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PubMed2006

Antimony-antimony bond formation by reductive elimination from a hafnium bis(stibido) complex.

The bis(stibido) complex CpCp*Hf(SbMes2)2 (2) was prepared and structurally characterized. Complex 2 reacts with 2 equiv of xylylisocyanide to give the bis-insertion product CpCp*Hf[C(SbMes2)=N(2,6-MeC6H3)]2 (4). The reaction of 2 with oxidants (I2 and O2) or donors (carbon monoxide and diphenylacetylene) or thermolysis promotes the reductive elimination of Sb2Mes4.

Journal Article↗
PubMed2006

[Pretreatment of lead-antimony alloy and determination of antimony and selenium using ICP-AES].

The sample was obtained from original sample using "sawing method" and was dissolved with a mixed solvent of nitric acid and tartaric acid. After the sample solution was pretreated with a series of methods, Sb and Se were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that the recovery of standard addition of Sb was 96.2% and that of Se was 92.1%, and that the relative standard deviations (n=11) were smaller than 3.56%. The method is efficient, accurate and easy to operate, and has been applied to the determination of Sb and Se in Pb-Sb alloy products with satisfactory results.

English Abstract↗
PubMed1995

In vitro antileishmanial properties of tri- and pentavalent antimonial preparations.

To better understand the antileishmanial effects of antimonial agents we synthesized complexes of tri- and pentavalent antimony with mannan. The 50% inhibitory concentrations (IC50s) of these agents, along with those of potassium antimony tartrate [Sb(III)] and sodium stibogluconate [Sb(V)], were determined for promastigotes and intramacrophage amastigotes. The trivalent antimonial agents were more potent than the pentavalent agents. Although the IC50s were 60- to more-than-600-fold higher for promastigotes than for amastigotes, similar intracellular antimony concentrations in both life forms were measured after incubation with all four drugs at their respective IC50s. Macrophages accumulated antimony during a 4-h exposure that was retained intracellularly for at least 3 days. Amastigotes inside macrophages had a higher antimony content 6 days after a single 4-h treatment than they did immediately after treatment, suggesting that macrophages serve as a reservoir for antimonial agents and prolong parasite exposure. Macrophages concentrated antimony from the medium with potassium antimony tartrate, trivalent antimony-mannan, and pentavalent antimony-mannan treatments. N-Acetylcysteine antagonized the antileishmanial effects of these three drugs against intracellular amastigotes; in contrast, it had minimal effects on the action of sodium stibogluconate.

Acetylcysteine↗
PubMed2006

Role of residual Sb(III) in meglumine antimoniate cytotoxicity and MRP1-mediated resistance.

Despite the clinical use of pentavalent antimonials for more than half a century, their metabolism in mammals and mechanisms of action and toxicity remain poorly understood. It has been proposed that the more active and toxic trivalent antimony form Sb(III) plays a critical role in their antileishmanial activity and toxicity. The aim of this work was to investigate the role of residual Sb(III) both in the antileishmanial/antitumoral activities of the pentavalent meglumine antimoniate and in the MRP1 (multidrug resistance-associated protein 1)-mediated resistance to this drug. Samples of meglumine antimoniate differing in their amount of residual Sb(III) (meglumine antimoniate synthesized either from SbCl(5) or from KSb(OH)(6) as well as commercially-available meglumine antimoniate) were evaluated in vitro and in vivo on Leishmania amazonensis infections, as well as for their cytotoxicity to normal and MRP1-overexpressing GLC4 cell lines. Although in vitro the two most effective drugs contained the highest levels of Sb(III), no correlation was found in vivo between the antileishmanial activity of meglumine antimoniate and its residual Sb(III) content, suggesting that residual Sb(III) contributes only marginally to the drug antileishmanial activity. On the other hand, the GLC4 cells growth inhibition data strongly suggests a marked contribution of residual Sb(III). Additionally, the potassium salt of antimoniate (non-complexed form of Sb(V)) was found to be more cytotoxic than meglumine antimoniate. Although MRP1-overexpressing GLC4 cells showed a marked resistance to trivalent antimonials, cross-resistance to meglumine antimoniate was observed only for the products that contained relatively high levels of Sb(III) (at least 0.03% by weight), suggesting that MRP1 mediates resistance to Sb(III) but not to Sb(V). In conclusion, our data strongly suggest that residual Sb(III) in pentavalent antimonial drugs does not contribute significantly to their antileishmanial activity, but is responsible for their cytotoxic activity against mammalian cells and the MRP1-mediated resistance to these drugs.

Animals↗
PubMed1996

Mutagenicity, carcinogenicity and teratogenicity of antimony compounds.

The paper reviews the information available concerning the mutagenic, teratogenic and carcinogenic effects of antimony. A claim that antimony compounds could have mutagenic properties is based on insufficient and not particularly relevant data. Additional experiments, particularly with organic antimony compounds, would be desirable, but from what we know already, one may be confident that antimony is less a mutagenic risk than many other metals such as As, Cr, Ni, among others. Evidence for a carcinogenic risk of antimony in experimental animals was judged by the IARC sufficient for antimony trioxide and limited for antimony trisulfide. In man, IARC considered antimony trioxide as possibly carcinogenic. However, exposure in all studies on which these conclusions are based also involved other proven or likely carcinogenic compounds. Studies with pure antimony compounds, especially those used in therapy, need to be performed to clarify the situation. Although some indications exist that antimony trioxide could interfere with embryonic and fetal development, the studies seem not entirely conclusive. It is regrettable that, at least to our knowledge, the outcome of pregnancy in women treated with antimony compounds for leishmaniasis has not been studied. In conclusion, it appears that mutagenic, carcinogenic and teratogenic risks of antimony compounds, if they exists at all, are not very important.

Animals↗
PubMed1987

Toxicity of antimony and its compounds.

Experimental and clinical experience with compounds containing antimony have shown that the trivalent compounds are generally more toxic than the pentavalent ones. APT can cause severe pain and tissue necrosis and is therefore not given by intramuscular or subcutaneous injection. APT has the actions and uses of AST, but it is less soluble and more irritating than the sodium salt which is therefore more suitable for intravenous use. Trivalent antimony compounds are toxic when used topically. Adverse effects are similar for all trivalent compounds, and include nausea, vomiting, weakness and myalgia, abdominal colic, diarrhoea, and skin rashes, including pustular eruptions. Hypersensitivity reactions also occur. Respiratory symptoms include cough, dyspnoea, and chronic lung changes. Cardiotoxicity is the most important and may produce arrhythmias, myocardial depression and damage, Stokes-Adams attacks, heart failure, and cardiac arrest. Hepatic damage and necrosis, as well as blood dyscrasias, may occur. Toxic effects on the kidney may follow chronic use. Continuous treatment with small doses of antimony may give rise to symptoms of subacute poisoning, similar to those of chronic arsenic poisoning, due to accumulation of antimony in the body, especially if trivalent compounds are used, because of their long biological half-lives. Reproductive disorders and chromosome damage have been reported; antimony compounds are, therefore, potentially toxic to reproduction and have mutagenic, and oncogenic potential. Antimony compounds should, therefore, not be used during pregnancy or in the presence of hepatic, renal, or heart disease. Pentavalent antimony preparations especially the organic compounds, together with non-metallic synthetic preparations, such as the diamidines, have now replaced APT for use in leishmaniasis. Because of the toxicity of antimony compounds, investigations have been undertaken to reduce their adverse effects by combining them with chelating agents. These preparations appear to have reduced the toxic effects of antimony without affecting the efficacy of the preparations. Liposome-encapsulated antimony products have, more recently, been shown to be much less toxic because of the reduced dose of the antimony compound required for effective therapy. The historical uses of antimony were based on the belief that the topical and systemic adverse effects, for example, skin eruptions and diarrhoea and vomiting, were signs that the condition being treated was responding by being brought to the surface to relieve congestion at the diseased area. There is no evidence in topical use, but there is evidence that such use can cause severe reactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

Inhibition of DNA-double strand break repair by antimony compounds.

DNA double strand breaks (DSBs), induced by gamma-irradiation in Chinese hamster ovary cells, were used to examine whether antimony compounds affect the repair of DNA damage. The cells were first incubated with antimony trichloride or antimony potassium tartrate (both Sb(III)) for 2 h, and then irradiated with gamma-rays at a dose of 40 Gy. The DNA DSB was quantified with pulsed field gel electrophoresis immediately after irradiation (non-repair group) as well as at 30 min post-irradiation (repair group). The degree of repair inhibition was determined by the differences in the amount of DNA DSB between non-repair and repair groups. Both antimony compounds inhibited repair of DNA DSB in a dose dependent manner. In trichloride, 0.2 mM antimony significantly inhibited the rejoining of DSB, while 0.4 mM was necessary in potassium antimony tartrate. The mean lethal doses, D(0), for the treatment with antimony trichloride and antimony potassium tartrate, were approximately 0.21 and 0.12 mM, respectively. This indicates that the repair inhibition by antimony trichloride occurred in the dose range near D(0), but the antimony potassium tartrate inhibited the repair at doses where most cells lost their proliferating ability. This is the first report to indicate that antimony compounds may inhibit the repair of radiation-induced DNA DSB.

Animals↗
PubMed2003

Influence of arsenic on antimony methylation by the aerobic yeast Cryptococcus humicolus.

The anamorphic basidomycetous yeast Cryptococcus humicolus was shown by hydride generation-gas chromatography-atomic absorption spectrometry to methylate inorganic antimony compounds to mono-, di-, and trimethylantimony species under oxic growth conditions. Methylantimony levels were positively correlated with initial substrate concentrations up to 300 mg Sb l(-1) as potassium antimony tartrate (K-Sb-tartrate). Increasing concentrations of K-Sb-tartrate increased the ratio of di- to trimethylantimony species, indicating that methylation of dimethylantimony was rate limiting. Antimony methylation capability in C. humicolus was developed after the exponential growth phase and was dependent upon protein synthesis in the early stationary phase. Inclusion of inorganic arsenic (III) or (V) species alongside antimony in culture incubations enhanced antimony methylation. Pre-incubation of cells with inorganic arsenic (III) further induced antimony methylation capability, whereas pre-incubation with inorganic antimony (III) did not. Exposure of cells to inorganic arsenic-either through pre-incubation or provision during cultivation-influenced the antimony speciation; involatile trimethylantimony species was the sole methylated antimony species detected, i.e. mono- and dimethylantimony species were not detected. Competitive inhibition of antimony methylation was observed at high arsenic loadings. These data indicate that antimony methylation is a fortuitous process, catalysed at least in part by enzymes responsible for arsenic methylation.

Aerobiosis↗
PubMed2003

Comparing polyaluminum chloride and ferric chloride for antimony removal.

Antimony has been one of the contaminants required to be regulated, however, only limited information has been collected to date regarding antimony removal by polyaluminium chloride (PACl) and ferric chloride (FC). Accordingly, the possible use of coagulation by PACl or FC for antimony removal was investigated. Jar tests were used to determine the effects of solution pH, coagulant dosage, and pre-chlorination on the removal of various antimony species. Although high-efficiency antimony removal by aluminum coagulation has been expected because antimony is similar to arsenic in that both antimony and arsenic are a kind of metalloid in group V of the periodic chart, this study indicated: (1) removal density (arsenic or antimony removed per mg coagulant) for antimony by PACl was about one forty-fifth as low as observed for As(V); (2) although the removal of both Sb(III) and Sb(V) by coagulation with FC was much higher than that of PACl, a high coagulant dose of 10.5mg of FeL(-1) at optimal pH of 5.0 was still not sufficient to meet the standard antimony level of 2 microg as SbL(-1) for drinking water when around 6 microg as SbL(-1) were initially present. Consequently, investigation of a more appropriate treatment process is necessary to develop economical Sb reduction; (3) although previous studies concluded that As(V) is more effectively removed than As(III), this study showed that the removal of Sb(III) by coagulation with FC was much more pronounced than that of Sb(V); (4) oxidation of Sb(III) with chlorine decreased the ability of FC to remove antimony. Accordingly, natural water containing Sb(III) under anoxic condition should be coagulated without pre-oxidation.

Aluminum Hydroxide↗
PubMed2003

The distribution and speciation of antimony in river water, sediment and biota in Yodo River, Japan.

In 1993, the Japanese government set the guideline concentration of 2 microg l(-1) for antimony in natural water and drinking water as an item for precautionary monitoring in consideration of its chronic toxicity, however in 1999 the guideline value was tentatively canceled to examine the health risk of antimony through the accumulation of more information and data for detailed risk assessment. In this study, the distribution of antimony in the river water environment including water, sediment, aquatic plants and fishes was surveyed in the Yodo River basin. The characteristics of antimony distribution between river water and sediment were determined by the batch sorption experiments, focusing on the difference in oxidation state. This study suggests that biota in the Yodo River basin have antimony at concentrated levels. Some of the sewage treatment plants seemed to influence the concentration of antimony in river water. It was shown that the pentavalent antimony is dominant in river water and especially paramount downstream of the sewage treatment plants, though the trivalent antimony is dominant in industrial use. According to the sorption experiments of antimony on river sediment, the trivalent antimony is sorbed faster and more in partition than the pentavalent antimony.

Animals↗
PubMed2004

Oral delivery of meglumine antimoniate-beta-cyclodextrin complex for treatment of leishmaniasis.

The need for daily parenteral administration represents one of the most serious limitations in the clinical use of pentavalent antimonials against leishmaniasis. In this work, we investigated the ability of beta-cyclodextrin to enhance the oral absorption of antimony and to promote the oral efficacy of meglumine antimoniate against experimental cutaneous leishmaniasis. The occurrence of interactions between beta-cyclodextrin and meglumine antimoniate was demonstrated through the changes induced in the spin lattice relaxation times of protons in both compounds. When free and complexed meglumine antimoniate were given orally to Swiss mice, plasma antimony levels were found to be about three times higher for the meglumine antimoniate-beta-cyclodextrin complex than for the free drug. Antileishmanial efficacy was evaluated in BALB/c mice experimentally infected with Leishmania amazonensis. Animals treated daily with the complex (32 mg of Sb/kg of body weight) by the oral route developed significantly smaller lesions than those treated with meglumine antimoniate (120 mg of Sb/kg) and control animals (treated with saline). The effectiveness of the complex given orally was equivalent to that of meglumine antimoniate given intraperitoneally at a twofold-higher antimony dose. The antileishmanial efficacy of the complex was confirmed by the significantly lower parasite load in the lesions of treated animals than in saline-treated controls. This work reports for the first time the effectiveness of an oral formulation for pentavalent antimonials.

Administration, Oral↗