Synthesis and evaluation of novel pyrroles and pyrrolopyrimidines as anti-hyperglycemic agents

A series of pyrrole and pyrrolopyrimidine derivatives were examined for their in vivo antihyperglycemic activity. Compounds Ia-c,e, and IVg showed promising antihyperglycemic activity equivalent to a well-known standard antihyperglycemic drug, Glimepiride (Amaryl, 4 mg/kg). In this paper, we examine and discuss the structure-activity relationships and antihyperglycemic activity of these compounds.

Purification and cloning of nicosulfuron-degrading enzymes from Bacillus subtilis YB1

The nicosulfuron-degrading enzymes from Bacillus subtilis strain YB1 were purified and their genes were cloned. The proteins of bacterial culture filtrate were precipitated with ammonium sulfate or acetone. The extracellular proteins concentrated by acetone were purified from DEAE-Sepharose Fast Flow chromatography. The four protein peaks eluted from DEAE-column were separated and purified by native PAGE. Three components (P1-1, P3-2, P4-3) had nicosulfuron-degrading activity, and component P4-3 degradated 57.5% of this compound. The molecular weights of the components were 33.5, 54.8 and 37.0 kDa, respectively. The amino acid sequences of nicosulfuron-degrading enzymes from B. subtilis YB1 were determined by MALDI-TOF-MS, indicating these enzymes as manganese ABC transporter, vegetative catalase 1 and acetoin dehydrogenase E1, respectively. Using PCR amplification, genes 918, 1428, 1026 bp in size were detected for the enzymes studied.

Study on the photodegradation of amidosulfuron in aqueous solutions by LC-MS/MS

Sulfonylurea herbicides are extensively widespread for the protection of a variety of crops and vegetables because of their low application rates, high selectivity and low persistency in the environment; unfortunately, their low persistence does not always correspond to a lower toxicity, since new species potentially more toxic and stable than the precursor herbicides can form, owing to natural degradation processes. Here, the photodegradation of amidosulfuron in aqueous solutions was studied by high-performance liquid chromatography with diode array detection and tandem mass spectrometry to identify the degradation products in order to outline the environmental fate of the molecules generating from the simulation of one of the natural processes that can occur, i.e., photoinduced degradation. The photodegradation process results in a first order kinetic reaction with a t 1/2 value of 276 h (11.5 days) and a kinetic constant of 0.0027 h(-1), and three possible degradation products were identified. The results obtained are then compared to those obtained in previous works carried out in comparable experimental conditions about nicosulfuron and tribenuron-methyl, two sulfonylurea herbicides belonging to different classes, and to literature data: hypotheses on the existence of preferential degradation pathways are then drawn, in consequence of the molecular structure of the sulfonylurea pesticide. In particular, the use of organic solvents to obtain complete solubilization of the sample plays a fundamental role and deeply influences the degradation processes that, therefore, not always fully adhere to the actual natural photodegradation pathways. Moreover, considerations about toxicity were driven since the complete mineralisation of the sample is not reached: even when the parent pesticides are totally degraded, they are, however, transformed into other organic compounds showing, if subject to ecotoxicological tests, at least the same toxicity of the precursor herbicides. The evidence here presented suggests that, at least for the class of sulfonylurea pesticides, their professed low persistence actually does not produce any real advantage.

Abatement kinetics of 30 sulfonylurea herbicide residues in water by photocatalytic treatment with semiconductor materials

Sulfonylurea herbicides (SUHs) are a family of environmentally compatible herbicides but their high water solubility, moderate to high mobility through the soil profile, and slow degradation rate make them potential contaminants of groundwater as demonstrated in this paper. The photodegradation of a mixture of 30 SUHs in aqueous suspensions of semiconductor materials (ZnO and TiO2 in tandem with Na2S2O8 as electron acceptor) under artificial light (300-460 nm) irradiation was investigated. As expected, the influence of both semiconductors on the degradation of SUHs was very significant in all cases. Photocatalytic experiments show that the addition of photocatalyst, especially for the ZnO/Na2S2O8 system, greatly improves the removal of SUHs compared with photolytic tests, significantly increasing the reaction rates. The first-order equation (monophasic model) satisfactorily explained the disappearance process although it overlooked small residues remaining late in the process. These residues are important from an environmental point of view and the Hoerl function (biphasic model), was a better predicter of the results obtained. In our conditions, the average time required for 90% degradation was about 3 and 30 min for ZnO/Na2S2O8 and TiO2/Na2S2O8 systems, respectively.

Multivariate development and validation of a stability-indicating HPLC method for the determination of glimepiride in tablets

This paper describes the multivariate development of a stability-indicating HPLC method for the quantification of glimepiride in pharmaceutical tablets. Full factorial design, Doehlert design, and response-surface methodology were used in conjunction with the desirability function approach. This procedure allowed the adequate separation of glimepiride from all degradant peaks in a short analysis time (about 9 min). This HPLC method uses potassium phosphate buffer (pH 6.5; 27.5 mmol/L)-methanol (34 + 66, v/v) mobile phase at a flow rate of 1.0 mL/min and UV detection at 228 nm. A Waters Symmetry C18 column (250 x 4.6 mm, 5.0 pm) at controlled room temperature (25 degrees C) was used as the stationary phase. The method was validated according to International Conference on Harmonization guidelines and demonstrated linearity from 2 to 40 mg/L glimepiride, selectivity, precision, accuracy, and robustness. The LOD and LOQ were 0.315 and 1.050 mg/L, respectively. The multivariate strategy adopted in this work can be successfully applied in routine laboratories because of its fast optimization without the additional cost of columns or equipment.

Effects of chlorimuron-ethyl application with or without urea fertilization on soil ammonia-oxidizing bacteria and archaea

Chlorimuron-ethyl (CE) has been widely used in modern agriculture, but little is known regarding the influence of CE on ammonia-oxidizing bacteria (AOB) and archaea (AOA) populations in soils. In this study, microcosm incubation of aquic brown soil was conducted for 60 d. Associated changes in the population sizes of AOB and AOA in response to CE application with or without urea fertilization were examined via quantitative real-time PCR (qPCR) assays of the ammonia monooxygenase gene (amoA). The half-life of CE ranged from 11.80 d to 14.54 d in the tested soil. Compared to the untreated control, the application of CE alone had no strong effects on soil pH, and urea fertilization temporarily increased soil pH in the first 7 days. The abundance of the AOA amoA gene was greater than the abundance of the AOB amoA gene in all treatments, but both were significantly suppressed by CE application in a dose-dependent manner. Urea fertilization generally increased AOB and AOA amoA gene abundances, except that the AOA amoA gene level was slightly reduced at the early stage of the incubation period. AOB and AOA preferred different N levels for growth, with AOB only growing significantly at high NH4(+) levels and AOA growing substantially at low NH₄(+) levels. The stimulation effects of urea fertilization on AOA and AOB amoA gene abundances were strongly suppressed by the CE application. This study indicated that the CE application substantially suppressed soil nitrification via inhibiting the AOB and AOA population regardless of urea fertilization, which resulted in significant changes in the soil NH₄(+)-N and NO₃(-)-N levels. Furthermore, AOB and AOA inhabiting separate ecological niches with different NH₄(+) levels played various roles in N cycling.

Biodegradation of nicosulfuron by a Talaromyces flavus LZM1

The fungal strain LZM1 was isolated from activated sludge and found to be capable of utilizing nicosulfuron as the sole nitrogen source for growth. Based on morphological and internal transcribed spacer evaluations, LZM1 was identified as a Talaromyces flavus strain. Under optimum conditions (pH 6.1, 29°C), T. flavus LZM1 degraded 100% of the initially added nicosulfuron (100 mg L(-1)) within 5d. T. flavus LZM1 was also found to be highly efficient in degrading tribenuron methyl, chlorsulfuron, bensulfuron methyl, ethametsulfuron methyl, cinosulfuron, and rimsulfuron. Metabolites from nicosulfuron degradation were identified by liquid chromatography mass spectrometry, and a possible degradation pathway was deduced. These results show that T. flavus LZM1 may possess potential to be used in bioremediation of nicosulfuron-contaminated environments.

Chromatography and high-resolution mass spectrometry for the characterization of the degradation products of the photodegradation of amidosulfuron: an analytical approach

Simulated sunlight irradiation causing degradation of amidosulfuron, a pyrimidinylsulfonylurea herbicide, has been investigated in aqueous solution. The main degradation products were followed up by ultrahigh-pressure liquid chromatography with a UV detector (UHPLC-UV) and identified by combining ultrahigh-pressure liquid chromatography-mass spectrometry (UHPLC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). On the basis of the retrosynthetic analysis, the most identified degradation products were mainly due to the losses of methylsulfamic acid (CH₅NO₃S), sulfocarbamic acid (CH₃NO₅S), carbamic acid (CH₃NO₂), methyl(methylsulfonyl)sulfamic acid (C₂H₇NO₅S₂), N-methylmethanesulfonamide (C₂H₇NO₂S), and sulfonic acid (H₂SO₄) molecules. Accordingly, O and S-demethylation as well as hydroxylation processes were also observed. Sum formulas of the main degradation products were assigned, and a mechanical pathway is proposed.

Development of affinity microcolumns for drug-protein binding studies in personalized medicine: interactions of sulfonylurea drugs with in vivo glycated human serum albumin

This report used high-performance affinity microcolumns to examine the changes in binding by sulfonylurea drugs to in vivo glycated HSA that had been isolated from individual patients with diabetes. An immunoextraction approach was developed to isolate HSA and glycated HSA from clinical samples, using only 20 μL of plasma or serum and 6-12 nmol of protein to prepare each affinity microcolumn. It was found that the affinity microcolumns could be used in either frontal analysis or zonal elution studies, which typically required only 4-8 min per run. The microcolumns had good stability and allowed data to be obtained for multiple drugs and experimental conditions over hundreds of sample application cycles. Both the overall binding, as measured by frontal analysis, and site-specific interactions, as examined by zonal elution, showed good agreement with previous data that had been obtained for in vitro glycated HSA with similar levels of modification. It was also possible to directly compare the changes in site-specific binding that occurred between sulfonylurea drugs or as the level of HSA glycation was varied. This method is not limited to clinical samples of glycated HSA but could be adapted for work with other modified proteins of interest in personalized medicine.

The determination of toxicities of sulphonylurea and phenylurea herbicides with quantitative structure-toxicity relationship (QSTR) studies

Sulphonylurea and phenylurea herbicides are two groups of herbicides that are most commonly used worldwide. Quantitative structure-toxicity relationship models were derived for estimating the acute oral toxicity of these herbicides to male rats. The 20 chemicals of the training set and the seven compounds of external testing set were described by means of using descriptors for lipophilicity, polarity and molecular geometry, as well as the calculation of quantum chemical descriptors for energy. Model development to predict the toxicity of sulphonylurea and phenylurea herbicides in different matrices was carried out using multiple-linear regression. The model was validated internally and externally. In the present study, QSTR model was used for the first time to understand the inherent relationships between the sulphonyl and phenylurea-type herbicide molecules and their toxic behaviour. Such studies provide mechanistic insight about structure-toxicity relationships and assist in the design of less toxic herbicides.

Study of sorption of two sulfonylurea type of herbicides and their additives on soils and soil components

The sorption of two sulfonylurea type herbicides (chlorsulfuron: (1-(2-chlorophenylsulfonyl)-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea; tribenuron methyl: (methyl-2-[N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-3-(methyl-ureido)-sulfonyl]-benzoate) was studied on sand and chernozem soil adsorbents. Experimental results for solutions prepared from the pure ingredients were compared to those prepared from the appropriate formulated commercial products. At small concentrations, the extent of adsorption of the active ingredient was higher than from the formulation containing solutions. Environmental fate and effects of the forming agents are less investigated because they rarely have concentration limits recommended by authorities. In addition to the adsorption of active ingredients, therefore, the sorption behavior of a widely used additive Supragil WP (sodium diisopropyl naphthalene sulphonate) was also studied. This dispersant is an anionic forming agent applied in a lot of pesticide formulations. Using three different soils (sand, brown forest, chernozem) as adsorbents two-step isotherms were obtained. The role of the soil organic matter (OM) was significant in the adsorption mechanism because the adsorbed amounts of the dispersant correlated with the specific surface area as well as with the total organic carbon (TOC) content of the soils. The sorption behavior indicates the operation of hydrophobic interaction mechanism between the soil OM and the dispersant. These results are supported by our further sorption experiments on clays, too. Zeta potential measurements seem to be promising for the interpretation of multi-step isotherms. The application of this technique proved that higher concentrations of the anionic forming agent assisted the peptization of soil organic matter (SOM) resulting in stable colloidal solution dominated by negative charges. Since the pesticides investigated are also anionic at the studied pH (7 and 8.3) the dissolved organics lead to the enhancement of the mobility of both the sulfonylureas and dispersant.

Influence of pH, light cycle, and temperature on ecotoxicity of four sulfonylurea herbicides towards Lemna gibba

In chemical regulation, e.g. the EU Water Framework Directive, REACH, or the Pesticide Directive, standardized ecotoxicological tests are applied to evaluate and rank the hazard of compounds and for deriving environmental quality standards (EQS). Standardized test methods prescribe fixed testing conditions e.g. specific temperature, pH, light intensity etc. However, environmental conditions under which the organisms live are rarely identical to the standard conditions. Thus, the ecotoxicity of compounds found in standard test is not only a function of the compounds inherent physico-chemical properties but is also affected by test conditions. It is therefore important to study the effect of changes in test conditions in order to get reliable input ecotoxicity data for assessing the potential risk posed by a compound. The objective of this study was to investigate the implications of changing test conditions on the toxicity of four sulfonylurea herbicides (SUs). The toxicity of the four SUs towards Lemna gibba was investigated at three pH levels (6, 7.5 and 9), at two temperatures (15 and 24 °C) and two light regimes (continuous and 12:12 h light:dark cycle) The EC50 increased twofold to tenfold for the four SUs when pH was increased from 6 to 9. Decreasing the temperature from 24 to 15 °C or introducing a dark:light cycle did not cause any trends in changes in toxicity. The results show that test conditions can have an effect on the toxicity and this should be considered when the standard test results are used for derivation of EQS.

New formulation approaches to improve solubility and drug release from fixed dose combinations: case examples pioglitazone/glimepiride and ezetimibe/simvastatin

Low aqueous solubility is often a limiting aspect to the bioavailability of poorly soluble, but highly permeable drugs (class II compounds according to the Biopharmaceutics Classification System - BCS) administered in single drug products or as fixed dose combinations. The aim of the present series of experiments was to improve the solubility and dissolution of two fixed dose combination formulations (FDC), each consisting of two BCS class II drugs. The first FDC contained a weak acid (glimepiride) and a weak base (pioglitazone), while the second FDC contained two compounds (simvastatin and ezetimibe) that are essentially non-ionised over the physiological pH range. The formulation approaches used were as follows: (a) an inclusion complex with hydroxypropyl-β-cyclodextrin (HP-β-CD), (b) a solid dispersion with Soluplus, a new highly water soluble polyvinyl caprolactam - polyvinyl acetate - polyethylene glycol graft copolymer and (c) a ternary inclusion complex with both HP-β-CD and Soluplus. Solid state analysis was performed for the pure drugs, and all formulations using powder X-ray diffraction (PXRD). The in vitro performance of the different formulation approaches, as gauged by solubility and dissolution experiments, was compared with that of the marketed products containing the respective fixed dose combinations, Tandemact 30 mg/4 mg tablets and Inegy 10 mg/40 mg tablets. The FDCs of the pure drugs and the marketed products showed very poor (and especially for pioglitazone, strongly pH-dependent) dissolution. By contrast, all binary and ternary inclusion complexes showed enhanced release for both drugs in the FDC. The ternary inclusion complex generated synergistic improvement in solubility and dissolution results for both FDCs. For example, in pH conditions of the fasted small intestine after a test duration of 240 min, we observed 100% dissolution of both drugs from the ternary pioglitazone/glimepiride (30 mg/4 mg) complex formulation, whereas from the marketed formulation less than 5% pioglitazone, and only 25% glimepiride dissolved. Using the same conditions, 60% ezetimibe and 85% simvastatin dissolved from the ternary ezetimibe/simvastatin (10 mg/40 mg) complex formulation, whereas with less than 5% ezetimibe and 10% simvastatin dissolved after 240 min, the marketed FDC formulation showed poor dissolution. Based on the results of the present study, the bioavailability of both drugs in the fixed dose combination is likely to be increased after oral administration of the new formulations, especially when the fixed dose combination is formulated as a ternary complex consisting of HP-β-CD and Soluplus.

Degradation of nicosulfuron by Bacillus subtilis YB1 and Aspergillus niger YF1

The optimal degrading conditions for the nicosulfuron degradation by Bacillus subtilis YB1 and Aspergillus niger YF1, and site of their action on nicosulfuron were studied. The results showed that the degradation efficiency of free cells of B. subtilis YB1 and A. niger YF1 was respectively 87.9 and 98.8% in basic medium III containing 2 mg/l of nicosulfuron after inoculation with 1 ml of culture containing 2.3 x 10(7) CFU ml(-1) and incubation for 5 days at 35 degrees C. Moreover, the degradation rate of nicosulfuron by the mixture of microorganisms was much higher than for every of them taken separately in the same conditions. The mass spectrometric analysis of the products degraded by B. subtilis YB1 revealed that the sulfonylurea bridge in nicosulfuron molecule had been broken. Extracellular (EXF) and endocellular (ENF) fractions obtained from bacterium and fungus were tested for the ability to degrade nicosulfuron. The degradation efficiency of fractions extracted from B. subtilis YBI was 66.8% by EXF and 15.8% by ENF, but neither EXF nor ENF extracted from A. niger YFI had the activity of degrading nicosulfuron.

Linear and non-linear quantitative structure-activity relationship models on indole substitution patterns as inhibitors of HIV-1 attachment

The antiviral drugs that inhibit human immunodeficiency virus (HIV) entry to the target cells are already in different phases of clinical trials. They prevent viral entry and have a highly specific mechanism of action with a low toxicity profile. Few QSAR studies have been performed on this group of inhibitors. This study was performed to develop a quantitative structure-activity relationship (QSAR) model of the biological activity of indole glyoxamide derivatives as inhibitors of the interaction between HIV glycoprotein gp120 and host cell CD4 receptors. Forty different indole glyoxamide derivatives were selected as a sample set and geometrically optimized using Gaussian 98W. Different combinations of multiple linear regression (MLR), genetic algorithms (GA) and artificial neural networks (ANN) were then utilized to construct the QSAR models. These models were also utilized to select the most efficient subsets of descriptors in a cross-validation procedure for non-linear log (1/EC50) prediction. The results that were obtained using GA-ANN were compared with MLR-MLR and MLR-ANN models. A high predictive ability was observed for the MLR, MLR-ANN and GA-ANN models, with root mean sum square errors (RMSE) of 0.99, 0.91 and 0.67, respectively (N = 40). In summary, machine learning methods were highly effective in designing QSAR models when compared to statistical method.

Photocatalytic degradation of five sulfonylurea herbicides in aqueous semiconductor suspensions under natural sunlight

In the present study, the photocatalytic degradation of five sulfonylurea herbicides (chlorsulfuron, flazasulfuron, nicosulfuron, sulfosulfuron and triasulfuron) has been investigated in aqueous suspensions of zinc oxide (ZnO), tungsten (VI) oxide (WO(3)), tin (IV) oxide (SnO(2)) and zinc sulfide (ZnS) at pilot plant scale under natural sunlight. Photocatalytic experiments, especially those involving ZnO photocatalysis, showed that the addition of semiconductors in tandem with the oxidant (Na(2)S(2)O(8)) strongly enhances the degradation rate of the herbicides in comparisons carried out with photolytic tests. The degradation of the herbicides follows a first order kinetics according to the Langmuir-Hinshelwood model. In our conditions, the amount of time required for 50% of the initial pesticide concentration to dissipate (t(½)) ranged from 8 to 27 min (t(30W)=0.3-1.2 min) for sulfosulfuron and chlorsulfuron, respectively in the ZnO/Na(2)S(2)O(8) system. None of the studied herbicides was found after 120 min of illumination (except chlorsulfuron, 0.2 μg L(-1)).

Biodegradation of bensulphuron-methyl by a novel Penicillium pinophilum strain, BP-H-02

A fungal strain able to rapidly degrade bensulphuron-methyl (BSM), called BP-H-02, was isolated for the first time from soil that had been contaminated with BSM for several years. BP-H-02 can use BSM as the sole carbon and energy source for growth in a mineral salt medium. Based on morphological and internal transcribed spacer (ITS) analysis, BP-H-02 was identified as Penicillium pinophilum. Under optimal conditions (pH 6.5, temperature 30 °C and 200 mg/L VSSinoculum), more than 87% of the initially added BSM (50mg/L) was degraded after 60 h. Metabolites were identified as 2-amino-4,6-dimethoxypyrimidine and 1-(4,6-dimethoxypyrimidin-2-yl) urea by liquid chromatography-mass spectrometry (LC-MS), and a possible degradation pathway was deduced. In a soil bioremediation experiment, inoculation of soil with BP-H-02 promoted the degradation of BSM more effectively than did the control. These results revealed that BP-H-02 can biodegrade bensulphuron-methyl efficiently and could potentially be used to bioremediate sulphonylurea herbicides contamination.

The structure-activity relationship in herbicidal monosubstituted sulfonylureas

BACKGROUND

The herbicide sulfonylurea (SU) belongs to one of the most important class of herbicides worldwide. It is well known for its ecofriendly, extreme low toxicity towards mammals and ultralow dosage application. The original inventor, G Levitt, set out structure-activity relationship (SAR) guidelines for SU structural design to attain superhigh bioactivity. A new approach to SU molecular design has been developed.

RESULTS

After the analysis of scores of SU products by X-ray diffraction methodology and after greenhouse herbicidal screening of 900 novel SU structures synthesised in the authors' laboratory, it was found that several SU structures containing a monosubstituted pyrimidine moiety retain excellent herbicidal characteristics, which has led to partial revision of the Levitt guidelines.

CONCLUSIONS

Among the novel SU molecules, monosulfuron and monosulfuron-ester have been developed into two new herbicides that have been officially approved for field application and applied in millet and wheat fields in China. A systematic structural study of the new substrate-target complex and the relative mode of action in comparison with conventional SU has been carried out. A new mode of action has been postulated.

Nitrous oxide and methane emission from a flooded rice field as influenced by separate and combined application of herbicides bensulfuron methyl and pretilachlor

Combination of divergent active principles to achieve broad-spectrum control is gaining popularity to manage the weed menace in intensive agriculture. However, such application could have non-target impacts on the soil processes affecting soil ecology and environmental interactions. A field experiment was conducted to investigate the impact of separate and combined applications of herbicides bensulfuron methyl and pretilachlor on the emission of N(2)O and CH(4), and related soil and microbial parameters in a flooded alluvial field planted to rice cv Lalat. Single application of the herbicide bensulfuron methyl or pretilachlor resulted in a significant reduction of N(2)O and CH(4) emissions while the combination of these two herbicides distinctly increased N(2)O and CH(4) emissions. Cumulative N(2)O emissions (kg N(2)O-N) followed the order of bensulfuron methyl (0.35 kg ha(-1))<pretilachlor (0.36 kg ha(-1))<control (0.45 kg ha(-1))<bensulfuron methyl 0.6%+pretilachlor 6.0% single dose (0.49 kg ha(-1))<bensulfuron methyl 0.6%+pretilachlor 6.0% double dose (0.54 kg ha(-1)). Cumulative CH(4) emissions (kg CH(4)), on the other hand, followed the order of bensulfuron methyl (47.89 kg ha(-1))<pretilachlor (73.17 kg ha(-1))<bensulfuron methyl 0.6%+pretilachlor 6.0% single dose (93.50 kg ha(-1))<control (106.54 kg ha(-1))<bensulfuron methyl 0.6%+pretilachlor 6.0% double dose (124.67 kg ha(-1)). The inhibitory effect of separate application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% on N(2)O emission was linked to lower mineral N, lower denitrifying and nitrifying activity and low denitrifier and nitrifier populations. Inhibitory effect on CH(4) emission, on the contrary, was linked to prevention in the drop of redox potential, lower readily mineralizable carbon (RMC) and microbial biomass carbon (MBC) contents as well as lower methanogenic and higher methanotrophic bacterial population. Admittedly, stimulatory effect of combined application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% at double dose on N(2)O and CH(4) emission was related to reversal of the identified indicators of inhibition. Results indicate that while individual application of herbicides bensulfuron methyl 0.6% or pretilachlor 6.0% can reduce N(2)O and CH(4) emission from flooded soil planted to rice, their combined application at normal dose can keep the emission at a comparatively lower level with significantly higher grain yield as compared to the herbicides applied alone.

Adsorption and desorption of herbicide monosulfuron-ester in Chinese soils

Monosulfuron-ester is a new, low rate, sulfonylurea herbicide that is being promoted for annual broadleaf and gramineal weed control; however, there is a lack of published information on its behavior in soils. The adsorption and desorption of monosulfuron-ester by seven type soils were measured using a batch equilibrium technique. The results showed that the Freundlich equation fitted its adsorption and desorption well, and the Freundlich constant values (K(f-ads)) ranged from 0.88 to 5.66. Adsorption isotherms were nonlinear with 1/n(f-ads) values < 1. Soil pH, organic matter (OM), and clay content were the main factors influencing its adsorption and desorption. Adsorption and desorption were negatively correlated with pH 4.0-8.0 while positively correlated with OM and clay content. The adsorption of monosulfuron-ester was mainly a physical process, because its free energy (deltaG) in seven soils was less than 40 kJ/mol. Monosulfuron-ester adsorption by three soils increased with increasing CaCl2 concentration using CaCl2 as a background electrolyte. Monosulfuron-ester desorption was hysteretic in all tested soils.

Simulating concentration of bensulphuron-methyl in a drainage canal of a paddy block using a rice pesticide model

A pesticide fate and transport model (PCPF-B) was developed to predict the runoff of pesticides from paddy plots to a drainage canal in a paddy block based on the plot scale model (PCPF-1). The block-scale model now comprises three modules: (1) a module for pesticide application, (2) a module for pesticide behaviour in paddy fields, and (3) a module for pesticide concentration in the drainage canal. The PCPF-B model was first evaluated using published data in a single plot and then was applied to predict the concentration of bensulphuron-methyl in one paddy block in the Sakura river basin, Ibaraki, Japan, where a detailed field survey was conducted. The PCPF-B model simulated well the concentration of bensulphuron-methyl in individual paddy plots. It also reflected the runoff pattern of bensulphuron-methyl at the block outlet, although overestimation of bensulphuron-methyl concentrations occurred due to uncertainty in water balance estimation. A sensitivity analysis showed that the soil adsorption coefficient of the herbicide had the greatest influence on the concentrations and cumulative loss of bensulphuron-methyl to the drainage canal.

Effects of monosulfuron on growth, photosynthesis, and nitrogenase activity of three nitrogen-fixing cyanobacteria

Application of monosulfuron, a new sulfonylurea herbicide, produced a simulative effect on heterocyst formation and nitrogenase activity but an inhibitory effect on photosynthesis, i.e., a lower net photosynthetic rate, fewer photosynthetic pigments, and a smaller Fv/Fm ratio at increasingly higher monosulfuron concentrations (0.001-10 mg/l) for three nonspecific filamentous nitrogen-fixing cyanobacteria: Anabaena azollae, A. flos-aquae, and A. azotica. The decrease in biliprotein of algal cells was less than that of carotenoid and chlorophyll-a. Monosulfuron was more readily degraded and less accumulated in A. azotica compared with A. azollae and A. flos-aquae. The three algae exhibited varying degrees of sensitivity to monosulfuron: Calculated 50% inhibition concentrations (IC(50)s) of algal growth and no observed-effect concentration (NOEC) values after 4 days of treatment were 0.014 and 0.005, 0.029 and 0.019, and 0.22 and 0.075 mg/l for A. flos-aquae, A. azollae, and A. azotica, respectively. Normal agricultural use of monosulfuron at postemergence rates of 0.3-0.8 mg/l in rice fields will likely be toxic to these three ubiquitous nitrogen-fixing cyanobacteria. Low-dose monosulfuron application (<0.1 mg/l) enables growth of the more tolerant A. azotica as biofertilizer, and the use of photosynthetic efficiency and growth rates as sensitive-indicator indexes of toxicity to nitrogen-fixing cyanobacteria are recommended.

Examination of the translocation of sulfonylurea herbicides in sunflower plants by matrix-assisted laser desorption/ionisation mass spectrometry imaging

Pesticides are widely used in agriculture to control weeds, pests and diseases. Successful control is dependent on the compound reaching the target site within the organism after spray or soil application. Conventional methods for determining uptake and movement of herbicides and pesticides include autoradiography, liquid scintillation and chromatographic techniques such as high-performance liquid chromatography (HPLC). Autoradiography using radiolabelled compounds provides the best indication of a compound's movement within the plant system. Autoradiography is an established technique but it relies on the synthesis of radiolabelled compounds. The distribution of four sulfonylurea herbicides in sunflower plants has been studied 24  h after foliar application. The use of matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) images of protonated molecules and fragment ions (resulting from fragmentation at the urea bond within the sulfonylurea herbicides) has provided evidence for translocation above and below the application point. The translocation of nicosulfuron and azoxystrobin within the same plant system has also been demonstrated following their application to the plant stem. This study provides evidence that MALDI-MSI has great potential as an analytical technique to detect and assess the foliar, root and stem uptake of agrochemicals, and to reveal their distribution through the plant once absorbed and translocated.

Chromatographic studies of changes in binding of sulfonylurea drugs to human serum albumin due to glycation and fatty acids

This report examines the use of high-performance affinity chromatography as a screening tool for studying the change in binding by sulfonylurea drugs to the protein human serum albumin (HSA) during diabetes. The effects of both the non-enzymatic glycation of HSA and the presence of fatty acids on these interactions were considered using a zonal elution format. It was found that there was a significant increase (i.e., 2.7- to 3.6-fold) in the relative retention of several sulfonylurea drugs (i.e., acetohexamide, tolbutamide, glybenclamide and gliclazide) on columns containing normal versus glycated HSA. The addition of various long chain fatty acids to the mobile phase gave the same trend in retention for the tested drugs on both the HSA and glycated HSA columns, generally leading to lower binding. Most of the fatty acids examined produced similar or moderately different relative shifts in retention; however, palmitic acid was found to produce a much larger change in retention on columns containing glycated HSA versus normal HSA under the conditions used in this study.

Biodegradation of chlorimuron-ethyl by the bacterium Klebsiella jilinsis 2N3

Enrichment culturing of sludge taken from an industrial wastewater treatment pond led to the identification of a bacterium (Klebsiella jilinsis H. Zhang) that degrades chlorimuron-ethyl with high efficiency. Klebsiella jilinsis strain 2N3 grows with chlorimuron-ethyl as the sole nitrogen source at the optimal temperature range of 30-35 degrees C and pH values between 6.0-7.0. In liquid medium, the degradation activity was further induced by chlorimuron-ethyl. Degradation rates followed the pesticide degradation kinetic equation at concentrations between 20 and 200 mg L(-1). Using initial concentrations of 20 and 100 mg L(-1), the degradation rates of chlorimuron-ethyl were 83.5 % and 92.5 % in 12 hours, respectively. At an initial concentration higher than 200 mg L(-1), the degradation rate decreased slightly as the concentration increased. The 2N3 strain also degraded the sulfonylurea herbicides ethametsulfuron, metsulfuron-methyl, nicosulfuron, rimsulfuron, and tribenuron-methyl. This study provides scientific evidence and support for the application of K. jilinsis in bioremediation to reduce environmental pollution.

Stability-indicating validated HPLC method for simultaneous determination of oral antidiabetic drugs from thiazolidinedione and sulfonylurea groups in combined dosage forms

For type 2 diabetes treatment, combinations of drugs from the thiazolidinedione and sulfonylurea groups are now available in the same tablet or capsule. Therefore, a stability-indicating and validated HPLC method was developed for simultaneous determination of pioglitazone, rosiglitazone, and glipizide in combined dosage forms. The examined drugs were subjected to different conditions such as acid and base, temperature, and UV light, and degradation of pioglitazone and glipizide was observed under thermal and acidic stress. However, selectivity of the presented method for pioglitazone, rosiglitazone, and glipizide assay against their degradation products was confirmed. It was also demonstrated to be robust, resisting small deliberate changes in pH of the buffer, flow rate, and percentage of acetonitrile in the mobile phase. The presented method utilizes a LiChrospher RP18 column (125 x 4.0 mm), acetonitrile in phosphate buffer at pH 4.3 (40 + 60, v/v) as the mobile phase, and UV detection at 225 nm for pioglitazonel glipizide or 245 nm for rosiglitazone/glipizide. The method was validated with respect to linearity, precision, and accuracy. Finally, the elaborated procedure was applied for the QC of pioglitazone/glipizide and rosiglitazone/glipizide mixtures.

Synthesis of a high-purity chemical library reveals a potent inducer of oxidative stress

Synthesis of high-purity biogenic heterocyclic library enabled identification of a small molecule, which potently inhibited proliferation of several cancer cell lines and induces rapid oxidative stress. This agent elicited unusual mechanism of cell death induction, which entailed activation of both caspase-dependent and independent pathways.

Of the vulnerability of orphan complex proteins: the case study of the E. coli IscU and IscS proteins

IscS and IscU, the two central protein components of the iron sulfur cluster assembly machinery, form a complex that is still relatively poorly characterized. In an attempt to standardize the purification of these proteins for structural studies we have developed a protocol to produce them individually in high concentration and purity. We show that IscS is a rather robust protein as long as it is produced in a PLP loaded form and that this co-factor is essential for fold stability and enzyme activity. In contrast to previous evidence, we also propose that, in contrast with previous evidence, IscU is a thermodynamically stable protein with a well defined fold but, when produced in isolation, is a 'complex-orphan protein' that is prone to unfolding if not stabilised by a co-factor or a protein partner. Our work will facilitate further structural and functional studies of these proteins and eventually lead to a better understanding of the whole machinery.

The effect of mixing two herbicides mesotrione and nicosulfuron on their photochemical reactivity on cuticular wax film

There are growing concerns about the environmental impacts of pesticides with a consequent increasing demand for meaningful and accurate information on their consumption and use pattern. Pesticides reactivity towards light is rarely considered at the leaf surface after crop treatment although it is directly impacting the pesticide efficiency. We have established a test on thin wax films which mimic well the leaf surface. Under simulated solar light herbicides mesotrione and nicosulfuron as well as their mixture are photoreactive. For both herbicides considered separately, there is a strong accelerating effect of adjuvants compared to the pure active ingredient. Mesotrione, a triketonic herbicide was very reactive with a half-life of photolysis of 2h. Nicosulfuron, a sulfonylurea, has a half-life of photolysis of 32 h. The mixing of the two formulated herbicides had an accelerating effect on both herbicide decay rates. The products formed when considering the pure molecule were mainly the result of photohydrolysis, oxidation and cyclisation. While pesticide photostability on crops is not evaluated for registration, this study demonstrates that these photochemical tests could be useful to improve the pesticide effectiveness and reduce the applied dose.

Synthesis of novel aryl(heteroaryl)sulfonyl ureas of possible biological interest

The course of reaction of aryl and heteroaryl sulfonamides with diphenylcarbonate (DPC) and 4-dimethylaminopyridine (DMAP) was found to depend on the pKa of the sulfonamide used. Aryl sulfonamides with pK_a ~ 10 gave 4-dimethylamino-pyridinium arylsulfonyl-carbamoylides, while the more acidic heteroaryl sulfonamides (pK_a ~ 8) furnished 4-dimethylaminopyridinium heteroarylsulfonyl carbamates. Both the carbamoylides and carbamate salts reacted with aliphatic and aromatic amines with the formation of appropriate aryl(heteroaryl)sulfonyl ureas, and therefore, can be regarded as safe and stable substitutes of the hazardous and difficult to handle aryl(heteroaryl)sulfonyl isocyanates.

Leaching of three sulfonylurea herbicides during sprinkler irrigation

Sulfonylurea herbicides are widely applied on the Canadian prairies to control weeds in a variety of crops. Several sulfonylurea herbicides are mobile in soil, and there is concern about their possible movement to ground water. This study was performed to assess the susceptibility of three sulfonylurea herbicides commonly used in prairie crop production to leach under a worst-case scenario. Thifensulfuron-methyl, tribenuron-methyl, and rimsulfuron were applied to a 9-ha tile-drained field, and then approximately 300 mm of irrigation water were applied over a 2-wk period using a center pivot. The commencement of tile-drain flow corresponded to the rise of the water table above tile-drain depth, and peak flow rates corresponded to the greatest depths of ground water above the tile drains. The volume of irrigation water intercepted by the tile drains in each quadrant was determined by site hydrology and represented <10% of the irrigation water applied. Concentrations of thifensulfuron-methyl, tribenuron-methyl, and rimsulfuron in the tile-drain effluent ranged (analysis by liquid chromatography/tandem mass spectrometry) from 2.0 to 248 ng L(-1), not detected (nd) to 55 ng L(-1), and nd to 497 ng L(-1), respectively. Total herbicide transport from the root zone in each quadrant was estimated at <0.5% of the amount of each sulfonylurea herbicide applied. Thifensulfuron-methyl was the only herbicide detected in ground water, with concentrations ranging from 1.2 to 2.5 ng L(-1). With the frequency and amount of rainfall typically encountered in the prairie region of Canada, detectable concentrations (>1 ng L(-1)) of these sulfonylurea herbicides in ground water would be unlikely.

Effects of a municipal sewage sludge amendment on triasulfuron soil sorption and wheat growth

The influence of municipal sewage sludge (SL) as a soil amendment on the sorption and activity of the herbicide triasulfuron (TRS, [2-(2-chloroethoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide]) was studied. Weed control was checked in a greenhouse on a wheat (Triticum turgidum L. subsp. durum) crop. At the highest SL amount allowed by Italian regulation, TRS sorption onto soil increased by 7 times and weed control was unaffected. A vegetative bloom and an early heading phase were noted. To compare inorganic fertilization (N, P, and K) and SL amendment, a greenhouse fertilization experiment was carried out. The SL-amended crop developed larger leaf surfaces, higher biomass, and a forward heading compared to that fertilized with N, P, and K. The SL hormone-like activity was evaluated by measuring auxin- and gibberellin-like activity of sewage sludge.

Sorption behavior of bensulfuron-methyl on andisols and ultisols volcanic ash-derived soils: contribution of humic fractions and mineral-organic complexes

Bensulfuron-methyl sorption was studied in Andisol and Ultisol soils in view of their characteristic physical and chemical properties, presenting acidic pH and variable charge. Humic and fulvic acids (HA and FA) and humin (HUM) contributions were established. Sorption was studied by using two synthetic sorbents, an aluminum-silicate with iron oxide coverage and the same sorbent coated with humic acid. Freundlich model described Bensulfuron-methyl behavior in all sorbents (R(2) 0.969-0.998). K(f) for soils (8.3-20.7 microg(1-1/n) mL(1/n) g(-1)) were higher than those reported in the literature. Organic matter, halloysite or kaolinite, and specific surface area contributed to the global process. The highest K(f) for HA, FA and HUM were 539.5, 82.9, and 98.7 microg(1-1/n) mL(1/n) g(-1). Model sorbents described the participation of variable charge materials with high adsorption capacity. The constant capacitance model was used to assess effects of Bensulfuron-methyl adsorption on the distribution of SOH, SOH(2)(+) and SO(-) sites of sorbents.

Toxicological responses in wheat Triticum aestivum under joint stress of chlorimuron-ethyl and copper

It was observed in this work that joint effects of chlorimuron-ethyl and copper on chlorophyll content, the peroxidases (POD) activity, superoxide dismutases (SOD) activity and soluble protein content in leaves and roots of wheat were markedly significant. The chlorophyll content and the SOD activity in wheat under joint stress of chlorimuron-ethyl and copper were obviously higher than that under single stress of chlorimuron-ethyl. However, joint effect of chlorimuron-ethyl and copper on the decrease of soluble protein content in roots was more serious than that under single stress of chlorimuron-ethyl. The effect of copper dominated the change of POD activity and soluble content in leaves and roots of wheat under joint stress of chlorimuron-ethyl and copper. It was suggested that the change of enzyme activity was related to the change of soluble protein content in roots under single and joint stress of chlorimuron-ethyl and copper.

Effectiveness of mechanochemical treatment with cyclodextrins on increasing solubility of glimepiride

We investigated the enhancement of the solubility of glimepiride (GLM), a poorly water soluble anti-diabetes drug, by cogrinding it with various cyclodextrins (CDs) using a ball mill. The phase solubility profiles of GLM with beta-CD and its derivatives were classified as A(L)-type, indicating the formation of a 1 : 1 stoichiometric water-soluble complex. When GLM crystals were coground with beta-CD using a ball mill for 48 h, the aqueous solubility of GLM increased to approximately 250 microg/mL. The powder X-ray diffraction pattern showed that the peak intensity of crystalline GLM decreased after cogrinding. Endothermic peaks of around 208 degrees C, which were assigned to the fusion of GLM crystals, disappeared in the DSC measurement of the ground mixture. After cogrinding, two sharp peaks assigned to sulfonylurea and benzoyl carbonyl stretching bands varied to broaden the peak to around 1700 cm(-1) in the C=O stretching region. These results suggested the formation of a complex between GLM and beta-CD during cogrinding.

Synthesis and biological evaluation of sulfonylurea and thiourea derivatives substituted with benzenesulfonamide groups as potential hypoglycemic agents

A novel class of sulfonylurea and thiourea derivatives substituted with benzenesulfonamide groups were designed and synthesized. The target compounds were assayed for the effects on the insulin release of isolated rat pancreatic islets and the glucose transport in adipocytes of rats. Some of them exhibited high potency. Compound 10 also had potent antiplatelet activity and showed an excellent property to protect collagen-epinephrine-induced mice mortality as well as plasma glucose-lowering activity in vivo. The preliminary pharmacological profile of compound 10 showed that it might be useful in the treatment of diabetics with cardiovascular and nephropathy complications.

Phytotoxicity of four herbicides on Ceratophyllum demersum, Vallisneria natans and Elodea nuttallii

The physiological effects of 4 herbicides (butachlor, quinclorac, bensulfuron-methyl and atrazine) on 3 submerged macrophytes (Ceratophyllum demersum, Vallisneria natans and Elodea nuttallii) were tested in laboratory. The variables of the relative growth rate and the photosynthetic pigment content showed that all of the tested herbicides affected the growth of the plants obviously, even at the lowest concentration (0.0001 mg/L). Except for the C. demersum treated with quinclorac at 0.005 and 0.01 mg/L, the relative growth rates of the plants were inhibited significantly (p < 0.01). Statistical analysis of chlorophyll a (Chl-a) contents was carried out with both the t-test and one-way ANOVA to determine the difference between the treatment and control. The results showed that Chl-a contents of the plants in all treatment groups were affected by herbicides significantly, except for the C. demersum treated with bensulfuron-methyl at 0.0005 mg/L. The decrease in Chl-a content was positively correlated to the dosage of the herbicides in most treatment groups. It was suggested that herbicides in water bodies might potentially affect the growth of aquatic macrophytes. Since the Chl-a content of submerged macrophytes responded to the stress of herbicides sensitively and directly, it could be used as a biomaker in environmental monitoring or in the ecological risk assessment of herbicide contamination.

Adsorption characteristic of bensulfuron-methyl at variable added Pb2+ concentrations on paddy soils

The combined pollution of heavy metal Pb2+ and bensulfuron-methyl (BSM), originating from chemical herbicides, in agro-ecological environments has become commonplace in southern China. The adsorption of BSM on three paddy soils in the presence of Pb2+ was examined using high-performance liquid chromatograph (HPLC). Results indicated that adsorption of BSM could accurately be described by a Freundlich isotherm equation with correlation constant (R) > 0.98, irrespective of the presence of spiked Pb2+. Of the various factors influencing BSM sorption, soil pH appeared to be the most influential. The constant K(f) of Freundlich isotherm equation tended to increase with increasing Pb2+ concentration in soil which indicated that the spiked of Pb2+ in paddy soils would promote the sorption of BSM. deltaG(theta) of BSM in three paddy soils was less than 40 kJ/mol in all treatments, indicating the adsorption of BSM is mainly physical in nature. The elution of soil dissolved organic matter (DOM) enhanced the adsorption of BSM in paddy soils. The mechanisms involved in the promotion effects of the spiked Pb2+ on BSM adsorption might be the modified surface characteristics of paddy soil solids due to the soil acidification and the increase of soil organic matter concentration because of DOM binding.

Transformation kinetics and mechanism of the sulfonylurea herbicides pyrazosulfuron ethyl and halosulfuron methyl in aqueous solutions

Pyrazosulfuron ethyl (PE) and halosulfuron methyl (HM) are two new highly active sulfonylurea herbicides that have been widely used for weed control in a variety of vegetables and other crops. These two herbicides have similar molecular structures, differing only in the substitutions on the pyrazole ring. Chemical hydrolysis is a primary process affecting the environmental fate of sulfonylurea pesticides. The hydrolytic transformation kinetics of PE and HM were investigated as a function of pH and temperature. For both herbicides, the hydrolysis rate was pH-dependent and increased with increasing temperature. The hydrolysis of both sulfonylureas was much faster in acidic or basic media than under neutral conditions. Identification of hydrolytic products by liquid chromatography-mass spectrometry (LC-MS) suggested that both PE and HM were subject to cleavage and contraction of the sulfonylurea bridge. The hydrolysis rate of HM was significantly higher than that of PE in alkaline solutions, despite their structural similarity. A chlorine substitution on HM's pyrazole ring makes HM more susceptible to bridge contraction than PE under basic conditions. The hydrolysis of HM and PE was relatively unaffected by the presence of cyclic oligosaccharides (cyclodextrins), indicating that natural OH-containing organic compounds occurring in aquatic environments may have little impact on the transformation of these sulfonylurea herbicides.

MIA-QSAR evaluation of a series of sulfonylurea herbicides

BACKGROUND

A series of sulfonylurea herbicides has been modelled using a 2D image-based QSAR approach known as MIA-QSAR (Multivariate Image Analysis applied to QSAR), and highly predictive models have been built.

RESULTS

Two MIA-QSAR models were built, one group being divided into training and test sets, and the other composed of the entire series of compounds. Statistically significant MIA-QSAR models rendered high correlation coefficients of experimental versus fitted pK(i)(app) (AHAS apparent inhibition constant) and satisfactory parameters of external validation and leave-one-out cross-validation. Comparison with the results obtained from classical 2D QSAR demonstrated some advantages of the modelling using MIA descriptors.

CONCLUSION

Both MIA-QSAR models showed high predictive ability, comparable with that of a reference methodology based on 3D descriptors. The method is suggested as a suitable tool for predicting novel herbicides.

Characterization of nicosulfuron availability in aged soils

Sorption-desorption interactions of pesticides with soil determine their availability for transport, plant uptake, and microbial degradation. These interactions are affected by the physical-chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. This research evaluated changes in sorption/availability of nicosulfuron (2-[[[[(4,6-dimethoxy-2-pyrimidinyl]amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3-pyridinecarboxamide) herbicide with aging in different soils, using a radiolabeled ((14)C) tracer. Aging significantly increased sorption. For instance, after the 41-day incubation, calculated K d,app increased by a factor of 2 to 3 in Mollisols from the Midwestern United States and by a factor of 5 to 9 in Oxisols from Brazil and Hawaii, as compared to freshly treated soils. In view of this outcome, potential transport of nicosulfuron would be overpredicted if freshly treated soil K d values were used to predict transport. The fact that the nicosulfuron solution concentration decreased faster than the soil concentration with time suggested that the increase in sorption was because the rate of degradation in solution and on labile sites was faster than the rate of desorption of the neutral species from the soil particles. It may have also been due to nicosulfuron anion diffusion to less accessible sites with time, leaving the more strongly bound neutral molecules for the sorption characterization. Regardless of the mechanism, these results are further evidence that increases in sorption during pesticide aging should be taken into account during the characterization of the sorption process for mathematical models of pesticide degradation and transport.

Anisotropic and hydrogen bonding effects in phenylglyoxamides and mandelamides: theoretical and NMR conformational evaluation

Interesting anisotropic effects were observed for phenylglyoxamides and their respective mandelamides. Such effects were observed in experimental (1)H and (13)C NMR (in CDCl(3), CD(3)OD, and DMSO-d(6) solvents) and in some cases with good correlation to theoretical (1)H and (13)C NMR DFT-GIAO (B3LYP/6-311++G**//B3LYP/6-31G*) calculations. A systematic conformational analysis of these compounds was performed in a two-step methodology, using PM3 and DFT (B3LYP/6-31G*) calculations; with good accomplishment and computational time economy. It was observed that intramolecular hydrogen bonding plays a significant role in the conformation of such compounds. Finally, a geminal nonequivalence of an N-CH(2) moiety, in one of the alkyl side chain (R1 = R2), was found for the tertiary mandelamides studied.

Preparation of molecularly imprinted solid phase extraction using bensulfuron-methyl imprinted polymer and clean-up for the sulfonylurea-herbicides in soybean

A pre-treatment methodology based on the molecularly imprinted solid phase extraction (MI-SPE) procedure was developed for the determination of bensulfuron-methyl (BSM), tribenuron-methyl (TBM), metsulfuron-methyl (MSM) and nicosulfuron (NS) in soybean samples. A molecular imprinted polymer (MIP) was prepared by precipitation polymerization using BSM as the template molecule, alpha-methacrylic acid (MAA) as the functional monomer, trimethylolpropane trimethacrylate (TRIM) as the cross-linker and dichloromethane as the porogen. The binding behaviors of the template BSM and its analogues on the MIP were evaluated by high performance liquid chromatography (HPLC). Then, solid phase extraction (SPE) with a BSM molecularly imprinted polymer (BSM-MIP) as adsorbent was investigated and the optimum loading, washing, and eluting conditions for MI-SPE of the selected BSM, MSM, TBM, and NS were established. The optimized MI-SPE procedure was used to extract the sulfonylureas and a high recovery was obtained in the soybean samples.

Structure and mechanism of inhibition of plant acetohydroxyacid synthase

Plants and microorganisms synthesize valine, leucine and isoleucine via a common pathway in which the first reaction is catalysed by acetohydroxyacid synthase (AHAS, EC 2.2.1.6). This enzyme is of substantial importance because it is the target of several herbicides, including all members of the popular sulfonylurea and imidazolinone families. However, the emergence of resistant weeds due to mutations that interfere with the inhibition of AHAS is now a worldwide problem. Here we summarize recent ideas on the way in which these herbicides inhibit the enzyme, based on the 3D structure of Arabidopsis thaliana AHAS. This structure also reveals important clues for understanding how various mutations can lead to herbicide resistance.

Structure and mechanism of inhibition of plant acetohydroxyacid synthase

Plants and microorganisms synthesize valine, leucine and isoleucine via a common pathway in which the first reaction is catalysed by acetohydroxyacid synthase (AHAS, EC 2.2.1.6). This enzyme is of substantial importance because it is the target of several herbicides, including all members of the popular sulfonylurea and imidazolinone families. However, the emergence of resistant weeds due to mutations that interfere with the inhibition of AHAS is now a worldwide problem. Here we summarize recent ideas on the way in which these herbicides inhibit the enzyme, based on the 3D structure of Arabidopsis thaliana AHAS. This structure also reveals important clues for understanding how various mutations can lead to herbicide resistance.

Synthesis and evaluation of N-acylsulfonamide and N-acylsulfonylurea prodrugs of a prostacyclin receptor agonist

N-Acylsulfonamide and N-acylsulfonylurea derivatives of the carboxylic acid prostacyclin receptor agonist 1 were synthesized and their potential as prodrug forms of the carboxylic acid was evaluated in vitro and in vivo. These compounds were converted to the active compound 1 by hepatic microsomes from rats, dogs, monkeys, and humans, and some of the compounds were shown to yield sustained plasma concentrations of 1 when they were orally administered to monkeys. These types of analogues, including NS-304 (2a), are potentially useful prodrugs of 1.

BM-520, an original TXA2 modulator, inhibits the action of thromboxane A2 and 8-iso-prostaglandin F2α in vitro and in vivo on human and rodent platelets, and aortic vascular smooth muscles from rodents

Thromboxane A(2) (TXA(2)) and 8-iso-PGF(2alpha) are two prostanoid agonists of the thromboxane A(2) receptor (TP), whose activation has been involved in platelet aggregation and atherosclerosis. Agents able to counteract the actions of these agonists are of great interest in the treatment and prevention of cardiovascular events. Here, we investigated in vitro and in vivo the pharmacological profile of BM-520, a new TP antagonist. In our experiments, this compound showed a great binding affinity for human washed platelets TP receptors, and prevented human platelet activation and aggregation induced by U-46619, arachidonic acid and 8-iso-PGF(2alpha). The TP receptor antagonist property of BM-520 was confirmed by its relaxing effect on rat aorta smooth muscle preparations precontracted with U-46619 and 8-iso-PGF(2alpha). Further, its TP antagonism was also demonstrated in vivo in guinea pig after a single intravenous injection (10 mg kg(-1)). We conclude that this novel TP antagonist could be a promising therapeutic tool in pathologies such as atherosclerosis where an increased production of TXA(2) and 8-iso-PGF(2alpha), as well as TP activation are well-established pathogenic events.

Organic amendments from olive cake as a strategy to modify the degradation of sulfonylurea herbicides in soil

Amending soil with products rich in organic matter, such as raw olive cake or alperujo and its compost and vermicompost, could be a simple bioremediation strategy for soil pollutants such as pesticides. To investigate this hypothesis in relation to sulfonylurea herbicides, these amendments were applied to a Mediterranean agricultural soil at rates 4 times higher than agronomical dosage to stimulate biodegradation of chlorsulfuron, prosulfuron, and bensulfuron, added in a mixture to the soils. Degradation studies were conducted in microbially active and sterile soils to check the importance of biological and chemical degradation of sulfonylurea herbicides in nonamended and amended soil. The addition of alperujo stimulated soil microbial activity, as determined by dehydrogenase activity measurements, but it did not enhance the degradation of the sulfonylurea herbicides. In contrast, compost and vermicompost slightly favored the biological degradation of bensulfuron during the first week of incubation. Chlorsulfuron and prosulfuron were mainly degraded by chemical pathways in all substrates, which is probably due to a competitive or inhibitory phenomenon observed between chlorsulfuron and bensulfuron. The first-order kinetic equation satisfactorily explained the experimental data for chlorsulfuron and prosulfuron; however, a biphasic model, such as that proposed by Hoerl, better predicted the results obtained for bensulfuron.

Design, Synthesis, and SAR Study of a Series of N-Alkyl-N‘-[2-(aryloxy)-5-nitrobenzenesulfonyl]ureas and -cyanoguanidine as Selective Antagonists of the TPα and TPβ Isoforms of the Human Thromboxane A2 Receptor

The prostanoid thromboxane (TX)A2 exerts its proaggregant and constrictive actions upon binding to the specific TXA2 receptor (TP), a member of the G-protein coupled receptor superfamily. In humans, TXA2 signals through two distinct TP isoforms, TPalpha and TPbeta. Herein, we describe the design, synthesis, and SAR study of a series of original N-alkyl-N'-[2-(aryloxy)-5-nitrobenzenesulfonyl]ureas and -cyanoguanidine. The SAR study was based on the results of a functional assay, TP-mediated intracellular calcium ([Ca2+]i) mobilization performed on the two separate isoforms. Optimal nature and position of several structural moieties was defined for both activity and selectivity toward TPalpha and TPbeta isoforms. Three compounds (9h, 9af, and 9ag), showing increased selectivity for TPbeta relative to TPalpha (23.2:1, 18.1:1, 19.9:1, respectively), were selected for further experiments, and their activity was confirmed in a platelet aggregation assay. This study represents the first extended SAR study dealing with the identification of isoform selective antagonists for the human TXA2 receptor.

[Changes of Cd forms on wheat root-soil interface under stress of combined Cd and chlorimuron-ethyl]

With rhizobox experiment, this paper studied the changes of Cd forms on wheat root-soil interface under the stress of combined cadmium (Cd) and chlorimuron-ethyl. The root-soil interface (0-5 mm) was separated into 6 parts every other 1 mm, and the sampling time was 14, 21, 28, 35 and 42 days after treatment. The correlativity between Cd forms and Cd absorption by wheat was made to assess the availability of each Cd form. The results showed that exchangeable Cd showed different spatial effect during various growth periods. The trend of carbonate-bound Cd and Fe-Mn oxide-bound Cd transforming to exchangeable Cd was weaken, but the trend of the two Cd forms transforming to residual Cd was strengthened from root-center zone to non-rhizosphere. The concentration of organic-bound Cd varied significantly in neighboring root zone. During the whole experiment period, the concentrations of carbonate-bound Cd, Fe-Mn oxide-bound Cd and organic-bound Cd decreased, while that of residual Cd increased. Correlation analysis suggested that exchangeable Cd and organic-bound Cd nearby the root were the main Cd forms that could be absorbed by wheat. It could be concluded that the transformation of carbonate-bound Cd and Fe-Mn oxide-bound Cd and the concentration of exchangeable Cd were affected by chlorimuron-ethyl significantly.