Thiosemicarbazone scaffold for the design of antifungal and antiaflatoxigenic agents: evaluation of ligands and related copper complexes

Phenanthroline and Schiff Base associated Cu(II)-coordinated compounds containing N, O as donor atoms for potent anticancer activity

As an inherent metal ion, copper has been the subject of investigation for developing a novel antitumoral compound that exhibits fewer adverse effects. Copper serves as a cofactor in multiple enzymes, generates reactive oxygen species (ROS), facilitates tumour evolution, metastasis and angiogenesis and has been detected at elevated concentrations in the serum and tissues of various human cancer types. In the given setting, utilising two methodologies in developing novel Copper-based pharmaceuticals for anti-cancer applications is standard practice. These approaches involve either the sequestration of unbound Copper ions or the synthesis of Copper complexes that induce cellular apoptosis. In the past four decades, the latter system has been used, leading to numerous reviews that have examined the anticancer characteristics of a wide range of Copper complexes. These analyses have consistently demonstrated that multiple factors frequently influence the efficacy of these compounds. This review examines the possible anticancer properties of copper and Cu(II) complexes that incorporate Schiff base ligands containing 1,10-phenanthroline. The present study will comprehensively analyse the examined cell lines and mechanistic research associated with each complex.

Exploring the synthesis, structure, spectroscopy and biological activities of novel 4-benzylidene-1-(2-(2,4-dichloro phenyl)acetyl) thiosemicarbazide derivatives: An integrated experimental and theoretical investigation

BACKGROUND

Novel α-amylase inhibitors play a crucial role in managing diabetes and obesity, contributing to improved public health by addressing these challenging and prevalent conditions. Moreover, the synthesis of anti-oxidant agents is essential due to their potential in combating oxidative stress-related diseases and promoting overall health.

OBJECTIVE

Synthesis of thoisemicarbazone derivatives of 2,4-dichlorophenyl acetic acid and to screened them for their biological activities.

METHOD

Thiosemicarbazone derivatives (4-13) were synthesized by refluxing 2,4-dichlorophenyl acetic acid with sulfuric acid in ethanol to get the ester (2), which was further refluxed with thiosemicarbazide to get compound (3). Finally, different aromatic aldehydes were refluxed with compound (3) in ethanol in catalytic amount of acetic acid to obtained the final products (4-13). Using modern spectroscopic techniques including HR-ESI-MS, 13C-, and 1H NMR, the structures of the created derivatives were confirmed.

RESULTS

The synthesized derivatives showed excellent to good inhibitory activity in the range of IC50 values of 4.95 ± 0.44 to 69.71 ± 0.05 µM against α-amylase enzyme when compared to standard drug acarbose (IC50 = 21.55 ± 1.31 µM). In case of iron chelating activity, these products showed potent activity better than standard EDTA (IC50 = 66.43 ± 1.07 µM) in the range of IC50 values of 22.43 ± 2.09 to 61.21 ± 2.83 µM. However, the obtained products also show excellent to good activity in the range of IC50 values of 28.30 ± 1.17 to 64.66 ± 2.43 µM against hydroxyl radical scavenging activity when compared with standard vitamin C (IC50 = 60.51 ± 1.02 µM). DFT used to calculate different reactivity factors including ionization potential, electronegativity, electron affinity, chemical softness, and chemical hardness were calculated using frontier molecular orbital (FMO) computations. The molecular docking studies for the synthesized derivatives with α-amylase were carried out using the AutoDock Vina to understand the binding affinities with active sites of the protein.

Allium cepa tests: A plant-based tool for the early evaluation of toxicity and genotoxicity of newly synthetized antifungal molecules

Many fungal genera such as Aspergillus, Penicillium, Fusarium and Alternaria are able to produce, among many other metabolites, the aflatoxins, a group of toxic and carcinogenic compounds. To reduce their formation, synthetic fungicides are used as an effective way of intervention. However, the extensive use of such molecules generates long-term residues into the food and the environment. The need of new antifungal molecules, with high specificity and low off-target toxicity is worth. The aim of this study was to evaluate: i) the toxicity and genotoxicity of newly synthesized molecules with a good anti-mycotoxic activity, and ii) the suitability of the Allium cepa multi-endpoint assay as an early screening method for chemicals. Eight compounds were tested for toxicity by using the A. cepa bulb root elongation test and for genotoxicity using the A. cepa bulb mitotic index, micronuclei and chromosome aberrations tests. Three molecules showed no toxicity, while two induced mild toxic effects in roots exposed to the highest dose (100 µM). A more pronounced toxic effect was caused by the other three compounds for which the EC50 was approximately 50 μM. Furthermore, all molecules showed a clear genotoxic activity, both in terms of chromosomal aberrations and micronuclei. Albeit the known good antifungal activity, the different molecules caused strong toxic and genotoxic effects. The results indicate the suitability of experiments with A. cepa as a research model for the evaluation of the toxic and genotoxic activities of new molecules in plants before they are released into the environment.

Antiproliferative Activity and DNA Interaction Studies of a Series of N4,N4-Dimethylated Thiosemicarbazone Derivatives

The exploitation of bioactive natural sources to obtain new anticancer agents with novel modes of action may represent an innovative and successful strategy in the field of medicinal chemistry. Many natural products and their chemical analogues have been proposed as starting molecules to synthesise compounds with increased biological potential. In this work, the design, synthesis, and characterisation of a new series of N4,N4-dimethylated thiosemicarbazone Cu(II), Ni(II), and Pt(II) complexes are reported and investigated for their in vitro toxicological profile against a leukaemia cell line (U937). The antiproliferative activity was studied by MTS assay to determine the GI50 value for each compound after 24 h of treatment, while the genotoxic potential was investigated to determine if the complexes could cause DNA damage. In addition, the interaction between the synthesised molecules and DNA was explored by means of spectroscopic techniques, showing that for Pt and Ni derivatives a single mode of action can be postulated, while the Cu analogue behaves differently.

Natural products in crop protection: thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles as antifungal agents and their mechanism of action

BACKGROUND

Phytopathogenic fungi can cause a direct loss in economic value of agriculture. Especially Valsa mali Miyabe et Yamada, a devastating phytopathogenic disease especially threatening global apple production, is very difficult to control and manage. To discover new potential antifungal agents, a series of thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles were prepared. Their antifungal activities were first tested against six typically phytopathogenic fungi including Curvularia lunata, Valsa mali, Alternaria alternate, Fusarium graminearum, Botrytis cinerea and Fusarium solani. Then their mechanism of action against V. mali was investigated.

RESULTS

Derivatives displayed potent antifungal activity against V. mali. Notably, 3-acetyl-N-benzylindole thiosemicarbazone (IV-1: EC₅₀ : 0.59 μg mL^-1 ), whose activity was comparable to that of a commercial fungicide carbendazim (EC₅₀ : 0.33 μg mL^-1 ), showed greater than 98-fold antifungal activity of the precursor indole. Moreover, compound IV-1 displayed good protective and therapeutic effects on apple Valsa canker disease. By scanning electron microscope (SEM) and RNA-Seq analysis, it was demonstrated that compound IV-1 can destroy the hyphal structure and regulate the homeostasis of metabolism of V. mali via the ergosterol biosynthesis and autophagy pathways.

CONCLUSION

3-Acetyl-N-(un)substituted benzylindoles thiosemicarbazones (IV-1-IV-5) can be studied as leads for further structural modification as antifungal agents against V. mali. Particularly, these ergosterol biosynthesis and autophagy pathways can be used as target receptors for design of novel green pesticides for management of congeneric phytopathogenic fungi. © 2023 Society of Chemical Industry.

(Z)-2-(1-(5-Methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)ethylidene)-N-phenylhydrazine-1-carbothioamide

Reaction of equimolar equivalents of 1-(5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)ethan-1-one (1) and N-phenylhydrazinecarbothioamide (2) in boiling ethanol containing a catalytic amount of concentrated hydrochloric acid for 4 h gave (Z)-2-(1-(5-methyl-1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)ethylidene)-N-phenylhydrazine-1-carbothioamide (3) with 88% yield. The structure of 3 was established using single-crystal X-ray diffraction and magnetic resonance spectroscopy.

Synthesis of Novel Aminothiazole Derivatives as Promising Antiviral, Antioxidant and Antibacterial Candidates

It is well-known that thiazole derivatives are usually found in lead structures, which demonstrate a wide range of pharmacological effects. The aim of this research was to explore the antiviral, antioxidant, and antibacterial activities of novel, substituted thiazole compounds and to find potential agents that could have biological activities in one single biomolecule. A series of novel aminothiazoles were synthesized, and their biological activity was characterized. The obtained results were compared with those of the standard antiviral, antioxidant, antibacterial and anticancer agents. The compound bearing 4-cianophenyl substituent in the thiazole ring demonstrated the highest cytotoxic properties by decreasing the A549 viability to 87.2%. The compound bearing 4-trifluoromethylphenyl substituent in the thiazole ring showed significant antiviral activity against the PR8 influenza A strain, which was comparable to the oseltamivir and amantadine. Novel compounds with 4-chlorophenyl, 4-trifluoromethylphenyl, phenyl, 4-fluorophenyl, and 4-cianophenyl substituents in the thiazole ring demonstrated antioxidant activity by DPPH, reducing power, FRAP methods, and antibacterial activity against Escherichia coli and Bacillus subtilis bacteria. These data demonstrate that substituted aminothiazole derivatives are promising scaffolds for further optimization and development of new compounds with potential influenza A-targeted antiviral activity. Study results could demonstrate that structure optimization of novel aminothiazole compounds may be useful in the prevention of reactive oxygen species and developing new specifically targeted antioxidant and antibacterial agents.

Acetylene containing 2-(2-hydrazinyl)thiazole derivatives: design, synthesis, and in vitro and in silico evaluation of antimycobacterial activity against Mycobacterium tuberculosis

Mycobacterium tuberculosis resistance to commercially available drugs is increasing day by day. To address this issue, various strategies were planned and are being implemented. However, there is a need for new drugs and rapid diagnostic methods. For this endeavour, in this paper, we present the synthesis of acetylene containing 2-(2-hydrazinyl) thiazole derivatives and in vitro evaluation against the H37Rv strain of Mycobacterium tuberculosis. Among the developed 26 acetylene containing 2-(2-hydrazinyl) thiazole derivatives, eight compounds inhibited the growth of Mycobacterium tuberculosis with MIC values ranging from 100 μg ml^-1 to 50 μg ml^-1. The parent acetylene containing thiosemicarbazones showed promising antimycobacterial activity by inhibiting up to 75% of the Mycobacterium at 50 μg ml^-1. In addition, in silico studies were employed to understand the binding mode of all the novel acetylene-containing derivatives against the KasA protein of the Mycobacterium. Interestingly, the KasA protein interactions with the compounds were similar to the interactions of KasA protein with thiolactomycin and rifampicin. Cytotoxicity study results indicate that the compounds tested are non-toxic to human embryonic kidney cells.

Antifungal and antiaflatoxigenic assessment of new Cu(II)-pq complexes against Aspergillus parasiticus, in dark conditions and under visible irradiation

The issue of food contamination by fungi and aflatoxins; constitutes a serious concern not only for human/animal health but also for agriculture and the economy. Aflatoxins are secondary metabolites produced by certain filamentous fungi and contaminate a variety of foodstuffs. In this context, control of fungal growth and aflatoxin contamination appears to be important. The present study aimed to investigate new Cu(I) and Cu(II)-quinoxaline complexes, namely [Cu(2,2´-pq)(NO3)](NO3) (1), [Cu(2,2´-pq)2(NO3)](NO3)·6H2O (2) and [Cu(2,2΄-pq)2](BF4) (3), where 2,2´-pq is 2-(2'-pyridyl quinoxaline), as antifungal agents against Aspergillus parasiticus. All complexes, the ligand and the starting material Cu(NO3)2-3H2O, regardless of the concentration used, caused inhibition of A. parasiticus growth ranged from 8.52 to 33.33%. The fungal growth inhibition was triggered when irradiation in visible (λ > 400 nm) was continuously applied (range 18.36-57.20%). The highest inhibitory activity was exhibited by the complex [Cu(2,2´-pq)2(NO3)](NO3)·6H2O and for this reason, it was selected to be studied for its ability to suppress aflatoxin B1 produced by A. parasiticus. AFB1 production after the irradiation process was found to be suppressed by 25% compared to AFB1 produced in dark conditions.

Copper(II) complexes based on thiosemicarbazone ligand: Preparation, crystal structure, Hirshfeld surface, energy framework, antiMycobacterium activity, in silico and molecular docking studies

Considering the promising previous results on the remarkable activity exhibited by cobalt(III) and manganese(II) thiosemicarbazone compounds as antibacterial agents, the present study aimed to prepare and then evaluate the antibacterial activity of two different types of Cu(II) complexes based on a 2-acetylpyridine-N(4)-methyl-thiosemicarbazone ligand (Hatc-Me), a monomer complex [CuCl(atc-Me)] and a novel dinuclear complex [{Cu(μ-atc-Me)}₂μ-SO₄]. The compounds were characterized by infrared spectra, ultraviolet visible and CHN elemental analysis. In addition, the crystalline structures of the complexes were determined by single-crystal X-ray diffraction. In both cases, the Schiff base ligand coordinated in a tridentate mode via the pyridine nitrogen, imine nitrogen and sulfur atoms. The two Cu(II) atoms in the dimer are five coordinate, consisting of three NNS-donor atoms from the thiosemicarbazone ligand connected by a sulfate bridge. The Hirshfeld surface and energy framework of the complexes were additionally analyzed to verify the intermolecular interactions. The biological activity of the Cu(II) salts, the free ligand and its Cu(II) complexes was evaluated against six strains of mycobacteria including Mycobacterium tuberculosis. The complexes showed promising results as antibacterial agents for M. avium and M. tuberculosis, which ranged from 6.12 to 12.73 μM. Furthermore, molecular docking analysis was performed and the binding energy of the docked compound [{Cu(μ-atc-Me)}₂μ-SO₄] with M. tuberculosis and M. avium strains were extremely favorable (-11.11 and - 14.03 kcal/mol, respectively). The in silico results show that the complexes are potential candidates for the development of new antimycobacterial drugs.

The AFLATOX® Project: Approaching the Development of New Generation, Natural-Based Compounds for the Containment of the Mycotoxigenic Phytopathogen Aspergillus flavus and Aflatoxin Contamination

The control of the fungal contamination on crops is considered a priority by the sanitary authorities of an increasing number of countries, and this is also due to the fact that the geographic areas interested in mycotoxin outbreaks are widening. Among the different pre- and post-harvest strategies that may be applied to prevent fungal and/or aflatoxin contamination, fungicides still play a prominent role; however, despite of countless efforts, to date the problem of food and feed contamination remains unsolved, since the essential factors that affect aflatoxins production are various and hardly to handle as a whole. In this scenario, the exploitation of bioactive natural sources to obtain new agents presenting novel mechanisms of action may represent a successful strategy to minimize, at the same time, aflatoxin contamination and the use of toxic pesticides. The Aflatox® Project was aimed at the development of new-generation inhibitors of aflatoxigenic Aspergillus spp. proliferation and toxin production, through the modification of naturally occurring molecules: a panel of 177 compounds, belonging to the thiosemicarbazones class, have been synthesized and screened for their antifungal and anti-aflatoxigenic potential. The most effective compounds, selected as the best candidates as aflatoxin containment agents, were also evaluated in terms of cytotoxicity, genotoxicity and epi-genotoxicity to exclude potential harmful effect on the human health, the plants on which fungi grow and the whole ecosystem.

Advances in Understanding of the Copper Homeostasis in Pseudomonas aeruginosa

Thirty-five thousand people die as a result of more than 2.8 million antibiotic-resistant infections in the United States of America per year. Pseudomonas aeruginosa (P. aeruginosa) is classified a serious threat, the second-highest threat category of the U.S. Department of Health and Human Services. Among others, the World Health Organization (WHO) encourages the discovery and development of novel antibiotic classes with new targets and mechanisms of action without cross-resistance to existing classes. To find potential new target sites in pathogenic bacteria, such as P. aeruginosa, it is inevitable to fully understand the molecular mechanism of homeostasis, metabolism, regulation, growth, and resistances thereof. P. aeruginosa maintains a sophisticated copper defense cascade comprising three stages, resembling those of public safety organizations. These stages include copper scavenging, first responder, and second responder. Similar mechanisms are found in numerous pathogens. Here we compare the copper-dependent transcription regulators cueR and copRS of Escherichia coli (E. coli) and P. aeruginosa. Further, phylogenetic analysis and structural modelling of mexPQ-opmE reveal that this efflux pump is unlikely to be involved in the copper export of P. aeruginosa. Altogether, we present current understandings of the copper homeostasis in P. aeruginosa and potential new target sites for antimicrobial agents or a combinatorial drug regimen in the fight against multidrug resistant pathogens.

Therapeutic potential of N4-substituted thiosemicarbazones as new urease inhibitors: Biochemical and in silico approach

Urease enzyme plays a key role in pathogenesis of gastritis and peptic ulcers. Its inhibition averts our bodies from many disorders including formation of urinary calculi. In agriculture, the high urease content causes severe environmental and hence economic problems. Due to deficiency of effective and safer drugs to tackle the aforementioned disorders, the quest for new scaffolds becomes mandatory in the field of medicinal chemistry. In this regard, we herein report a new series of N⁴-substituted thiosemicarbazones 3a-v as potential candidates for urease inhibition. These new N⁴-substituted thiosemicarbazones 3a-v of distant chemical scaffolds were characterized by advanced spectroscopic techniques, such as FTIR, ¹HNMR, ¹³CNMR, ESI-MS and in the case of compound 3g by single crystal X-ray analysis. The compounds were evaluated for their urease inhibitory potential. All newly synthesized compounds showed significant urease inhibitions with IC₅₀ values in range of 2.7 ± 0.320-109.2 ± 3.217 μM. Molecular docking studies were used for interactions pattern and structure-activity relationship for all compounds, which demonstrated excellent binding interactions with the active site residues, such as hydrogen bonding, π-π interactions, π-H and nickel atom coordination.

Synthesis and biological screening of thiosemicarbazones of substituted 3-acetylcoumarins having d-glucose moiety

Thiosemicarbazones 5a-j were synthesized with yields of 45-68% by condensation of 3-acetylcoumarins 3a-j and tetra-O-acetyl-β-d-thiosemicarbazide 4. All obtained thiosemicarbazones were screened for anti-microorganic activities against bacteria (B. subtilis, S. aureus, S. epidermidis, E. coli, P. aeruginosa, K. pneumoniae, S. typhimurium) and fungi (A. niger, C. albicans, S. cerevisiae, and A. flavus). Some compounds had significant inhibitory activity with MICs of 0.78-3.125 μM in comparison with 5a, including 5e,h,i for S. aureus, and 5c,f,i for S. epidermidis (Gram-(+) bacteria), 5c,f,g for E.coli, 5f for K. pneumoniae, 5b,c,g for P. aeruginosa, and 5i for S. typhimurium (Gram-(-) bacteria), 5d,h,i for A. niger, 5i for A. flavus, 5b,d,e,h for C. albicans, and 5i for S. cerevisiae. Compounds exhibited excellent activity against tested microorganism with MIC = 0.78 μM, including 5h,i (against S. aureus), 5h (against C. albicans), and 5i (against S. cerevisiae).

Double Gamers-Can Modified Natural Regulators of Higher Plants Act as Antagonists against Phytopathogens? The Case of Jasmonic Acid Derivatives

As key players in biotic stress response of plants, jasmonic acid (JA) and its derivatives cover a specific and prominent role in pathogens-mediated signaling and hence are promising candidates for a sustainable management of phytopathogenic fungi. Recently, JA directed antimicrobial effects on plant pathogens has been suggested, supporting the theory of oxylipins as double gamers in plant-pathogen interaction. Based on these premises, six derivatives (dihydrojasmone and cis-jasmone, two thiosemicarbazonic derivatives and their corresponding complexes with copper) have been evaluated against 13 fungal species affecting various economically important herbaceous and woody crops, such as cereals, grapes and horticultural crops: Phaeoacremonium minimum, Neofusicoccum parvum, Phaeomoniella chlamydospora, Fomitiporia mediterranea, Fusarium poae, F. culmorum, F. graminearum, F. oxysporum f. sp. lactucae,F. sporotrichioides, Aspergillus flavus, Rhizoctonia solani,Sclerotinia spp. and Verticillium dahliae. The biological activity of these compounds was assessed in terms of growth inhibition and, for the two mycotoxigenic species A. flavus and F. sporotrichioides, also in terms of toxin containment. As expected, the inhibitory effect of molecules greatly varied amongst both genera and species; cis-jasmone thiosemicarbazone in particular has shown the wider range of effectiveness. However, our results show that thiosemicarbazones derivatives are more effective than the parent ketones in limiting fungal growth and mycotoxins production, supporting possible applications for the control of pathogenic fungi.

Antifungal Drug Repurposing

Control of fungal pathogens is increasingly problematic due to the limited number of effective drugs available for antifungal therapy. Conventional antifungal drugs could also trigger human cytotoxicity associated with the kidneys and liver, including the generation of reactive oxygen species. Moreover, increased incidences of fungal resistance to the classes of azoles, such as fluconazole, itraconazole, voriconazole, or posaconazole, or echinocandins, including caspofungin, anidulafungin, or micafungin, have been documented. Of note, certain azole fungicides such as propiconazole or tebuconazole that are applied to agricultural fields have the same mechanism of antifungal action as clinical azole drugs. Such long-term application of azole fungicides to crop fields provides environmental selection pressure for the emergence of pan-azole-resistant fungal strains such as Aspergillus fumigatus having TR34/L98H mutations, specifically, a 34 bp insertion into the cytochrome P450 51A (CYP51A) gene promoter region and a leucine-to-histidine substitution at codon 98 of CYP51A. Altogether, the emerging resistance of pathogens to currently available antifungal drugs and insufficiency in the discovery of new therapeutics engender the urgent need for the development of new antifungals and/or alternative therapies for effective control of fungal pathogens. We discuss the current needs for the discovery of new clinical antifungal drugs and the recent drug repurposing endeavors as alternative methods for fungal pathogen control.

Sisters in structure but different in character, some benzaldehyde and cinnamaldehyde derivatives differentially tune Aspergillus flavus secondary metabolism

Great are the expectations for a new generation of antimicrobials, and strenuous are the research efforts towards the exploration of diverse molecular scaffolds-possibly of natural origin - aimed at the synthesis of new compounds against the spread of hazardous fungi. Also high but winding are the paths leading to the definition of biological targets specifically fitting the drug's structural characteristics. The present study is addressed to inspect differential biological behaviours of cinnamaldehyde and benzaldehyde thiosemicarbazone scaffolds, exploiting the secondary metabolism of the mycotoxigenic phytopathogen Aspergillus flavus. Interestingly, owing to modifications on the parent chemical scaffold, some thiosemicarbazones displayed an increased specificity against one or more developmental processes (conidia germination, aflatoxin biosynthesis, sclerotia production) of A. flavus biology. Through the comparative analysis of results, the ligand-based screening strategy here described has allowed us to delineate which modifications are more promising for distinct purposes: from the control of mycotoxins contamination in food and feed commodities, to the environmental management of microbial pathogens, to the investigation of specific structure-activity features for new generation drug discovery.

Thiosemicarbazone nano-formulation for the control of Aspergillus flavus

Nanoparticles are widely studied for applications in medical science. In recent years, they have been developed for agronomical purposes to target microbial pest such as bacteria, fungi, and viruses. Nanoparticles are also proposed to limit the use of pesticides, whose abuse is causing environmental impact and human health concerns. In this study, nanoparticles were obtained by using poly-(ε-caprolactone), a polyester chosen for its biocompatibility and biodegradability properties. Poly-(ε-caprolactone) nanoparticles were formulated by using poly(vinyl alcohol) or Pluronic® F127 as non-ionic surfactants, and then loaded with benzophenone or valerophenone thiosemicarbazone, two compounds that inhibit aflatoxin production by Aspergillus flavus. The different types of nanoparticles were compared in terms of size, polydispersity index, morphology, and drug loading capacity. Finally, their effects were investigated on growth, development, and aflatoxin production in the aflatoxigenic species Aspergillus flavus, a ubiquitous contaminant of maize, cereal crops, and derived commodities. Aflatoxin production was inhibited to various extents, but the best inhibitory effect was obtained with respect to sclerotia production that was most effectively suppressed by both benzophenone and valerophenone thiosemicarbazone-loaded nanoparticles. These data support the idea that it is possible to use such nanoparticles as an alternate to pesticides for the control of mycotoxigenic sclerotia-forming fungi.

Guedes da Silva MF, Marzano C. Synthesis, Characterization and Biological Activity of Novel Cu(II) Complexes of 6-Methyl-2-Oxo-1,2-Dihydroquinoline-3-Carbaldehyde-4n-Substituted Thiosemicarbazones

Three new 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-thiosemicarbazones-N-4-substituted pro-ligands and their Cu(II) complexes (1, -NH2; 2, -NHMe; 3, -NHEt) have been prepared and characterized. In both the X-ray structures of 1 and 3, two crystallographically independent complex molecules were found that differ either in the nature of weakly metal-binding species (water in 1a and nitrate in 1b) or in the co-ligand (water in 3a and methanol in 3b). Electron Paramagnetic Resonance (EPR) measurements carried out on complexes 1 and 3 confirmed the presence of such different species in the solution. The electrochemical behavior of the pro-ligands and of the complexes was investigated, as well as their biological activity. Complexes 2 and 3 exhibited a high cytotoxicity against human tumor cells and 3D spheroids derived from solid tumors, related to the high cellular uptake. Complexes 2 and 3 also showed a high selectivity towards cancerous cell lines with respect to non-cancerous cell lines and were able to circumvent cisplatin resistance. Via the Transmission Electron Microscopy (TEM) imaging technique, preliminary insights into the biological activity of copper complexes were obtained.

In vitro and in vivo anticancer activity of tridentate thiosemicarbazone copper complexes: Unravelling an unexplored pharmacological target

Certain metal complexes can have a great antitumor activity, as the use of cisplatin in therapy has been demonstrating for the past fifty years. Copper complexes, in particular, have attracted much attention as an example of anticancer compounds based on an endogenous metal. In this paper we present the synthesis and the activity of a series of copper(II) complexes with variously substituted salicylaldehyde thiosemicarbazone ligands. The in vitro activity of both ligands and copper complexes was assessed on a panel of cell lines (HCT-15, LoVo and LoVo oxaliplatin resistant colon carcinoma, A375 melanoma, BxPC3 and PSN1 pancreatic adenocarcinoma, BCPAP thyroid carcinoma, 2008 ovarian carcinoma, HEK293 non-transformed embryonic kidney), highlighting remarkable activity of the metal complexes, in some cases in the low nanomolar range. The copper(II) complexes were also screened, with good results, against 3D spheroids of colon (HCT-15) and pancreatic (PSN1) cancer cells. Detailed investigations on the mechanism of action of the copper(II) complexes are also reported: they are able to potently inhibit Protein Disulfide Isomerase, a copper-binding protein, that is recently emerging as a new therapeutic target for cancer treatment. Good preliminary results obtained in C57BL mice indicate that this series of metal-based compounds could be a very promising weapon in the fight against cancer.

Synthesis and spectral characterizations of water soluble Cu(ii) complexes containing N-heterocyclic chelates: cell-proliferation, antioxidant and nucleic acid/serum albumin interactions

Water soluble N-heterocyclic copper(ii) complexes were synthesized, characterized and studied their DNA/protein binding interactions, antioxidation and antiproliferative potentials. The complex 4 found to be better than other complexes.

Antiaflatoxigenic Thiosemicarbazones as Crop-Protective Agents: A Cytotoxic and Genotoxic Study

Aflatoxins are secondary fungal metabolites that can contaminate feed and food. They are a cause of growing concern worldwide, because they are potent carcinogenic agents. Thiosemicarbazones are molecules that possess interesting antiaflatoxigenic properties, but in order to use them as crop-protective agents, their cytotoxic and genotoxic profiles must first be assessed. In this paper, a group of thiosemicarbazones and a copper complex are reported as compounds able to antagonize aflatoxin biosynthesis, fungal growth, and sclerotia biogenesis in Aspergillus flavus. The two most interesting thiosemicarbazones found were noncytotoxic on several cell lines (CRL1790, Hs27, HFL1, and U937), and therefore, they were submitted to additional analysis of mutagenicity and genotoxicity on bacteria, plants, and human cells. No mutagenic activity was observed in bacteria, whereas genotoxic activity was revealed by the Alkaline Comet Assay on U937 cells and by the test of chromosomal aberrations in Allium cepa.

Sabotage at the Powerhouse? Unraveling the Molecular Target of 2-Isopropylbenzaldehyde Thiosemicarbazone, a Specific Inhibitor of Aflatoxin Biosynthesis and Sclerotia Development in Aspergillus flavus, Using Yeast as a Model System

Amongst the various approaches to contain aflatoxin contamination of feed and food commodities, the use of inhibitors of fungal growth and/or toxin biosynthesis is showing great promise for the implementation or the replacement of conventional pesticide-based strategies. Several inhibition mechanisms were found taking place at different levels in the biology of the aflatoxin-producing fungal species such as Aspergillus flavus: compounds that influence aflatoxin production may block the biosynthetic pathway through the direct control of genes belonging to the aflatoxin gene cluster, or interfere with one or more of the several steps involved in the aflatoxin metabolism upstream. Recent findings pointed to mitochondrial functionality as one of the potential targets of some aflatoxin inhibitors. Additionally, we have recently reported that the effect of a compound belonging to the class of thiosemicarbazones might be related to the energy generation/carbon flow and redox homeostasis control by the fungal cell. Here, we report our investigation about a putative molecular target of the 3-isopropylbenzaldehyde thiosemicarbazone (mHtcum), using the yeast Saccharomyces cerevisiae as model system, to demonstrate how the compound can actually interfere with the mitochondrial respiratory chain.

(E)-2-(2-Hy-droxy-3-methyl-benzyl-idene)-N-methyl-hydrazine-1-carbo-thio-amide: supra-molecular assemblies in two-dimensions mediated by N-H⋯S and C-H⋯π inter-actions

In the title compound, C10H13N3OS, the azomethine C=N double bond has an E configuration. The phenyl ring and methyl-hydrazine carbo-thio-amide moiety [maximum deviation = 0.008 (2) Å] are twisted slightly with a dihedral angle of 14.88 (10)°. In the crystal, mol-ecules are linked into sheets parallel to the ab plane via N-H⋯S hydrogen bonds and C-H⋯π inter-actions.

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

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