Determination and dissipation of fipronil and its metabolites in/on sugarcane crop

Fipronil has label claim for managing shoot borer and root borer of sugarcane. The dissipation and metabolism of fipronil in/on sugarcane crop have been studied under tropical field condition by employing a modified quick, easy, cheap, effective, rugged and safe sample preparation method and gas chromatography equipped with electron capture detector. The method could provide 90.27–98.97% recoveries of target analytes from cane leaves and stem with relative standard deviations of less than 5%. The sulphide, desulfinyl and sulfone metabolites of fipronil were detected along with the parent compound even in the 0-day samples of sugarcane leaves and stem collected 2 h post-foliar spraying. The total residues comprising fipronil and its three major metabolites got dissipated to 4.366 µg/g from the initial deposit of 12.977 µg/g within a day after foliar spray. Fipronil sulphide and fipronil desulfinyl were the major metabolites on sugarcane crop. The residues (both parent compound and total residues) reached below the detectable level of 0.005 µg/g on 7 and 15 days after treatment on stem and leaves, respectively. Half-life of fipronil was less than a day on sugarcane crop. The total residues had the half-life of 1.66 and 0.91 days on leaves and stem, respectively.     

Photomineralization of phenol on Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: synergistic photocatalysis by semiconductors

Phenol gets adsorbed on Al₂O₃ and mineralizes under UV light in the presence of dissolved O₂. The degradation exhibits first-order kinetics and its rate increases linearly with the light intensity and decreases with pH. 2,4-Diphenoxycyclohexanone and 2,6-diphenoxycyclohex-3-ene-1-ol are the intermediates of the reaction. While particulate TiO₂, ZnO, ZnS, Fe₂O₃, CuO, CdO, and Nb₂O₅ individually photocatalyze the degradation, each semiconductor exhibits synergistic photocatalysis, an enhanced photodegradation, when present along with Al₂O₃, indicating electron abstraction by illuminated semiconductors from the phenol adsorbed on Al₂O₃.     

Synthesis, complete NMR spectral assignments, and antifungal screening of new 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one oxime derivatives

Abstract  

A series of differently substituted 2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one oximes have been synthesized and their ¹H and ¹³C NMR chemical shifts have been unambiguously assigned using H,H-COSY, NOESY, HSQC, and HMBC spectral data. On the basis of the NMR studies, irrespective of the nature and position of the substituents, all reported compounds exist in twin-chair conformation with equatorial disposition of the phenyl groups at C-2 and C-4 of the 3-azabicyclononane moiety. Among the synthesized oxime derivatives, compounds with halo-substituents at ortho/para positions of the phenyl showed good antifungal profile against all tested organisms.     

The Impact of Wireless Sensor Network in the Field of Precision Agriculture: A Review

Wireless Personal Communications - Precision agriculture (PA) is an interdisciplinary concept of integrating information technology in agriculture to increase the production and quality of the...     

Electrochemical Detection of Alloxan on Reduced Graphene Oxide Modified Glassy Carbon Electrode

Alloxan is a toxic reagent that strongly induces the diabetes by destroying insulin‐producing β‐cells in the pancreas of living organisms. The reduction product of alloxan is dialuric acid, which is responsible for the intracellular generation of ROS to enhance the stress in living cells to cause kidney disease or diabetic nephropathy. Herein, we studied for the first time the electrochemical properties of alloxan on reduced graphene oxide modified glassy carbon electrode (rGO/GCE) in 0.1 M phosphate buffer solution (PBS) at pH 7. The obtained results were compared with graphene oxide modified GCE (GO/GCE) and bare GCE surfaces. The modified rGO/GCE showed well defined redox couple with 10 fold increase in both reduction as well as oxidation peak current for alloxan than that of GO/GCE and bare GCE. Differential pulse voltammetry (DPV) technique shows the linear increase in both oxidation and reduction peak current of alloxan in the range of 30 μM to 3 mM with LOD of 1.2 μM. An amperometric signal of alloxan is also increases with respect to each addition of 50 μM of alloxan on rGO/GCE at constant potential of ?0.05 V. The linear range of alloxan is observed between 50 μM to 750 μM (S/N=3). This kind of rGO/GCE surface is more suitable platform or sensor matrix for estimating unknown concentration of alloxan molecule in the real biological systems.     

Antigonon leptopus: a potent biological source for extermination of fish bacterial pathogens Providencia and Aeromonas

This study pertains to the phytochemical components and the biological properties of the weed, Antigonon leptopus Hook. & Arn. (AUT/PUS/064). Phytochemical screening of methanolic leaf extract of A. leptopus revealed the presence of saponin, phenolic compounds, tannins, flavonoids, alkaloids, fixed oils and amino acids. Accordingly, 12 phytochemical components were analysed and characterised by GC–MS. Antibacterial activity was evaluated against fish and clinical pathogens. Fish pathogens, Providencia vermicola (MTCC 5578) and Aeromonas hydrophila (MTCC 646) were more sensitive to the methanolic leaf extract than clinical pathogens. A useful information was obtained from the phytochemistry of A. leptopus leaves, which would pave way to further applications to treat fish diseases and for utility in the pharmaceutical field.     

Simultaneous determination of tebuconazole,trifloxystrobin, and its metabolite trifloxystrobin acid residues in gherkin under field conditions

A rapid, simple, and selective analytical method for the simultaneous determination of tebuconazole, trifloxystrobin, and its metabolite trifloxystrobin acid residues in gherkin and soil was developed and validated by gas chromatography coupled with mass spectrometry. The samples were extracted with acetonitrile and cleaned up by dispersive solid‐phase extraction with primary secondary amine sorbent. The limit of quantification of the method was 0.05 mg/kg for all three compounds. The method was validated using blank samples spiked at three levels and recoveries ranged from 83.5 to 103.8% with a relative standard deviation of 1.2 to 4.8%. The developed method was validated and applied for the analysis of a degradation study sample. The residues of trifloxystrobin and tebuconazole were found to dissipate following first‐order kinetics with half‐life ranging between 3.31–3.38 and 3.0–3.04 days, respectively, for two different dosages. Pesticide residues were below the European Union maximum residue level after seven days for trifloxystrobin (0.2 mg/kg) and ten days for tebuconazole (0.05 mg/kg), which suggested the use of this fungicide mixture to be safe to humans. These results can be utilized in formulating the spray schedule and safety evaluation on trifloxystrobin and tebuconazole in gherkin crop.     

Synthesis and stereochemistry of highly crowded N-benzylpiperidones

A series of N-benzylated 3,5-diakyl-2,6-diarylpiperidin-4-ones 4–8 were conveniently synthesized in significant yields of 68–88% by N-benzylation of the corresponding 2,6-diaryl-3,5-dimethylpiperidin-4-ones 1–3 using different benzyl bromides. Initially, the new piperidone 2,6-bis(4-ethoxyphenyl)-3,5-dimethylpiperidin-4-one 3 was synthesized by the condensation of 1:1:2 M ratio of 3-pentanone, ammonium acetate and para-ethoxybenzaldehyde in ethanolic medium. All the synthesized new compounds 3–8 were characterized by their analytical and spectral (IR, ¹H and ¹³C NMR) interpretations. The stereochemistry of the new piperidone 3 was elucidated as chair conformation with an equatorial orientation of all substituents, suggested by its vicinal couplings from ¹H NMR spectrum. To investigate the impact on piperidone stereochemistry as well as NMR chemical shifts, all the N-benzylated products 4–8 were compared with their corresponding precursors, and as a result, it is clearly established that all the synthesized N-benzyl piperidones exist in the chair conformation with an equatorial orientation of all the substituents at C-2, C-3, C-5, C-6 and N. Contrary to the probability all N-benzylated compounds retain the same conformation and configuration as their precursors, however, a remarkable change on the chemical shifts are observed. For the further unambiguous confirmation of stereochemistry, the 1-benzyl-3,5-dimethyl-2,6-diphenylpiperidin-4-one 4 was examined by single-crystal X-ray diffraction. The compound 4, C₂₆H₂₇NO, crystallized in a P-1 space group under triclinic system with unit cell dimensions a, b, c (Å) and α, β, γ (°) of 10.156(2), 11.002(2), 11.348(4) and 116.74(4), 100.81(3), 100.17(3), respectively.     

BF3·SiO2 is a simple and efficient Lewis acid catalyst for the one-pot synthesis of polyfunctionalized piperidin-4-ones

Abstract  

A range of Lewis acid catalysts were used for a series of one-pot multi-component reactions. Of them, silica-supported boron trifluoride (BF₃·SiO₂) was found to be an effective catalyst for the promotion of the modified Mannich condensation of ketones, aldehydes, and ammonium acetate in 1:2:1 molar ratio to afford 3,5-dialkyl-2,6-diarylpiperidin-4-ones in high yields of 80–92%. Also this simple, easily prepared, and reusable catalyst executed the condensation very effectively in a significantly shorter reaction duration (about 1–4 h) than the conventional method, which requires 1 day or more and involves a tedious work-up procedure. Further, this protocol ensures the stereospecificity; accordingly, all the synthesized piperidones adopted a chair conformation with an equatorial orientation of all substituents at C-2, C-3, C-5, and C-6.