Chitosan/PVA silver nanocomposite for butachlor removal: Fabrication, characterization, adsorption mechanism and isotherms.

Silver nanoparticle (AgNP) incorporated chitosan-Polyvinyl alcohol (Ch/PVA) hydrogel nanocomposite was fabricated by repeated freeze-thaw treatment using glutaraldehyde as crosslinker for removal of herbicide butachlor from aqueous solution. Ch/PVA hydrogel provided a matrix for in-situ immobilization of AgNPs and were characterized by various physicochemical techniques. AgNPs of size 5-20 nm possessed crystalline structure, led to increase in thermal stability and surface area after incorporation into Ch/PVA hydrogel. Ch/PVA hydrogel nanocomposite showed maximum adsorption of butachlor (86.55 %) at 30 °C and pH 3.0, while Ch/PVA-Ag showed a slight increase in adsorption of butachlor following pseudo-second order kinetics. Langmuir and Freundlich models with different error functions (R2, R2adj, RSME, χ2 and RSS), confirmed monolayer adsorption of butachlor.

Efficient Removal of Butachlor and Change in Microbial Community Structure in Single-Chamber Microbial Fuel Cells.

Microbial electrochemical technology provides an inexhaustible supply of electron acceptors, allowing electroactive microorganisms to generate biocurrent and accelerate the removal of organics. The treatment of wastewater contaminated by butachlor, which is a commonly used chloroacetamide herbicide in paddy fields, is a problem in agricultural production. In this study, butachlor was found to be removed efficiently (90 ± 1%) and rapidly (one day) in constructed single-chamber microbial fuel cells (MFCs). After the addition of sodium acetate to MFCs with butachlor as the sole carbon source, electricity generation was recovered instead of increasing the degradation efficiency of butachlor. Meanwhile, the microbial community structure was changed in anodic and cathodic biofilms after the addition of butachlor, following the bioelectrochemical degradation of butachlor. High-throughput sequencing showed the proliferation of Paracoccus and Geobacter in MFCs with butachlor as the sole carbon source and of Thauera butanivorans in MFCs with butachlor and sodium acetate as concomitant carbon sources. These species possess the ability to oxidize different substituents of butachlor and have important potential use for the bioremediation of wastewater, sediments, and soils.

Extraction of acetanilide herbicides in naked oat (Avena nuda L.) by using ionic-liquid-based matrix solid-phase dispersion-foam flotation solid-phase extraction.

The herbicides in naked oat (Avena nuda L.) samples were extracted, separated, and determined by using ionic-liquid-based matrix solid-phase dispersion-solvent flotation coupled with high-performance liquid chromatography. The experimental parameters were optimized and evaluated by a univariate method and orthogonal experiment. A good linear relationship was obtained in the range of 5-5000 µg/kg, and the linear correlation coefficient are between 0.9989∼0.9993. The quantification limits for alachlor, metazachlor, propanil, acetochlor, pretilachlor, metolachlor, and butachlor are 5.03, 2.62, 2.73, 4.58, 7.28, 5.05, 5.78 µg/kg, respectively. The average recoveries of the acetanilide herbicides at spiked concentrations of 10, 100, and 500 µg/kg ranged from 92.1 to 104.7%, and relative standard deviations were equal to or lower than 2.9%.

Extraction and separation of acetanilide herbicides in beans based on metal-organic framework MIL-101 (Zn) as sorbent.

An extraction method based on metal-organic framework has been developed and applied to acetanilide herbicides, including metazachlor, propanil, pretilachlor, and butachlor, in black beans, red beans, and kidney beans. The acetanilide herbicides are extracted with a mixture of ethyl acetate and n-hexane. The extract solution is absorbed and purified with metal-organic framework MIL-101 (Zn). The separation and determination of four acetanilide herbicides were implemented by high-performance liquid chromatography. The experimental parameters were evaluated by a univariate method and orthogonal experiments. The presented method can obtain effective extraction and purification. The detection limits for metazachlor, propanil, pretilachlor, and butachlor were 0.58, 0.90, 1.78 and 1.18 µg/kg, respectively. The average recoveries of the acetanilide herbicides at spiked concentrations of 10, 50, and 100 µg/kg ranged from 86.9% to 119.0%, and relative standard deviations were equal to or lower than 2.80%.

Isolation, characterization, and structural elucidation of 4-methoxyacetanilide from marine actinobacteria Streptomyces sp. SCA29 and evaluation of its enzyme inhibitory, antibacterial, and cytotoxic potential.

Marine actinobacteria are less explored than their terrestrial counterparts as potential source of natural products. The present study was aimed to elucidate the bioactive potential of metabolites produced by marine-derived actinobacterial strain Streptomyces sp.SCA29 isolated from Havelock Island, Andaman and Nicobar Islands, India. The potential isolate SCA29 was identified as Streptomyces sp. by phenotypic, genotypic (16S-rRNA) and phylogenetic analyses. The crude bioactive compound was extracted using organic solvents. The compounds were subjected to separation and purification by column chromatography which yielded six fractions. Each fraction was assayed for inhibition of α-glucosidase and α-amylase enzymes, antagonistic activity against bacterial pathogens, and cytotoxic activity against various cell lines. The fraction F3c was considered to be highly active owing to its significant inhibition potential against α-glucosidase and α-amylase enzymes with IC50 values as 44.26 and 53.19 µg/mL, respectively. The active fraction showed antibacterial activity against test bacterial pathogens with the MIC value ranged from 3.90 to 31.25 µg/mL. The compound also exhibited concentration-dependent cytotoxicity on various cell lines without significant effect against human normal cells. The bioassay-guided fractionation of extract led to the identification of 4-methoxyacetanilide, an acetamide derivative. The structure of the bioactive compound was confirmed by HR-MS, NMR (1H and 13C) and FT-IR spectra, and by comparison with literature data.

Rice and wheat straw ashes: Characterization and modeling of pretilachlor sorption kinetics and adsorption isotherm.

The rice straw ash (RSA) and wheat straw ash (WSA) were explored as low cost adsorbent for pretilachlor removal from water. The ashes were characterized and sorption behavior of pretilachlor was evaluated. Kinetics study suggested that the modified Elovich model best explained the pretilachlor sorption on both the ashes. The adsorption data were analyzed using 2-, 3- and 4-parameter models and nine error functions were used to compute the best fit isotherm by nonlinear regression analysis. The pretilachlor was more sorbed onto the RSA (22.0-92.2%) than the WSA (11.4-61.4%) and percent adsorption decreased with increase in the herbicide concentration in solution. Isotherm model optimization analysis suggested that the Freundlich and the Temkin isotherms were the best models to predict the pretilachlor adsorption onto the RSA and the WSA. The error analysis suggested that the reciprocal of the observed squared (ROS) and the reciprocal of the predicted squared (RPS) error functions provided the best determination of the adsorption constants for the Freundlich and the Temkin isotherms, respectively. The RSA, which exhibited higher pretilachlor sorption potential, can be utilized as low cost adsorbent for pesticide removal from contaminated water.

Adsorption-desorption of dimethenamid and fenarimol onto three agricultural soils as affected by treated wastewater and fresh sewage sludge-derived dissolved organic carbon.

The use of treated wastewaters (TWW) in agriculture is widening in areas suffering drought, such as southern Europe, to preserve freshwater supply for human consumption. The composition of TWW, especially concerning their organic carbon (OC) content, has been demonstrated to influence the processes governing the behavior of non-ionic pesticides in soils. Three OC-poor agricultural soils (SV, RM1 and RM3) from the province of Granada (Spain) were chosen for the assessment of the adsorption and desorption of the herbicide dimethenamid (DIM) and the fungicide fenarimol (FEN). TWW and sewage sludge extracts at different dissolved OC (DOC) concentrations (30, 90 and 300 mg L-1) were considered to evaluate their effect on pesticide adsorption-desorption. As expected by their properties, DIM and FEN were weakly and moderately adsorbed to the soils, respectively. Soil OC seemed to be the major factor controlling FEN adsorption, whereas the mineral fraction played a key role in DIM adsorption, especially in RM1 with high clay:OC ratio. Although TWW did not significantly modify the adsorption of pesticides, it enhanced DIM desorption from the three soils. Adsorption of FEN to SV and RM3 was directly related to the concentration of DOC, possibly due to co-sorption phenomena. Hysteretic desorption was found in all cases, indicating partially reversible adsorption. While FEN desorption was not altered by the solutions, the use of sludge extracts at the highest DOC concentration (300 mg L-1) enhanced DIM desorption as occurred with TWW. Interactions with DOC in solution seemed to predominate for this less hydrophobic compound, thus increasing the risk of natural waters contamination if TWW will be used.

Extraction of acetanilides in rice using ionic liquid-based matrix solid phase dispersion-solvent flotation.

Ionic liquid-based matrix solid phase dispersion-solvent flotation coupled with high performance liquid chromatography was developed for the determination of the acetanilide herbicides, including metazachlor, propanil, alachlor, propisochlor, pretilachlor, and butachlor in rice samples. Some experimental parameters, including the type of dispersant, the mass ratio of dispersant to sample, pH of sample solution, the type of extraction solvent, the type of ionic liquid, flotation time, and flow rate of N2 were optimized. The average recoveries of the acetanilide herbicides at spiked concentrations of 50, 125, and 250 µg/kg ranged from 89.4% to 108.7%, and relative standard deviations were equal to or lower than 7.1%, the limits of quantification were in the range of 38.0 to 84.7 µg/kg.

Discovery of efficient stimulators for adult hippocampal neurogenesis based on scaffolds in dragon's blood.

Reduction of hippocampal neurogenesis caused by aging and neurological disorders would impair neural circuits and result in memory loss. A new lead compound (N-trans-3',4'-methylenedioxystilben-4-yl acetamide 27) has been discovered to efficiently stimulate adult rats' neurogenesis. In-depth structure-activity relationship studies proved the necessity of a stilbene scaffold that is absent in highly cytotoxic analogs such as chalcones and heteroaryl rings and inactive analogs such as diphenyl acetylene and diphenyl ethane, and validated the importance of an NH in the carboxamide and a methylenedioxy substituent on the benzene ring. Immunohistochemical staining and biochemical analysis indicate, in contrast to previously reported neuroprotective chemicals, N-stilbenyl carboxamides have extra capacity for neuroproliferation-type neurogenesis, thereby providing a foundation for improving the plasticity of the adult mammalian brain.

Efficient sample preparation method based on solvent-assisted dispersive solid-phase extraction for the trace detection of butachlor in urine and waste water samples.

In this work, an efficient sample preparation method termed solvent-assisted dispersive solid-phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre-concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 µL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 µg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent-assisted dispersive solid-phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples.

Liquid Chromatographic Separation and Thermodynamic Investigation of Mirabegron Enantiomers on a Chiralpak AY-H Column.

Liquid chromatographic separation of mirabegron enantiomers on Chiralpak AY-H, a column coated with amylose tris-(5-chloro-2-methylphenylcarbamate) as a chiral stationary phase, was studied under normal phase conditions. The influence of ethanol content (30-45%) and column temperature (20-40°C) on retention, resolution and separation were evaluated. Apparent thermodynamic parameters deduced from Van't Hoff plots were used to understand chiral separation mechanisms, and the chiral separation was enthalpy driven. The optimized chromatographic conditions were using a mixture solution of n-hexane, ethanol and diethyl amine (55 : 45 : 0.1, v/v/v) as a mobile phase at a flow rate of 1.0 mL/min. The column temperature and UV detector were set at 35°C and 254 nm, respectively. The method was validated to be simple, accuracy, sensitive and robust according to the ICH guidelines, and it was suitable for the routine quality control of mirabegron enantiomers for pharmaceutical industries.

Identification of a selective inhibitor of murine intestinal alkaline phosphatase (ML260) by concurrent ultra-high throughput screening against human and mouse isozymes.

Alkaline phosphatase (AP) isozymes are present in a wide range of species from bacteria to man and are capable of dephosphorylation and transphosphorylation of a wide spectrum of substrates in vitro. In humans, four AP isozymes have been identified-one tissue-nonspecific (TNAP) and three tissue-specific-named according to the tissue of their predominant expression: intestinal (IAP), placental (PLAP) and germ cell (GCAP) APs. Modulation of activity of the different AP isozymes may have therapeutic implications in distinct diseases and cellular processes. For instance, changes in the level of IAP activity can affect gut mucosa tolerance to microbial invasion due to the ability of IAP to detoxify bacterial endotoxins, alter the absorption of fatty acids and affect ectopurinergic regulation of duodenal bicarbonate secretion. To identify isozyme selective modulators of the human and mouse IAPs, we developed a series of murine duodenal IAP (Akp3-encoded dIAP isozyme), human IAP (hIAP), PLAP, and TNAP assays. High throughput screening and subsequent SAR efforts generated a potent inhibitor of dIAP, ML260, with specificity for the Akp3-, compared to the Akp5- and Akp6-encoded mouse isozymes.

Simultaneous determination of multiresidual phenyl acetanilide pesticides in different food commodities by solid-phase cleanup and gas chromatography-mass spectrometry.

An efficient and sensitive multiresidue method has been developed for quantification and confirmation of 25 phenyl acetanilide pesticides in a wide variety of food commodities including maize, spinach, mushroom, apple, soybean, chestnut, tea, beef, cattle liver, chicken, fish, and milk. Analytes were extracted with acetone-n-hexane (1:2, v/v) followed by cleanup using SPE. Several types of adsorbents were evaluated. Neutral aluminum and graphitized carbon black cartridge showed good cleanup efficiency. The extract was determined by GC-MS in the selected ion monitoring mode using one target and two qualitative ions for each analyte. The limits of detection were 0.01 mg/kg for all analytes. The average recoveries ranged from 66.9 to 110.6% (mean 88.8%) and RSDs were in the range 2.0-19% (mean 10.5%) across three fortification levels. The proposed method was successfully applied to real samples in routine analysis and a satisfactory result was obtained.

A novel reverse phase stability indicating RP-UPLC method for the quantitative determination of fifteen related substances in Ranolazine drug substance and drug product.

A gradient reverse-phase ultra performance liquid chromatographic (RP-UPLC) method was developed for the quantitative determination of Ranolazine and potential process-related impurities (starting materials, positional isomers, degradants and byproducts) at the level of 0.1 µg mL(-1) to 0.3 µg mL(-1). Fifteen potential impurities were identified in the crude samples during the process development. Tentative structures for all the impurities were assigned based on m/z values from LC-MS/MS analysis. This method can be used for the quality control of both drug substance and drug product. All these impurities were separated with a gradient UPLC method by using a polar embedded Waters Acquity BEH RP18 100 mm × 2.1 mm,1.7 µm column, monobasic sodium buffer, a basic organic modifier and acetonitrile in the mobile phase. Further, this method is also capable of separating a major oxidative degradant Di-N-oxide. Impurities having electron donating groups(+I effect) on the phenyl ring increased the retention by improved п-п interactions. The drug was subjected to the International Conference on Harmonization (ICH)-prescribed hydrolytic, oxidative, photolytic and thermal stress conditions. The performance of the method was validated according to the present ICH guidelines for specificity, limit of detection, limit of quantification, linearity, accuracy, precision, ruggedness and robustness.

HPLC separation of acetaminophen and its impurities using a mixed-mode reversed-phase/cation exchange stationary phase.

Determination of acetaminophen and its main impurities: 4-nitrophenol, 4'-chloroacetanilide, as well as 4-aminophenol and its degradation products, p-benzoquinone and hydroquinone has been developed and validated by a new high-performance liquid chromatography method. Chromatographic separation has been obtained on a Hypersil Duet C18/SCX column, using gradient elution, with a mixture of phosphate buffer (pH = 4.88) and methanol as a mobile phase. Analysis time did not exceed 14.5 min and good resolutions, peak shapes and asymmetries have resulted. The linearity of the method has been tested in the range of 5.0-60 µg/mL for acetaminophen and 0.5-6 µg/mL for the other compounds. The limits of detection and quantification have been also established to be lower than 0.1 µg/mL and 0.5 µg/mL, respectively. The method has been successfully applied for the analysis of commercial acetaminophen preparations.

[Study on the chemical constituents of endophytic fungus Fimetariella rabenhorstii isolated from Aquilaria sinensis].

OBJECTIVE: To study the chemical constituents of endophytic fungus Fimetariella rabenhorsti isolated from Aquilaria sinensis. METHODS: Chemical constituents of the fungus were isolated and purified by column chromatography and their structures were elucidated on the basis of spectral data. RESULTS: Five compounds were isolated and identified as 4-hydroxy-phenylethyl alcohol (1),nicotinic acid (2), D-galacitol(3), 2-anilino-1,4-naphthoquinone (4), N-phenylacetamide (5). CONCLUSION: Compounds 1-5 are isolated from the genus Fimetariella for the first time, compound 5 is rare in natural products.

Determination of acetanilide herbicides in cereal crops using accelerated solvent extraction, solid-phase extraction and gas chromatography-electron capture detector.

A method was developed to determine eight acetanilide herbicides from cereal crops based on accelerated solvent extraction (ASE) and solid-phase extraction (SPE) followed by gas chromatography-electron capture detector (GC-ECD) analysis. During the ASE process, the effect of four parameters (temperature, static time, static cycles and solvent) on the extraction efficiency was considered and compared with shake-flask extraction method. After extraction with ASE, four SPE tubes (graphitic carbon black/primary secondary amine (GCB/PSA), GCB, Florisil and alumina-N) were assayed for comparison to obtain the best clean-up efficiency. The results show that GCB/PSA cartridge gave the best recoveries and cleanest chromatograms. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, limit of detection (LOD), limit of quantitation (LOQ), precision and recovery were studied. At 0.05 mg/kg spiked level, recoveries and precision values for rice, wheat and maize were 82.3-115.8 and 1.1-13.6%, respectively. For all the herbicides, LOD and LOQ ranged from 0.8 to 1.7 µg/kg and from 2.4 to 5.3 µg/kg, respectively. The proposed analytical methodology was applied for the analysis of the targets in samples; only three herbicides, propyzamid, metolachlor and diflufenican, were detected in two samples.

Novel liquid-liquid-solid microextraction method with molecularly imprinted polymer-coated stainless steel fiber for aqueous sample pretreatment.

A novel liquid-liquid-solid microextraction (LLSME) method was developed to overcome the well-known water-compatibility problem of molecularly imprinted polymers (MIPs). The enrichment factors with MIP-LLSME method were within 70-210 for trace chloroacetanilide herbicides under optimized extraction conditions. The method was characterized by simplicity, low solvent-consumption and high selectivity, and it was suitable for the one-step pretreatment of various aqueous samples such as river water and farm water.

Molecularly imprinted polymer coated on stainless steel fiber for solid-phase microextraction of chloroacetanilide herbicides in soybean and corn.

A molecularly imprinted polymer (MIP) with metolachlor as template was firstly coated on stainless steel fiber through chemical bonding strategy to solve the fragility problem of silica fiber substrate for solid-phase microextraction. The surface pretreatment of stainless steel fiber and the polymerization conditions were investigated systematically to enhance the preparation feasibility and MIP coating performance, and then a porous and highly cross-linked MIP coating with 14.8-microm thickness was obtained with over 200 times re-usability which was supported by non-fragile stainless steel fiber adoption. The MIP coating possessed specific selectivities to metolachlor, its metabolites and other chloroacetanilide herbicides with the factors of 1.1-4.6. Good extraction capacities of metolachlor, propisochlor and butachlor were found with MIP coating under quick adsorption and desorption kinetics, and the detection limits of 3.0, 9.6 and 38 microg L(-1) were achieved, respectively. Moreover, the MIP-coated stainless steel fiber was evaluated for trace metolachlor, propisochlor and butachlor extraction in the spiked soybean and corn samples, and the enrichment factors of 54-60, 27-31 and 15-20 were obtained, respectively.

[Sorption and desorption behavior of the herbicide mefenacet on soils].

The sorption-desorption experiments of the herbicide mefenacet on five soils with different physicochemical properties were conducted using bath equilibrium methods, and the effects of soil organic matter and pH value on sorption of this herbicide were also investigated. The results showed that the sorption and desorption behaviors of mefenacet on soils could be well described by both the linear model and Freundlich model. Sorption distribution coefficients K(oc) for five tested soil are between 849.5 L x kg(-1) and 1 818.8 L x kg(-1), which shows that mefenacet can be well adsorbed on soils. It is found that the sorption coefficients, K(d), K(f), and K(f) (1/n) had good correlation with organic matter content (OM) in soils. It is obviously suggested that organic matter was the dominant factor affecting the sorption of mefenacet on soils. For the same soil, the sorption amount of mefenacet decreased with the increase of pH value. The desorption hysteresis of mefenacet was revealed in the single-cycle sorption and desorption experiments, which indicated a weak transferability of this herbicide in soils.