Thiol-Yne Click Postsynthesis of a Sulfonate Group-Enriched Magnetic Microporous Organic Network for Efficient Extraction of Benzimidazole Fungicides

The lack of functional groups or binding sites largely hindered the broad application of microporous organic networks (MONs). Herein, we report the fabrication of the sulfonate group-enriched magnetic MON composite (MMON-SO₃H@SO₃Na) via the combination of the sulfonic acid group containing the monomer and thiol-yne click postmodification for efficient magnetic solid-phase extraction (MSPE) of benzimidazole fungicides (BZDs) from complex sample matrices. The well-defined core-shell-structured MMON-SO₃H@SO₃Na was obtained and served as an advanced adsorbent for MSPE for concentrating and monitoring trace BZDs. The MMON-SO₃H@SO₃Na with numerous sulfonate groups provides plenty of ion-exchange, hydrogen-bonding, and π-π sites, leading to the favorable affinity to BZDs via multiple interaction mechanisms. The MMON-SO₃H@SO₃Na-based MSPE-high-performance liquid chromatography method afforded a wide linear range, low limits of detection, large enrichment factors, good precisions, and reusability for BZDs. Trace BZDs in complex vegetables and fruit samples were successfully detected by the established method. The MMON-SO₃H@SO₃Na also exhibited good selectivity toward multiple types of polar contaminants containing hydrogen-bonding sites and aromatic structures. This work provided a new postsynthesis strategy for constructing novel and multifunctioned magnetic MONs for preconcentration of trace analytes in a complex matrix.

Design and Construction of the Gadolinium Oxide Nanorod-Embedded Graphene Aerogel: A Potential Application for Electrochemical Detection of Postharvest Fungicide

The rapid development of electrochemical sensors holds great promise to serve as next generation point-of-care safety devices. However, the practical performances of electrochemical sensors are cruelly limited by stability, selectivity, and sensitivity. These issues have been well addressed by introducing rational designs into the modified electrode for achieving the required performances. Herein, we demonstrate the gadolinium oxide nanorods embedded on the graphene aerogel (GdO NRs/GA) for a highly selective electrochemical detection of carbendazim (CDM). The GdO NRs/GA nanocomposite was characterized using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission gun scanning electron microscopy, transmission electron microscopy with elemental mapping, and energy-dispersive spectrometry. The GdO NRs/GA-modified electrode shows a much improved electrochemical performance compared to other electrodes. Interestingly, the GdO NRs are strongly anchored in the GA matrix, which provides a more sufficient pathway for the rapid electron and ion transportation. On the basis of these findings, our proposed sensor achieves a wide detection range from 0.01 to 75 μM with a correlation coefficient of 0.996 and a low detection limit of 3.0 nM. Most markedly, the real-time monitoring of the proposed electrochemical sensor was proved by the successful determination of CDM in environmental samples. Our research work has opened a novel way to the rationale for the construction of highly efficient practical electrochemical sensors.

Degradation of Carbendazim in Soil: Effect of Sewage Sludge-Derived Biochars

Application of biochar in soils can affect the soil properties and, in turn, the fate of pesticides. Batch experiments were conducted to investigate the effect of sewage sludge-derived biochars on the dissipation of a fungicide carbendazim in soil, and the transformation of carbendazim in soil was also studied. Results showed that the dissipation of carbendazim was fastest in a loamy soil SD with a half-life of 11.0 d among the three kinds of soils tested in this study. A dual effect (both acceleration and inhibition) of sewage sludge-derived biochars on carbendazim degradation in soil was reported. The addition of 10% biochars produced at 700 °C (BC 700) in soil could accelerate the carbendazim degradation, but an inhibitory effect was observed for 10% BC 300 or BC 500. Degradation of carbendazim was significantly inhibited when 0.5 or 5% BC 700 was added in soil but accelerated when the amendment ratio of BC 700 was increased to 10%. Such complex effects of the sewage sludge biochar should be taken into consideration in risk assessment of pesticides and the biochar effects on soil remediation. Eight metabolites of carbendazim were characterized, seven of which were reported in unamended soil for the first time. The metabolic pathways of carbendazim in soil are proposed.

Determination of 107 Pesticide Residues in Wolfberry with Acetate-buffered Salt Extraction and Sin-QuEChERS Nano Column Purification Coupled with Ultra Performance Liquid Chromatography Tandem Mass Spectrometry

A multi-residue method for the determination of 107 pesticide residues in wolfberry has been developed and validated. Similar pretreatment approaches were compared, and the linearity, matrix effect, analysis limits, precision, stability and accuracy were validated, which verifies the satisfactory performance of this new method. The LODs and LOQs were in the range of 0.14–1.91 µg/kg and 0.46–6.37 µg/kg, respectively. The recovery of analytes at three fortification levels (10 µg/kg, 50 µg/kg, 100 µg/kg) ranged from 63.3–123.0%, 72.0–118.6% and 67.0–118.3%, respectively, with relative standard deviations (RSDs) below 15.0%. The proposed method was applied to the analysis of fifty wolfberry samples collected from supermarkets, pharmacies and farmers’ markets in different cities of Shandong Province. One hundred percent of the samples analyzed included at least one pesticide, and a total of 26 pesticide residues was detected in fifty samples, which mainly were insecticides and bactericide. Several pesticides with higher detection rates were 96% for acetamiprid, 82% for imidacloprid, 54% for thiophanate-methyl, 50% for blasticidin-S, 42% for carbendazim, 42% for tebuconazole and 36% for difenoconazole in wolfberry samples. This study proved the adaptability of the developed method to the detection of multiple pesticide residues in wolfberry and provided basis for the research on the risks to wolfberry health.

Sorption of carbendazim and linuron from aqueous solutions with activated carbon produced from spent coffee grounds: Equilibrium, kinetic and thermodynamic approach

Spent coffee grounds (SCG) have been used for the production of activated carbon (AC) by impregnation with different ratios of phosphoric acid at 600 °C, Xp (H₃PO₄/coffee): 3:1^30%, 4:1^30%, 3:1^50% and 4:1^50%. The obtained AC was characterized by BET, FTIR and SEM. BET surface area corresponds to 803.422 m² g^-1. The influences of the main parameters such as contact time, the pesticides initial concentration, adsorbent dose, pH and temperature on the efficiency of separation process were investigated during the batch operational mode. Results were modeled by adsorption isotherms: Langmuir, Freundlich and Temkin isotherms, which gave satisfactory correlation coefficients. The maximum adsorption capacities calculated from the Langmuir isotherms were 11.918 mg g^-1 for carbendazim and 5.834 mg g^-1 for linuron at room temperature. Adsorption kinetics of carbendazim and linuron have been studied by the pseudo-first-order, the pseudo-second-order and the intraparticle diffusion model. The results of adsorption kinetics have been fitted the best by pseudo-second-order model. The resulted data from FTIR characterization pointed to the presence of many functional groups on the AC surface. SCG adsorbent, as an eco-friendly and low-cost material, showed high potential for the removal of carbendazim and linuron from aqueous solutions.

Restricted Access Volatile Supramolecular Solvents for Single-Step Extraction/Cleanup of Benzimidazole Anthelmintic Drugs in Milk Prior to LC-MS/MS

In this work, a restricted access volatile supramolecular solvent (RAM-VOL-SUPRAS) directly synthesized in milk is proposed for the first time for the simultaneous extraction and cleanup of benzimidazole anthelmintic drugs in milk meant for human consumption. The RAM-VOL-SUPRAS was formed by the self-assembly and coacervation of hexanol in tetrahydrofuran induced by the water content in milk. Benzimidazoles legislated by the European Union were quantitatively extracted (80-110%), and proteins were precipitated by the action of THF and the amphiphile; extraction of carbohydrates was avoided by a size exclusion mechanism, and lipids were removed during hexanol evaporation. The analytical methodology was fully validated according to Commission Decision 2002/657/EC. Method detection limits from 0.03 to 0.14 μg L^-1 were well below the maximum residue limits legislated in milk for these drugs, with interday precisions at maximum residue levels below 13%. This novel methodology guarantees a rapid and reliable tool for daily and routine laboratory analyses in the field of food quality control.

A Rapid and Optimized LC-MS/MS Method for the Simultaneous Extraction and Determination of Sofosbuvir and Ledipasvir in Human Plasma

A new validated bioanalytical method based on LC tandem MS has been developed for the simultaneous extraction and determination of sofosbuvir and ledipasvir in human plasma using antiviral daclatasvir as an internal standard (IS). Liquid-liquid extraction of samples was used for the purification and preconcentration of the analytes from a human plasma matrix. Good and consistent recoveries were obtained, with average extraction recoveries of 91.61 and 88.93% for sofosbuvir and ledipasvir, respectively. The chromatographic separation of the three analytes was achieved within only 2.8 min by an isocratic mobile phase consisting of 10 mM ammonium acetate, which was then adjusted to pH 4.0 by acetic acid-acetonitrile-0.1% methanolic formic acid (12 + 25 + 63, v/v/v) flowing through a C18 Zorbax eclipse plus column (5 μm, 100 × 4.6 mm; Agilent). Multiple reaction monitoring transitions were measured in positive ion mode for sofosbuvir, ledipasvir, and daclatasvir (IS). A detailed validation of the method was performed and the standard curves were found to be linear in the range of 0.5 to 2500 and 5 to 2100 ng/mL for sofosbuvir and ledipasvir, respectively, applying weighted (1/X(2)) linear regression. The developed method was applied to the analysis of the two drugs after a single oral administration of Harvoni 400/90 mg film-coated tablets containing 400 mg sofosbuvir and 90 mg ledipasvir to four healthy volunteers.

Nickel Oxide Nanoparticle-Deposited Silica Composite Solid-Phase Extraction for Benzimidazole Residue Analysis in Milk and Eggs by Liquid Chromatography-Mass Spectrometry

A novel nickel oxide nanoparticle-deposited silica (SiO2@NiO) composite was prepared via liquid-phase deposition (LPD) and then employed as a solid-phase extraction (SPE) sorbent. When the SPE was coupled with liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS) analysis, an analytical platform for the sensitive determination of benzimidazole residues in egg and milk was established. The limits of detection of nine benzimidazoles were in the range of 0.8-2.2 ng/mL in milk and 0.3-2.1 ng/g in eggs, respectively, which was 5-10 times superior to the methods with other adsorbents for SPE. The recoveries of nine benzimidazoles spiked in milk and egg ranged from 70.8 to 118.7%, with relative standard deviations (RSDs) being less than 18.9%. This work presented the excellent extraction performance of NiO on benzimidazoles for the first time, and the applicability of the LPD technique used as sorbents for trace analysis in complex matrices was also demonstrated.

[Degradation of carbendazim in paddy soil and the influencing factors]

The influences of microorganism, soil moisture and cadmium (Cd) on degradation of carbendazim in paddy soil were investigated with laboratory microcosm experiments. The results showed that the half-life of carbendazim (5.0 mg x kg(-1) and 10.0 mg x kg(-1)) in sterilized soils was 12.6-13.8 times of those in non-sterilized soils. The half-life of carbendazim was decreased by 32.1%-37.1% when the soils were inoculated with carbendazim-degrading strains. When the soil moisture was increased from 40% to 60% or 80% of water holding capacity, the half life of carbendazim was decreased by 46.2% or 74.0%, respectively. Low level of Cd (5 mg x kg(-1)) enhanced the degradation of carbendazim in soils with half-life time decreased by 32.1%-52.4%, but high level of Cd (50 mg x kg(-1)) inhibited the degradation of carbendazim in soils with half-life time increased by 92.6%-103.0%. For the soils inoculated with carbendazim-degrading strains, the half life of carbendazim was decreased by 34.0% -34.4% with the addition of low level of Cd (5.0 mg x kg(-1)), while the half life time was increased by 74.4% -109.4% with the addition of high level of Cd (50 mg x kg(-1)). The results demonstrate that indigenous microorganisms is a critical factor that influences carbendazim degradation in soils, and that carbendazim-degrading strains, high soil moisture and low Cd level enhance the degradation of carbendazim.

New benzimidazole derivatives with potential cytotoxic activity--study of their stability by RP-HPLC

Obtained benzimidazole derivatives, our next synthesized heterocyclic compounds, belong to a new group of chemical bondings with potential anticancer properties (Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2006, J Liguid Chrom Rel Tech 29: 2367-2385; Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2008, Wiad Chem 62: 11-12, in Polish; Błaszczak-Świątkiewicz & Mikiciuk-Olasik, 2011, J Liguid Chrom Rel Tech 34: 1901-1912). We used HPLC analysis to determine stability of these compounds in 0.2% DMSO (dimethyl sulfoxide). Optimisation of the chromatographic system and validation of the established analytical method were performed. Reversed phases (RP-18) and a 1:1 mixture of acetate buffer (pH 4.5) and acetonitrile as a mobile phase were used for all the analysed compounds at a flow rate 1.0 mL/min. The eluted compounds were monitored using a UV detector, the wavelength was specific for compounds 6 and 9 and compounds 7 and 10. The retention time was specific for all four compounds. The used method was found to have linearity in the concentration range of (0.1 mg/mL-0.1 μg/mL) with a correlation coefficient not less than r(2)=0.9995. Statistical validation of the method proved it to be a simple, highly precise and accurate way to determine the stability of benzimidazole derivatives in 0.2% DMSO. The recoveries of all four compounds examined were in the range 99.24-100.00%. The developed HPLC analysis revealed that the compounds studied remain homogeneous in 0.2% DMSO for up to 96 h and that the analysed N-oxide benzimidazole derivatives do not disintegrate into their analogues - benzimidazole derivatives. Compounds 8, 6 and 9 exhibit the best cytotoxic properties under normoxic conditions when tested against cells of human malignant melanoma WM 115.

Assessment of the BCR sequential extraction procedure for thallium fractionation using synthetic mineral mixtures

This work focused on the specific behavior of Tl-bearing phases in the BCR (Community Bureau of Reference) sequential extraction (SE) scheme, namely Tl-bearing ferrihydrite, goethite, birnessite, calcite, illite, sphalerite and feldspar in their simple model mixtures with quartz. Several significant discrepancies between the obtained and expected behaviors of these phases in the BCR SE were observed. The amount of Tl released as the exchangeable/acid-extractable fraction (55-82% of the total Tl content) showed a substantial H(+)-promoted dissolution of all Fe(III) and Mn(III, IV) oxides (corresponding to up to 61% of solid Fe dissolved) and incongruent (increased) extraction of Tl from ferrihydrite and goethite. Reductive conditions of the second SE step were insufficient to complete goethite dissolution with corresponding Tl amount retained in the solid phase. Similarly, insufficient oxidation of sphalerite and lower Tl recovery of the oxidisable fraction was identified. In contrast, the BCR SE seems to produce well predictable results of Tl leaching from Tl-bearing calcite and feldspar. Only 70% of total Tl content was extracted from Tl-modified illite in the exchangeable/acid-extractable step, while 30% was associated with the reducible and residual fractions, i.e., Tl was strongly fixed to the illite matrix.

[Determination of benomyl, carbendazim and thiabendazole in apple juice concentrate using solid-phase extraction coupled with ion exchange chromatography]

A method was developed for the determination of benomyl, carbendazim and thiabendazole in apple juice concentrate by solid-phase extraction coupled with ion exchange chromatography (IEC). The sample was diluted with water, and then benomyl was degradated completely to carbendazim at 80 degrees C, and purified by an SCX solid-phase extraction column. Liquid chromatographic analysis was performed on the instrument of Agilent 1200 series equipped with a diode-array detector and autosampler. The column was LC-SCX (25 cm x 4.6 mm, 5 microm). The mobile phase was 0.1 mol/L KH2PO4 (pH 2.5)-acetonitrile (70:30, v/v) with a flow rate of 1.0 mL/min. The presented method showed good linear relationship with good precision and accuracy at the range of 0.02 - 2.0 mg/L for carbendazim and thiabendazole. The detection limits were 0. 004 mg/kg for carbendazim and thiabendazole. The method was characterized with acceptable sensitivity to meet the requirements for monitoring these pesticides in apple juice concentrate.

Hydrolysis and transesterification reactions of candesartan cilexetil observed during the solid phase extraction procedure

Candesartan cilexetil is an angiotensin receptor antagonist widely used in the treatment of high blood pressure. This prodrug is metabolised into candesartan, which blocks the receptors AT1 for angiotensin II decreasing the blood pressure levels. During the development of a solid phase extraction procedure for the chromatographic determination of eight antihypertensive compounds, lack of linearity and reproducibility was observed only for candesartan cilexetil. Due to this fact, a stability study for this prodrug was performed. It showed that the lack of linearity and reproducibility was based on hydrolysis and transesterification processes which occurred during the drying step after elution with methanol into glass tubes. These phenomena could be reproduced artificially under basic conditions, which demonstrated the presence of basic residues in glass tubes. The study of this potential hydrolysis and transesterification reactions is very important to assure that labile drugs containing ester groups remain unaffected.

Three new sesquiterpenoids from the aerial parts of Homalomena occulta

Three new eudesmane-type sesquiterpenoids, compounds 1-3, and eight known constituents, including mucrolidin (4), 1beta,4beta,7alpha-trihydroxyeudesmane (5), 1beta,4beta,6beta,11-tetrahydroxyeudesmane (6), oplodiol (7), bullatantriol (8), acetylbullatantriol (9), homalomenol (10), and maristeminol (11), were isolated from the aerial parts of Homalomena occulta. Their structures were determined by interpretation of spectroscopic and mass-spectrometric data, and their antimicrobial activities toward six different bacterial strains were tested. Most of the compounds showed weak antibacterial activities in an agar-diffusion assay.

Cytotoxic Prenylated Phenolic Compounds from the Twig Bark ofGarcinia xanthochymus

Three new hydroxylated xanthones with prenyl or geranyl substituents, compounds 1-3, were isolated from the twig bark of Garcinia xanthochymus, along with the four known compounds 1,4,5,6-tetrahydroxy-7,8-diprenylxanthone (4), 1,3,5,6-tetrahydroxy-4,7,8-triprenylxanthone (5), garciniaxanthone E (6), and 6-prenylapigenin (7). Their structures were elucidated by extensive spectroscopic analysis, including 1D- and 2D-NMR as well as HR-MS experiments. All compounds showed moderate cytotoxicities against breast cancer (MDA-MB-435S) and lung adenocarcinoma (A549) cell lines, but lacked antifungal activity against Candida albicans.

Determination of benzimidazole fungicides in soil samples using microwave-assisted micellar extraction and liquid chromatography with fluorescence detection

A simple and fast analytical method was developed for the determination of benzimidazole fungicides (benomyl, carbendazim, thiabendazole, and fuberidazole) in soil samples. The analytes were extracted from the soil samples by means of conventional microwave-assisted extraction, using the non-ionic surfactants polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monooalkyl ether (Genapol X-080) as extractants. Determinations were made by using liquid chromatography with direct fluorescence detection. The use of an analytical column Symmetry C-18 offered short retention times of analytes without the need of any pH regulators with mobile phase methanol-water (50 + 50, v/v). The best results were obtained using 5% (v/v) POLE as extractant with recoveries of the fungicides in spiked soil samples between 71 and 105%. The results were compared with those obtained when Soxhlet extraction was applied to the same soil samples.

Synthesis and purification of fluorinated benzimidazole and benzene nucleoside-5'-triphosphates

The expression "universal base" is very often used to express hybridization properties and recognition patterns of nucleosides. Their behaviour in biological applications, however, is of great interest regarding, e.g.,' their incorporation by polymerases. The 4,6-difluorobenzimidazole and the 2,4-difluorobenzene nucleoside analogues have proven to be universal bases that do not discriminate between the four natural nucleobases in RNA duplexes. Therefore, we synthesized the corresponding triphosphates to evaluate their behavior in polymerase catalyzed reactions and to investigate their ability to serve as substrates for the T7 RNA polymerase.

Implications of Fungicidal Effects of Benzimidazole Compounds on Duddingtonia flagrans in Integrated Nematode Parasite Management in Livestock

An in vitro trial with carbendazim fungicide on the growth profile of the predatory fungus Duddingtonia flagrans was undertaken and in vivo trials in sheep and buffaloes, fed on chlamydospores of D. flagrans and administered albendazole anthelmintic, were conducted. Although no growth inhibition was detected at a carbendazim concentration of 0.05 ppm, growth inhibition was recorded of 50% and above at concentrations of 0.25 and 1.00 ppm (p < 0.001) and of around 90% at concentrations of 2.00 to 5.00 ppm (p <0.0001). Scanty recovery of the fungus was made from faecal culture 48 h following a single dose of albendazole both in sheep and buffaloes. However, profuse fungal recovery was made from 96 h post dosing onwards. When the drug was used as an intraruminal slow-release capsule, no faecal fungal recovery could be made from day 3 after administration of the capsule, when the albendazole sulphoxide concentration was around 1.0 microg/ml. However, profuse and scanty fungal recovery could be made on days 1 and 2, respectively, after administration of the capsule, when the plasma albendazole sulphoxide concentration was around 0.4 and 0.9 microg/ml, respectively. The implications for use of a combination of anthelmintics and biological control in sustainable parasite control programmes are discussed.

Subcritical water extraction to evaluate desorption behavior of organic pesticides in soil

We evaluated the feasibility of extracting organic pesticides in soil using a hot-water percolation apparatus at 105 degrees C and 120 kPa pressure. Efficiency of the method was assessed by extracting six selected pesticides (acetochlor, atrazine, diazinon, carbendazim, imidacloprid, and isoproturon) from previously equilibrated soil at 13.6-65.8 mg/kg concentration range. Studies were performed on brown forest soil with clay alluviation (Luvisol). The method developed was compared to the traditional batch equilibrium method in terms of desorbed amount of pesticides from soil and extraction time. Pesticides in the liquid phase from the batch sorption experiment and in the effluent from the hot-water percolation were quantified by high-performance liquid chromatography with UV detection. The results of the percolation experiment are in close correlation with those of the conventional soil testing method. Desorbed quantities by hot-water percolation were 85% acetochlor, 62% atrazine, 65% carbendazim, 44% diazinon, 95% imidacloprid, and 84% isoproturon, whereas using batch equilibrium method 101, 66, 64, 37, 81, and 90% were desorbed, expressed as the percentage of the adsorbed amount of pesticide on soil following equilibration. The average time for hot-water extraction was 3.45 min, in contrast to the 16 h time consumption of the traditional batch method. The effect of temperature on stability of selected compounds was also evaluated using pesticide-spiked sand without soil. Recoveries of analytes ranged between 84.6 and 91.1% with reproducibility of 7.9-10.2%, except for diazinon, for which recovery was 59.4% with 14.4% relative standard deviation since decomposition occurred at elevated temperature. The percolation process has been described by a first-order kinetic equation. The parameters calculated from the equation provide an opportunity to estimate the amount of compound available for desorption, the rate of desorption processes in the studied soil-pesticide-water system, and modeling the leaching process to obtain additional information on the environmental behavior of the examined pesticide.

Biosynthetic pathway to the cancer chemopreventive secoisolariciresinol diglucoside-hydroxymethyl glutaryl ester-linked lignan oligomers in flax (Linum usitatissimum) seed

Application of stable and radioisotope precursor/tracer experiments resulted in the identification of various phenylpropanoid, monolignol, and lignan metabolites involved in the biosynthesis of the cancer chemopreventive secoisolariciresinol diglucoside (SDG; 1)-containing ester-linked "polymer(s)" in flax (Linum usitatissimum) seed. Individual analysis of size-segregated flax seed capsules at five early stages of their development provided a metabolic profile of intermediates leading to "biopolymer" biosynthesis. The use of (1)H and (13)C NMR and HRMS analyses resulted in the identification of 6a-HMG (hydroxymethyl glutaryl) SDG (17) and 6a,6a'-di-HMG SDG (18) as the two major components of the ester-linked "biopolymer(s)". Based on metabolic tracer analyses and relative radioisotopic incorporations throughout each of these five stages of seed development, a biochemical pathway is proposed from phenylalanine to SDG (1), with subsequent mono- and di-substitutions of SDG (1) with HMG CoA. These metabolites then serve as precursors for formation of the SDG-HMG ester-linked oligomers. Results from this study will facilitate future isolation and characterization of the proteins and enzymes involved in biosynthesis of the SDG-HMG ester-linked oligomers in flax seed.

Influence of Bulky N-Substituents on the Formation of Lanthanide Triple Helical Complexes with a Ligand Derived from Bis(benzimidazole)pyridine: Structural and Thermodynamic Evidence

The planar aromatic tridentate ligand 2,6-bis(1-S-neopentylbenzimidazol-2-yl)pyridine (L(11)) reacts with Ln(III) (Ln = La-Lu) in acetonitrile to give the successive complexes [Ln(L(11))(n)](3+) (n = 1-3). However, stability constants determined by spectrophotometry and NMR titrations show that formation of the tris complexes is not favored, log K(3) being around 1 for La(III) and Eu(III), while no such species could be evidenced for the smaller Lu(III) ion. The X-ray structures of L(11) (monoclinic, P2(1), a = 13.4850(12) A, b = 12.0243(11) A, c = 16.4239(14) A, beta = 103.747(7) degrees ), [La(ClO(4))(2)(L(11))(2)](3)[La(ClO(4))(2)(H(2)O)(L(11))(2)](ClO(4))(4).15MeCN (1a, monoclinic, P2(1), a = 21.765(4) A, b = 30.769(6) A, c = 21.541(5) A, beta = 116.01(3) degrees ), and [Eu(L(11))(3)](ClO(4))(3).4.28MeCN (5a, monoclinic, P1, a = 14.166(3) A, b = 19.212(4) A, c = 21.099(4) A, alpha = 108.91(3) degrees, beta = 98.22(3) degrees, gamma = 108.40(3) degrees ) have been solved. In 1a, two different types of complex cations are evidenced, both containing 10-coordinate La(III) ions. In the first type, both perchlorate anions are bidentate, while in the second type, one perchlorate is monodentate, the 10th coordination position being occupied by a water molecule. In 5a the three ligands are not equivalent. Ligands A and B are wrapped in a helical way and are mirror images of each other, while ligand C lies almost perpendicular to the two other ones. This stems from the steric hindrance generated by the bulky neopentyl groups with the consecutive loss of any stabilizing interstrand pi-stacking interactions. This explains the low stability of the tris complexes and the difficulty of isolating them and points to the importance of the steric factors in the design of self-assembled triple helical lanthanide-containing functional edifices [Ln(L(i))(3)](3+).

Stereoselective chiral inversion of pantoprazole enantiomers after separate doses to rats

(+/-)-Pantoprazole ((+/-)-PAN), (+/-)-5-(difluoromethoxy)-2-[[3.4-dimethoxy-2-pyridinyl)methyl]sul finyl]- 1H-benzimidazole) is a chiral sulfoxide that is used clinically as a racemic mixture. The disposition kinetics of (+)-PAN and (-)-PAN given separately has been studied in rats. Serum levels of (+)- and (-)-PAN and its metabolites, pantoprazole sulfone (PAN-SO2), pantoprazole sulfide (PAN-S), 4'-O-demethyl pantoprazole sulfone (DMPAN-SO2), and 4'-O-demethyl pantoprazole sulfide (DMPAN-S) were measured by HPLC. Following single intravenous or oral administration, both enantiomers were rapidly absorbed and metabolized, resulting in similar serum concentrations, suggesting that the two enantiomers have approximately the same disposition kinetics. The major metabolite of both (+)- and (-)-PAN was PAN-SO2, while DMPAN-SO2 was also detected as a minor metabolite. Serum levels of PAN-S and DMPAN-S could not be quantified after intravenous or oral administration of either enantiomer. Significant chiral inversion occurred after intravenous and oral administration of (+)-PAN. The AUCs of (-)-PAN after intravenous and oral dosing of (+)-PAN were 36.3 and 28.1%, respectively of those of total [(+) + (-)] PAN. In contrast, the serum levels of (+)-PAN were below quantitation limits after intravenous or oral administration of (-)-PAN. Therefore, chiral inversion was observed only after administration of (+)-PAN, supporting the hypothesis that stereoselective inversion from (+)-PAN to (-)-PAN occurs in rats.

Quantitative gas chromatographic analysis of [1-(4-piperidinyl)-1,3-dihydro-2H-benzimidazole-2-one], the basic metabolite of bezitramide (Burgodin), in human urine

A gas chromatographic procedure with nitrogen-phosphorus detection was developed for the quantitative determination of 1-(4-piperidinyl)-1,3-dihydro-2H-benzimidazole-2-one, the basic metabolite of the narcotic analgesic bezitramide (Burgodin), in urine. Gas chromatography with mass spectrometric detection was used for confirmation. An internal standard with great structural resemblance to the basic metabolite was synthesized in our laboratory. For the isolation of the compound from urine, a liquid-liquid extraction with chloroform/isopropanol was performed. The extract was derivatized with pentafluorobenzoylchloride immediately before chromatographic analysis. The calibration curve was linear over a broad concentration range (10 to 1000 ng/mL). The quantitation limit was 10 ng/mL, and at a 250-ng/mL concentration, coefficients of variation of 2.8 and 3.4% were obtained for within-day and between-day precision, respectively. The selectivity and accuracy of the method were satisfactory. Out of 150 urine samples, mainly from persons suspected of using bezitramide or from known drug abusers, 22 samples revealed basic metabolite concentrations that ranged from 17.0 to 1695.5 ng/mL. The described method allows the quantitation of the basic metabolite of bezitramide with high sensitivity, selectivity, and precision. It can also be used to determine bezitramide abuse and to establish bezitramide overdoses.

Chiral resolution of pantoprazole sodium and related sulfoxides by complex formation with bovine serum albumin in capillary electrophoresis

The separation of enantiomers of pantoprazole sodium, omeprazole and lansoprazole by capillary zone electrophoresis using bovine serum albumin (BSA) as the chiral selector is described. Baseline separation of the three structurally related drugs was obtained after optimization of the most important experimental parameters. For this purpose, influences such as BSA concentration, pH and concentration of 1-propanol as organic modifier on the separation were investigated. Increasing concentrations of BSA improved the chiral resolution but lowered the sensitivity of the detection system. Discrimination of the enantiomers was observed only in a narrow pH range of 7-8. An optimum of pH 7.4 was a good compromise in terms of enantio-resolution and peak shape. 1-Propanol when added to the buffer system, improved the peak shape of the analytes and the resolution. The optimized method has been validated for pantoprazole sodium and is useful for routine analysis.

Bis-benzimidazole dyes, Hoechst 33258 and Hoechst 33342: radioiodination, facile purification and subcellular distribution

A simple HPLC method is presented for the purification of DNA binding bis-benzimidazole dyes Hoechst 33258, Hoechst 33342 and 131I-iodoHoechst 33258. The mobile phase, consisting of methanol and aqueous ammonia (0.2%) in the ratio 2:3, resolved and separated the radiochemical from unlabeled ligand and other reagents used in the reaction, thereby resulting in high radiochemical purity and yield. The iodinated Hoechst 33258 did not show any selective binding to nuclear DNA when cell fractionation studies were performed with cultured mammalian cells as well as in mice testes. Fluorescence microscopy studies with V79 cells stained with these dyes, showed the superiority of Hoechst 33342 in selective localization in nuclear DNA compared to Hoechst 33258. The difference in behavior of these two dyes in terms of binding to nuclear DNA, and hence their ability to provide protection against damage caused by ionizing radiation, may be explained on the basis of the molecular charge. The high chemotoxicity of Hoechst 33342 observed in the present studies suggests that its usefulness as a radioprotector against chronic irradiation of tissue by incorporated radionuclides may be limited.

Chiral chromatography and multivariate quantitative structure-property relationships of benzimidazole sulphoxides

Various benzimidazole sulphoxides were chirally resolved employing an amylase-based chiral stationary phase. The structure-property relationships of these compounds were investigated using calculated physicochemical properties, molecular modelling and multivariate statistical techniques. A data set of 254 molecular descriptors was used to represent the series of compounds. Analysis of the data set using principal components analysis and non-linear mapping suggested that the separation factor of each enantiomeric pair was associated with nine molecular properties and, in particular, molar refractivity of the Z substituent and the partial charge of atom 6. The separation factor of a sulphoxide not used in the analysis was well predicted thus suggesting that these models may be used to generalize.

Matrix solid phase dispersion isolation and liquid chromatographic determination of five benzimidazole anthelmintics in fortified beef liver

A multiresidue method for isolation and liquid chromatographic determination of 5 benzimidazole anthelmintics (thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole) in beef liver tissue is presented. Blank or benzimidazole-fortified liver samples (0.5 g) were blended with octadecylsilyl derivatized silica packing material (C18, 18% load, endcapped, 2 g). A column made from the C18/liver matrix was first washed with hexane (8 mL), following which the benzimidazoles were eluted with acetonitrile. The acetonitrile extract was then passed through an activated alumina column. The eluate contained benzimidazole analytes that were free from interfering compounds as determined by UV detection (photodiode array, 290 nm). Correlation coefficients of standard curves for individual benzimidazoles isolated from fortified samples, using internal standardization, were linear (0.996 +/- 0.002 to 0.999 +/- 0.001) with average relative percentage recoveries from 62.0 +/- 6.7 to 86.8 +/- 8.6% for the concentration range (100-3200 ng/g) examined. The interassay variability was 7.0 +/- 4.1 to 12.9 +/- 10.2% with an intra-assay variability from 2.2 to 4.0%.

Methodology for the analysis of benzimidazole anthelmintics as drug residues in animal tissues

Methodology for the analysis of 8 benzimidazoles as residues in bovine liver is reported. Spiked tissues were extracted by homogenization in saline and ammonium hydroxide and blending with diatomaceous earth. This matrix was packed into a column, and the benzimidazoles were eluted with ethyl acetate. After the sample was further purified, benzimidazoles were separated and quantitated by liquid chromatography with ultraviolet detection (290 nm). Liver tissue samples obtained from cattle which had undergone a drug depletion study of fenbendazole administered per os were analyzed using these methods. The results of these analyses and the application of this approach to multiresidue analysis of drugs in animal tissues are discussed.

High-performance liquid chromatographic determination of formate as benzimidazole in biological samples

Formate was determined as benzimidazole by high-performance liquid chromatography after reaction with o-phenylenediamine at 130 degrees C for 2 h in 1 M perchloric acid. The useful concentration range was 1.6-40 mumol/l and the determination limit was 20 pmol. The recoveries from rat liver homogenate and human urine were 90.3 +/- 2.9 and 89.4 +/- 2.5%, respectively. Using this method, the activity of formaldehyde dehydrogenase in biological samples could be measured, and also the formate concentration in the liver and urine of rats to which methanol had been administered.

Identification of the main urinary metabolites of omeprazole after an oral dose to rats and dogs

The structures of seven urinary metabolites of omeprazole following high oral doses to rats and dogs were determined unambiguously by combining different analytical and spectroscopic techniques including derivatization and stable isotopes. Omeprazole was metabolized by aromatic hydroxylation at position 6 in the benzimidazole ring followed by glucuronidation. There was also oxidative O-dealkylation of both methoxy groups, and aliphatic hydroxylation of a pyridine methyl group followed by oxidation to the corresponding carboxylic acid. Due to the experimental design, implying no pH control of collected samples, all metabolites were isolated as sulfides. They were formed in both species with quantitative variations in the metabolic pattern. As far as identified metabolites are concerned, aromatic hydroxylation and subsequent glucuronide formation were the major biotransformation routes in the dog. In the rat, aliphatic hydroxylation and the formation of the carboxylic acid represented the major metabolic pathways. The identified metabolites corresponded approximately to 50% (rat) and 70% (dog) of the amount excreted in the 0-24-hr urine (about 12% of the given dose in both species).