Acenaphthenequinone thiosemicarbazone and its transition metal complexes: synthesis, structure, and biological activity

New imidazole-2-thiones linked to acenaphythylenone as dual DNA intercalators and topoisomerase II inhibitors: structural optimization, docking, and apoptosis studies

In this article, a new series of 2-((3,5-disubstituted-2-thioxo-imidazol-1-yl)imino)acenaphthylen-1(2H)-ones were synthesized. Imidazole-2-thione with acenaphthylen-one gave a hybrid scaffold that integrated key structural elements essential for DNA damage via direct DNA intercalation and inhibition of the topoisomerase II enzyme. All the synthesized compounds were screened to detect their DNA damage using a terbium fluorescent probe. Results demonstrated that 4-phenyl-imidazoles 5b and 5e in addition to 4-(4-chlorophenyl)imidazoles 5h and 5j would induce detectable potent damage in ctDNA. The four most potent compounds as DNA intercalators were further evaluated for their antiproliferative activity against HepG2, MCF-7 and HCT-116 utilizing the MTT assay. The highest anticancer activity was recorded with compounds 5b and 5h against the breast cancer cell line MCF-7 which were 1.5- and 3- folds more active than doxorubicin, respectively. Therefore, imidazole-2-thione tethered acenaphthylenone derivatives can be considered as promising scaffold for the development of effective dual DNA intercalators and topoisomerase II inhibitors.

Evaluation of anticancer activity of novel platinum(II) bis(thiosemicarbazone) complex against breast cancer

The study aims to synthesize a novel bis(thiosemicarbazone) derivative based on platinum (thioPt) and evaluate its anticancer properties against MFC-7 and MDA-MB-231 breast cancer cells. A new platinum complex was synthesised by reacting K2PtCl4 with 2,2'-(1,2-diphenylethane-1,2-diylidene)bis(hydrazine-1-carbothioamide) in ethanol in the presence of K2CO3. In the obtained complex, the platinum atom is coordinated by a conjugated system = N-NC-S-The structures of the new compound were characterised using NMR spectroscopy, HR MS, IR, and X-ray structural analysis. The obtained results of the cytotoxicity assay indicate that compound thioPt had potent anticancer activity (MCF-7: 61.03 ± 3.57 µM, MDA-MB-231: 60.05 ± 5.40 µM) with less toxicity against normal MCF-10A breast epithelial cells, even compared to the reference compound (cisplatin). In addition, subsequent experiments found that thioPt induces apoptosis through both an extrinsic (↑caspase 8 activity) and intrinsic (↓ΔΨm) pathway, which ultimately leads to an increase in active caspase 3/7 levels. The induction of autophagy and levels of proteins involved in this process (LC3A/B and Beclin-1) were examined in MCF-7 and MDA-MB-231 breast cancer cells exposed to tested compounds (thio, thioPt, cisPt) at a concentration of 50 µM for 24 h. Based on these results, it can be concluded that thio and thioPt do not significantly affect the autophagy process. This demonstrates their superiority over cisplatin, which can stimulate cancer cell survival through its effect on stimulation of autophagy.

Structural and Functional Diversity in Rigid Thiosemicarbazones with Extended Aromatic Frameworks: Microwave-Assisted Synthesis and Structural Investigations

The long-standing interest in thiosemicarbazones (TSCs) has been largely driven by their potential toward theranostic applications including cellular imaging assays and multimodality imaging. We focus herein on the results of our new investigations into: (a) the structural chemistry of a family of rigid mono(thiosemicarbazone) ligands characterized by extended and aromatic backbones and (b) the formation of their corresponding thiosemicarbazonato Zn(II) and Cu(II) metal complexes. The synthesis of new ligands and their Zn(II) complexes was performed using a rapid, efficient and straightforward microwave-assisted method which superseded their preparation by conventional heating. We describe hereby new microwave irradiation protocols that are suitable for both imine bond formation reactions in the thiosemicabazone ligand synthesis and for Zn(II) metalation reactions. The new thiosemicarbazone ligands, denoted HL, mono(4-R-3-thiosemicarbazone)quinone, and their corresponding Zn(II) complexes, denoted ZnL₂, mono(4-R-3-thiosemicarbazone)quinone, where R = H, Me, Ethyl, Allyl, and Phenyl, quinone = acenapthnenequinone (AN), aceanthrenequinone (AA), phenanthrenequinone (PH), and pyrene-4,5-dione (PY) were isolated and fully characterized spectroscopically and by mass spectrometry. A plethora of single crystal X-ray diffraction structures were obtained and analyzed and the geometries were also validated by DFT calculations. The Zn(II) complexes presented either distorted octahedral geometry or tetrahedral arrangements of the O/N/S donors around the metal center. The modification of the thiosemicarbazide moiety at the exocyclic N atoms with a range of organic linkers was also explored, opening the way to bioconjugation protocols for these compounds. The radiolabeling of these thiosemicarbazones with ⁶⁴Cu was achieved under mild conditions for the first time: this cyclotron-available radioisotope of copper (t_1/2 = 12.7 h; β+ 17.8%; β- 38.4%) is well-known for its proficiency in positron emission tomography (PET) imaging and for its theranostic potential, on the basis of the preclinical and clinical cancer research of established bis(thiosemicarbazones), such as the hypoxia tracer ⁶⁴Cu-labeled copper(diacetyl-bis(N4-methylthiosemicarbazone)], [⁶⁴Cu]Cu(ATSM). Our labeling reactions proceeded in high radiochemical incorporation (>80% for the most sterically unencumbered ligands) showing promise of these species as building blocks for theranostics and synthetic scaffolds for multimodality imaging probes. The corresponding "cold" Cu(II) metalations were also performed under the mild conditions mimicking the radiolabeling protocols. Interestingly, room temperature or mild heating led to Cu(II) incorporation in the 1:1, as well as 1:2 metal: ligand ratios in the new complexes, as evident from extensive mass spectrometry investigations backed by EPR measurements, and the formation of Cu(L)₂-type species prevails, especially for the AN-Ph thiosemicarbazone ligand (L^-). The cytotoxicity levels of a selection of ligands and Zn(II) complexes in this class were further tested in commonly used human cancer cell lines (HeLa, human cervical cancer cells, and PC-3, human prostate cancer cells). Tests showed that their IC₅₀ levels are comparable to that of the clinical drug cis-platin, evaluated under similar conditions. The cellular internalizations of the selected ZnL₂-type compounds Zn(AN-Allyl)₂, Zn(AA-Allyl)₂, Zn(PH-Allyl)₂, and Zn(PY-Allyl)₂ were evaluated in living PC-3 cells using laser confocal fluorescent spectroscopy and these experiments showed exclusively cytoplasmic distributions.

Research Progress on the Biological Activities of Metal Complexes Bearing Polycyclic Aromatic Hydrazones

Due to the abundant and promising biological activities of aromatic hydrazones, it is of great significance to study the biological activities of their metal complexes for the research and development of metal-based drugs. In this review, we focus on the metal complexes of polycyclic aromatic hydrazones, which still do not receive much attention, and summarize the studies related to their biological activities. Although the large number of metal complexes in phenylhydrazone prevent them all from being summarized, the significant value of polycyclic aromatic hydrocarbons themselves (such as naphthalene and anthracene) as pharmacophores are also considered. Therefore, the bioactivities of the metal complexes of naphthylhydrazone and anthrahydrazone are focused on, and the recent research progress on the metal complexes of anthrahydrazone by the authors is also included. In terms of biological activities, these complexes mainly show antibacterial and anticancer activities, along with less bioactivities. The present review demonstrates that the structural design and bioactivities of these complexes are fundamental, which also indicates a certain structure-activity relationship (SAR) in some substructural areas. However, a systematic and comprehensive conclusion of the SAR is still not available, which suggests that more attention should be paid to the bioactivities of the metal complexes of polycyclic aromatic hydrazones since their potential in structural design and biological activity remains to be explored. We hope that this review will attract more researchers to devote their interest and energy into this promising area.

Functional, Aromatic, and Fluorinated Monothiosemicarbazones: Investigations into Their Structures and Activity toward the Gallium-68 Incorporation by Microwave Irradiation

We report on the synthesis and spectroscopic characterization of a new series of coordinating monothiosemicarbazones incorporating aromatic backbones, featuring O/N/S donor centers monosubstituted with different aliphatic, aromatic, fluorinated, and amine-functionalized groups at their N centers. Their ability to bind metal ions such as Zn(II) and Ga(III) was explored, and the formation of two different coordination isomers of the Zn(II) complex was demonstrated by X-ray diffraction studies using synchrotron radiation. These studies showed the planar geometry for the coordinated mono(thiosemicarbazone) ligand and that the metal center can adopt either a heavily distorted tetrahedral Zn center (placed in an N/S/S/N environment, with CN = 4) or a pseudo-octahedral geometry, where the Zn(II) center is in the O/N/S/S/N/O environment, and CN = 6. Furthermore, 2-(4,5-dimethyl-2-thiazolyl)-3,5-diphenyl-2H-tetrazolium bromide (MTT) assays and cellular imaging in living cells were subsequently performed in two different cancer cell lines: PC-3 (a standard cell line derived from a bone metastasis of a stage IV prostate cancer) and EMT6 (a commercial murine mammary carcinoma cell line). The radiolabeling of new functional and aromatic monothiosemicarbazones with either gallium-68 (under pH control) or fluorine-18 is discussed. The potential of this class of compounds to act as synthetic scaffolds for molecular imaging agents of relevance to positron emission tomography was evaluated in vitro, and the cellular uptake of a simultaneously fluorinated and [⁶⁸Ga]-labeled mono(thiosemicarbazone) was investigated and is reported here.

Spectral, Molecular Modeling, and Biological Activity Studies on New Schiff's Base of Acenaphthaquinone Transition Metal Complexes

The newly synthesized Schiff's base derivative, N-allyl-2-(2-oxoacenaphthylen-1(2H)-ylidene)hydrazine-1-carbothioamide, has been characterized by different spectral techniques. Its reaction with Co(II), Ni(II), and Zn(II) acetate led to the formation of 1 : 1 (M:L) complexes. The IR and NMR spectral data revealed keto-thione form for the free ligand. On chelation with Co(II) and Ni(II), it behaved as mononegative and neutral tridentate via O, N¹, and S donors, respectively, while it showed neutral bidentate mode via O and N¹ atoms with Zn(II). The electronic spectra indicated that all the isolated complexes have an octahedral structure. The thermal gravimetric analyses confirmed the suggested formula and the presence of coordinated water molecules. The XRD pattern of the metal complexes showed that both Co(II) and Ni(II) have amorphous nature, while Zn(II) complex has monoclinic crystallinity with an average size of 9.10 nm. DFT modeling of the ligand and complexes supported the proposed structures. The calculated HOMO-LUMO energy gap, ΔE_H-L, of the ligand complexes was 1.96–2.49 eV range where HAAT < Zn(II) < Ni(II) < Co(II). The antioxidant activity investigation showed that the ligand and Zn(II) complex have high activity than other complexes, 88.5 and 88.6%, respectively. Accordingly, the antitumor activity of isolated compounds was examined against the hepatocellular carcinoma cell line (HepG2), where both HAAT and Zn(II) complex exhibited very strong activity, IC₅₀ 6.45 ± 0.25 and 6.39 ± 0.18 μM, respectively.

Functionalized 1,3-Thiazolidin-4-Ones from 2-Oxo-Acenaphthoquinylidene- and [2.2]Paracyclophanylidene-Thiosemicarbazones

The reactions of dialkyl acetylenedicarboxylates with various 2-oxo-acenaphthoquinylidene- and 4-acetyl[2.2]paracyclophanylidene-thiosemicarbazones were investigated. Using simple experimental procedures, 1,3-Thiazolidin-4-ones derived from acenaphthequinone or [2.2]paracyclophane were obtained as major products in good yields. In the case of allyl derivative of acenaphthoquinylidene-thiosemicarbazones, a complex structure of tetramethyl 5-(2-(((Z,E)-N-allyl-N′-(2-oxoacenaphthylen-1(2H)-ylidene)carbamohydrazonoyl)thio)-1,2,3-tris-(methoxycarbonyl)-cyclopropyl)-4-methoxy-7-oxabicyclo[2.2.1]hepta-2,5-diene-1,2,3,6-tetracarboxylate was formed. Single crystal X-ray analysis was used as an efficient tool to confirm the structure of the synthesized compounds as well as different spectroscopic data (¹H-NMR, ¹³C-NMR, 2D-NMR, mass spectrometry and elemental analysis). The mechanism of the obtained products was discussed.

Synthesis, structural and spectroscopic studies of 2-oxoacenaphthylen-1(2H)-ylidene nicotinohydrazide

The synthesis of a new hydrazone, 2-oxoacenaphthylen-1(2H)-ylidene nicotinohydrazide, and its structural and spectroscopic characterization is reported. The obtained powder was recrystallized from DMSO and ethanol that afforded small crystals used for single-crystal X-ray diffraction studies. The compound was found to crystallize in two polymorphs, depending on the crystallization conditions. One of the polymorphs (form I) crystallizes in the centrosymmetric P2₁/c monoclinic space group, the other (form II) crystallizes in the non-centrosymmetric, but achiral, orthorhombic space group P2₁2₁2₁. Conformation of the molecules is similar in both polymorphs, but the network of weak intermolecular interactions determining the crystal packing is different. In form II an additional C-H⋯O bond connects molecules related by the screw-axis running parallel to the a-axis. Crystals of both polymorphs were also screened by FT-IR and Raman microscopy; a detailed analysis of the spectra and comparison with those of the isolated molecule calculated by ab-initio HF/MP2 and DFT/B3LYP methods using a correlation consistent cc-pVDZ basis set is presented. In addition, UV-vis and NMR studies were performed in solution.

Applications of "Hot" and "Cold" Bis(thiosemicarbazonato) Metal Complexes in Multimodal Imaging

The applications of coordination chemistry to molecular imaging has become a matter of intense research over the past 10 years. In particular, the applications of bis(thiosemicarbazonato) metal complexes in molecular imaging have mainly been focused on compounds with aliphatic backbones due to the in vivo imaging success of hypoxic tumors with PET (positron emission tomography) using (64) CuATSM [copper (diacetyl-bis(N4-methylthiosemicarbazone))]. This compound entered clinical trials in the US and the UK during the first decade of the 21(st) century for imaging hypoxia in head and neck tumors. The replacement of the ligand backbone to aromatic groups, coupled with the exocyclic N's functionalization during the synthesis of bis(thiosemicarbazones) opens the possibility to use the corresponding metal complexes as multimodal imaging agents of use, both in vitro for optical detection, and in vivo when radiolabeled with several different metallic species. The greater kinetic stability of acenaphthenequinone bis(thiosemicarbazonato) metal complexes, with respect to that of the corresponding aliphatic ATSM complexes, allows the stabilization of a number of imaging probes, with special interest in "cold" and "hot" Cu(II) and Ga(III) derivatives for PET applications and (111) In(III) derivatives for SPECT (single-photon emission computed tomography) applications, whilst Zn(II) derivatives display optical imaging properties in cells, with enhanced fluorescence emission and lifetime with respect to the free ligands. Preliminary studies have shown that gallium-based acenaphthenequinone bis(thiosemicarbazonato) complexes are also hypoxia selective in vitro, thus increasing the interest in them as new generation imaging agents for in vitro and in vivo applications.

Novel synthesis of palladium (II) complexes derived from 3-arylsydnone-4-carbaldehyde N(4)-phenylthiosemicarbazones and biological activity

Objectives

The aim of this research is to investigate whether the oxygen atom O(6) in the sydnone ring of 3-arylsydnone-4-carbaldehyde N(4)-phenylthiosemicarbazones (HArSYTSCs, 3a–d) is a good electron donor atom upon metal complexation. Furthermore, ligands 3a–d and the corresponding palladium complexes (Pd(ArSYTSC)Cl, 4a–d) would be expected to find their potent biological activities.

Methods

The desired palladium complexes 4a–d were first synthesized from thiosemicarbazones 3a–d. Then, the antiproliferative activity of ligands 3a–d and complexes 4a-d were tested against human hepatocellular carcinoma and human cervical epithelioid carcinoma (HeLa) cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl trazolium bromide (MTT) assay.

Key findings

According to X-ray analyses, ligands 3a–d are bonded to the Pd (II) center in an O, N, S-tridentate coordination mode through sydnone carbonyl oxygen O(6), azomethine nitrogen and the thiolate sulfur atom. The carbonyl oxygen of the sydnone ring is found to be a good electron donor site upon metal complexation. Moreover, MTT assay results reveal that the palladium complexes 4a–d have greater antiproliferative activity than 5-fluorouracil. In particular, the complexes exhibit obvious better activity than the corresponding ligands 3a–d against HeLa cell.

Conclusions

The results indicate that the synthesized novel palladium complexes have greater antiproliferative activity than both 5-fluorouracil and the corresponding ligands against HeLa cell. Accordingly, the study of sydnonyl complexes bearing anticancer activities may support the development of coordination chemistry.

Ruthenium(II) complexes containing quinone based ligands: synthesis, characterization, catalytic applications and DNA interaction

1,2-Naphthaquinone reacts with amines such as semicarbazide, isonicotinylhydrazide and thiosemicarbazide in high yield procedure with the formation of tridentate ligands HL(n) (n=1-3). By reaction of ruthenium(II) starting complexes and quinone based ligands HL(n) (n=1-3), a series of ruthenium complexes were synthesized and characterized by elemental and spectroscopic methods (FT-IR, electronic, (1)H, (13)C, (31)P NMR and ESI-MS). The ligands were coordinated to ruthenium through quinone oxygen, imine nitrogen and enolate oxygen/thiolato sulfur. On the basis of spectral studies an octahedral geometry may be assigned for all the complexes. Further, the catalytic oxidation of primary, secondary alcohol and transfer hydrogenation of ketone was carried out. The DNA cleavage efficiency of new complexes has also been tested.

Ethyl 4-(1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-2-yl)benzoate

The title compound, C₂₁H₁₅NO₄, was synthesized by reducing the Schiff base obtained from acenaphthenequinone and ethyl-4-aminobenzoate. The dihedral angle between the essentially planar 1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinoline ring system [maximum deviation = 0.061 (2) Å] and the benzene ring is 75.08 (10)°. In the crystal, mol­ecules are connected via weak inter­molecular C—H⋯O hydrogen bonds, forming a two-dimensional network. The ethyl group is disordered over two sets of sites with a refined occupancy ratio of 0.502 (12):0.498 (12).

Development of [103Pd]-labeled-bis(N 4-methylthiosemicarbazone) complexes as possible therapeutic agents

Due to interesting tumor seeking properties of bis-thiosemicarbazones, two radio palladium- bis -thiosemicarbazone complexes, i.e., [103Pd]-pyruvaldehyde- bis(N 4-methylthiosemicarbazone) ([103Pd] PTSM) and [103Pd]- di-acetyl-bis (N 4-methylthiosemicarbazone) ([103Pd]ATSM) were prepared according to the analogy of radio copper homologs. Palladium-103 (t 1/2=16.96 d) was produced via the 103Rh(p,n) 103Pd nuclear reaction with proton energy 18 MeV. The final activity was eluted in form of Pd(NH3)2Cl2 in order to react with bis -thiosemicarbazones to yield [103Pd]-labeled compounds. Chemical purity of the product was confirmed to be below the accepted limits by polarography. [103Pd]-labeled bis -thiosemicarbazones were prepared with a radiochemical yield of more than 80% at room temperature after 60–90 min by vortexing a mixture of thiosemicarbazones and Pd activity in ethanol. The purification of the labeled compounds performed by reverse phase column chromatography using C18 plus Sep-Pak. Radiochemical purity of more than 99% specific activity of about 12500–13000 Ci/mol was obtained. The stability of the complexes was checked in final product and presence of human serum at 37 °C up to 48 h. The partition co-efficients of the final complexes were determined. The initial physico-chemical properties of the labeled compounds were compared to those of their copper homologues.

Vibrational spectra of palladium 5-nitrofuryl thiosemicarbazone complexes: experimental and theoretical study

The vibrational spectroscopic behavior of a series of 16 palladium(II) complexes with 8 bioactive nitrofuran containing thiosemicarbazones as ligands has been studied in the solid state. The IR and Raman spectra of these complexes and the free nitrofuran thiosemicarbazone ligands were recorded and analyzed. Experimental spectra were satisfactorily described by density functional theory (DFT) calculations. The combination of experimental and theoretical methods allowed us to perform the characterization of the main vibrations that show the mode of coordination of the thiosemicarbazone moiety to palladium even though these vibration bands are located in spectral regions showing a complicated pattern due to the presence of vibrations of the nitrofuran moiety and combination modes involving furan vibrations. A characteristic vibrational spectroscopic pattern has been defined for Pd(II) 5-nitrofuryl thiosemicarbazone complexes. This systematic knowledge may be useful for the analysis of the spectroscopic behavior of other coordination compounds holding the 5-nitrofuran thiosemicarbazone moiety.

Antioxidant, pro-oxidant effect of the thiosemicarbazone derivative Schiff base (4-(1-phenylmethylcyclobutane-3-yl)-2-(2-hydroxybenzylidenehydrazino) thiazole) and its metal complexes on rats

Adverse biological activities of thiosemicarbazone (TSC) and Schiff base (SB) derivatives have been widely studied in rats and in other animal species using different doses, times and routes of administration. However, there are few studies describing changes in some biochemical parameters in vivo which are indicative of oxidative stress in biological systems and of morphological changes of tissues. In this study, the rats were injected subcutaneously with a new thiosemicarbazone thiazole ring containing a Schiff base (LH) and its Cu(L)2 and Zn(L)2 complexes (25 mg kg(-1) body weight) and then sacrificed after 1, 2, 4, 8, 16, 32 and 64 days. The aim of this study was to determine the effect of the new compounds on the serum antioxidant vitamins (A, E, C), selenium (Se), malondialdehyde (MDA) levels, erythrocyte GSH-Px enzyme activity and morphological changes in the liver, kidney and adrenal gland tissues. It was observed that erythrocyte GSH-Px activity, serum MDA and vitamins A, E concentrations were statistically changed (p < 0.02), but serum levels of selenium, and vitamin C were not changed. In conclusion, the parameters measured show that Cu(L)2 caused considerable oxidative stress and Zn(L)2 behaved as an antioxidant. No oxidative stress in LH was observed compared to the control group.

Hybrid density functional theory investigation of a series of alloxan-based thiosemicarbazones and semicarbazones

Recently, the synthesis and the NMR characterization of a series of eight alloxan-based thiosemicarbazones and semicarbazones were reported. These compounds exhibit a strongly hydrogenbonded hydrazinic proton that is a part of a characteristic six-membered ring. This proton is highly deshielded and resonates far downfield in the proton NMR spectra. In this report, mPW1PW91/6-31+G(d,p) calculations have been used to investigate the structure and other molecular properties of this series of eight compounds. The relationship between the 1H and 13C NMR chemical shifts and various geometric parameters was investigated, and linear relationships for proton peaks that are involved in hydrogen-bond interactions were found.

Antitumor metallothiosemicarbazonates: structure and antitumor activity of palladium complex of phenanthrenequinone thiosemicarbazone

The crystal structure of the potential antitumor metal compound, viz. chloro, mono(phenanthrenequinone thiosemicarbazonato) palladium(II) dimethyl formamide solvate, is reported. The central palladium(II) atom is in a square planar environment provided by the tridentate, monoanionic thiosemicarbazone ligand and the ancillary chloride ion. The compound exhibited remarkable activity against drug-sensitive and drug-resistant breast cancer cell lines and was relatively nontoxic toward the normal mammary epithelial cells. The drug-induced killing effect against breast cancer cell lines was predominantly mediated via apoptosis, a physiologic form of cell death.

Effects on rat testes of the thiosemicarbazone derivative Schiff base (4-(1-phenylmethylcyclobutane-3-yl)-2-(2-hydroxybenzylidenehydrazino)thiazole) and its cadmium(II) complex

The aim of this study was to investigate structural and biochemical changes in testes of rats treated with the thiosemicarbazone derivative thiazole ring Schiff base, (4-(1-phenyl-methylcyclobutane-3-yl)-2-(2-hydroxybenzylidene-hydrazino) thiazole (L), and its Cd(II) complex (CdL(2)). The animals were divided into three groups. Group I was designated as control. The rats in groups II and III were injected subcutaneously with L or CdL(2) respectively at 150-mg kg(-1) doses at 3-day intervals for 15 days. At the end of the study, blood samples were collected for biochemical analysis, and testes were removed for histological examinations. Serum levels of vitamin A, E and MDA of the L-injected group were similar to the control group. While CdL(2) treatment decreased serum vitamin A and E levels, it increased the MDA level compared to other groups. Histologically, the testes structures of L-treated animals were similar to the control. Spermatogenic cells in seminiferous tubules of CdL(2)-treated animals displayed necrosis. Nuclei of spermatogonia and primary spermatocytes were pyknotic and heterochromatic. Homogenous pink particles were present in place of the spermatids. The interstitial areas were oedematous and intertubular vessels were plugged. In conclusion, the present results indicate that L does not cause biochemical and morphological alterations, but its Cd(II) complex has degenerative effects in normal rat testes.

Synthesis, characterization and biological activity of copper complexes with pyridoxal thiosemicarbazone derivatives. X-ray crystal structure of three dimeric complexes

A dimeric copper complex of the unsubstituted pyridoxal thiosemicarbazone (H(2)L), [[Cu(HL)(OH(2))](2)]Cl(2).2H(2)O, previously tested on Friend murine cell lines has been recently resynthesized to evaluate its behavior on different murine and human leukemic cell lines and has been compared, in vitro and in vivo, with its monomeric counterpart [Cu(H(2)L)(OH(2))Cl]Cl. On TS/A murine adenocarcinoma cell line in vitro, both compounds significantly inhibit cell proliferation at micromolar concentrations, although the dimeric compound is more active. Despite this cytotoxicity they lack in vivo activity on TLX5 lymphoma. The unsubstituted dimeric [[Cu(HL)(OH(2))](2)]Cl(2).2H(2)O induces apoptosis on CEM and U937 human cell lines, with IC(50) concentrations of 1.2 x 10(-5) and 6.7 x 10(-6) M, respectively, but it is inactive on K562. Moreover, it alters significantly the cell cycle of U937 and CEM lines and decreases the telomerase activity of U937. To verify if other dimeric copper complexes show relevant biological activity new complexes with N-substituted pyridoxal thiosemicarbazones have been synthesized and characterized using spectroscopic techniques. Three of them, namely [Cu(Me(2)-HL)Cl](2).6H(2)O (Me(2)-H(2)L=pyridoxal N1,N1-dimethylthiosemicarbazone) (1), [Cu(MeMe-HL)Cl](2)Cl(2).4H(2)O (MeMe-HL=pyridoxal N1,N2-dimethylthiosemicarbazone) (2), [Cu(Et-H(2)L)Cl](2)Cl(2).2H(2)O (Et-H(2)L=pyridoxal N1-ethylthiosemicarbazone) (3), were also characterized by X-ray diffractometry. These complexes are dimeric and all three present a square pyramidal coordinative geometry with the ligand showing an SNO tridentate behavior. Their biological activities have been tested in vitro on U937, CEM and K562 cell lines to ascertain their effectiveness in comparison to the corresponding unsubstituted complex [[Cu(HL)(OH(2))](2)]Cl(2).2H(2)O. Compound 1 shows weak proliferation inhibition on all three cell lines, but it does not induce apoptosis and it does not inhibit telomerase activity, compound 2 is not effective at low concentration and is toxic at higher doses; compound 3 inhibits CEM cell growth better than complex 1 but it does not exert any other biological effect.

High nuclearity nickel compounds with three, four or five metal atoms showing antibacterial activity

The effect on DNA and the antibacterial activity of a series of high nuclearity nickel compounds with three, four and five metal atoms were examined. The compounds have a mixed ligand composition with salicylhydroxamic acid and di-2-pyridyl-ketonoxime as chelate agents. In the trinuclear compound Ni(3)(shi)(2)(Hpko)(2)(py)(2)(1), two metal ions show a square planar geometry while the third one is in an octahedral environment. The compounds with four and five nickel atoms construct metallacrown cores with two distinct connectivities. The tetranuclear vacant metallacrown [12-MC(Ni(II)N(Hshi)2(pko)2)-4](2+) shows the connectivity pattern [-O-Ni-O-N-Ni-N-](2), while the pentanuclear ([Ni(II)][12-MC(Ni(II)N(shi)2(pko)2)-4])(2+) follows the pattern [-Ni-O-N-](4). Two distinct arrangements of the chelates around the ring metal ions were observed; a 6-5-6-5-6-5-6-5 arrangement for the [12-MC(Ni(II)N(Hshi)2(pko)2)-4] core and a 6-6-5-5-6-6-5-5 arrangement for the [12-MC(Ni(II)N(shi)2(pko)2)-4] core. Magnetic variable temperature susceptibility study of the trinuclear compound revealed the presence of one paramagnetic nickel(II) ion with strong crystal field dependence, with D=5.0(4) cm(-1), g(xy)=2.7(3) and g(z)=2.3(3). The effect of the synthesized Ni(II) complexes on the integrity and electrophoretic mobility of nucleic acids was examined. Only compounds 2, 3 and 4 altered the mobility of pDNA, forming high molecular weight concatamers at low concentrations or precipitates at higher concentrations. Antibacterial activity screening of the above compounds suggests that nickel compounds 2, 3 and 4 were the most active and can act as potent antibacterial agents.

New methyl pyruvate thiosemicarbazones and their copper and zinc complexes: synthesis, characterization, X-ray structures and biological activity

By reacting thiosemicarbazides substituted on the aminic nitrogen with both alkyl or aryl groups, and methyl pyruvate a new group of methylpyruvate thiosemicarbazones (Hmpt) derivatives was obtained. These ligands were then treated with copper and zinc inorganic salts. All isolated compounds were characterized using spectroscopic methods. The single crystal structural analysis of the ligands Me-Hmpt x 0.5H2O 1, Et-Hmpt x H2O 2, Ph-Hmpt 5, Meph-Hmpt 6 showed that only compound 6 presents significant deviation from planarity. The X-ray structure of [Zn(Me-Hmpt)Cl2] x H2O 8 showed that in this complex Me-Hmpt behaves as a neutral ligand SNO terdentate and that the penta coordination is achieved by chloride ions according to spectroscopic and elemental analyses. On the basis of the analytical data the same behavior is proposed for the other zinc complexes. All the ligands in copper complexes seem to be monodeprotonated; nevertheless the same SNO behavior is expected. Tests on cell proliferation of human leukemic cell line U937 showed that the copper complex Cu(Et-mpt)Cl x H2O is the most active compound among those reported even though it is not able to induce apoptosis.

Synthesis, characterisation, X-ray structure and biological activity of three new 5-formyluracil thiosemicarbazone complexes

Three new complexes of transition metals as copper, nickel and cobalt with 5-formyluracil thiosemicarbazone (H3ut) have been synthesised and characterised by single-crystal X-ray diffraction. In all compounds the ligand behaves as SNO terdentate. In the copper complex the coordination geometry is square pyramidal with the ligand lying on the basal plane and two water molecules that complete the metal environment, the nickel compound is surrounded by six donor atoms (three of the ligand, two water oxygen atoms and a chlorine atom) in an octahedral fashion, and cobalt also shows an octahedral geometry but determined only by two terdentate ligand molecules. These three compounds have been tested on human leukemic cell lines K562 and CEM. The nickel and cobalt complexes have demonstrated low activity in cell growth, while the copper complex that is more active has been tested also on a third leukemic human cell line (U937), but it was not able to induce apoptosis on all cell lines.

Transition-metal complexes of isatin-beta-thiosemicarbazone. X-ray crystal structure of two nickel complexes

Manganese, iron, cobalt, nickel, copper and zinc complexes of isatin-beta-thiosemicarbazone (H2L) have been synthesized and spectroscopically characterized The X-ray crystal structures of two nickel complexes, namely [Ni(HL)2]. EtOH (1) and [Ni(HL)2]. 2DMF (2), reveal a distorted octahedral coordination with the monodeprotonated ligand that behaves as an O,N,S terdentate. Different packing interactions are determined by the presence of different crystallization solvents, i.e., ethanol in 1 and dimethylformamide (DMF) in 2. 1H and 13C NMR studies of the ligand and zinc complexes in solution were carried out and a complete assignment for the ligand was made by homodecoupling, gradient assisted 2D 1H-13C HMQC and HMBC NMR spectroscopy. Biological studies, carried out in vitro on human leukaemic cell lines U937, have shown that the free ligand and the copper (II) complex are more active in the inhibition of cell proliferation than the nickel complexes. No compound was able to induce apoptosis.