscopy to determine their structures in solution in relation to single-crystal X-Ray diffraction data. In a second part, the antifungal and antioxidative activities are explored and the high potential of these coordination compounds compared to the uncoordinated ligands is demonstrated for these properties. Finally, DFT calculation provides important support to the solution studies by identifying the most stable isomers in each [Mo2O2S2]2+/Ligand system, while the determination of HUMO and LUMO levels is performed to explain the antioxidative properties of these systems.

In Vitro and In Vivo Development of a β-Lactam-Metallo-β-Lactamase Inhibitor: Targeting Carbapenem-Resistant Enterobacterales

β-lactams are the most prescribed class of antibiotics due to their potent, broad-spectrum antimicrobial activities. However, alarming rates of antimicrobial resistance now threaten the clinical relevance of these drugs, especially for the carbapenem-resistant Enterobacterales expressing metallo-β-lactamases (MBLs). Antimicrobial agents that specifically target these enzymes to restore the efficacy of last resort β-lactam drugs, that is, carbapenems, are therefore desperately needed. Herein, we present a cyclic zinc chelator covalently attached to a β-lactam scaffold (cephalosporin), that is, BP1. Observations from in vitro assays (with seven MBL expressing bacteria from different geographies) have indicated that BP1 restored the efficacy of meropenem to ≤ 0.5 mg/L, with sterilizing activity occurring from 8 h postinoculation. Furthermore, BP1 was nontoxic against human hepatocarcinoma cells (IC₅₀ > 1000 mg/L) and exhibited a potency of (K_iapp) 24.8 and 97.4 μM against Verona integron-encoded MBL (VIM-2) and New Delhi metallo β-lactamase (NDM-1), respectively. There was no inhibition observed from BP1 with the human zinc-containing enzyme glyoxylase II up to 500 μM. Preliminary molecular docking of BP1 with NDM-1 and VIM-2 sheds light on BP1's mode of action. In Klebsiella pneumoniae NDM infected mice, BP1 coadministered with meropenem was efficacious in reducing the bacterial load by >3 log₁₀ units' postinfection. The findings herein propose a favorable therapeutic combination strategy that restores the activity of the carbapenem antibiotic class and complements the few MBL inhibitors under development, with the ultimate goal of curbing antimicrobial resistance.

Tuning the nuclearity of [Mo2O2S2]2+-based assemblies by playing with the degree of flexibility of bis-thiosemicarbazone ligands

[MoV2O₂S₂]²⁺-based thiosemicarbazone complexes appear as very promising molecules for biological applications due to the intrinsic properties of their components. This paper deals with the synthesis and characterization of six coordination complexes obtained by the reaction of [MoV2O₂S₂]²⁺ clusters with bis-thiosemicarbazone ligands that contain flexible or rigid spacers between the two thiosemicarbazone units. Interestingly, structural characterization by single-crystal X-ray diffraction, MALDI-TOF MS technique and NMR spectroscopy revealed that the nuclearity of the complex is controlled by the nature of the spacer between the thiosemicarbazone units. Binuclear complexes, namely [MoV2O₂S₂(L^1-3)], are isolated with flexible spacers while tetranuclear complexes [(MoV2O₂S₂)₂(L^4-6)₂] are formed when the bis-thiosemicarbazone ligands are built on rigid spacers.

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.

Advances in thiosemicarbazone metal complexes as anti-lung cancer agents

The great success of cisplatin as a chemotherapeutic agent considerably increased research efforts in inorganic biochemistry to identify more metallic drugs having the potential of treating lung cancer. Metal coordination centres, which exhibit a wide range of coordination numbers and geometries, various oxidised and reduced states and the inherent ligand properties offer pharmaceutical chemists a plethora of drug structures. Owing to the presence of C=N and C=S bonds in a thiosemicarbazone Schiff base, N and S atoms in its hybrid orbital has lone pair of electrons, which can generate metal complexes with different stabilities with most metal elements under certain conditions. Such ligands and complexes play key roles in the treatment of anti-lung cancer. Research regarding metallic anti-lung cancer has advanced considerably, but there remain several challenges. In this review, we discuss the potential of thiosemicarbazone Schiff base complexes as anti-lung cancer drugs, their anti-cancer activities and the most likely action mechanisms involving the recent families of copper, nickel, platinum, ruthenium and other complexes.

Dihydroxyphenyl-substituted thiosemicarbazone: A potent scaffold for the development of metallo-β-lactamases inhibitors and antimicrobial

The superbug infection mediated by metallo-β-lactamases (MβLs) has grown into anemergent health threat, and development of MβL inhibitors is an ideal strategy to combat the infection. In this work, twenty-five thiosemicarbazones 1a-e, 2a-e, 3a-e, 4a-d, 5a-d and 6a-b were synthesized and assayed against MβLs ImiS, NDM-1 and L1. The gained molecules specifically inhibited NDM-1 and ImiS, exhibiting an IC₅₀ value in the range of 0.37-21.35 and 0.45-8.76 µM, and 2a was found to be the best inhibitor, with an IC₅₀ of 0.37 and 0.45 µM, respectively, using meropenem (MER) as substrate. Enzyme kinetics and dialysis tests revealed and confirmed by ITC that 2a is a time-and dose-dependent inhibitor of ImiS and NDM-1, it competitively and reversibly inhibited ImiS with a K_i value of 0.29 µM, but irreversibly inhibited NDM-1. Structure-activity relationship disclosed that the substitute dihydroxylbenzene significantly enhanced inhibitory activity of thiosemicarbazones on ImiS and NDM-1. Most importantly, 1a-e, 2a-e and 3a-b alone more strongly sterilized E. coli-ImiS and E. coli-NDM-1 than the MER, displaying a MIC value in the range of 8-128 μg/mL, and 2a was found to be the best reagent with a MIC of 8 and 32 μg/mL. Also, 2a alone strongly sterilized the clinical isolates EC01, EC06-EC08, EC24 and K. pneumonia-KPC-NDM, showing a MIC value in the range of 16-128 μg/mL, and exhibited synergistic inhibition with MER on these bacteria tested, resulting in 8-32-fold reduction in MIC of MER. SEM images shown that the bacteria E. coli-ImiS, E. coli-NDM-1, EC24, K. pneumonia-KPC and K. pneumonia-KPC-NDM treated with 2a (64 μg/mL) suffered from distortion, emerging adhesion between individual cells and crumpled membranes. Mice tests shown that monotherapy of 2a evidently limited growth of EC24 cells, and in combination with MER, it significantly reduced the bacterial load in liver and spleen. Docking studies suggest that the 2,4-dihydroxylbenzene of 2a acts as zinc-binding group with the Zn(II) and the residual amino acids in CphA active center, tightly anchoring the inhibitor at active site. This work offered a promising scaffold for the development of MβLs inhibitors, specifically the antimicrobial for clinically drug-resistant isolates.

Enhanced anticancer potency with reduced nephrotoxicity of newly synthesized platin-based complexes compared with cisplatin

As a platinum-containing anticancer drug, cisplatin is the keystone for treating many malignancies. Nephrotoxicity is the main dose-limiting toxicity, and several hydration therapies and supplementary strategies are utilized to reduce cisplatin-induced kidney damage, so the discovery and development of effective and safe antitumor drugs are still on the path of human health. Herein, a new four-coordinated Pt complex [Pt(TSC)Cl] using N(4)-phenyl-2-formylpyridine thiosemicarbazone (HTSC) was synthesized and characterized by single-crystal X-ray diffraction, ¹HNMR, FT-IR, LC/MS and CHN elemental analysis. The Pt(TSC)Cl complex revealed antiproliferative activity against A549, MCF-7 and Caco-2 cell lines with a low micromolar IC₅₀ (200–1.75 µM). Specifically, the Pt(TSC)Cl complex displayed more selectivity in Caco-2 cells (IC₅₀ = 2.3 µM) than cisplatin (IC₅₀ = 107 µM) after 48 h of treatment. Moreover, compared with cisplatin, a known nephrotoxic drug, the Pt(TSC)Cl complex exhibited lower nephrotoxicity against Hek293 normal cells. We also found that the Pt(TSC)Cl complex can effectively prevent cancer cell propagation in sub-G1 and S phases and induce apoptosis (more than 90%). Real time PCR and western analysis demonstrated that the expression pattern of apoptotic genes and proteins is according to the intrinsic apoptosis pathway through the Bax/Bcl-2-Casp9-Casp3/Casp7 axis. Collectively, our findings indicated that the Pt(TSC)Cl complex triggers apoptosis in Caco-2 cell lines, while low nephrotoxicity was shown and may be considered a useful anticancer drug candidate for colorectal cancers for further optimization and growth.

Synthesis, Structures, and Solution Studies of a New Class of [Mo2O2S2]-Based Thiosemicarbazone Coordination Complexes

This paper deals with the synthesis, structural studies, and behavior in solution of unprecedented coordination complexes built by the association of a panel of 14 representative thiosemicarbazone ligands with the cluster [Mo₂O₂S₂]²⁺. These complexes have been thoroughly characterized both in the solid state and in solution by XRD and by NMR, respectively. In particular, HMBC ¹H{¹⁵N} and ¹H DOSY NMR experiments bring important elements for understanding the complexes' behavior in solution. These studies demonstrate that playing on the nature and the position of various substituents on the ligands strongly influences the coordination modes of the ligands as well as the numbers of isomers in solution, mainly 2 products for the majority of complexes and up to 5 for some of them.

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.

N-acylhydrazones confer inhibitory efficacy against New Delhi metallo-β-lactamase-1

The expression of β-lactamases, especially metallo-β-lactamases (MβLs) in bacteria is one of the main causes of drug resistance. In this work, an effective N-acylhydrazone scaffold as MβL inhibitor was constructed and characterized. The biological activity assays indicated that the synthesized N-acylhydrazones 1-11 preferentially inhibited MβL NDM-1, and 1 was found to be the most effective inhibitor with an IC₅₀ of 1.2 µM. Analysis of IC₅₀ data revealed a structure-activity relationship, which is that the pyridine and hydroxylbenzene substituents at 2-position improved inhibition of the compounds on NDM-1. ITC and enzyme kinetics assays suggested that it reversibly and competitively inhibited NDM-1 (K_i = 0.29 ± 0.05 µM). The synthesized N-acylhydrazones showed synergistic antibacterial activities with meropenem, reduced 4-16-fold MIC of meropenem on NDM-1- producing E. coli BL21 (DE3), while 1 restored 4-fold activity of meropenem on K. pneumonia expressing NDM-1 (NDM-K. pneumoniae). The mice experiments suggested that 1 combined meropenem to fight against NDM-K. pneumoniae infection in the spleen and liver. Cytotoxicity assays showed that 1 and 2 have low cytotoxicity. This study offered a new framework for the development of NDM-1 inhibitors.

Protective Effects of an Oxovanadium(IV) Complex with N2O2 Chelating Thiosemicarbazone on Small Intestine Injury of STZ-Diabetic Rats

Vanadium compounds are being investigated as potential therapeutic agents in the treatment of many health problems, primarily diabetes. We aimed to provide the effect of N(1)-4-hydroxysalicylidene-N(4)-salicylidene-S-methyl-isothiosemicarbazidato-oxovanadium(IV) (VOL) on small intestinal injury in experimental male diabetic rats. Four groups were created of 3.0-3.5-month-old rats. The rats were made diabetic by a single dose of streptozotocin (STZ) at 65 mg/kg and grouped as follows: control animals, VOL-given control animals, STZ-induced diabetic animals and STZ-induced diabetic animals given VOL. A daily dose of 0.2 mM/kg vanadium complex was administered orally for 12 days after the inducement of diabetes. On the 12th day, small intestine tissue samples were taken. According to the data obtained from the biochemical analysis, reduced glutathione (GSH) level, catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST), superoxide dismutase (SOD), Na⁺/K⁺-ATPase and paraoxanase (PON) activities were increased, whereas sialic acid (SA), xanthine oxidase (XO) and disaccharidases (maltase and saccharidase) activities were decreased in the small intestine tissue of VOL-treated diabetic rats. Microscopic examinations revealed a remarkable decrease in the mucosal necrotic areas, discontinuity in the brush border, deterioration of the villi integrity and oedema inside the villi, but with a mild decrease in the inflammatory cells, deterioration and loss of integrity of the gland in the small intestine of VOL-treated diabetic rats. Moreover, VOL treatment markedly decreased the proliferation of villus cells and especially inflammatory cells in the small intestine of diabetic rats. According to the obtained data, the administration of VOL is a potentially convenient strategy to reducing small intestine injury in diabetic rats.

Diaryl-substituted thiosemicarbazone: A potent scaffold for the development of New Delhi metallo-β-lactamase-1 inhibitors

The superbug infection caused by New Delhi metallo-β-lactamase (NDM-1) has become an emerging public health threat. Inhibition of NDM-1 has proven challenging due to its shuttling between pathogenic bacteria. A potent scaffold, diaryl-substituted thiosemicarbazone, was constructed and assayed with metallo-β-lactamases (MβLs). The obtained twenty-six molecules specifically inhibited NDM-1 with IC₅₀ 0.038-34.7 µM range (except 1e, 2e, and 3d), and 1c is the most potent inhibitor (IC₅₀ = 0.038 µM). The structure-activity relationship of synthetic thiosemicarbazones revealed that the diaryl-substitutes, specifically 2-pyridine and 2-hydroxylbenzene improved inhibitory activities of the inhibitors. The thiosemicarbazones exhibited synergistic antimycobacterial actions against E. coli-NDM-1, resulted a 2-512-fold reduction in MIC of meropenem, while 1c restored 16-256-, 16-, and 2-fold activity of the antibiotic on clinical isolates ECs, K. pneumonia and P. aeruginosa harboring NDM-1, respectively. Also, mice experiments showed that 1c had a synergistic antibacterial ability with meropenem, reduced the bacterial load clinical isolate EC08 in the spleen and liver. This work provided a highly promising scaffold for the development of NDM-1 inhibitors.

Thiosemicarbazone Complexes of Transition Metals as Catalysts for Cross-Coupling Reactions

Catalysis of cross-coupling reactions under phosphane-free conditions represents an important ongoing challenge. Although transition metal complexes based on the thiosemicarbazone unit have been known for a very long time, their use in homogeneous catalysis has been studied only relatively recently. In particular, reports of cross-coupling catalytic reactions with such complexes have appeared only in the last 15 years. This review provides a survey of the research in this area and a discussion of the prospects for future developments.

Experimental and quantum chemical study оn the DNA/protein binding and the biological activity of a rhodium(iii) complex with 1,2,4-triazole as an inert ligand

A rhodium(iii) complex with 1,2,4-triazole and a pincer type nitrogen-donor ligand was synthesized, and its interaction with biomolecules was examined.

Anticancer and biological properties of a Zn-2,6-diacetylpyridine bis(thiosemicarbazone) complex

Herein, to develop a multi-target anticancer metal agent and achieve a "1 + 1 > 2" pharmaceutical effect, we rationally designed and synthesized five complexes (C1-C5) by synergistically exploiting the properties of Zn(ii) and a series of modified 2,6-diacetylpyridine bis(thiosemicarbazone) ligands. By investigating the structure-activity relationships, we found that the binuclear Zn(ii) complex (C5) acts against human bladder cancer cells (T-24) with significant cytotoxicity. We subsequently determined the multiple anticancer mechanisms of C5 to T-24 cells, including inhibiting the activity of topoisomerase I (Topo I), blocking the cell cycle in the S phase, and inducing apoptosis and autophagy in T-24 cells. Furthermore, C5 inhibited the migration of T-24 cells and showed a significant cytostatic effect in the T-24 3D spheroid model.