Inhibition of clinically significant bacterial organisms in vitro by 2-acetylpyridine thiosemicarbazones

Co(ii), Ni(ii), Cu(ii) and Cd(ii)-thiocarbonohydrazone complexes: spectroscopic, DFT, thermal, and electrical conductivity studies

New and stable coordinated compounds have been isolated in a good yield. The chelates have been prepared by mixing Co(ii), Ni(ii), Cu(ii), and Cd(ii) metal ions with (1E)-1-((6-methyl-4-oxo-4H-chromen-3-yl)methylene)thiocarbonohydrazide (MCMT) in 2 : 1 stoichiometry (MCMT : M²⁺). Various techniques, including elemental microanalyses, molar conductance, thermal studies, FT-IR, ¹H-NMR, UV-Vis, and XRD spectral analyses, magnetic moment measurements, and electrical conductivity, were applied for the structural and spectroscopic elucidation of the coordinating compounds. Further, computational studies using the DFT-B3LYP method were reported for MCMT and its metal complexes. MCMT behaves as a neutral NS bidentate moiety that forms octahedral complexes with general formula [M(MCMT)₂Cl(OH₂)]Cl·XH₂O (M = Cu²⁺; (X = ½), Ni²⁺, Co²⁺; (X = 1)); [Cd(MCMT)₂Cl₂]·½H₂O. There is good confirmation between experimental infrared spectral data and theoretical DFT-B3LYP computational outcomes where MCMT acts as a five-membered chelate bonded to the metal ion through azomethine nitrogen and thiocarbonyl sulphur donors. The thermal analysis is studied to confirm the elucidated structure of the complexes. Also, the kinetic and thermodynamic parameters of the thermal decomposition steps were evaluated. The measured optical band gap values of the prepared compounds exhibited semiconducting nature. AC conductivity and dielectric properties of the ligand and its complexes were examined, which showed that Cu(ii) complex has the highest dielectric constant referring to its high polarization and storage ability.

Thiosemicarbazones as Potent Anticancer Agents and their Modes of Action

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Thiosemicarbazones (TSCs) are a class of Schiff bases usually obtained by the condensation of thiosemicarbazide with a suitable aldehyde or ketone. TSCs have been the focus of chemists and biologists due to their wide range of pharmacological effects. One of the promising areas in which these excellent metal chelators are being developed is their use against cancer. TSCs have a wide clinical antitumor spectrum with efficacy in various tumor types such as leukemia, pancreatic cancer, breast cancer, non-small cell lung cancer, cervical cancer, prostate cancer and bladder cancer. To obtain better activity, different series of TSCs have been developed by modifying the heteroaromatic system in their molecules. These compounds possessed significant antineoplastic activity when the carbonyl attachment of the side chain was located at a position α to the ring nitrogen atom, whereas attachment of the side chain β or γ to the heterocyclic N atom resulted in inactive antitumor agents. In addition, replacement of the heterocyclic ring N with C also resulted in a biologically inactive compound suggesting that a conjugated N,N,S-tridentate donor set is essential for the biological activities of thiosemicarbazones. Several possible mechanisms have been implemented for the anticancer activity of thiosemicarbazones.

Thiosemicarbazone derivatives: Design, synthesis and in vitro antimalarial activity studies

Different types of thiosemicarbazone derivatives were designed and tested for their Drug-Like Molecular (DLM) nature by using Lipinski and Veber rules. Subsequently, compounds with DLM properties were synthesized and characterized by spectral methods. In vitro antimalarial activity studies of the synthesized thiosemicarbazone derivatives have been carried out against Plasmodium falciparum, 3D7 strain using fluorescence assay method and found that the compounds, (E)-2-(1-(4-fluorophenyl)ethylidene)hydrazine-1-carbothioamide (6), (E)-2-(1-(3-bromophenyl) ethylidene) hydrazine-1-carbothioamide (15) and (E)-2-(3,4,5-trimethoxybenzylidene) hydrazine-1-carbothioamide (29) showed notable antimalarial activity with EC₅₀ values of 13.54 μM, 15.83 μM and 14.52 μM respectively.

Semicarbazone derivatives as promising therapeutic alternatives in leishmaniasis

In the present study, we investigated the in vitro and in vivo leishmanicidal activity of synthetic compounds, containing a semicarbazone scaffold as a peptide mimetic framework. The leishmanicidal effect against amastigotes of Leishmania amazonensis was also evaluated at concentration of 100 μM-0.01 nM. The derivatives 2e, 2f, 2g and 1g, beyond the standards miltefosine and pentamidine, significantly diminished the number of L. amazonensis amastigotes in macrophages. These derivatives were also active against amastigotes of L. braziliensis. As 2g presented potent leishmanicidal activity against the amastigotes of L. amazonensis in macrophages, we also investigated the in vivo leishmanicidal activity of this compound against L. amazonensis. Approximately 10⁵L. amazonensis promastigotes were subcutaneously inoculated into the dermis of the right ear of BALB/c mice, which were subsequently treated with 2g (p.o. or i.p.), miltefosine (p.o.) or glucantime (i.p.) at 30 μmol/kg/day x 28 days. Thus, a similar reduction in the lesion size was observed after the administration of 2g through oral (63.7 ± 10.1%) and intraperitoneal (61.8 ± 3.7%) routes. A larger effect was observed after treatment with miltefosine (97.7 ± 0.4%), and glucantime did not exhibit activity at the dose administered. With respect to the ear parasite load, 2g diminished the number of parasites by p.o. (30.5 ± 5.1%) and i.p. (33.3 ± 4.3%) administration. In addition, 2g induced in vitro apoptosis, autophagy and cell cycle alterations on L. amazonensis promastigotes. In summary, the derivative 2g might represent a lead candidate for antileishmanial drugs, as this compound displayed pronounced leishmanicidal activity.

In vitro and in vivo cytotoxic activity and human serum albumin interaction for a methoxy-styryl-thiosemicarbazone

Thiosemicarbazone is a class of compounds with potential applications in medicine, presenting high capacity to inhibit the growth of cancer cells as well as low toxicity. Because of high interest in anticancer studies involving thiosemicarbazones as new chemotherapeutic agents, a synthetic thiosemicarbazone derivative, 4-N-(2'-methoxy-styryl)-thiosemicarbazone (MTSC) was evaluated in vivo against Ehrlich carcinoma in an animal model. In vivo results demonstrated that MTSC treatment induced the survival of mice and altered significantly the body weight of the surviving mice 12 days after tumor inoculation. Treatment with 30 mg/kg of MTSC exhibited effective cytotoxic activity with T/C values of 150.49% (1 dose) and 278% (2 doses). Its interaction with human serum albumin (HSA), which plays a crucial role in the biodistribution of a wide variety of ligands, was investigated by multiple spectroscopic techniques at 296 K, 303 K, and 310 K, as well as by theoretical calculations. The interaction between HSA and MTSC occurs via ground-state association in the subdomain IIA (Sudlow's site I). The binding is moderate (K_a ≈ 10⁴ M^-1), spontaneous, entropically, and enthalpically driven. Molecular docking results suggested hydrogen bonding and hydrophobic interactions as the main binding forces. Overall, the interaction HSA:MTSC could provide therapeutic benefits, improving its cytotoxic efficacy and tolerability.

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.

Adsorption and quantum chemical studies on the inhibition potentials of some thiosemicarbazides for the corrosion of mild steel in acidic medium

Three thiosemicarbazides, namely 2-(2-aminophenyl)-N phenylhydrazinecarbothioamide (AP4PT), N,2-diphenylhydrazinecarbothioamide (D4PT) and 2-(2-hydroxyphenyl)-N-phenyl hydrazinecarbothioamide (HP4PT), were investigated as corrosion inhibitors for mild steel in H(2)SO(4) solution using gravimetric and gasometric methods. The results revealed that they all inhibit corrosion and their % inhibition efficiencies (%IE) follow the order: AP4PT > HP4PT > D4PT. The %IE obtained from the gravimetric and gasometric experiments were in good agreement. The thermodynamic parameters obtained support a physical adsorption mechanism and the adsorption followed the Langmuir adsorption isotherm. Some quantum chemical parameters were calculated using different methods and correlated with the experimental %IE. Quantitative structure activity relationship (QSAR) approach was used on a composite index of some quantum chemical parameters to characterize the inhibition performance of the studied molecules. The results showed that the %IE were closely related to some of the quantum chemical parameters, but with varying degrees. The calculated/theoretical %IE of the molecules were found to be close to their experimental %IE. The local reactivity has been studied through the Fukui and condensed softness indices in order to predict both the reactive centers and to know the possible sites of nucleophilic and electrophilic attacks.

Iron and Cobalt Complexes of 2,6-Diacetylpyridine-bis(R-thiosemicarbazone) (R=H, phenyl) Showing Unprecedented Ligand Deviation from Planarity

The syntheses, characterization, and single-crystal X-ray crystal structures are reported for four complexes of iron and cobalt with the pentadentate ligands, 2,6-diacetylpyridinebis(thiosemicarbazone) (H(2)L(1)) and 2,6-diacetylpyridinebis-(phenylthiosemicarbazone) (H(2)L(2)), including a cobalt dimer displaying a deviation from planarity which is unprecedented for this class of ligands and allows the ligand to occupy five positions of a pseudo-octahedral coordination sphere. This dimer reacts with KCN to produce a mononuclear complex of relevance to the active site of cobalt nitrile hydratase.

Antimicrobial activity of some schiff bases derived from benzoin, salicylaldehyde, aminophenol and 2,4 dinitrophenyl hydrazine

The antibacterial and antifungal activities of three schiff bases were evaluated against some pathogenic bacteria and fungi. Parallel experiments were also carried out with standard drugs (Kanamycin for bacteria and Nystatin for fungi). Two compounds [N-(1-phenyl-2-hydroxy-2phenylethylidine)-2',4' dinitrophenyl hydrazine, abbreviated as PDH and N-(2-hydroxy benzylidine)-2'-hydroxy imine, abbreviated as HHP] showed significant antimicrobial activities. The rest one [N-(1-phenyl 2-hydroxy-2 phenyl ethylidine) 2'-hydroxy phenyl imine, abbreviated as PHP] showed moderate activity. All these three compounds were found to possess pronounced cytotoxic effect. These compounds can be considered as potent antimicrobial agents.

Syntheses, crystal structures and antimicrobial activities of 6-coordinate antimony(III) complexes with tridentate 2-acetylpyridine thiosemicarbazone, bis(thiosemicarbazone) and semicarbazone ligands

Five novel antimony(III) complexes with the mono- and bis(thiosemicarbazone) ligands of 2N1S or 4N2S donor atoms, N'-[1-(2-pyridyl)ethylidene]morpholine-4-carbothiohydrazide (Hmtsc, L1) and bis[N'-[1-(2-pyridyl)ethylidene]]-1,4-piperazinedicarbothiohydrazide (H(2)ptsc, L7), and the tridentate semicarbazone ligand of 2N1O donor atoms, 2-acetylpyridine semicarbazone (Hasc, L2b), were prepared by reactions of SbCl(3) or SbBr(3), and characterized by elemental analysis, TG/DTA, FT-IR and (1)H NMR spectroscopy. The crystal and molecular structures of five antimony(III) complexes were determined by single-crystal X-ray structure analysis. The neutral, 6-coordinate antimony(III) complexes ([Sb(mtsc)Cl(2)] 1, [Sb(mtsc)Br(2)] 2, [Sb(asc)Cl(2)] 3 and [Sb(asc)Br(2)] 4) are depicted with one electron pair (5s(2)) of the antimony(III) atom, deprotonated forms of multidentate thiosemicarbazone or semicarbazone ligands, and two monodentate halogen ligands, respectively. In the dimer complex 5 ([Sb(2)(ptsc)Cl(4)]) with the ligand in which two tridentate thiosemicarbazone moieties are connected by the piperazine moiety, each antimony(III) was also described as a neutral 6-coordinate structure. These antimony(III) complexes were thermally stable around 200 degrees C. Water-soluble antimony(III) complexes 1 and 2 showed moderate antimicrobial activities against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and -negative bacteria (Escherichia coli and Pseudomonas aeruginosa), yeasts (Candida albicans and Saccharomyces cerevisiae) and molds (Aspergillus niger and Penicillium citrinum). Complex 5 showed moderate antimicrobial activities against four bacteria, and two molds, while the ligand itself showed only modest antimicrobial activities against selected bacteria (B. subtilis, E. coli and S. aureus). The molecular structures and antimicrobial activities of antimony(III) complexes were compared with those of bismuth(III) complexes in the same 15 group in the periodic table.

Synthesis and structure-activity correlation studies of metal complexes of alpha-N-heterocyclic carboxaldehyde thiosemicarbazones in Shewanella oneidensis

This investigation involved the synthesis of metal complexes to test the hypothesis that structural changes and metal coordination in pyridine thiosemicarbazones affect cell growth and cell proliferation in vitro. Thiosemicarbazones are well known to possess antitumor, antiviral, antibacterial, antimalarial, and other activities. Extensive research has been carried out on aliphatic, aromatic, heterocyclic and other types of thiosemicarbazones and their metal complexes. Due to the pronounced reactivity exhibited by metal complexes of heterocyclic thiosemicarbazones, synthesis and structural characterization of di-2-pyridylketone ⁴N-phenyl thiosemicarbazone and diphenyl tin (Sn) and platinum (Pt) complexes were undertaken. Shewanella oneidensis MR-1, a metal ion-reducing bacterium, was used as a model organism to explore the biological activity under aerobic conditions. A comparision of the cytotoxic potential of selected ligand and metal-complex thiosemicarbazones on cell growth in wild type MR-1 and mutant DSP-010 Shewanella oneidensis strains at various concentrations (0, 5, 10, 15, 20 or 25 ppm) was performed. The wild type (MR-1) grown in the presence of increasing concentrations of Sn- thiosemicarbazone complexes was comparatively more sensitive (mean cell number = 4.8 × 10⁸ ± 4.3 × 10⁷ SD) than the DSP-010, a spontaneous rifampicillin derivative of the parent strain (mean cell number = 5.6 × 10⁸ ± 6.4 × 10⁷ SD) under comparable aerobic conditions (p=0.0004). No differences were observed in the sensitivity of the wild and mutant types when exposed to various concentrations of diphenyl Pt- thiosemicarbazone complex (p= 0.425) or the thiosemicarbazone ligand (p=0.313). Growth of MR-1 in the presence of diphenyl Sn- thiosemicarbazone was significantly different among treatment groups (p=0.012). MR-1 cell numbers were significantly higher at 5ppm than at 10 to 20ppm (p = 0.05). The mean number of DSP-010 variant strain cells also differed among diphenyl Sn- thiosemicarbazone complex treated groups (p=0.051). In general, there was an increasing trend in the number of cells from about 5.0 × 10⁸ cells (methanol control group) to about 6.0 × 10⁸ cells (25ppm). The number of cells in methanol control group was significantly lower than cell numbers at 20ppm and 25ppm (p = 0.05), and numbers at 5ppm treatment were lower than at 20 and 25ppm (p = 0.05). Furthermore, a marginally significant difference in the number of MR-1 cells was observed among diphenyl Pt- thiosemicarbazone complex treatment groups (p = 0.077), and an increasing trend in the number of cells was noted from ~5.0 × 10⁸ cells (methanol control group) to ~5.8 × 10⁸ cells (20ppm). In contrast, the DSP-010 variant strain showed no significant differences in cell numbers when treated with various concentrations of diphenyl Pt- thiosemicarbazone complex (p = 0.251). Differences in response to Sn- metal complex between MR-1 and DSP-010 growing cultures indicate that biological activity to thiosemicarbazone metal complexes may be strain specific.

Cyclooctadiene Ru(II) complexes of thiophene-2-carboxaldehyde-derived thiosemicarbazones: synthesis, characterization and antiamoebic activity

Thiosemicarbazones (TSC) 1-10 were synthesized by condensing substituted thiosemicarbazide with thiophene-2-carboxaldehyde. These thiosemicarbazones were further reacted with [Ru(eta4-C8H12)(CH3CN)2Cl2] to form complexes of the type [Ru(eta4-C8H12)(TSC)Cl2] 1a-10a. Thiosemicarbazones exhibited antiamoebic activity in the range IC50=1.09-5.42 microM. In vitro assessment of antiamoebic activity indicated that the thiosemicarbazones 3, IC50=1.67 microM, 4, IC50=1.11 microM and 6, IC50=1.09 microM showed substantially less IC50 value than metronidazole (IC50=1.87 microM), a commonly used drug against amoebiasis. Cyclooctadiene Ru(II) complexes of thiosemicarbazones showed significant improvement in antiamoebic activity (IC50=0.30-1.39 microM). All the complexes possess noteworthy potencies and showed less IC50 values than metronidazole against HK-9 strain of Entamoeba histolytica. Among all the complexes, the most promising antiamoebic activities was shown by the complexes 4a and 6a (IC50=0.31 microM of 4a and IC50=0.30 microM of 6a versus metronidazole).

Copper complexes of imidazole-2-, pyrrole-2- and indol-3-carbaldehyde thiosemicarbazones: inhibitory activity against fungi and bacteria

Copper complexes of thiosemicarbazones of imidazole-2-carbaldehyde, pyrrole-2-carbaldehyde and indole-3-carbaldehyde were synthesised and characterised. The antimicrobial properties of the free ligands and their complexes were evaluated against yeasts, moulds and bacteria (Gram-positive and Gram-negative). Some copper chelates exhibited a moderate inhibitory activity, better than that of the corresponding free ligands. In particular, the pyrrole derivative [Cu(HL(2))(2)] proved to be a wide spectrum agent, showing an interesting inhibition of the growth of all Gram-positive bacteria and fungi tested at concentrations of 12-50 microg/mL. In contrast, a selective effect was observed for imidazole and indole chelates against fungi and Gram-positive bacteria, respectively.

Novel bidentate complexes of Cu(II) derived from 5-nitrofuran-2-carboxaldehyde thiosemicarbazones with antiamoebic activity against E. histolytica

The novel analogues of 5-nitrofuran-2-carboxaldehyde thiosemicarbazones 1-10 were synthesized and their copper(II) complexes 1a-10a were obtained by means of coordination with cupric chloride. All these compounds have been characterized by elemental analysis, IR, electronic spectra and thermogravimetric patterns while ligands have also been characterized by 1H NMR spectral studies. These copper complexes are bidentate and possess octahedral geometry around Cu(II) ion. Their antiamoebic activities were carried out to ascertain their effectiveness in comparison to their corresponding thiosemicarbazones. A number of these complexes possess noteworthy potencies towards HK-9 strain of Entamoeba histolytica in vitro. The complexes 2a-7a, 9a and 10a showed less IC50 value than metronidazole, the drug of choice for amoebiasis. Moreover, complexes 2a and 9a have shown the most promising antiamoebic activities (IC50 = 0.38 microM of 2a and IC50 = 0.34 microM of 9a versus IC50 = 1.81 microM of metronidazole). These results indicate that the metallated thiosemicarbazone may be lead molecule to inhibit growth of E. histolytica.

Synthesis, characterization and in vitro anti-amoebic activity of new palladium(II) complexes with 5-nitrothiophene-2-carboxaldehyde N(4)-substituted thiosemicarbazones

Reaction between [Pd(DMSO)(2)Cl(2)] (DMSO=dimethylsulfoxide) and N(4)-substituted thiosemicarbazones derived from 5-nitrothiophene-2-carboxaldehyde (L) afforded the complexes [Pd(L)Cl(2)]. These new complexes have been characterized by elemental analyses and spectroscopic studies. Spectroscopic studies reveal that thionic sulfur and azomethine nitrogen atom of thiosemicarbazones are coordinated to metal ion. The testing of the anti-amoebic activity of these complexes against the protozoan parasite Entamoeba histolytica suggests that compound 9, 10, and 11 might be endowed with important anti-amoebic properties since they showed less IC(50) values than metronidazole. Moreover, compound 11 displays notable amoebicidal activity than metronidazole (IC(50) values of 0.79 microM vs 1.93 microM, respectively).

Syntheses, crystal structures and antimicrobial activities of monomeric 8-coordinate, and dimeric and monomeric 7-coordinate bismuth(III) complexes with tridentate and pentadentate thiosemicarbazones and pentadentate semicarbazone ligands

Novel bismuth(III) complexes 1-4 with the tridentate thiosemicarbazone ligand of 2N1S donor atoms [Hmtsc (L1); 2-acetylpyridine (4N-morpholyl thiosemicarbazone)], the pentadentate double-armed thiosemicarbazone ligand of 3N2S donor atoms [H2dmtsc (L3); 2,6-diacetylpyridine bis(4N-morpholyl thiosemicarbazone)] and the pentadentate double-armed semicarbazone ligand of 3N2O donor atoms [H2dasc (L4b); 2,6-diacetylpyridine bis(semicarbazone)], were prepared by reactions of bismuth(III) nitrate or bismuth(III) chloride and characterized by elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FTIR and NMR (1H and 13C) spectroscopy. The crystal and molecular structures of complexes 1, 2a, 2b and 4b, and the "free" ligand L1 were determined by single-crystal X-ray structure analysis. The dimeric 7-coordinate bismuth(III) complex [Bi(dmtsc)(NO3)]2, 1, and the monomeric 7-coordinate complexes [Bi(Hdasc)(H2O)](NO3)2.H2O (major product), 2a, and [Bi(dasc)(H2O)]NO3.H2O (minor product), 2b, all with pentagonal bipyramidal bismuth(III) centers, are depicted with one electron pair (6s2) of the bismuth(III) atom, deprotonated forms of multidentate thiosemicarbazone or semicarbazone ligands, and monodentate NO3 or H2O ligands, respectively. These complexes are related to the positional isomers of one electron pair of the bismuth(III) atom; 1 has an electron pair positioned in the pentagonal plane (basal position), while 2a and 2b have an electron pair in the apical position. The monomeric 8-coordinate complex [Bi(mtsc)2(NO3)], 4b, which was obtained by slow evaporation in MeOH of the 1.5 hydrates 4a, was depicted with one electron pair of the bismuth(III) atom, two deprotonated mtsc- ligand and one nitrate ion. On the other hand, crystals of the complex "[Bi(mtsc)Cl2]", 3, prepared by a reaction of BiCl3 with L1 showed several polymorphs (3a, 3b, 3c and 3d) due to coordination and/or solvation of dimethyl sulfoxide (DMSO) used in the crystallization. Bismuth(III) complexes 1 and 4a showed selective and effective antibacterial activities against Gram-positive bacteria. The structure-activity relationship was discussed.

Synthesis, characterization and in vitro Antiamoebic Activity of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones and their Palladium (II) and Ruthenium (II) Complexes

Synthesis of new Palladium(II) and Ruthenium(II) complexes of the type, [Pd(L)Cl(2)] and [Ru(eta(4)-C(8)H(12))(L)Cl(2)] [where, L = thiosemicarbazones derived from 5-nitrothiophene-2-carboxaldehyde and cycloalkylaminothiocarbonyl hydrazines] have been isolated by the reaction of [Pd(DMSO)(2)Cl(2)] and [Ru(eta(4)-C(8)H(12))(CH(3)CN)(2)Cl(2)] with 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones. The spectral data revealed that the thiosemicarbazones act as bidentate ligands, making use of thionic sulphur and the azomethine nitrogen atom for coordination to the central metal ion. Microdilution method was used for the assessment of antiamoebic activity of all the compounds against HK-9 strain of Entamoeba histolytica. Among all the thiosemicarbazones, 5-NT-4-BPTSCN (3) showed significant antiamoebic activity (IC(50) - 2.56 microM). Enhancement of antiamoebic activity resulted by introducing palladium and ruthenium metals in the thiosemicarbazone moiety. All the Pd(II) and Ru(II) complexes of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones were found more active then their respective ligands. The complexes 1a-4a, 1b and 3b showed antiamoebic activity.

New palladium(II) complexes of 5-nitrothiophene-2-carboxaldehyde thiosemicarbazones. synthesis, spectral studies and in vitro anti-amoebic activity

Thiosemicarbazones (1-7) and their palladium(II) complexes (1a-7a) of the type [Pd(TSCN)Cl(2)] (where TSCN=thiosemicarbazone) were prepared from 5-nitro thiophene-2-carboxaldehyde and [Pd(DMSO)(2)Cl(2)], respectively. Coordination via the thionic sulphur and the azomethine nitrogen atom of the thiosemicarbazones to the metal ion were confirmed by spectral data. These compounds were screened in vitro against (HK-9) strain of Entamoeba histolytica possess amoebicidal properties. Enhancement of antiamoebic activity resulted due to the introduction of palladium metal in the thiosemicarbazone moiety. The most promising of the group tested are [Pd(5-N-2-TCA-COTSCN)Cl(2)] and [Pd(5-N-2-TCA-AdmTSCN)Cl(2)] comparable to that of metronidazole.

Synthesis, spectral studies and screening for amoebicidal activity of new palladium(II) complexes derived from thiophene-2-carboxaldehyde thiosemicarbazones

In view of the antiamoebic properties observed for many thiophene-2-carboxaldehyde thiosemicarbazones, a series of N(4)-substituted thiosemicarbazones metal complexes derived from thiophene-2-carboxaldehyde was prepared for evaluation against Entamoeba histolytica. Reaction of thiophene-2-carboxaldehyde with cycloalkylaminothiocarbonylhydrazines having different amines gave the corresponding thiosemicarbazones. Reaction of latter with [Pd(DMSO)(2)Cl(2)] gave requisite palladium thiosemicarbazone complexes of the type [Pd(TSC)Cl(2)] (where TSC=thiosemicarbazones). Screening of antiamoebic activity of these compounds was assayed in vitro against (HM-1:1MSS) strain of E. histolytica. Enhancement of antiamoebic resulted from introducing palladium metal in the thiosemicarbazone moiety. Among the studied compounds, [Pd(2-TCA-1,2,3,4-THQTSC)Cl(2)] (2a) showed better activity.