Novel Ru(III) Complexes with Some Benzothiazole Derivatives: Synthesis, Physicochemical and Pharmacological Investigations.

In this work we present 3 new complexes of Ruthenium (III) with a general formula HL[Ru(L)2Cl4], where L=benzothiazole, 2-methylbenzothiazole and 2-mercaptobenzothiazole. The syntheses were carried out in polar medium under argon. The compounds obtained were characterised by IR-, (1)H-NMR- (13)C-NMR-, UV-VIS-spectroscopy and conductivity measurements. The ligands behaved as monodentate, bounding Ru(III) through the nitrogen atoms from the heterocycle. The cytotoxicity of the new complexes was tested against 2 human leukemic cell lines (K-562 and KE-37), using the MTT-dye reduction assay. The Ru(III) coordination compound with 2-methylbenzothiazole displayed superior activity compared to the other novel complexes. Its IC50 values were comparable to that of the reference cytotoxic drug cisplatin. In general, the ligands displayed only marginal inhibitory effects on the human leukemic cell lines. Moreover, the ability of the complexes to trigger apoptosis was evaluated using a commercially available DNA-fragmentation ELISA kit and the obtained data indicated that their proapoptotic effects well correlate to the MTT-bioassay data.

Platinum(IV) complexes with some derivatives of 5-methyl-5-(4-pyridyl) hydantoin. Synthesis, study and comparative pharmacological investigation.

3 Pt(IV) complexes with 3-ethyl-5-methyl-5-(4-pyridyl)hydantoin (4), 3-propyl-5-methyl-5-(4-pyridyl)hydantoin (5) and 3-benzyl-5-methyl-5-(4-pyridyl)hydantoin (6) with general formulae cis-[Pt(L)2Cl4] were synthesized. The novel compounds were characterized by elemental analysis, IR, 1H, 13C, NMR spectra in solid state and in solution. The studies showed that the ligands coordinate to the platinum ions in a monodentate manner through the nitrogen atom from the pyridine ring. The cytotoxic activity in vitro of newly synthesized complexes as well as their previously prepared analogous of Pt(IV) with other derivatives like 3-amino-5-methyl-5-(4-pyridyl)hydantoin (1), 5-methyl-5-(4-pyridyl)hydantoin (2), 3,5-dimethyl-5-(4-pyridyl)hydantoin (3) was screened against a panel of human tumor cell lines. The tested compounds displayed cytotoxic activity which was invariably superior with the Pt(IV) complex with 3-benzyl-5-methyl-5-(4-pyridyl)hydantoin (6) causing 50% inhibition of cellular viability at micromolar concentration, though the activity of the other studied Pt(IV) complexes proved to greatly decrease in the order 5-4-3-2-1.

Interaction of 5-amino-1,3,4-thiadiazole-2-thiol and its violuric acid adduct with Pt(II) - crystals structures, spectroscopic properties and cytotoxic activity.

The coordination properties of Pt(II) with 5-amino-1,3,4-thiadiazole-2-thiol [CAS 2349-67-9] (L 1 ) and its novel violurate adduct (L 2 ), both in solution and in solid state, are studied by means of conventional IR-spectroscopy, single crystal X-ray diffraction and thermal methods. The complex compounds of L 1 and L 2 , with general formulas [Pt(C2H2N3S2)2] and [Pt(C6H4N6S2O3)(Cl)]Cl respectively, are obtained. Quantum chemical calculations of the ligands are performed with a view to obtain electronic structure and optical properties of the ligands L 1 and L 2 , respectively. The cell viability of the ligands and metal complexes on a panel of human tumor cell lines is evaluated.

Effect of justicidin B - a potent cytotoxic and pro-apoptotic arylnaphtalene lignan on human breast cancer-derived cell lines.

Justicidin B produced by genetically transformed cultures of Linum leonii was tested for cytotoxic activity and induction of apoptosis in MDA-MB-231 and MCF-7 breast cancer derived cell lines. The tested lignan evoked strong, concentration dependent cytotoxicity in both cell lines, whereby MCF-7 proved to be far more sensitive as compared to MDA-MB-231. The 24 h treatment of both cell lines increased the level of apoptotic DNA fragmentation; however the proapoptotic activity is completely inhibited if the cells are co-incubated with the non-selective pan-caspase inhibitor Boc-Asp(OMe)-fluoromethyl ketone (PCI), which implies that justicidin B, activates programmed cell death via caspase -dependent mechanisms. Exposure of MDA-MB-231 cells with justicidin B leads to concentration dependent decrease in the expression of NFkB; whereas the treatment of MCF-7, is consistent with strong increase in the expression of this transcription factor.

Synthesis, NMR characterization and in vitro cytotoxicity evaluation of new poly(oxyethylene aminophosphonate)s.

The synthesis of four novel poly(oxyethylene aminophosphonate)s through an addition of poly(oxyethylene H-phosphonate)s to N-(4-dimethylaminobenzylidene)-p-toluidine or N-furfurylidene-p-toluidine is reported. The IR and 1H, 13C and 31P NMR data of the poly(aminophosphonate)s are given. The polymers consist of aminophosphonate and poly(ethylene glycol) (PEG) units only. They are expected to act in vivo as prodrugs of the aminophosphonates and will be interesting as a new class of biodegradable polymer drug carriers. The cytotoxicity of the synthesized poly(aminophosphonate)s and two previously described analogues, was tested against a panel of human tumor cell lines, using cisplatin as reference cytotoxic agent. The presence of 2-furyl-p-toluidino moiety with a longer PEG (13 units) chain were identified as structural prerequisites affording superior activity, while the analogues originating from the Schiff bases N-(4-dimethylaminobenzylidene)-p-toluidine and N,N-dimethyl-N'-furfurylidene-1,3-diaminopropane were generally less active. In all sub-series of polymers the reduction of the PEG chain length from 13 to 4 units led to a significant reduction in relative potency. The established cytotoxicity, which in most of the polymers was comparable to that of cisplatin give us reason to consider the presented polymers as a novel class of aminophosphonate-based cytotoxic agents.

Production of podophyllotoxin in Linum linearifolium in vitro cultures.

For the first time, callus and suspension cultures of Linum linearifolium were initiated. Podophyllotoxin (PTOX), a strong antitumor precursor, was isolated from the calli and suspension, as a main lignan besides smaller amount of 6-methoxypodophyllotoxin (6MPTOX). L. linearifolium is now the third Linum species of section Syllinum, with PTOX as the main lignan. The amounts of lignans, especially PTOX, found in L. linearifolium cell cultures are quite high within the studied Linum species until now. The antiproliferative effects of extracts were tested in a panel of human tumor cell lines, using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide]-dye reduction assay. The lignan mixtures caused concentration-dependent inhibition of malignant cell proliferation and showed moderate cytotoxic activity. The results clearly demonstrate that the lignan mixture of L. linearifolium exerts inhibitory effects against malignant cells.

Effects of cycloartane saponins from hairy roots of Astragalus membranaceus Bge., on human tumor cell targets.

For the first time three different natural compounds, isolated from hairy roots of Astragalus membranaceus, cultivated in airlift bioreactor were tested for their cytotoxic potential and apoptosis induction in a panel of human tumor cell lines. Root cultures, cultivated in bioreactor gave 18.5 g l(-1) dry wt roots with the highest astragaloside production in vitro up to now - 1.64% (astragaloside I), 1.12% (astragaloside II) and 1.08% (astragaloside III). In this manner the production in airlift bioreactor can be used as means of reliable supply of cycloartane saponins to extend the research to human clinical studies.

Nanoparticles formed from PNIPAM-g-PEO copolymers in the presence of indomethacin.

Biocompatible double-hydrophilic PNIPAM-g-PEO copolymers containing 0.3-3.2 mol% PEO grafts were synthesized and utilized to prepare indomethacin (IMC)-loaded core-shell nanoparticles by dialysis and nanoprecipitation methods. IMC loading was conducted at room temperature using the organic solvents ethanol and DMF, which induced phase separation in the copolymers aqueous solutions due to the cononsolvency of PNIPAM. In ethanol-water solutions, the cononsolvency-induced phase separation of the copolymers promoted effective drug incorporation into the formed micellar structures. In DMF-water system, the formation of the nanoparticles did not correspond to the cononsolvent region of PNIPAM-g-PEO. In this case, hydrophobic interactions between PNIPAM and IMC allowed the copolymer self-association and drug loading. Irrespective of the solvents or preparation methods applied, the drug loading content (DLC) depended on the drug-to-copolymer feed weight ratio. DLC was relatively low at the 0.5:1 ratio but it significantly increased at the ratios of 0.75:1 and 1:1 (DLC approximately 90%). The particle size was strongly affected by the different mechanisms of nanoparticles formation. The nanoprecipitation from ethanol produced significantly smaller particles (<150 nm) with narrow size distribution than the dialysis from DMF. The velocity of indomethacin release from the nanoparticles was influenced by the amount of encapsulated drug, the process being faster at lower DLC.

Synthesis, NMR characterization and in vitro antitumor evaluation of new aminophosphonic acid diesters.

The synthesis of three novel alpha-aminophosphonic acid diesters N,N-dimethyl-[N'-methyl(diethoxyphosphonyl)-(2-furyl)]-1,3-diaminopropane, p-[N-methyl(diethoxyphosphonyl)-(2-furyl)]toluidine and p-[N-methyl(diethoxyphosphonyl)-(4-dimethylaminophenyl)]toluidine through an addition of diethyl phosphite to N,N-dimethyl-N'-furfurylidene-1,3-diaminopropane, N-furfurylidene-p-toluidine and N-(4-dimethylaminobenzylidene)-p-toluidine, respectively, is reported. The alpha-aminophosphonates have been characterized by elemental analysis, IR and NMR ((1)H, (13)C and (31)P) spectra. The compounds were tested for antiproliferative effects against 4 human leukemic cell lines, namely LAMA-84, K-562 (chronic myeloid leukemias), HL-60 (acute promyelocyte leukemia) and HL-60/Dox (multi-drug-resistant sub-line, characterized by overexpression of MRP-1 (ABC-C1)) and were found to exert concentration-dependent cytotoxic effects. A representative aminophosphonate compound was shown to induce oligonucleosomal DNA fragmentation which implies that the induction of cell death through apoptosis plays an important role for its cytotoxicity mode of action.

Cytotoxic effects of hyperatomarin, a prenylated phloroglucinol from Hypericum annulatum Moris subsp. annulatum, in a panel of malignant cell lines.

The cytotoxic effects of hyperatomarin - a prenylated phloroglucinol isolated from Hypericum annulatum Moris subsp. annulatum were assessed in a broad spectrum of tumor cell lines originating from leukemias, lymphomas and solid malignancies. The tested compound exerted strong concentration-dependent cytotoxic effects (IC50 values ranging 0.14-15.7 µM), comparable to and even outclassing in some cell lines those of the established anti-cancer drug daunorubicin. Exposure of different human tumor cell lines to hyperatomarin resulted in strong mono- and oligo-nucleosomal fragmentation of genomic DNA, as evidenced by 'Cell death detection' ELISA kit and by DNA-electrophoresis, which unambiguously indicates that the induction of apoptosis is implicated in the cytotoxic mode of action of the tested compound.

Cytotoxic Mannich bases of 6-(3-aryl-2-propenoyl)-2(3H)-benzoxazolones.

A series of 12 new Mannich bases with chalcone core structure were synthesized as potential antineoplastic agents, via N-aminomethylation of two parent 6-(3-aryl-2-propenoyl)-2(3H)-benzoxazolones. The newly synthesized compounds as well as the chalcone prototypes were evaluated for cytotoxicity in the human pre-B-cell leukemia cell line BV-173 using the MTT-dye reduction assay. The tested compounds exhibited concentration-dependent cytotoxic effects at low micromolar concentrations. Ten of the Mannich bases characterized by significant activity in BV-173 were further evaluated against the chronic myeloid leukemia cell line K-562 and were found to suppress the growth of these cells at relatively higher concentrations as compared to the former tumor model. Selected Mannich bases induced programmed cell death in BV-173 at a concentration of 2.5muM as evidenced by the encountered DNA-laddering. Taken together our data suggest that the presented heterocyclic chalcone derived Mannich bases necessitate detailed pharmacological evaluation in order to define further the structure activity relationships, in a larger spectrum of tumor models and to elucidate the mechanisms implicated in the observed cytotoxic effects.

Synthesis, Structural Characterization, and Cytotoxic Activity of Novel Paramagnetic Platinum Hematoporphyrin IX Complexes: Potent Antitumor Agents.

Three novel stable Pt(III) complexes with distorted octahedral structure and (dz2)1 ground state have been obtained in the course of Pt(II)-hematoporphyrin IX ((7,12-bis(1-hydroxyethyl)-3,8,13,17-tetramethyl-21H-23H-porphyn-2,18-dipropionic acid), Hp) interaction in alkaline aqueous medium and aerobic conditions. A redox interaction also takes place together with the complexation process leading to the formation of Pt(III) species and organic radicals. The processes in the reaction system and the structure of the complexes formed cis-[Pt(III)(NH3)2(Hp-3H)(H2O)2]H2O1, [Pt(III)(Hp-3H)(H2O)2]H2O2, and [Pt((O,O)Hp-2H)Cl(H2O)3] 3, were studied by UV-Vis, IR, EPR and XPS spectra, thermal (TGS, DSC), potentiometric and magnetic methods. The newly synthesized complexes show promising cytotoxic activity comparable with that of cis-platin in in vitro tests against a panel of human leukemia cell lines. The observed cytotoxicity of the complex 2 against SKW-3 cells (KE-37 derivative) is due to induction of cell death through apoptosis.

Synthesis, physicochemical characterization and preliminary pharmacological in vitro evaluation of two novel cytotoxic benzophenone-linked 3,3-dimethyltriazenes.

The synthesis, physicochemical characterization and preliminary pharmacological evaluation of the cytotoxic effects of two novel substances, 1-(4-benzoylphenyl)-3,3-dimethyltriazene and 1-(2-benzoylphenyl)-3,3-dimethyltriazene is presented. The cytotoxicity of the novel benzophenone-linked triazenes and of ten other 1-phenyl-3,3-dimethyl triazene derivatives as well as of the referent alkylating drug melphalan was assessed using the MTT-dye reduction assay. A panel of human tumor cell lines was used: the chronic lymphoid leukemia SKW-3, the acute promyelocyte leukemia HL-60 and its multi-drug-resistant subline HL-60/Dox. Both novel compounds showed strong cytotoxic activity, comparable to that of the referent alkylating agent melphalan, whereas the ten ring-substituted 1-phenyl-3,3-dimethyl triazenes proved to be far less active in vitro. DNA-fragmentation analysis indicated that after 24 h treatment the novel benzophenone-linked triazenes induced programmed cell death in HL-60 cells.

New zirconium (IV) complexes of coumarins with cytotoxic activity.

Complexes of zirconium (IV) with some bis-coumarin ligands have been synthesized. The zirconium (IV) complexes with bis-coumarins were characterized by different physicochemical methods-elemental analysis, IR-, and (1)H-NMR-spectroscopies and mass spectral data. The spectral data of zirconium (IV) complexes were interpreted on the basis of comparison with the spectra of the free ligands. The results of the ligands and their complexes, based on spectral data are informative and useful for suggestion of the metal-ligand binding mode. Cytotoxic screening by MTT assay was carried out. In the present study we performed comparative evaluation of the cytotoxic effects of the three newly synthesized zirconium complexes against the acute myeloid leukemia derived HL-60 and the chronic myeloid leukemia LAMA-84. The preliminary cytotoxicity screening program revealed that the investigated zirconium complexes induced 50% inhibition of the cell viability of HL-60 and LAMA-84 cells at micromolar concentrations and thus could be considered as biologically active. Independently of the tumor test system evaluated the complex of bis(4-hydroxy-2-oxo-2H-chromen-3-yl)-(1H-pyrazol-3-yl)-methane proved superior to the remaining agents with respect to the IC(50) values obtained. The complexes of both the other coumarins evaluated proved to be less potent than the corresponding free ligands, as evidenced by the IC(50) values obtained. Thus the zirconium complexes with coumarin ligands represent a novel class of antiproliferative agents, which deserve further attention in search of anticancer lead compounds.

Comparative assessment of the cytotoxic effects of carboxylato-bridged dinuclear platinum (II) complexes against human tumor cell lines.

The cytotoxic effects of a series of carboxylato-bridged dinuclear platinum (II) complexes with acetate (BAP), propionate (BPP) and valerate (BVP) ligands were evaluated in a panel of human tumor cell lines. BAP proved to be the most potent antineoplastic agent, whose cytotoxic effect reached and even outclassed that of the referent drug cisplatin. This compound also exerted substantial efficacy against a broader spectrum of tumor models including the multidrug-resistant HL-60/Dox cell line. In the latter case, BAP showed lower resistance index than cisplatin. BAP was furthermore found to induce apoptosis in different cell lines as evidenced by DNA-laddering and Cell-death ELISA. Our experimental data give us reason to conclude that the dinuclear Pt(II) complex with acetate ligands is perspective for further detailed pharmacological and toxicological evaluation as an antineoplastic drug candidate.

Cytotoxic activity of a podophyllotoxin-like lignan from Linum tauricum Willd.

The present study describes the preliminary evaluation of the cytotoxic activity of a podophyllotoxin-like compound 4'-demethyl-6-methoxypodophyllotoxin (4'-DM-6-Mptox), isolated as one of the main lignans of Linum tauricum Willd. ssp. tauricum. The cytotoxic effects 4'-DM-6-Mptox were assessed by the MTT-dye reduction assay against the human leukemic cell lines HL-60, BV-173 and LAMA-84. DNA-fragmentation analysis and NF-kB inhibition assay were performed in order to elucidate some of the mechanistic aspects of the cytotoxic action of the investigated compound. 4'-DM-6-Mptox was found to exert prominent cytotoxicity, with IC50 values being several-fold lower than those of the referent antineoplastic agent etoposide. The DNA-fragmentation analysis revealed that 4'-DM-6-Mptox treatment triggered apoptosis in BV-173 and HL-60 cells. In our hands 4'-DM-6-Mptox was found to induce concentration-dependent NF-kB inhibition in HeLa cells as assessed by the IL-6 luciferase gene reporter assay, which though not quite prominent, at least partly contributes to the cytotoxic potential of the tested lignan. On the basis of the results obtained it could be concluded that 4'-DM-6-Mptox necessitates further pharmacological and toxicological evaluation as a possible chemotherapeutic agent. Furthermore due to its relatively high concentrations in the described plant source the possibility for its use as a precursor for the semisynthetic production of lignan-based drugs, could be considered.