Pyridine-derived thiosemicarbazones and their tin(IV) complexes with antifungal activity against Candida spp

Impact of casein binding on thermal degradation of oxytetracycline: kinetics, products, and their toxicity

This work systematically investigated the effect of casein on the thermal transformation behavior of oxytetracycline (OTC). Fluorescence quenching and isothermal titration calorimetry experiments confirmed that OTC binds spontaneously to casein via non-covalent interactions. The -N(CH3)2 group in OTC was identified as the primary binding site. Casein-bound OTC was prepared using a combination of dialysis and ultrafiltration. During thermal treatment, the degradation of free OTC followed zero-order kinetics, whereas casein-bound OTC adhered to first-order kinetics. Seven identical thermal transformation products were identified, but the quantities of these products varied significantly depending on the existing form of OTC molecule. The binding of casein weakened the reactivity of the -N(CH3)2 group while enhancing the reactivity of degradation sites on the adjacent ring, resulting in decreased production of three lower-toxic products and increased production of four higher-toxicity products. Cytotoxicity assays revealed that heating increased the overall toxicity of OTC, particularly in its bound form.

Spectroscopic Characterization, Cyclic Voltammetry, Biological Investigations, MOE, and Gaussian Calculations of VO(II), Cu(II), and Cd(II) Heteroleptic Complexes

A novel hydrazone ligand (o-H₂BMP) N-(benzo[d]thiazol-2-yl)-3-oxo-3-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)propanamide alongside its Cu(II), Cd(II), and VO(II) complexes were prepared and structurally characterized via various spectroscopic analyses (Fourier transform infrared spectroscopy, UV-visible spectroscopy, ¹H/¹³C NMR spectroscopy, liquid chromatography coupled to mass spectrometry, and electron paramagnetic resonance spectroscopy) as well as by elemental analysis, thermal gravimetry analysis/differential thermal analysis, and magnetic moment measurements. Powder X-ray diffraction analysis was also performed for the free ligand and its metal complexes to determine the crystallographic structures and atomic spacing. It also provided information on unit cell dimensions and the average crystallite size. Furthermore, geometric optimization and computational studies were carried out by applying Gaussian (09) software based on density-functional theory coupled with the B3LYP functional and LANL2DZ/6-31+G(d,p) mixed basis set to evaluate some distinct features such as molecular electrostatic potential, E _HOMO, and E _LUMO. Moreover, electrochemical measurements were performed for Cu(II) in the absence/presence of the chelating agent to predict the effect of complexation interaction in the solution state study. As part of the biological examination, antioxidant and antimicrobial assays were conducted for each compound individually, in addition to cytotoxicity evaluations via MTT assays for all isolated complexes compared to the corresponding metal salts. The MOE (molecular operating environment) approach was also applied to model the interface between the isolated compounds and proteins that were expressed in breast cancer at the atomic level.

New iron(III) complexes with 2-formylpyridine thiosemicarbazones: Synthetic aspects, structural and spectral analyses and cytotoxicity screening against MCF-7 human cancer cells

2-Formylpyridine thiosemicarbazone - iron (III) chelates [F e L 2 ] C l • 2 H 2 O {L = L1 (C1) [HL 1  = 4-(4-Nitrophenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide] and L = L2 (C2) [HL 2  = 4-(2,5-Dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide]} were prepared. The two ligand anions in each complex resulted in saturation of the iron coordination number and consequently the existence of these complexes as 1:1 electrolytes. As well, the iron in these complexes exhibits low-spin electronic configuration. X-ray crystallography of complex C1 indicated its triclinic crystal system and P1 ‾ space group. In addition, it proved the ligation through a thiol sulfur atom and two nitrogen atoms of pyridine and azomethine groups. This is while the presence of two water molecules of crystallization in the complex structure was also indicated. The ligand HL 1 was selected for cytotoxicity screening against human MCF-7, A-549, HEPG-2 and HCT-116 cancer cells and the most enhanced activities were detected against the breast cells. Against these cells, the compounds HL 1 , HL 2 , C1 and C2 induced cytotoxicity, respectively, with IC50 values of 52.4, 145.4, 34.3 and 62.0 μM. However, against the healthy BHK cells, HL 1 and HL 2 caused cytotoxicity, respectively, with IC50 values of 54.8 and 110.6 μM and cytotoxicity with percent viabilities of 56.7 and 55.4% of the BHK cells by the complexes (137.4 μM of C1 and 131.9 μM of C2) was determined. These activities against MCF-7 cells are less significant compared with the measured value for doxorubicin. But this standard is more toxic to normal cells than the thiosemicarbazones (IC50 (doxorubicin) = 9.66 μM against MCF-7 cells and 36.42 μM against BHK cells).

Highly Efficient Spectrophotometric Determination of Cu2+ ion in Aqueous Medium Using a thiosemicarbazone–derivative Ligand

A new simple spectrophotometric method for the determination of Cu²⁺ ion was developed using an thiosemicarbazone compound, 2-{4-[Bis(2-chloroethyl)amino]benzylidene}-N-[(4-methylthio)phenyl]hydrazinecarbothioamide (TSC). A simultaneous color change was observed (from colorless to bright yellow) by the addition of Cu²⁺ ion to the TSC ligand solution. The maximum absorbance of the TSC ligand measured at 366 nm was decreased by the presence of Cu²⁺ ion. The graphs of absorbance obtained by means of the Job's method and the molar-ratio method proposed a complex formation with a 1:2 Cu²⁺-TSC ligand stoichiometry. The molar-ratio method with emission measurements also confirmed the stoichiometry. The complex stability constant of TSC-Cu²⁺ complex (K) was evaluated to be 1.76 × 10⁵. The proposed spectrophotometric method was associated with the change in absorbance at 366 nm owing to the interaction between the TSC ligand and Cu²⁺ ion. From the spectrophotometric titration data, it was pointed out that TSC ligand (1.5 × 10^- 5 mol L^-1) selectively reacted with Cu²⁺ ion in DMSO/water (1:1, v/v, citrate buffer at pH = 6.0). The calibration curve for Cu²⁺ ion was obtained with a good linearity in the range of 0.0191-0.3241 mg L^-1. The detection limit for Cu²⁺ ion was 0.0063 mg L^-1. The proposed method was achievemently implemented in real water samples (drink water, tap water and, distilled water). Satisfactory recoveries were confirmed at three different concentrations. The method presented a relative standard deviation (RSD%) of less than 3.08%.

Zinc(II) complexes bearing N,N,S ligands: Synthesis, crystal structure, spectroscopic analysis, molecular docking and biological investigations about its antifungal activity

In the present work, the synthesis, characterization, antifungal activity, molecular docking study and in silico approach of five thiosemicarbazone derivatives and their corresponding zinc(II) complexes are described. The compounds were characterized by elemental analysis, IR, UV-Vis and NMR spectroscopic measurements, molar conductivity measurements, emission spectra, high-resolution mass spectrometry and X ray study. The antifungal activity of the free ligands and synthesized compounds was preliminarily evaluated against Candida albicans (ATCC 90028), Candida tropicalis (ATCC 13803) and Candida glabrata (ATCC 2001), by the minimum inhibitory concentration (MIC) assay. Two complexes, 4 (MIC = 3.18 to 6.37 μM) and 5 (MIC = 25.95 μM for all) showed promising results, being highly active against all strains evaluated. The X-ray analyses shown that the complex 2 crystallizes in the centrosymmetric space group P2₁/c of the monoclinic system and the coordination sphere around zinc(II) atom is better described as slightly distorted octahedral. The Hirshfeld surface (HS) analysis showed that non-classical H···H and C···H/H···C contacts contribute with 65.9% while the S···H and N···H (21%) and Cl···H and O···H interactions (12%) complete the HS area. The molecular docking results, performed against CYP51 enzyme (sterol 14α-demethylase) of C. albicans and C. glabrata shows that the complexes 4 (ΔG = -10.75 and - 12.90 kcal/ mol) and 5 (ΔG = -11.12 and - 14.53 kcal/ mol) showed the highest binding free energies of all compounds. The ADME-Tox (absorption, distribution, metabolism, excretion and toxicity) in silico parameters evaluated showed promising results for all compounds.

Thiosemicarbazones and Derived Antimony Complexes: Synthesis, Structural Analysis, and In Vitro Evaluation against Bacterial, Fungal, and Cancer Cells

Two antimony complexes {[Sb(L1)Cl2] C1 and [Sb(L2)Cl2] C2} with the thiosemicarbazone ligands {HL1 = 4-(2,4-dimethylphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide and HL2 = 4-(2,5-dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide} were introduced. The structures were elucidated on the basis of a CHNS analysis, spectroscopic techniques (UV-Vis and FT-IR), and DMF solution electrical conductivities. Single crystal X-ray diffraction analysis of complex C1 assigned the complex pseudo-octahedral geometry and triclinic P-1 space group. Only the ligand HL1 and its derived complex C1 displayed antifungal activities against Candida albicans and this activity was enhanced from 10 mm to 21 mm for the respective complex, which is the same activity given by the drug “Amphotericin B”. The ligands HL1 and HL2 gave inhibitions, respectively, of 14 and 10 mm against Staphylococcus aureus and 15 and 10 mm against Escherichia coli; however, complexes C1 and C2 increased these inhibitions to 36 and 32 mm against Staphylococcus aureus and 35 and 31 mm against Escherichia coli exceeding the activities given by the ampicillin standard (i.e., 21 mm against Staphylococcus aureus and 25 mm against Escherichia coli). Against MCF-7 human breast cancer cells, the IC50 values of HL1 (68.9 μM) and HL2 (145.4 μM) were notably enhanced to the values of 34.7 and 37.4 μM for both complexes, respectively. Further, the complexes induced less toxicity in normal BHK cells (HL1 (126.6 μM), HL2 (110.6 μM), C1 (>210.1 μM), and C2 (160.6 μM)). As a comparison, doxorubicin gave an IC50 value of 9.66 μM against MCF-7 cells and 36.42 μM against BHK cells.

Trivalent Cobalt Complexes with NNS Tridentate Thiosemicarbazones: Preparation, Structural Study and Investigation of Antibacterial Activity and Cytotoxicity against Human Breast Cancer Cells

New complexes of trivalent cobalt with substituted thiosemicarbazone ligands having an NNS donor system {HL1 = 4-(4-nitrophenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide and HL2 = 4-(2,5-dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide} were synthesized via the in situ oxidation of divalent cobalt chloride accompanying its addition to the ligands. The complexes C1 and C2 were characterized via elemental (CHNS) analysis and 1H NMR, FT-IR and UV-Vis. spectroscopic data. Further, conductometric studies on the DMF solutions of the complexes indicated their 1:1 nature, and their diamagnetism revealed the low-spin trivalent oxidation state of the cobalt in the complexes. The X-ray diffraction analysis of complex C1 indicated that it crystallizes in the triclinic space group P-1. The metal exhibits an octahedral environment built by two anionic ligands bound via pyridine nitrogen, imine nitrogen and thiol sulfur atoms. The complex is counterbalanced by a chloride ion. In addition, two lattice water molecules were detected in the asymmetric unit of the unit cell. The ligand HL2 (20 mg/mL in DMSO) displayed inhibition zones of 10 mm against both S. aureus and E. coli, and the same concentration of the respective complex raised this activity to 15 and 12 mm against these bacterial strains, respectively. As a comparison, ampicillin inhibited these bacterial strains by 21 and 25 mm, respectively. Screening assay by HL1 on four human cancer cells revealed the most enhanced activity against the breast MCF-7 cells. The induced growth inhibitions in the MCF-7 cells by all compounds (0–100 μg/mL) have been detected. The ligands {HL1 and HL2} and complex C2 gave inhibitions with IC50 values of 52.4, 145.4 and 49.9 μM, respectively. These results are more meaningful in comparison with similar cobalt complexes, but less efficient compared with the inhibition with IC50 of 9.66 μM afforded by doxorubicin. In addition, doxorubicin, HL1 and HL2 induced cytotoxicity towards healthy BHK cells with IC50 values of 36.42, 54.8 and 110.6 μM, but surviving fractions of 66.1% and 62.7% of these cells were detected corresponding to a concentration of 100 μg/mL of the complexes (136.8 μM of C1 and 131.4 μM of C2).

Evaluation of Toxicity and Oxidative Stress of 2-Acetylpyridine-N(4)-orthochlorophenyl Thiosemicarbazone

Thiosemicarbazones are well known for their broad spectrum of action, including antitumoral and antiparasitic activities. Thiosemicarbazones work as chelating binders, reacting with metal ions. The objective of this work was to investigate the in silico, in vitro, and in vivo toxicity and oxidative stress of 2-acetylpyridine-N(4)-orthochlorophenyl thiosemicarbazone (TSC01). The in silico prediction showed good absorption by biological membranes and no theoretical toxicity. Also, the compound did not show cytotoxicity against Hep-G2 and HT-29 cells. In the acute nonclinical toxicological test, the animals treated with TSC01 showed behavioral changes of stimulus of the central nervous system (CNS) at 300 mg/kg. One hour after administration, a dose of 2000 mg/kg caused depressive signs. All changes disappeared after 24 h, with no deaths, which suggest an estimated LD50 of 5000 mg/kg and GSH 5. The group treated with 2000 mg/kg had an increase of water consumption and weight gain in the second week. The biochemical parameters presented no toxicity relevance, and the analysis of oxidative stress in the liver found an increase of lipid peroxidation and nitric oxide. However, histopathological analysis showed organ integrity was maintained without any changes. In conclusion, the results show the low toxicological potential of thiosemicarbazone derivative, indicating future safe use.

Chitosan-Based Films with 2-Aminothiophene Derivative: Formulation, Characterization and Potential Antifungal Activity

In this study, films of chitosan and 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile (6CN), a 2-aminothiophene derivative with great pharmacological potential, were prepared as a system for a topical formulation. 6CN-chitosan films were characterized by physicochemical analyses, such as Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electronic microscopy (SEM). Additionally, the antifungal potential of the films was evaluated in vitro against three species of Candida (C. albicans, C. tropicalis, and C. parapsilosis). The results of the FTIR and thermal analysis showed the incorporation of 6CN in the polymer matrix. In the diffractogram, the 6CN-chitosan films exhibited diffraction halos that were characteristic of amorphous structures, while the micrographs showed that 6CN particles were dispersed in the chitosan matrix, exhibiting pores and cracks on the film surface. In addition, the results of antifungal investigation demonstrated that 6CN-chitosan films were effective against Candida species showing potential for application as a new antifungal drug.

Antifungal activity of thiosemicarbazones, bis(thiosemicarbazones), and their metal complexes

Fungi are ubiquitous in nature, and typically cause little or no environmental or pathogenic damage to their plant, animal, and human hosts. However, a small but growing number of pathogenic fungi are spreading world-wide at an alarming rate threatening global ecosystem health and proliferation. Many of these emerging pathogens have developed multi-drug resistance to front line therapeutics increasing the urgency for the development of new antifungal agents. This review examines the development of thiosemicarbazones, bis(thiosemicarbazones), and their metal complexes as potential antifungal agents against more than 65 different fungal strains. The fungistatic activity of the compounds are quantified based on the zone of inhibition, minimum inhibitory concentration, or growth inhibition percentage. In this review, reported activities were standardized based on molar concentrations to simplify comparisons between different compounds. Of all the fungal strains reported in the review, A. niger in particular was very resistant towards a majority of tested compounds. Our analysis of the data shows that metal complexes are typically more active than non-coordinated ligands with copper(II) and zinc(II) complexes generally displaying the highest activity.

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.

Recent developments of metal-based compounds against fungal pathogens

This review provides insight into the rapidly expanding field of metal-based antifungal agents. In recent decades, the antibacterial resistance crisis has caused reflection on many aspects of public health where weaknesses in our medicinal arsenal may potentially be present - including in the treatment of fungal infections, particularly in the immunocompromised and those with underlying health conditions where mortality rates can exceed 50%. Combination of organic moieties with known antifungal properties and metal ions can lead to increased bioavailability, uptake and efficacy. Development of such organometallic drugs may alleviate pressure on existing antifungal medications. Prodigious antimicrobial moieties such as azoles, Schiff bases, thiosemicarbazones and others reported herein lend themselves easily to the coordination of a host of metal ions, which can vastly improve the biocidal activity of the parent ligand, thereby extending the library of antifungal drugs available to medical professionals for treatment of an increasing incidence of fungal infections. Overall, this review shows the impressive but somewhat unexploited potential of metal-based compounds to treat fungal infections.

Di-n-but-yl[N'-(3-meth-oxy-2-oxidobenzyl-idene)-N-phenyl-carbamohydrazono-thio-ato]tin(IV): crystal structure, Hirshfeld surface analysis and computational study

The title diorganotin Schiff base derivative, [Sn(C4H9)2(C15H13N3O2S)], features a penta-coordinated tin centre defined by the N,O,S-donor atoms of the di-anionic Schiff base ligand and two methyl-ene-C atoms of the n-butyl substituents. The resultant C2NOS donor set defines a geometry inter-mediate between trigonal-bipyramidal and square-pyramidal. In the crystal, amine-N-H⋯O(meth-oxy) hydrogen bonding is found in a helical, supra-molecular chain propagating along the b-axis direction. The chains are assembled into a layer parallel to (01) with methyl-ene-C-H⋯π(phen-yl) inter-actions prominent; layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surface showed the presence of weak methyl-ene-C-H⋯π(phen-yl) inter-actions and short H⋯H contacts in the inter-layer region. Consistent with the nature of the identified contacts, the stabilization of the crystal is dominated by the dispersion energy term.

Synthesis and Biological Evaluation of Novel Zn(II) and Cd(II) Schiff Base Complexes as Antimicrobial, Antifungal, and Antioxidant Agents

(E)-N,N-Dimethyl-2-((E-1-(2-(p-tolyl)hydrazono)propan-2-ylidene)hydrazine-1-carbothioamide (DMPTHP) and their Zn(II) and Cd(II) complexes have been synthesized and characterized. Different tools of analysis such as elemental analyses, IR, mass spectra, and 1H-NMR measurements were used to elucidate the structure of the synthesized compounds. According to these spectral results, the DMPTHP ligand behaved as a mononegatively charged tridentate anion. Modeling and docking studies were investigated and discussed. Novel Schiff base (DMPTHP) ligand protonation constants and their formation constants with Cd(II) and Zn(II) ions were measured in 50% DMSO solution at 15°C, 25°C, and 35°C at I = 0.1 mol·dm−3 NaNO3. The solution speciation of different species was measured in accordance with pH. Calculation and discussion of the thermodynamic parameters were achieved. Both log K1 and –ΔH1, for M(II)-thiosemicarbazone complexes were found to be somewhat larger than log K2 and –ΔH2, demonstrating a shift in the dentate character of DMPTHP from tridentate in 1 : 1 chelates to bidentate in 1 : 2; M : L chelates and steric hindrance were generated by addition of the 2nd molecule. The compounds prepared have significant activity as antioxidants, similar to ascorbic acid. It is hoped that the results will be beneficial to antimicrobial agent chemistry. The formed compounds acted as a potent antibacterial agent. Molecular docking studies were investigated and have proved that DMPTHP as antibacterial agents act on highly resistant strains of E. coli and also as an anticancer agent.

Synthesis, Spectroscopic Characterization, Structural Studies, and In Vitro Antitumor Activities of Pyridine-3-carbaldehyde Thiosemicarbazone Derivatives

Eight new thiosemicarbazone derivatives, 6-(1-trifluoroethoxy)pyridine-3-carbaldehyde thiosemicarbazone (1), 6-(4′-fluorophenyl)pyridine-3-carbaldehyde thiosemicarbazone (2), 5-chloro-pyridine-3-carbaldehyde thiosemicarbazone (3), 2-chloro-5-bromo-pyridine-3-carbaldehyde thiosemicarbazone (4), 6-(3′,4′-dimethoxyphenyl)pyridine-3-carbaldehyde thiosemicarbazone (5), 2-chloro-5-fluor-pyridine-3-carbaldehyde thiosemicarbazone, (6), 5-iodo-pyridine-3-carbaldehyde thiosemicarbazone (7), and 6-(3′,5′-dichlorophenyl)pyridine-3-carbaldehyde thiosemicarbazone (8) were synthesized, from the reaction of the corresponding pyridine-3-carbaldehyde with thiosemicarbazide. The synthesized compounds were characterized by ESI-Mass, UV-Vis, IR, and NMR (1H, 13C, 19F) spectroscopic techniques. Molar mass values and spectroscopic data are consistent with the proposed structural formulas. The molecular structure of 7 has been also confirmed by single crystal X-ray diffraction. In the solid state 7 exists in the E conformation about the N2-N3 bond; 7 also presents the E conformation in solution, as evidenced by 1H NMR spectroscopy. The in vitro antitumor activity of the synthesized compounds was studied on six human tumor cell lines: H460 (lung large cell carcinoma), HuTu80 (duodenum adenocarcinoma), DU145 (prostate carcinoma), MCF-7 (breast adenocarcinoma), M-14 (amelanotic melanoma), and HT-29 (colon adenocarcinoma). Furthermore, toxicity studies in 3T3 normal cells were carried out for the prepared compounds. The results were expressed as IC50 and the selectivity index (SI) was calculated. Biological studies revealed that 1 (IC50 = 3.36 to 21.35 μM) displayed the highest antiproliferative activity, as compared to the other tested thiosemicarbazones (IC50 = 40.00 to >582.26 μM) against different types of human tumor cell lines. 1 was found to be about twice as cytotoxic (SI = 1.82) than 5-fluorouracile (5-FU) against the M14 cell line, indicating its efficiency in inhibiting the cell growth even at low concentrations. A slightly less efficient activity was shown by 1 towards the HuTu80 and MCF7 tumor cell lines, as compared to that of 5-FU. Therefore, 1 can be considered as a promising candidate to be used as a pharmacological agent, since it presents significant activity and was found to be more innocuous than the 5-FU anticancer drug against the 3T3 mouse embryo fibroblast cells.

Syntheses, quantum mechanical modeling, biomolecular interaction and in vitro anticancer - Tubulin activity of thiosemicarbazones

A new series of thiosemicarbazones were designed and synthesized. Their structures were confirmed by spectral characterization and single crystal XRD studies. Compounds MTSC-2 and ETSC-3 crystallized in the orthorhombic crystal system with space group Pbc2₁ andPca2₁respectively. Density functional theory computational studies were performed on MTSC-2 and ETSC-3 along with natural bond orbital analysis and Mulliken population analysis to study the structural and electronic properties of the thiosemicarbazones. The HOMOs of the two thiosemicarbazones are -5.2943 and -5.1133 eV respectively while the LUMOs are -1.6879 and -1.6398 eV respectively. The energy gap is 3.6064 and 3.4736 eV respectively. Molecular docking studies were performed to determine the binding mode of the thiosemicarbazones against β-tubulin. The theoretical studies were further supplemented with tubulin polymerization inhibition assay. All the four thiosemicarbazones proved effective in inhibiting the polymerization of α- and β-tubulin heterodimers into microtubules. The anticancer activity of these compounds showed their extreme potency against A549 and HepG2 cancer cell lines with IC₅₀ values of 0.051 - 0.189 µm and 0.042 - 0.136 µm respectively. Compound PTSC-4 showed the highest activity both against tubulin and the two cancer cell lines. This was in correlation with the theoretical studies. Hence, these four compounds, specifically PTSC-4, can be considered to be potential leads in the development of non-metallic anticancer agents.

Zn(II) and Cd(II) thiosemicarbazones for stimulation/inhibition of kojic acid biosynthesis from Aspergillus flavus and the fungal defense behavior against the metal complexes' excesses

The complexes {[ZnL¹Cl] C1, [ZnL²Cl].0.5H₂O C2, [CdL¹Cl] C3, and [CdL²Cl] C4} were prepared from tridentate thiosemicarbazones {HL¹ = 4-(3-nitrophenyl)-1-((pyridin-2-yl)methylene) thiosemicarbazide and HL² = 4-(2,4-dimethoxyphenyl)-1-((pyridin-2-yl)methylene)thiosemicarbazide} and identified by elemental CHNS, spectroscopic {IR and UV-Vis.}, thermal and DMF solution electrical conductivity data. On another hand, kojic acid (KA) which represents important secondary metabolite with numerous hot spot applications was successfully biosynthesized from Aspergillus flavus and structurally analyzed by single crystal analysis. The Zn(II) complexes C1&C2 (0.3 mM) enhanced the KA biosynthesis by 70.87% and 42.26%, while 76.09% of C1 and 72.78% of C2 were absorbed by the fungal cells. The Cd(II) complexes C3&C4 at 0.3 mM inhibited KA production by 87.95% and 97.03% with Cd(II) consumption reaching to 40.09% & 37.3%, while 0.4 mM of C3&C4 resulted in 100% inhibition of kojic acid biosynthesis. Light microscopic analysis showed the fungal structural abnormalities and the cell antioxidant behavior was detected. These complexes could be highly applicable as new stimulators and inhibitors of kojic acid production.

Synthesis and Evaluation of the in vitro Antimicrobial Activity of Triazoles, Morpholines and Thiosemicarbazones

BACKGROUND

Microbial infections is a global public health problem. The aim of this work was to synthesize and evaluate the antimicrobial activity of novel triazoles, morpholines and thiosemicarbazones.

METHODS

Compounds were synthesized using 2,4-Dihydroxyacetophenone and 4-hydroxybenzaldehyde as starting materials. The antimicrobial activity of these compounds against bacteria and yeast was evaluated by the broth microdilution method.

RESULTS

The proposed route for synthesis gave high to moderate yields, moreover these compounds were successfully characterized by 1H NMR, 13C NMR and LC-MS. Antimicrobial testing indicated that the thiosemicarbazone and morphine derivatives had the best antimicrobial activity against the microorganisms tested with minimum inhibitory concentrations (MIC) between 0.29 and 5.30 µM. Thiosemicarbazone derivative (12) was able to inhibit the growth of C. tropicalis, with minimum fungicidal concentration (MFC) of 0.55 µM. In addition, this compound was active against E. coli, S. aureus and S. epidermidis, with MIC values ranging from 0.29 to 1.11 µM. Moreover, the morpholine derivative (15) had an MIC value of 0.83 µM against C. albicans and E. coli.

CONCLUSION

We have efficiently synthesized a series of eleven novel triazoles, thiosemicarbazones and morpholine derivatives using 2,4-Dihydroxyacetophenone and 4-hydroxybenzaldehyde as starting materials. Thiosemicarbazone derivative (12) showed promising antifungal and antibacterial activity and these findings suggest that this compound can be used as scaffolds to design new antimicrobial drugs.

Dibutyltin(IV) Complexes Derived from L-DOPA: Synthesis, Molecular Docking, Cytotoxic and Antifungal Activity

A series of organotin(IV) complexes was herein prepared and characterized. A one-pot synthetic strategy afforded reasonable to high yields, depending on the nature of the ligand. All new complexes were fully characterized by spectroscopic techniques, consisting of IR, MS and NMR (¹H, ¹³C and ¹¹⁹Sn). The in vitro cytotoxicity tests demonstrated that the organotin complexes produced a greater inhibition, versus cisplatin (the positive control), of the growth of six human cancer cell lines: U-251 (glioblastoma), K-562 (chronic myelogenous leukemia), HCT-15 (colorectal), MCF-7 (breast), MDA-MB-231 (breast) and SKLU-1 (non-small cell lung). The potency of this cytotoxic activity depended on the nature of the substituent bonded to the aromatic ring. All complexes exhibited excellent IC₅₀ values. The test compounds were also screened in vitro for their antifungal effect against Candida glabrata and Candida albicans, showing minimum inhibitory concentration (MIC) values lower than those obtained for fluconazole. A brine shrimp bioassay was performed to examine the toxic properties. Molecular docking studies demonstrated that the organotin(IV) complexes bind at the active site of topoisomerase I in a similar manner to topotecan, sharing affinity for certain amino acid side chains (Ile535, Arg364 and Asp533), as well as for similar DNA regions (DA113, DC112 and DT10).

Synthesis, structural and antimicrobial studies of binary and ternary complexes of a new tridentate thiosemicarbazone

A new thiosemicarbazone ligand was synthesized and characterized using spectroscopic techniques (UV-Vis and IR) and synchrotron x-ray powder diffraction. With M²⁺ = Mn²⁺, Zn²⁺ and Cd²⁺, coordination compounds of the type (M[L]₂) were isolated. In the presence of sodium dithiocarbamate salts (NadiEtdtc.3H₂O = sodium diethyldithiocarbamate trihydrate and Napipdtc = sodium piperidinedithiocarbamate), Zn²⁺ and Cd²⁺ were able to form ternary octahedral complexes where each metal binds a deprotonated (thiosemicarbazone) ligand, a monobasic dithiocarbamate ligand and a water molecule. In vitro biological evaluation tests of the free HL ligand and its metal complexes against selected fungal and bacterial cultures were performed. Compared with HL, the complexes displayed enhanced biological activities and ternary Zn (II) complexes displayed comparable antibacterial activities to the chloramphenicol standard.

Screening organometallic thiophene containing thiosemicarbazone ruthenium (II/III) complexes as potential anti-tumour agents

The new ruthenium (III) complex has been synthesized and characterized by elemental analysis, FT-IR, UV-Vis, EI-Mass, EPR spectroscopy, and magnetic susceptibility measurement. Cytotoxic effects of organoruthenium (II/III) complexes 1a, 1b, and 2a, and their ligands (TSC¹ and TSC²) in cultured human ovarian (A2780, SKOV-3, and OVCAR-3) and colon (DLD, CCD18Co, and Caco-2) cells have been investigated comparing reactivity of the Ru (II/III) complexes and their free TSC ligands. The complexes exhibit higher cytotoxicity in three cancer cell lines than in normal cells. The binding with CT-DNA and BSA of the all complexes were weak compared with their ligand in spite of the cellular uptake of these complexes into the cytoplasm and then nucleus while their cytotoxic effects were vice versa. All the results showed that Complex 1b has more efficient cytotoxicity on the colon cancer cells than ovarian cancer cells. However, Complex 2a is a better drug candidate especially for antitumor therapy of metastasized ovarian cancer.

Cyclometallated ruthenium(ii) complexes with 3-acetyl-2[H]-chromene-2-one derived CNS chelating ligand systems: synthesis, X-ray characterization and biological evaluation

The presented work focuses on the synthesis and biological evaluation of 3-acetylcoumarin Schiff bases and their cyclometallated ruthenium(ii) metallates.

Repurposing an inhibitor of ribosomal biogenesis with broad anti-fungal activity

The lack of new antifungal compounds with unique mechanisms of action is a concern for therapeutic management of patients. To identify inhibitors against human pathogenic fungi, we screened ~3000 compounds provided by the Developmental Therapeutics Program of NIH/NCI against a panel of pathogenic fungi including Candida species, Aspergillus fumigatus, and Cryptococcus neoformans. NSC319726 (a thiosemicarbazone) had broad antifungal activity in the range of 0.1–2.0 µg/ml and was also inhibitory to fluconazole-resistant isolates of Candida species. Synergy was demonstrated with NSC319726 and azoles, as well as caspofungin. The inhibitory concentration 50% (IC₅₀) of NSC319726 was 35–800-fold higher than the Minimum Inhibitory Concentration 50% (MIC₅₀ values), which indicates low compound toxicity to human cells in vitro. Transcriptome analysis of treated and untreated C. albicans using Gene Ontology (GO) revealed a large cluster of down regulated genes that encode translational proteins, especially those with ribosome biogenesis functions. As NSC319726 was first shown to have anti-cancer activity, its affects against human pathogenic fungi establish NSC319726 as a repurposed, off-patent compound that has potential antifungal activity. The minimal in vitro toxicity of lead optimized NSC319726 and its reasonable inhibitory activity against pathogens suggest advancing this compound to in vivo toxicity testing and protection studies against candidiasis.

A battery of assays as an integrated approach to evaluate fungal and mycotoxin inhibition properties and cytotoxic/genotoxic side-effects for the prioritization in the screening of thiosemicarbazone derivatives

Aflatoxins represent a serious problem for a food economy based on cereal cultivations used to fodder animal and for human nutrition. The aims of our work are two-fold: first, to perform an evaluation of the activity of newly synthesized thiosemicarbazone compounds as antifungal and anti-mycotoxin agents and, second, to conduct studies on the toxic and genotoxic hazard potentials with a battery of tests with different endpoints. In this paper we report an initial study on two molecules: S-4-isopropenylcyclohexen-1-carbaldehydethiosemicarbazone and its metal complex, bis(S-4-isopropenylcyclohexen-1-carbaldehydethiosemicarbazonato)nickel (II). The outcome of the assays on fungi growth and aflatoxin production inhibition show that both molecules possess good antifungal activities, without inducing mutagenic effects on bacteria. From the assays to ascertain that the compounds have no adverse effects on human cells, we have found that they are cytotoxic and, in the case of the nickel compound, they also present genotoxic effects.

Synthesis, cytotoxicity and antifungal activity of 5-nitro-thiophene-thiosemicarbazones derivatives

In the present work, twelve N-substituted 2-(5-nitro-thiophene)-thiosemicarbazones derivatives (L1-12) were synthesized, characterized and their in vitro cytotoxic and antifungal activities were evaluated against Candida sp. and Cryptococcus neoformans. The probable mechanisms of action have been investigated by sorbitol and ergosterol assays. Additionally, ultrastructural study by Scanning Electron Microscopy was performed with the L10 compound. All compounds were obtained in good yield and their chemical structures were characterized on basis of their physico-chemical and Nuclear Magnetic Resonance - NMR, Spectrophotometric Absorption in the Infrared - IR and High-resolution Mass Spectrometry - HRMS data. The results showed that all strains were more sensitive to the compound L10 except Candida tropicalis URM 6551. On the other hand, the cytotoxicity assay by incorporation of tritiated thymidine showed moderate cytotoxic activity on L8 of the 50 μg/mLat which had the best MIC-cytotoxicity relationship. Concerning the study of the possible mechanism of action, the compounds were not able to bind to ergosterol in the membrane, do not act by inhibiting the synthesis of fungal cell wall (sorbitol assay). However, the Scanning Electron Microscopy - SEM analysis shows significant morphological changes in shape, size, number of cells and hyphae, and cell wall indicating a possible mechanism of action by inhibition of enzymes related to the ergosterol biosynthesis pathway. Our results demonstrate that N-substituted 2-(5-nitro-thiophene)-thiosemicarbazones derivatives are potential antifungal agents with activity associated with inhibition of enzymes related to biosynthesis of ergosterol.

Spectrophotometric determination of Cu(II) in soil and vegetable samples collected from Abraha Atsbeha, Tigray, Ethiopia using heterocyclic thiosemicarbazone

Two selective and sensitive reagents, 2-acetylpyridine thiosemicarbazone (2-APT) and 3-acetylpyridine thiosemicarbazone (3-APT) were used for the spectrophotometric determination of Cu(II). Both reagents gave yellowish Cu(II) complex at a pH range of 8.0-10.0. Beer's law was obeyed for Cu(II)-2-APT and Cu(II)-3-APT in the concentration range of 0.16-1.3 and 0.44-1.05 µg/mL, respectively. The molar absorptivity and of Cu(II)-2-APT and Cu(II)-3-APT were 2.14 × 10(4) at 370 nm, and 6.7 × 10(3) L/mol cm at 350 nm, respectively, while the Sandell's sensitivity were 0.009 and 0.029 µg/cm(2) in that order. The correlation coefficient of the standard curves of Cu(II)-2-APT and Cu(II)-3-APT were 0.999 and 0.998, respectively. The detection limit of the Cu(II)-2-APT and Cu(II)-3-APT methods were 0.053 and 0.147 µg/mL, respectively. The results demonstrated that the procedure is precise (relative standard deviation <2 %, n = 10). The method was tested for Cu(II) determination in soil and vegetable samples. Comparisons of the results with those obtained using a flame atomic absorption spectrophotometer for Cu(II) determination also tested the validity of the method using paired sample t test at the 0.05 level showing a good agreement between them.

Synthesis and antimicrobial activity of tetradentate ligands bearing hydrazone and/or thiosemicarbazone motifs and their diorganotin(IV) complexes

Four novel ligands derived from 2,3-butanedione have been synthesized, two dissymmetric thiosemicarbazone/3-hydroxy-2-naphthohydrazone ligands, H₂L¹ (bearing 4-isopropyl-3-thiosemicarbazone) and H₂L² (containing 4-cyclohexyl-3-thiosemicarbazone) and the symmetric H₂L³, diacetyl bis(3-hydroxy-2-naphthohydrazone), and H₂L⁴, diacetyl bis(4-cyclohexyl-3-thiosemicarbazone). Their reactivity with SnR₂Cl₂ (R=methyl, n-butyl and phenyl) was explored and the resulting complexes were characterized by elemental analysis, molar conductivity, mass spectrometry, IR, ¹H, ¹³C and ¹¹⁹Sn NMR and seven of them also by single crystal X-ray diffraction. The results showed that the reactivity of the dissymmetric ligands is strongly different and while the cyclohexyl derivative is very stable, with isopropyl easily undergoes a symmetrization reaction to yield the corresponding symmetric ligands. The antimicrobial activity of the ligands and the corresponding diorganotin(IV) complexes was investigated in vitro against seven species of microorganisms and minimum inhibitory concentrations (MICs) were determined. The results showed that the ligand H₂L² and several of its derivatives, together with methyl and phenyl complexes of H₂L¹, have the ability of inhibiting the growth of tested bacteria and fungi to different extents. Bacillus subtilis and Staphylococcus aureus Gram positive strains were the most sensitive microorganisms.

A structural and biological study on the new 3,5-diacetyl-1,2,4-triazol bis(p-chlorophenylthiosemicarbazone) ligand and its bimetallic complexes

Preparation and characterization of the new ligand 3,5-diacetyl-1,2,4-triazol bis(⁴N-p-chlorophenylthiosemicarbazone), H₅L¹, and its bimetallic complexes [Pd(μ-H₃L¹)]₂ and [Pt(μ-H₃L¹)]₂, are described.