Naturally occurring phytotoxins in allelopathic plants help reduce herbicide dose in wheat

Field studies were carried out to evaluate the influence of allelopathic plant water extracts applied alone or tank-mixed with a reduced herbicide dose on the weeds of wheat. Water extracts of sorghum (Sorghum bicolor (L.) Moench.)?+?sunflower (Helianthus annuus L.)?+?mulberry (Morus alba L.) were used alone (each at 20?L?ha(-1)) or combined with iodo?+?mesosulfuron (3.6 and 7.2 g active ingredient (a.i.) ha(-1); 25 and 50% of the recommended dose, respectively). The recommended dose of herbicide, a weedy check and a weed-free treatment were included for comparison. Allelopathic water extracts alone suppressed the density of canary grass (Phalaris minor Retz.) and wild oat (Avena fatua L.) by 34-42%, and dry weight by 59-67%. The mixture of allelopathic plant water extracts combined with reduced doses of iodo?+?mesosulfuron gave weed control equal to the recommended dose of the herbicide. Integration of plant water extracts with reduced herbicide rates provide effective weed control and a wheat yield comparable to using the recommended herbicide dose.     

Synthesis and Herbicidal Activity of 2‐Alkyl(aryl)‐4‐amino‐3‐[alkyl(alkoxy)carbonyl]‐5‐cyano‐6‐[(3‐trifluoromethyl)phenoxy]‐pyridines

To find novel bleaching herbicide lead compounds, a series of novel 2‐alkyl(aryl)‐4‐amino‐3‐[alkyl(alkoxy)carbonyl]‐5‐cyano‐6‐[(3‐trifluoromethyl)phenoxy]‐pyridines was designed and synthesized by the multistep reactions. N,S‐acetal 1 reacted with 2 to obtain multisubstituted pyridines 3 in the presence of zinc nitrate as the catalyst. The target compounds 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l were formed by the oxidation of 3 , followed by the substitution with 3‐(trifluoromethyl)phenol in the presence of potassium carbonate. Their structures were confirmed by IR, ¹H NMR, EI‐MS, and elemental analyses. The preliminary bioassays indicated that some of them displayed moderate herbicidal activity against dicotyledonous weed Brassica campestris L at the concentration of 100 mg/L.     

New methods for determination of glyphosate and (aminomethyl)phosphonic acid in water and soil

New methods were developed to determine glyphosate, N-(phosphonomethyl)glycine, and its major metabolite, (aminomethyl)phosphonic acid in groundwater and soil. The methods involve ligand-exchange, anion-exchange and derivatisation and final identification and quantification by GC-MS. The limits of quantification in this experiment were 0.1 microg l(-1) for both compounds in water and 0.006 microg g(-1) for both compounds in soil. Decomposition in soil and occurrence in groundwater of the herbicide glyphosate was studied after its application for weed control on a Swedish railway embankment.     

新磺酰脲类化合物的合成及生物活性

以正在开发的新磷磺酰脲除草剂N-[2′-(4′-甲基)嘧啶基]-2-硝基苯磺酰脲的研究为基础,设计合成了19个脲桥经修饰的磺酰脲类化合物以及3个新型嘧啶中间体,产物结构经¹HNMR谱及元素分析确证.盆栽试验和离休ALS酶研究结果表明,所合成的化合物均表现出一定的除草活性,部分化合物的除草活性较好.     

Controlled release of acetochlor from poly (butyl methacrylate-diacetone acrylamide) based formulation prepared by nanoemulsion polymerisation method and evaluation of the efficacy

Acetochlor is an important herbicide for gramineous weeds and some small seed broadleaf weeds. Controlled-release formulations of herbicide are highly desirable not only for attaining the most effective utilisation of the weed control, but also for reducing environmental pollution. Acetochlor was incorporated in poly (butyl methacrylate-diacetone acrylamide) based formulation to obtain controlled release properties. The acetochlor nanocapsules were characterised by size distribution, infrared spectroscopy (IR) and field emission scanning electron microscopy (FESEM), and factors related to loading efficiency, swelling behaviour of the formulation were investigated. For this controlled-release formulation, the loading efficiency could reach about 50% (w/w). n, the diffusion parameter was indicative of the transport mechanism, and the values for ‘n’ were in the range of 0.28–0.61, which indicated that the release of acetochlor was diffusion-controlled. The time taken for 50% of the active ingredient to be released into water, t₅₀, was also calculated for the comparison of formulations in different conditions. The formulation with higher temperature and more diacetone acrylamide had lower value of t₅₀, which means a quicker release of the active ingredient. This study highlighted some pieces of evidence that improved herbicide incorporation and slower release were linked to potential interactions between the herbicide and the polymer.     

Electrochemical investigation of the interaction of 2,4-D and double stranded DNA using pencil graphite electrodes

2,4-dichlorophenoxyacetic acid (2,4-D) is an auxinic herbicide used to control broadleaf weeds. It is also a threatening factor for not only aquatic life but also human health due to its genotoxicity and endocrine disruptive property. Herein, the interaction between 2,4-D and double stranded DNA was investigated by using single-use pencil graphite electrodes (PGE) in combination with electrochemical techniques. The detection mechanism was based on the monitoring of the changes at the guanine oxidation signal obtained before/after surface-confined interaction of 2,4-D and DNA at the surface of PGE. The electrochemical characterization of the interaction was studied by using microscopic and electrochemical techniques. The response obtained by interaction in the presence of another herbicide, glyphosate, which is widely used with 2,4-D for weed control, was compared to the one occurred in the presence of 2,4-D. Electrochemical monitoring of the interaction between the herbicide whose active molecule was 2,4-D and DNA was also investigated. The detection (LOD) and quantification limits (LOQ) for 2,4-D and the herbicide could be obtained in the linear concentration ranges of 30–70 µg/mL and 10–30 µg/mL, respectively and LOD and LOQ values were found to be 2.85 and 9.50 µg/mL for both 2,4-D and the herbicide. The sensitivity of the biosensor was calculated as 0.087 µA.mL / µg.cm² .This is the first study in literature by means of not only voltammetric detection of 2,4-D and DNA interaction but also the herbicide-DNA interaction at the surface of PGE based on the changes at the guanine signal.     

A Study on the Phytotoxic Potential of the Seasoning Herb Marjoram (Origanum majorana L.) Leaves

In the search of new alternatives for weed control, spices appear as an option with great potential. They are rich in bioactive natural products and edible, which might minimize toxicity hazard. Marjoram (Origanum majorana L.) is an aromatic herb that has been widely employed as a seasoning herb in Mediterranean countries. Although marjoram boasts a plethora of therapeutic properties (painkiller, antibiotic, treatment for intestinal disorders, etc.), the potential for its extracts for weed control is still to be more thoroughly explored. In order to determine their phytotoxic potential, marjoram leaves were subjected to different bioguided extraction processes, using water, ethyl acetate, acetone or methanol. The most active extract (acetone) was sequentially fractionated to identify its most active compounds. This fractionation led to the isolation and identification of 25 compounds that were classified as monoterpenes, diterpenes or flavonoids. Among them, a new compound named majoradiol and several compounds are described in marjoram for the first time. The phytotoxicity of the major compounds to etiolated wheat coleoptiles was compared against that of the commercial herbicide (Logran^®), with similar or higher activity in some cases. These results confirm the extraordinary potential of the extracts from this edible plant to develop safer and more environmentally friendly herbicides.     

GC‐MSn and LC‐MS/MS couplings for the identification of degradation products resulting from the ozonation treatment of Acetochlor

The degradation of the chloracetamide herbicide acetochlor has been studied under simulated ozonation treatment plant conditions. The degradation of acetochlor included the formation of several degradation products that were identified using GC/ion‐trap mass spectrometry with EI and CI and HPLC/electrospray‐QqTOF mass spectrometry. Thirteen ozonation products of acetochlor have been identified. Ozonation of the deuterated herbicide combined to MSⁿ and high‐resolution mass measurement allowed effective characterization of the degradation products. At the exception of one of them, the product B (2‐chloro‐2', ethyl‐6', methyl‐acetanilide), none of the identified degradation products has been already reported in the literature. Post‐ozonation kinetics studies revealed that the concentrations of most degradation products evolved noticeably with time, particularly during the first hours following the ozonation treatment. This raises concerns about the fate of degradation products in the effluents of treatment plants and suggests the need for a better control on these products if their toxicity was demonstrated. Copyright © 2012 John Wiley & Sons, Ltd.     

Mass Spectrometry-Based Peptide Profiling of Haemolymph from Pterostichus melas Exposed to Pendimethalin Herbicide

Pendimethalin-based herbicides are used worldwide for pre-emergence selective control of annual grasses and weeds in croplands. The endurance of herbicides residues in the environment has an impact on the soil biodiversity and fertility, also affecting non-target species, including terrestrial invertebrates. Carabid beetles are known as natural pest control agents in the soil food web of agroecosystems, and feed on invertebrates and weed seeds. Here, a mass spectrometry untargeted profiling of haemolymph is used to investigate Pterostichus melas metabolic response after to pendimethalin-based herbicide exposure. Mass spectrometric data are examined with statistical approaches, such as principal component analysis, for possible correlation with biological effects. Those signals with high correlation are submitted to tandem mass spectrometry to identify the associated biomarker. The time course exposure showed many interesting findings, including a significant downregulation of related to immune and defense peptides (M-lycotoxin-Ls4a, Peptide hormone 1, Paralytic peptide 2, and Serine protease inhibitor 2). Overall, the observed peptide deregulations concur with the general mechanism of uptake and elimination of toxicants reported for Arthropods.     

A Simple and Sensitive Square Wave Stripping Pathway for the Analysis of Desmedipham Herbicide by Modified Carbon Paste Electrode Based on Hematite (α‐Fe2O3 Nanoparticles)

In the present study, desmedipham, used as an herbicide to control broad leaf weed in commonly sugar beet crops, was analyzed at the first time by cyclic voltammetry (CV) and square wave stripping voltammetry (SWSV) with the modified carbon paste electrode based on hematite nanoparticles (α‐Fe₂O₃?CPE). The modified α‐Fe₂O₃?CPE prepared by hematite (α‐Fe₂O₃ nanoparticles), which is very sensitive to carbon paste electrode (CPE) and glassy carbon electrode (GCE). Morphology of electrode surface detailed by scanning electron microscopy (SEM) and energy dispersive X‐ray analysis (EDX). The oxidation of desmedipham created irreversible well‐done two peaks at nearly +1.1 and +1.3 V. In order to obtain the best calibration graph, various important parameters such as pH, accumulation time, puls amplitude and frequency etc. were investigated. Under the optimum conditions, electrochemical behavior of desmedipham presented two linear working ranges at 0.15–1.20 mg/L and 1.20–4.50 mg/L. The limits of detection (LOD) for the desmedipham were calculated as 41.00 and 50.00 μg/L for the peak I and II, respectively. Furthermore, desmedipham was analyzed at high recovery in the presence of rizolex, fluometuron, teflubenzuron and some heavy metal ions. Consequently, the developed SWSV was successfully applied to evaluate desmedipham in spiked commercial strawberry juices at recoveries of 96.00–104.00 % with satisfactory relative standard deviations.     

Analysis of a Critical Residue Determining Herbicide Efficiency Sensitivity in Carboxyltransferase Domain of Acetyl-CoA Carboxylase from Poaceae by Homology Modeling and Free Energy Simulation

Carboxyltransferase domain(CT) of acetyl-coenzyme A carboxylase(ACCase, EC 6.4.1.2) from a family of Poaceae is an important target of commercial herbicide APPs for controlling grass weed growth. As the abuse of APPs herbicides, the resistant ACCase due to the mutation of a single residue(Ile→Leu), which is lo-cated in CT active site, is emergent in many populations and species of Poaceae. So it is urgent to understand the re-sistant mecha-nism so as to design new effect herbicides. Herein lies the complex of CT dimmer from Lolium rigi-dum and herbicide haloxyfop successfully constructed for wild type enzyme and Ile/Leu mutant, respectively, pro-viding a basis for explaining the resistance from microscopic structure. Moreover, the binding free energy difference between wild type and mutant enzymes was predicted in good agreement with the known observation, and the various contributions to it were analyzed, by Molecular mechanics-Poisson-Boltzmann surface area(MM-PBSA) method. The results indicate the van der Waals interaction difference between the protein and inhibitor, –22.94 kJ/mol of CT wild type lower than that of mutant, is the major reason for resistance. Structure analysis further suggests that van der Waals interaction difference is originated from the steric hindrance between the side chain of mutated residue Leu and the chiral methyl group of haloxyfop. All these findings enhance the understanding of resistant mechanism of ACCase to herbicide by Ile/Leu mutation and provide an important clue for the rational design of high effective herbicides.     

Imprinted Polymer – Modified Hanging Mercury Drop Electrode for Differential Pulse Adsorptive Stripping Voltammetric Analysis of a Diquat Herbicide

An imprinted polymer modified hanging mercury drop electrode (HMDE) in Model 303A system in conjunction with a PAR Model 264A Polarographic Analyzer/Stripping Voltammeter has been used for the selective analysis of a diquat herbicide viz., 5,6‐dihydropyrazino[1,2,3,4‐[lmn]‐1,10‐phenanthrolinium dichlorides in differential pulse cathodic stripping voltammetry mode. Complex aqueous samples (drinking water and agricultural soil suspension), spiked with a diquat herbicide, were directly analyzed by the adsorptive accumulation of the analyte over the working electrode (accumulation potential ?0.8 V (vs. Ag/AgCl), accumulation time 120 s, pH 7.0, supporting electrolyte 0.1 M KCl, scan rate 10 mV s^?1, pulse amplitude 25 mV). The limit of detection for diquat herbicide was found to be 0.34 nmol L^?1 (0.1 ppb, RSD 2%, S/N=2).     

Dynamic Self‐Assembly Adhesion of a Paraquat Droplet on a Pillar[5]arene Surface

The adhesion of herbicide droplets on leaf surfaces plays an important role in the herbicide's adsorption by crops. How to control the adhesive binding which occurs through dynamic self‐assembly between the macroscopic droplet and the surface is a challenging task. We introduce a host onto surfaces that controls the binding of guests in the paraquat droplets. The pillar[5]arene‐functional surface showed the selective binding of paraquat droplets via the host–guest interaction. The work is promising for improving the efficiency of herbicides.     

Synthesis and Herbicidal Activities of 3‐Trifluoromethyl‐5‐[3‐(trifluoromethyl)phenoxy]‐1,2,4‐Triazol‐4‐Schiff Bases

In order to find novel bleaching herbicide lead compounds, a series of novel 3‐(trifluoromethyl)‐4‐(arylimino)‐5‐[3‐(trifluoromethyl)phenoxy]‐1,2,4‐triazoles were designed and synthesized by the multi‐step reactions. Their structures were confirmed by IR, ¹H NMR, EI‐MS and elemental analyses. The preliminary bioassay indicated that compounds 4b , 4f , and 4h possessed 69.4%, 72.6%, and 88.5% inhibition against Brassica campestris L at the concentration of 100 mg/L. Generally speaking, this type of compounds exhibited weak herbicidal activity and might be not suitable as herbicide lead compound for further optimization.     

Voltammetric Detection of the Herbicide Metamitron at a Bismuth Film Electrode in Nondeaerated Solution

In this work, we present a novel application of bismuth film electrodes (BiFE) for the direct analysis of the herbicide metamitron (4‐amino‐3‐methyl‐6‐phenyl‐1,2,4‐triazin‐5one) in nondeaerated solutions by square‐wave voltammetry (SWV) and differential pulse amperometry. Bismuth films were plated ex‐situ onto carbon paste electrodes (CPE) by 240 s deposition at ?0.600 V from a 0.10 M acetate buffer (pH 4.5) containing 0.50 mM bismuth nitrate. Metamitron SWV analytical signals were registered in 0.10 M acetate buffer (pH 4.5) solutions, where the herbicide reduction takes place at ?0.675 V. The metamitron signals obtained with BiFE have the double sensitivity and a 50 mV positive potential shift when compared to those obtained with plain CPE. Under these conditions, the dynamic linear range of concentrations is comprised between 10 and 200 μM and the detection limit is 2 μM.     

Simultaneous determination of herbicide residues in tobacco using ultraperformance convergence chromatography coupled with solid‐phase extraction

A time‐saving and organic solvent efficient method to simultaneously determine six kinds of herbicide residues in tobacco using solid‐phase extraction for sample clean‐up and preconcentration and the highly sensitive ultraperformance convergence chromatography method was developed. Parameters for ultraperformance convergence chromatography, including the choice of stationary phase and modifiers, autobackpressure regulator pressure, column temperature, and the flow rate of mobile solvents, were optimized. The herbicide residues of napropamide, alachlor, quizalofop‐ethyl, diphenamid, metolachlor, and clomazone in tobacco samples were successfully separated and detected at levels as low as 0.0043–0.0086 mg/kg within 5 min using a nonpolar high strength silica C₁₈ selectivity for bases column and methanol as the cosolvent of the mobile phase of carbon dioxide (75–99.9%, v/v). Analysis of tobacco samples had recoveries of 69.8–95.0%, limit of quantitation of 0.0127–0.0245 mg/kg, limit of detection of 0.0043–0.0086 mg/kg, and correlation coefficient of >0.9990. Results support this method as an efficient alternative to current methodologies for the determination of herbicide residues in tobacco.     

Determination of the Herbicide Fluometuron by Photo‐induced Chemiluminescence in a Continuous‐flow Multicommutation Assembly

Abstract

This study was dealing with the chemiluminometric determination of the selective herbicide Fluometuron or 1,1‐dimethyl‐3‐(α,α,α‐trifluoro‐m‐tolyl)urea, (C₁₀H₁₁F₃N₂O) with a molecular weight 232.29 belongs to the phenyl urea herbicides family. The analytical strategy is based on the continuous‐flow manifold, multicommutation and the analyte pre‐treatment, the photo‐degradation.

The optimization of chemical (pH, medium, temperature, and organized media) and hydrodynamic parameters (volume of reagents and flow rate) was performed by univariant and multiparametric simplex procedure respectively. Analytical figures of merit and the effect of foreign substances were studied. The method resulted in quick, automated cost‐effective and clean procedure to determine the herbicide in spiked different samples of water and a formulation.     

Flow Injection Spectrophotometric Determination of 2,4‐D Herbicide

2,4‐Dichlorophenoxy acetic acid herbicide is spectrophotometrically determined by diazotization method in a flow injection assembly. The method is based on base hydrolysis of herbicides. The hydrolyzed product 2,4‐dichlorophenol is reacted with diazotized sulfanilic acid. The absorbance of the resulting coloured product was measured at 480 nm. The calibration graph is linear over the range of 0.2–20 μgmL^?1, with a relative standard deviation of (RSD) of 7.2% and sample throughput of 90 samples h^?1. The % recovery for determination of 2,4‐dichlorophenoxy acetic acid was found to be 92.0–95.3%. The method is easy, simple and faster than the established chromatographic method. The method was applied for determination of 2,4‐dichlorophenoxy acetic acid herbicide in commercial formulations and for residue determination in fruits and food samples.     

Electroanalytical Detection of the Pesticide Paraquat by Batch Injection Analysis

Abstract

The Batch‐Injection Analysis (BIA) technique has been applied to the electroanalytical detection of the herbicide paraquat by square wave voltammetry (SWV) during sample injection. The results obtained showed that the herbicide can be detected at µg l^?1 levels with small injection volumes (<100 µl). The time of each measurement was less than two seconds. The BIA method presents many advantages such as being extremely fast, with high reproducibility, good sensitivity and simple without pre‐addition of or changing the supporting electrolyte.     

High‐Level Incorporation of Silver in Gold Nanoclusters: Fluorescence Redshift upon Interaction with Hydrogen Peroxide and Fluorescence Enhancement with Herbicide

High‐level incorporation of Ag in Au nanoclusters (NCs) is conveniently achieved by controlling the concentration of Ag⁺ in the synthesis of bovine serum albumin (BSA)‐protected Au NCs, and the resulting structure is determined to be bimetallic Ag₂₈Au₁₀‐BSA NCs through a series of characterizations including energy‐dispersive X‐ray spectroscopy, mass spectroscopy, and X‐ray photoelectron spectroscopy, together with density functional theory simulations. Interestingly, the Ag₂₈Au₁₀ NCs exhibit a significant fluorescence redshift rather than quenching upon interaction with hydrogen peroxide, providing a new approach to the detection of hydrogen peroxide through direct comparison of their fluorescence peaks. Furthermore, the Ag₂₈Au₁₀ NCs are also used for the sensitive and selective detection of herbicide through fluorescence enhancement. The detection limit for herbicide (0.1 nm ) is far below the health value established by the U.S. Environmental Protection Agency; such sensitive detection was not achieved by using AuAg NCs with low‐level incorporation of Ag or by using the individual metal NCs.