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PubMed2005

Cytotoxic effects of novel polyoxotungstates and a platinum compound on human cancer cell lines.

The cytotoxicity of a new platinum compound Pt1 [2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedichloroplatin(II)] and six polyoxometalates (POM1-6) on two neuroblastoma cell lines (SHEP-SF and KCN) and an Ewing's Sarcoma cell line (CADO-ES-1) was studied. Cisplatin [cis-diamminedichloroplatinum(II)] and carboplatin [cis-diammine(cyclobutanedicarboxylato)platinum(II)] were used as reference agents. Using MTT tests, the cytotoxicity (LD50: lethal doses 50%) of the compounds were measured at different concentrations. After 72 h exposure, the LD50 data for the platinum-containing substances ranged between 4.47 x 10(-6) and 1.91 x 10(-4) M. The SHEP-SF cell line displayed the highest sensitivity to cisplatin. The novel platinum agent Pt1 had a similar cytotoxic effect to the reference agent cisplatin. Both cisplatin and Pt1 were more cytotoxic than carboplatin. The POMs reduced cell viability compared to untreated cells at concentrations between 8.4 x 10(-7) and 3.47 x 10(-5) M. POM1 ([(CH3)4N]2Na6.5(NH4)2[SnII1.5(WO2(OH))0.5(WO2)2(SbW9O33)2] x 32H2O) was the most effective polyoxoanion with a mean LD50 value of 8.83 x 10(-6) M in the three cell lines tested. With CADO-ES-1 and KCN cells, POM1 was found to be more effective than the platinum compounds cisplatin, carboplatin and Pt1.

Antineoplastic Agents↗
PubMed2005

Tungstate stimulates insulin release and inhibits somatostatin output in the perfused rat pancreas.

In the rat pancreas, infusion of sodium-tungstate stimulates basal insulin release in a dose-dependent manner. We have studied tungstate's effects on the insulin secretion elicited by various B-cell secretagogues. Somatostatin output was also measured. The study was performed in the perfused pancreas isolated from normal or somatostatin-depleted pancreases as induced by cysteamine pre-treatment. In control rats, tungstate co-infusion (5 mM) potentiated the insulin secretory responses to glucose (2.7-fold; P<0.01), arginine (2-fold; P<0.01), exendin-4 (3-fold; P<0.01), glucagon (4-fold; P<0.05), and tolbutamide (2-fold; P<0.01). It also inhibited the somatostatin secretory responses to glucose (90%; P<0.01), arginine (95%; P<0.01), glucagon (80%; P<0.025), exendin-4 (80%; P<0.05) and tolbutamide (85%; P<0.01). In somatostatin-depleted pancreases, the stimulatory effect of tungstate on basal insulin secretion and its potentiation of arginine-induced insulin output were comparable to those found in control rats. Our observations suggest an amplifying effect of tungstate on a common step in the insulin stimulus/secretion coupling process, and would rule out a paracrine effect mediated by the inhibition of somatostatin secretion induced by this compound.

Animals↗
PubMed1999

Increased myofibroblast contractile sensitivity in paraquat pretreated rat lung tissue.

In numerous tissues, contractility to certain characteristic agents is associated with cells other than muscle, e.g. actin-containing so-called myofibroblasts. Such cells are present in pulmonary interstitium of several mammalian species but their contractility has only been demonstrated from the proliferation of myofibroblasts in fibrotic lung tissues. This study has been done to evaluate such responses in normal tissues in contrast with fibrotic lungs and it was necessary to take account also of smooth muscle reactivity. Distinctive agonists: mepyramine and sodium tungstate characterised myofibroblast mediated contractility, in contrast with acetylcholine and barium chloride as specific smooth muscle stimulants. Histology and immunohistochemistry were used to evaluate the pharmacological results more precisely.

Acetylcholine↗
PubMed2005

The chemistry behind antioxidant capacity assays.

This review summarizes the multifaceted aspects of antioxidants and the basic kinetic models of inhibited autoxidation and analyzes the chemical principles of antioxidant capacity assays. Depending upon the reactions involved, these assays can roughly be classified into two types: assays based on hydrogen atom transfer (HAT) reactions and assays based on electron transfer (ET). The majority of HAT-based assays apply a competitive reaction scheme, in which antioxidant and substrate compete for thermally generated peroxyl radicals through the decomposition of azo compounds. These assays include inhibition of induced low-density lipoprotein autoxidation, oxygen radical absorbance capacity (ORAC), total radical trapping antioxidant parameter (TRAP), and crocin bleaching assays. ET-based assays measure the capacity of an antioxidant in the reduction of an oxidant, which changes color when reduced. The degree of color change is correlated with the sample's antioxidant concentrations. ET-based assays include the total phenols assay by Folin-Ciocalteu reagent (FCR), Trolox equivalence antioxidant capacity (TEAC), ferric ion reducing antioxidant power (FRAP), "total antioxidant potential" assay using a Cu(II) complex as an oxidant, and DPPH. In addition, other assays intended to measure a sample's scavenging capacity of biologically relevant oxidants such as singlet oxygen, superoxide anion, peroxynitrite, and hydroxyl radical are also summarized. On the basis of this analysis, it is suggested that the total phenols assay by FCR be used to quantify an antioxidant's reducing capacity and the ORAC assay to quantify peroxyl radical scavenging capacity. To comprehensively study different aspects of antioxidants, validated and specific assays are needed in addition to these two commonly accepted assays.

Antioxidants↗
PubMed2006

Dioxotungsten 1,2-benzenedithiolate complex stabilized by NH...S hydrogen bonds.

Novel dioxo-tungsten(VI) bis(1,2-benzenedithiolate) complexes with neighboring amide groups, as models for tungsten enzymes, (NEt4)2[W(VI)O2{1,2-S(2)-3,6-(RCONH)2C6H2}2] (R = CH3, t-Bu), were designed and synthesized. The presence of the NH...S hydrogen bond was confirmed through IR spectrometry and X-ray crystallographic analysis. In the W(VI)O2 complexes, the NH...S hydrogen bond trans to the oxo ligand is stronger than that cis to oxo. On the basis of comparisons with [W(VI)O2(1,2-S2C6H4)2](2-), the NH...S hydrogen bond positively shifted the W(VI)/W(V) redox potentials and depressed the reduction by benzoin or triphenylphosphine. These results suggest that the NH...S hydrogen bond stabilizes the oxo ligand through trans influence and regulates O-atom transfer in tungsten and molybdenum enzymes.

Aldehyde Oxidoreductases↗
PubMed1999

Cobalt.

Cobalt is a relatively rare magnetic element with properties similar to iron and nickel. The two valance states are cobaltous (II) and cobaltic (III) and the former is the most common valance used in the chemical industry. Cobalt occurs in nature primarily as arsenides, oxides, and sulfides. Most of the production of cobalt involves the metallic form used in the formation of cobalt superalloys. The term "hard metal" refers to compounds containing tungsten carbide (80-95%) combined with matrices formed from cobalt (5-20%) and nickel (0-5%). For the general population, the diet is the main source of exposure to cobalt. In the occupational setting, exposure to cobalt alone occurs primarily during the production of cobalt powders. In other industrial exposures (e.g., hard metal, diamond polishing), additional agents (tungsten) modulate the toxicity of cobalt. Cobalt is an essential element necessary for the formation of vitamin B12 (hydroxocobalamin); however, excessive administration of this trace element produces goiter and reduced thyroid activity. In 1966, the syndrome "beer drinker's cardiomyopathy" appeared in Quebec City, Canada, and was characterized by pericardial effusion, elevated hemoglobin concentrations, and congestive heart failure. An interstitial pulmonary fibrosis has been associated with industrial exposure to hard metal dust (tungsten and cobalt), but not to cobalt alone. Exposure to cobalt alone produces an allergic contact dermatitis and occupational asthma. Treatment of cobalt toxicity is primarily supportive.

Animals↗
PubMed1992

Suppressive effect of polyoxometalates on the cytopathogenicity of human immunodeficiency virus type 1 (HIV-1) in vitro and their inhibitory activity against HIV-1 reverse transcriptase.

One isopolyoxometalate and 42 heteropolyoxometalates consisting of 3 compounds with the trivacant Keggin structure, 2 with the lacunary Keggin structure, 30 with the Keggin structure, one with the Wells-Dawson structure and 6 with miscellaneous structures were tested for their suppressive effect on the cytopathogenicity of human immunodeficiency virus type 1 (HIV-1) in vitro and inhibitory activity against HIV-1 reverse transcriptase. In contrast to the leading interpretations which attribute the suppressive effect of polyoxometalates on the cytopathogenicity of HIV-1 to the inhibition of HIV-1 reverse transcriptase by these compounds, there was no distinct correlation observed between these two functions of polyoxometalates.

Antimony↗
PubMed1983

Correlation between structure of polyoxotungstates and their inhibitory activity on polymerases.

The 21-tungsto-9-antimonate (TA, HPA 23), a polyoxotungstate, has shown a significant antiviral activity in vivo and in vitro. It inhibits viral and bacterial DNA polymerases. In this paper, several compounds of two polyoxotungstic families, tungstoantimonates and tungstoarsenates, have been used to specify the mechanism of polymerase inhibition. It has been demonstrated that the inhibitory activity of polyoxotungstates is not related to the occupation of their coordinates sites by cations, nor to the nature of these bound cations. Kinetic studies and binding assays have shown that polyoxotungstates bind to the polymerases in competition with the nucleic acid template. This result seems to be related to their polyanionic nature. Furthermore, the size and charge of these compounds may play a prominent part in their affinity for the polymerases.

Antimony↗
PubMed2005

Reactivity of bis(mu-hydroxo) divanadium site in gamma-H2SiV2W10O40(4-) with hydroxo compounds.

The reactivity of divanadium-substituted silicotungstate, gamma-H2SiV2W10O40(4-) (I), with hydroxo compounds of alcohols, carboxylic acids, and water is reported. The reaction of the bis(mu-hydroxo) divanadium site in I with primary alcohols and formic acid smoothly proceeds to form corresponding monoesters and monoformate, respectively, and the crystal structures of the monomethyl and monoethyl esters and the monoformate of I are determined. The oxygen exchange between the hydroxo group and water proceeds easily. On the other hand, bulky compounds of 2-propanol, tert-butyl alcohol, and acetic acid hardly react with the bis(mu-hydroxo) divanadium site (equilibrium constant < 0.01) because of the steric crowding between the methyl groups and the polyoxometalate framework.

Alcohols↗
PubMed2005

The synthesis of silica nanospheres doped with polyoxometalates.

The hetero-polyoxometalate (POM) Na13[Eu(SiMoW10O39)2] displayed enhanced luminescence when coordinated to compounds with a common amine functionality. The POM was then doped into silica spheres and was found to be confined to the particle core when added with an amine-based polymer.

Microscopy, Electron↗
PubMed1990

Anti-HIV-1 activity, toxicity, and stability studies of representative structural families of polyoxometalates.

The anti-HIV-1 activity and toxicity of representative structural families of polyoxotungstates in human lymphocytes was determined. The 21 compounds examined include those derived from the following structural families: [NaSb9W21O86]18- (HPA-23), Xn+W12O40(8-n)- (Keggin), P2W18O62(6-) (Wells-Dawson), W6O19(2-) (Lindqvist), [NaP5W30O110]14- (Preyssler), and W10O32(4-) (decatungstate). The molecular architecture of each of these structural families is constituted principally by a network of bonds between d0 WVI and oxide ions. Of these, 10 show median effective concentration (EC50) values of approximately 1 microM and six have marked toxicity with a median inhibitory concentration (IC50) of less than 50 microM. Only compounds containing more than six metal atoms showed appreciable antiviral activity. Beyond this, however, no marked correlation existed between the molecular size, charge, or charge density of the polyoxometalates and their anti-HIV-1 activity. Examination of an exemplary class of polyoxotungstates, the phosphotungstates of formula A- and B-PW9O34(9-) under physiological conditions (buffered neutral aqueous media), illustrates that both isomers equilibrate rapidly to generate the same distribution of products and that this distribution depends principally on the buffer. These heretofore unappreciated complexities in the chemistry of these compounds under neutral aqueous conditions indicates interpretation or evaluation of these compounds in cell culture and other biological screens must be done with care.

Antimony↗
PubMed1988

Treatment of rabies in mice and foxes with antiviral compounds.

Thirty four chemical compounds were injected into rabies infected mice by intramuscular (i.m.) route. Twenty four compounds such as well known therapeutic agents: amantadine, lipacids, phenol compounds, didemnin-B, procaine, nucleosides analogues (ribavirin, tiazofurin, pyrazofurin) had no effect. Two compounds had a slight effect not justifying to consider them as possible therapeutic agents: selenazofurin and an analogue of ribavirin (RTA). Eight heteropolyanions (HPA), which have a related chemical structure, were efficient providing 100% protection. Nineteen compounds were injected into rabies infected mice by the intracerebral (i.c.) route. Fourteen compounds such as ribavirin, RTA, selenazofurin, tiazofurin and 9 HPA compounds had no effect. Five other HPA compounds (HPA 23-39-46-51-56) were efficient preventing the development of clinical infection in some mice. Whatever was the treatment route, treated surviving mice developed rabies neutralizing antibodies. No proof of viral multiplication was found in their brains. As some HPA compounds did produce a therapeutic effect in mice, two of them HPA 23 and HPA 39 were administered to rabies-infected foxes. In foxes the compounds prolonged the mean survival time and increased the number of survivors. These data suggest that chemotherapy might be worthwhile when vaccination was impossible.

Animals↗
PubMedDate not supplied

The cupric ion reducing antioxidant capacity and polyphenolic content of some herbal teas.

The total antioxidant capacity of the aqueous extracts of some endemic herbs-prepared as infusions by steeping these herbs in hot water--was assayed with bis(neocuproine)copper(II) chloride, also known as the cupric ion reducing antioxidant capacity (CUPRAC) reagent, which was easily accessible, rapid, stable and responsive to both hydrophilic and lipophilic antioxidants. The highest antioxidant capacities of some herbal teas available in the Turkish market were observed for scarlet pimpernel (Anagallis arvensis), sweet basil (Ocimum basilicum), green tea (Camellia sinensis) and lemon balm (Melissa officinalis), in this order (1.63, 1.18, 1.07, and 0.99 mmol trolox equivalent (TR)/g, respectively). For infusions prepared from ready-to-use tea bags, the CUPRAC values were highest for Ceylon blended ordinary tea (4.41), green tea with lemon (1.61), English breakfast ordinary tea (1.26) and green tea (0.94), all of which were manufactured types of C. sinensis. Following the strongest antioxidant herbs with capacities close to or slightly exceeding 1.0 mmol TR/g, sage, thyme, coriander, coltsfoot, blackberry and immortelle (Helichrysum) exhibited capacities around 0.5 mmol TR/g. The correlation of the Folin total phenolic content of herbal teas with their CUPRAC and ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) total antioxidant capacities gave linear curves with correlation coefficients of 0.966 and 0.936, respectively, showing that the CUPRAC assay results better correlated with total phenolic content of herbal teas. Absorbance versus concentration data at different dilutions and upon standard additions of model antioxidant compounds (trolox and quercetin) to herbal tea infusions showed that the absorbances (at 450 nm of the CUPRAC method) due to different antioxidant compounds in herbal tea infusions were additive; that is, the tested antioxidants did not chemically interact to cause apparent deviations from Beer's law.

Antioxidants↗
PubMed1981

In vivo effect of a new mineral condensed ion (HPA 39) on murine Friend leukaemia.

HPA 39 is a tungsto-antimoniate compound, closely related to the mineral consensed ion HPA 23, from which it differs only by the presence of a potassium instead of a sodium ion inside the central cage. A single parenteral injection of HPA 39 on the same day as virus inoculation decreased the splenomegaly induced by Friend virus in DBA/2 mice and protected 90% of the infected animals against leukaemia. It also lowered the virus content in spleen extracts compared to untreated animals. The efficiency of treatment with HPA 39 on leukaemic mice at a late stage of the disease suggested that the compound may act at the cellular level as well as by inducing virus growth inhibition. HPA 39 also induced an early decrease of peripheral blood reticulocytes, and of the most differentiated erythroblasts in the bone marrow 1 day after injection of the compound. Mineral condensed ions therefore appear to have multiple biological effects both in vitro and in vivo.

Animals↗
PubMed2003

Merits of polyoxotungstates as environmental remediation catalysts: a novel wet oxidation technology for refractory industrial pollutants.

The catalytic effect of silicadodecatungstate (SiW12O40(4-)) on the oxidation of nitrobenzene in subcritical water (T = 100-300 degrees C; P = 0.1-8.6MPa, pH = 2.6) was examined. In the absence of SiW12O40(4-) catalyst nitrobenzene oxidation slowed down significantly after a brief period of rapid degradation and an average of 40% nitrobenzene removal. The catalytic effect of SiW12O40(4-) becomes particularly pronounced after a temperature dependent induction period. Catalyzed wet air oxidation continued until the degradation of the parent compound was complete provided that experimental conditions were harsh enough (T > 200 degrees C). Product distribution analysis suggested that the oxidation paths for catalyzed and uncatalyzed wet air oxidation of nitrobenzene are similar, but the analysis was not definitive.

Catalysis↗
PubMed1991

Direct measurement of antiviral activities by a novel immunoassay with peroxidase-labeled complement C1q.

A novel immunoassay method for evaluating antiviral activities has been developed. The method involves the specific measurement of viral antigens produced in cells infected with herpes simplex virus (HSV) as a model by using the anti-HSV probe serum to detect HSV antigens and the peroxidase-labeled complement C1q to detect the immune complex formed. A new compound, heteropolyoxotungstate K7[PTi2W10O40]. 6H2O, was proven to have an anti-herpetic activity at the concentration of 5.0 micrograms/ml determined by the novel immunoassay.

Acyclovir↗
PubMed1989

Effects of suramin, HPA-23 and 3'-azidothymidine triphosphate on the reverse transcriptase of bovine leukaemia virus.

We used purified bovine leukaemia virus (BLV) to test the inhibitory effects of suramin, HPA-23, and 3'-azidothymidine triphosphate (N3dTTP) on the reverse transcriptase activity. The 50% inhibitory concentrations (ID50) of the compounds were determined to be 2.8 mumol/l (suramin), 8.0 mumol/l (HPA-23), and 0.17 mumol/l (N3dTTP). Kinetic analyses of suramin and HPA-23 inhibition are discussed. The observed inhibitory effects emphasize the suitability of BLV as a model virus for investigations of retrovirus chemotherapy.

Animals↗