Determination of Six Pyrazole Fungicides in Grape Wine by Solid-Phase Extraction and Gas Chromatography-Tandem Mass Spectrometry

Design, synthesis, antifungal activity and molecular docking of novel pyrazole-4-carboxamides containing tertiary alcohol and difluoromethyl moiety as potential succinate dehydrogenase inhibitors

BACKGROUND

Resistance problems with the long-term and frequent use of existing fungicides, and the lack of structure diversity of traditional pyrazole-4-carboxamide succinate dehydrogenase inhibitors, it is highly required to design and develop new fungicides to address the resistance issue.

RESULTS

Different from previous pyrazole-4-carboxamide succinate dehydrogenase inhibitors by breaking the norm of difluoromethyl at the C-3 position of pyrazole and introducing a tertiary alcohol group at the C-3 position, 27 novel pyrazole-4-carboxamide derivatives were designed, synthesized and characterized by proton (1 H) nuclear magnetic resonance (NMR), carbon-13 (13 C) NMR, fluorine-19 (19 F) NMR and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The crystal structures of compounds A14 and C5 were analyzed by single crystal X-ray diffraction. Their in vitro antifungal activities were evaluated against phytopathogen Fusarium graminearum, Botrytis cinerea, Phytophthora capsica, Sclerotinia sclerotiorum, Thanatephorus cucumeris. The results displayed that most of them exhibited significant antifungal activities against S. sclerotiorum at 50 mg/L, the half maximal effective concentration (EC50 ) data of A8 and A14 were 3.96 and 2.52 mg/L, respectively. Their in vivo antifungal activities were evaluated against Pseudoperonospora cubensis, Puccinia sorghi Schw, Colletotrichum gloeosporioides, F. graminearum, Erysiphe graminis, Thanatephorus cucumeris, the control efficacies of A6, B3, C3, and C6 against E. graminis reached 100% at a concentration of 400 mg/L. The molecular docking results showed that the binding mode of the target compounds containing tertiary alcohols were similar to that of fluxapyroxad in succinate dehydrogenase. In addition, tertiary alcohols were involved in the formation of hydrogen bonds.

CONCLUSION

The excellent in vitro and in vivo inhibitory activities of novel pyrazole-4-carboxamide derivatives against succinate dehydrogenase were reported for the first time, and they could be used as the potential lead compounds. © 2023 Society of Chemical Industry.

A chemometric strategy to automatically screen selected ion monitoring ions for gas chromatography-mass spectrometry-based pseudotargeted metabolomics

The pseudotargeted metabolomics based on gas chromatography-mass spectrometry (GC-MS) has the advantage of filtering out artifacts originating from sample treatment and accurately quantifying underlying compounds in the analyzed samples. However, this technique faces the problem of selecting high-quality selective ions for performing selected ion monitoring (SIM) on instruments. In this work, we proposed AntDAS-SIMOpt, an automatic untargeted strategy for SIM ion optimization that was accomplished on the basis of an experimental design combined with advanced chemometric algorithms. First, a group of diluted quality control samples was used to screen underlying compounds in samples automatically. Ions in each of the resolved mass spectrum were then evaluated by using the developed algorithms to identify the SIM ion. A Matlab graphical user interface (GUI) was designed to facilitate routine analysis, which can be obtained from http://www.pmdb.org.cn/antdassimopt. The performance of the developed strategy was comprehensively investigated by using standard and complex plant datasets. Results indicated that AntDAS-SIMOpt may be useful for GC-MS-based metabolomics.

Gold-based immunochromatographic strip assay for detecting dimethomorph in vegetables

Gold-based immunochromatographic strip assay for detecting dimethomorph in vegetables.

Determination of fipronil and bixafen pesticides residues using gas chromatography mass spectroscopy with matrix matching calibration strategy after binary dispersive liquid-liquid microextraction

The objective of this study was to determine bixafen and fipronil residues in domestic and industrial wastewater, soil and mint samples by binary dispersive liquid-liquid microextraction method (BDLLME) prior to gas chromatography-mass spectrometry (GC-MS). Extraction efficiency for the selected analytes was improved by optimizing the parameters such as solvent type, ratio and volume, dispersive solvent type/volume, mixing type and duration to increase overall analytical performance. Under the optimum chromatographic and extraction conditions, limits of detection values for bixafen and fipronil were determined as 7.3 and 6.1 µg L^-1, respectively. Spiking experiments were performed for domestic and industrial wastewater, soil and mint samples to evaluate applicability and accuracy of the proposed method. Recovery results for the samples were calculated in the range of 89.4%-112.6% via matrix matching calibration strategy. It was determined that the detection power of GC-MS system was improved 7.8 times for bixafen and 119 times for fipronil over LOD comparisons of conventional GC-MS and B-DLLME-GC-MS systems.

Combined heterologies for monoclonal antibody-based immunoanalysis of fluxapyroxad

Nowadays, instrumental methodologies and rapid bioanalytical techniques complement each other for the analysis of toxic chemical compounds. Fluxapyroxad was commercialized a few years ago as a fungicide and today it is being used worldwide to control a variety of pests. In the present study, the development of monoclonal antibody-based immunochemical methods for the analysis of this chemical in food samples was evaluated for the first time. Novel haptens were synthesized and protein bioconjugates were prepared. High-affinity and specific monoclonal antibodies to fluxapyroxad were generated from two haptens with alternative linker tethering sites. Haptens with linker site heterology and a structurally heterologous hapten with a minor modification of the molecule conformation and volume but with a significant alteration of the electronic density of the pyrazole moiety were evaluated for immunoassay development. Direct and indirect competitive immunoassays were characterized and optimized, showing IC50 values for fluxapyroxad of 0.14 and 0.05 ng mL-1, respectively. The combination of two heterologies was particularly adequate in the indirect format. The two developed immunoassays showed excellent recoveries and coefficients of variation in fluxapyroxad-fortified plums and four varieties of grapes. Finally, a good correlation was found between the indirect immunoassay and UPLC-MS/MS when fruit samples with incurred residues of fluxapyroxad were analyzed. These monoclonal antibody-based immunochemical methods hold great promise for fluxapyroxad monitoring.

Using miniature MS system with automatic blood sampler for preclinical pharmacokinetics study

AIM

Preclinical pharmacokinetic studies are an essential part of modern drug development. In this work, we explored a new solution with onsite analysis using a miniature MS system, which can significantly improve the efficiency of the preclinical study. Materials & methods: A miniature mass spectrometer was used with an automatic blood sampler for onsite quantitation of drug compounds in whole blood samples. Slug-flow microextraction was used to replace the in-lab sample preparation.

RESULTS & CONCLUSION

Animal studies were carried out using two drug compounds, using the auto sampler to take blood samples at preprogrammed time points. The miniature MS system was used to obtain drug concentrations, which were subsequently used to calculate the pharmacokinetic parameters.

Detection of Pesticide Residues in Food Using Surface-Enhanced Raman Spectroscopy: A Review

Pesticides directly pollute the environment and contaminate foods ultimately being absorbed by the human body. Their residues contain highly toxic substances that have been found to cause serious problems to human health even at very low concentrations. The gold standard method, gas/liquid chromatography combined with mass spectroscopy, has been widely used for the detection of pesticide residues. However, these methods have some drawbacks such as complicated pretreatment and cleanup steps. Recent technological advancements of surface-enhanced Raman spectroscopy (SERS) have promoted the creation of alternative detection techniques. SERS is a useful detection tool with ultrasensitivity and simpler protocols. Present SERS-based pesticide residue detection often uses standard solutions of target analytes in conjunction with theoretical Raman spectra calculated by density functional theory (DFT) and actual Raman spectra detected by SERS. SERS is quite a promising technique for the direct detection of pesticides at trace levels in liquid samples or on the surface of solid samples following simple extraction to increase the concentration of analytes. In this review, we highlight recent studies on SERS-based pesticide detection, including SERS for pesticide standard solution detection and for pesticides in/on food samples. Moreover, in-depth analysis of pesticide chemical structures, structural alteration during food processing, interaction with SERS substrates, and selection of SERS-active substrates is involved.

Fast Quantitation of Pyrazole Fungicides in Wine by Ambient Ionization Mass Spectrometry

Fungicides are widely used for growing the grapes that are used for making wines. Chromatography coupled with tandem mass spectrometry is usually time and labor consuming for quantitation of fungicides in wines. In this work, a simple ambient mass spectrometry method using paper capillary spray was developed for the fast quantitation of four pyrazole fungicides in wines. Direct analysis of the wine samples was achieved without any sample preparation, obtaining limits of quantitation as low as 2 ng/mL for all four pyrazole fungicides. Quality control experiments also showed adequate accuracy and precision for the analysis of pyrazole fungicides in wine products.