Toxicities of 4,5-Dihydroisoxazoles Against Root-Knot Nematodes and in Silico Studies of Their Modes of Action

N-Phenylnorbornenesuccinimide derivatives, agricultural defensive, and enzymatic target selection

BACKGROUND

Faced with the need to develop new herbicides with modes of action different to those observed for existing agrochemicals, one of the most promising strategies employed by synthetic chemists involves the structural modification of molecules found in natural products. Molecules containing amides, imides, and epoxides as functional groups are prevalent in nature and find extensive application in synthesizing more intricate compounds due to their biological properties. In this context, this paper delineates the synthesis of N-phenylnorbornenesuccinimide derivatives, conducts biological assays, and carries out in silico investigation of the protein target associated with the most potent compound in plant organisms. The phytotoxic effects of the synthesized compounds (2-29) were evaluated on Allium cepa, Bidens pilosa, Cucumis sativus, Sorghum bicolor, and Solanum lycopersicum.

RESULTS

Reaction of endo-bicyclo[2.2.1]hept-5-ene-3a,7a-dicarboxylic anhydride (1) with aromatic amines led to the N-phenylnorbornenesuccinic acids (2-11) with yields ranging from 75% to 90%. Cyclization of compounds (2-11) in the presence of acetic anhydride and sodium acetate afforded N-phenylnorbornenesuccinimides (12-20) with yields varying from 65% to 89%. Those imides were then subjected to epoxidation reaction to afford N-phenylepoxynorbornanesuccimides (21-29) with yields from 60% to 90%. All compounds inhibited the growth of seedlings of the plants evaluated. Substance 23 was the most active against the plants tested, inhibiting 100% the growth of all species in all concentrations. Cyclophilin was found to be the enzymatic target of compound 23.

CONCLUSION

These findings suggest that derivatives of N-phenylnorbornenesuccinimide are promising compounds in the quest for more selective and stable agrochemicals. This perspective reinforces the significance of these derivatives as potential innovative herbicides and emphasizes the importance of further exploring their biological activity on weeds. © 2024 Society of Chemical Industry.

Ethyl Butanoate, Constituent of Cassava Wastewater Volatiloma, a Potential Soil Fumigant Against Meloidogyne javanica

As a result of more restrictive legislation regarding the use of pesticides, over the last two decades, the demand for new soil fumigants has increased. These compounds can come from a variety of sources, including organic residues. In this study, we identified in the cassava wastewater volatiloma a molecule with potential to be developed as a new fumigant nematicide. Cassava wastewater (20 mL) releases volatile compounds toxic to Meloidogyne javanica second-stage juveniles (J2), causing J2 mortality up to 89%. Through gas chromatography–mass spectrometry, eight compounds were identified in the cassava wastewater volatiloma, with alcohols being the major class. The compounds ethyl butanoate and butyric acid identified in cassava wastewater volatiloma were selected for in vitro nematicidal activities and substrate fumigation tests. The lethal concentration predicted LC50–48 hr values (effective doses to kill 50% of M. javanica J2 population after 48 h of exposure) were 172.6 μg ∙ mL - 1 and 301.2 μg ∙ mL - 1 for butyric acid and ethyl butanoate, respectively. In a pot assay, the application of butyric acid and ethyl butanoate as a soil fumigant, at a dose of 0.5 mL ∙ kg - 1 substrate, significantly (P < 0.05) decreased M. javanica infectivity and reproduction compared to the negative control (water). However, ethyl butanoate proved to be a more efficient soil fumigant (P < 0.05) than butyric acid, as its application reduced the number of galls and eggs to the level of the commercial fumigant Dazomet. This study is the first to demonstrate the potential of ethyl butanoate as a soil fumigant against M. javanica.

Synthesis and Biological Activity of 2-(2-Amino-2-phenylethyl)-5-oxotetrahydrofuran-2-carboxylic Acid: A Microwave-Assisted 1,3-Dipolar Cycloaddition Approach

The microwave-assisted 1,3-dipolar cycloaddition of furanyl and benzyl oximes and several methyl acrylates effectively provided several isoxazoline when mediated by diacetoxyiodobenzene. The selected isoxazoline, methyl-5-(3-methoxy-3-oxopropyl)-3-phenyl-4,5-dihydro isoxazole-5-carboxylate, was rapidly transformed to the γ-lactone carboxylic acid, 2-(2-amino-2-phenylethyl)-5-oxotetrahydrofuran-2-carboxylic acid, in reasonable yield. The biological activity of this γ-lactone carboxylic acid increased the growth of E. coli organisms by about 44% and has a potential significance in stem cell research.

Lignin-Modified Electronegative Epoxy Resin Nanocarriers Effectively Deliver Pesticides against Plant Root-Knot Nematodes (Meloidogyne incognita)

It is highly desirable to fabricate a pesticide delivery system with excellent permeability to reduce the damage caused by root-knot nematodes in the soil. In this work, a novel electronegative pesticide nanocarrier was established by bonding anionic lignosulfonate with epoxy resin nanocarriers, which were loaded with abamectin (Aba). The results demonstrated that nanoparticles were negatively charged (-38.4 mV) spheres with an average size of 150 nm, and the encapsulation efficiency of nanocarriers for Aba was 93.4%. Polymer nanocarriers could prevent premature release of Aba and protect active ingredients from microbiological degradation. The adsorption strength of the soil to Aba loaded in nanocarriers was reduced by 6 to 10 times, so nanonematicides have remarkable soil mobility. Meanwhile, nanoparticles could easily penetrate the roots and nematodes. The application test confirmed that the control effect of this nanopesticide was 26-40% higher than that of the other agrochemicals. In consideration of its superior bioactivity and utilization rate, this pesticide delivery system has promising potential to control root-knot nematodes and improve the pesticide's utilization efficiency.

Chemical Nematicides: Recent Research Progress and Outlook

Plant-parasitic nematodes have caused huge economic losses to agriculture worldwide and seriously threaten the sustainable development of modern agriculture. Chemical nematicides are still the most effective means to manage nematodes. However, the long-term use of organophosphorus and carbamate nematicides has led to a lack of field control efficacy and increased nematode resistance. To meet the huge market demand and slow the growth of resistance, new nematicides are needed to enter the market. The rational design and synthesis of new chemical scaffolds to screen for new nematicides is still a difficult task. We reviewed the latest research progress of nematicidal compounds in the past decade, discussed the structure-activity relationship and mechanism of action, and recommended some nematicidal active fragments. It is hoped that this review can update the recent progress on nematicide discoveries and provide new ideas for the design and mechanism of action studies of nematicides.

Nematicidal Effect of Methyl Palmitate and Methyl Stearate against Meloidogyne incognita in Bananas

Banana plants (Musa spp.) are susceptible to infection by many plant-parasitic nematodes, including Meloidogyne incognita. In this study, a mixed fermentation broth of chicken manure (CM) and cassava ethanol wastewater (CEW) was used to inhibit M. incognita by reducing egg hatching and by having a lethal effect on second-stage juvenile nematodes (J2s). It also alleviated nematode damage and promoted banana plant growth. Using gas chromatography-mass spectrometry (GC-MS), we identified methyl palmitate and methyl stearate as bioactive compounds. These bioactive compounds repelled J2s and inhibited egg hatching; reduced root galls, egg masses, and nematodes in soil; and downregulated the essential parasitic nematode genes Mi-flp-18 and 16D10. A Caenorhabditis elegans offspring assay showed that low concentrations of the fermentation broth, methyl palmitate, and methyl stearate were safe for its life cycle. This study explored the effective and environmentally safe strategies for controlling root-knot nematodes.