An efficient and sensitive analytical method based on high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was established for the simultaneous separation and ...determination of glucosamine (GlcN)₁ and chitooligosaccharides (COS) ranging from (GlcN)₂ to (GlcN)₆ without prior derivatization. Detection limits were 0.003 to 0.016 mg/L (corresponding to 0.4-0.6 pmol), and the linear range was 0.2 to 10 mg/L. The optimized analysis was carried out on a CarboPac-PA100 analytical column (4 × 250 mm) using isocratic elution with 0.2 M aqueous sodium hydroxide-water mixture (10:90,
/
) as the mobile phase at a 0.4 mL/min flow rate. Regression equations revealed a good linear relationship (
² = 0.9979-0.9995,
= 7) within the test ranges. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated HPAEC-PAD method was readily applied for the quantification of (GlcN)
in a commercial COS technical concentrate. The established method was also used to monitor the acid hydrolysis of a COS technical concentrate to ensure optimization of reaction conditions and minimization of (GlcN)₁ degradation.
Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in ...COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na⁺, NH₄⁺, K⁺, Mg
, Ca
, and chloride, acetate and lactate anions was developed. Detection limits were 0.01-0.05 μM for cations and 0.5-0.6 μM for anions. The linear range was 0.001-0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate.
Quantifying dermal and inhalation exposure to pesticides is a critical component of the decision-making procedure for risk evaluation. For traditional determination of pesticide exposure, a large ...amount of organic solvent is inevitably used to extract pesticides from the sampling medium. This paper presents an environmentally benign method for determining potential dermal and inhalation exposure using water-soluble Allura Red as a pesticide surrogate. Only water is used to extract the Allura Red from the sampling medium. More importantly, the operator can attain an immediate visual impression of the exposure patterns. This visual contaminant dispersion can be helpful for the development of measures to improve operational safety through pesticide management. For validation of the method, comparative exposure analyses were carried out with representative lipophilic and hydrophilic pesticides (chlorpyrifos and nitenpyram) under similar application conditions. The results indicate that Allura Red had similar exposure distributions to those of the pesticides. The total exposure measured using Allura Red is higher but of roughly the same order of magnitude as the values obtained with the pesticides. Combined with the calculated margin of exposure, this environmentally friendly method could provide a very useful reference for exposure risk assessment in various pesticide use scenarios.
Point mutation G143A in the cytochrome b (Cyt b) protein commonly confers resistance to quinone outside inhibitor (QoI) fungicides in phytopathogenic fungi, including Corynespora cassiicola, which ...causes cucumber target spot disease. However, the effect of G143A on the binding between the QoI fungicide and the Cyt b protein, and the use of LAMP (loop-mediated isothermal amplification) to detect this point mutation had not been reported previously in C. cassiicola. In this study, the sensitivity of 131 C. cassiicola isolates—collected from Shandong province, China in 2019 and 2020—to pyraclostrobin was determined. The EC50 values ranged from 1.67 to 8.82 μg/mL, and sequencing results showed that all C. cassiicola isolates contained the G143A mutation. Molecular docking results suggested that G143A significantly alters the affinity of pyraclostrobin to the Cyt b protein. Following development of three LAMP primer pairs, the best reaction condition for LAMP analysis was 65 °C for 60 min, and the detection limit was 0.01 ng/μL of DNA containing the point mutation. In conclusion, the G143A mutation conferring pyraclostrobin resistance is widespread in C. cassiicola from Shandong province, and the LAMP method can be used to monitor QoI resistance in C. cassiicola caused by the G143A mutation in the field.
Because of its relatively high water solubility and mobility, 2,4-dichlorophenoxy acetic acid (2,4-D) has a high leaching potential threatening the surface water and groundwater. Controlled release ...formulations of 2,4-D could alleviate the adverse effects on the environment. In the present study, positive-charge functionalized mesoporous silica nanoparticles (MSNs) were facilely synthesized by incorporating trimethylammonium (TA) groups onto MSNs via a postgrafting method. 2,4-D sodium salt, the anionic form of 2,4-D, was effectively loaded into these positively charged MSN-TA nanoparticles. The loading content can be greatly improved to 21.7% compared to using bare MSNs as a single encapsulant (1.5%). Pesticide loading and release patterns were pH, ionic strength and temperature responsive, which were mainly dominated by the electrostatic interactions. Soil column experiments clearly demonstrated that MSN–TA can decrease the soil leaching of 2, 4-D sodium salt. Moreover, this novel nanoformulation showed good bioactivity on target plant without adverse effects on the growth of nontarget plant. This strategy based on electrostatic interactions could be widely applied to charge carrying agrochemicals using carriers bearing opposite charges to alleviate the potential adverse effects on the environment.
Pyraclostrobin, one of the most widely used fungicides globally, is highly toxic to aquatic organisms, which restricts its application in paddy fields. Most studies have focused on the molecular ...mechanism of pyraclostrobin toxicity; however, the exposure routes and target organs of pyraclostrobin in fish are poorly known. Here, we found that the lethal effects of aquatic exposure, head immersion, trunk immersion and oral exposure on the toxicity and accumulation of pyraclostrobin in adult zebrafish were different. The major pathway leading to pyraclostrobin accumulation, followed by high hazard to fish, was crossing over the gill rather than the intestine or skin. Additionally, serious histological abnormalities, mitochondrial dysfunction, energy deficiency and respiratory impairment occurred in the gills, while no overt change was observed in the heart and brain at the organic and cellular levels. This result suggested that the gill is the dominant portal and target organ of pyraclostrobin in fish, a fact that has been further verified by intravenous injection. The differences in the toxicity and translocation factor of crystalline and dissolved pyraclostrobin in fish demonstrated that reducing the concentration in the branchial environment is a vital direction for the future design of an effective toxicity regulation strategy to protect key sites from pyraclostrobin attack.
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•Pyraclostrobin induced high toxicity mainly via the gill.•The gills suffered from the more serious damage than the heart and brain.•Reducing the contact of pyraclostrobin with gills can effectively mitigate its threats to fish.
The cucumber target spot, caused by Corynespora cassiicola, is a major cucumber disease in China. Mefentrifluconazole, a new triazole fungicide, exhibits remarkable efficacy in controlling cucumber ...target spot. However, the resistance risk and mechanism remain unclear. In this study, the inhibitory activity of mefentrifluconazole against 101 C. cassiicola isolates was determined, and the results indicated that the EC
values ranged between 0.15 and 12.85 μg/mL, with a mean of 4.76 μg/mL. Fourteen mefentrifluconazole-resistant mutants of C. cassiicola were generated from six parental isolates in the laboratory through fungicide adaptation or UV irradiation. The resistance was relatively stable after ten consecutive transfers on a fungicide-free medium. No cross-resistance was observed between mefentrifluconazole and pyraclostrobin, fluopyram, prochloraz, mancozeb, or difenoconazole. Investigations into the biological characteristics of the resistant mutants revealed that six resistant mutants exhibited an enhanced compound fitness index (CFI) compared to the parental isolates, while others displayed a reduced or comparable CFI. The overexpression of CcCYP51A and CcCYP51B was detected in the resistant mutants, regardless of the presence or absence of mefentrifluconazole. Additionally, a two-way mixture of mefentrifluconazole and prochloraz at a concentration of 7:3 demonstrated superior control efficacy against the cucumber target spot, achieving a protection rate of 80%. In conclusion, this study suggests that the risk of C. cassiicola developing resistance to mefentrifluconazole is medium, and the overexpression of CcCYP51A and CcCYP51B might be associated with mefentrifluconazole resistance in C. cassiicola. The mefentrifluconazole and prochloraz two-way mixture presented promising control efficacy against the cucumber target spot.
To explore insecticides targeting the γ-aminobutyric acid (GABA) receptor, two series of novel isoxazoline derivatives containing sulfonic and carboxylic esters were designed and synthesized. Their ...insecticidal activities against Plutella xylostella, Mythimna separata, and Aedes aegypti larvae and their structure–activity relationship were investigated. The sulfonate-containing isoxazoline derivatives (10k–q) exhibited promising insecticidal activities against the three insect larvae. Compound 10o displayed excellent activities with LC50 values of 8.32, 5.23, and 0.35 μg/mL at 48 h against P. xylostella, M. separata, and A. aegypti larvae, respectively, which were better than or similar to those of avermectin. Furthermore, compound 10o exhibited a faster insecticidal effect than avermectin against M. separata. The mode of action of 10o was preliminarily verified by molecular docking, theoretical calculations, and measurement of glutamate decarboxylase and glutamic pyruvic transaminase activities. Compound 10o is a novel insecticidal candidate acting on GABA receptors, which could guide the discovery of isoxazoline insecticides.
An effective method for the synthesis of furans is developed via a tandem 1,2-acyloxy migration/intramolecular 3 + 2 cycloaddition/aromatization of enol ether-tethered propargylic esters. The ...reaction exhibits excellent functional group tolerance, broad substrate scope, and excellent chemoselectivity. The isolation of dihydrofuran intermediates in some cases gives more insight into the 3 + 2 cycloisomerization process.
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