Construction of oxime ester derivatives of osthole from Cnidium monnieri, and evaluation of their agricultural activities and control efficiency

Pest Manag Sci. 2020 Nov;76(11):3560-3567. doi: 10.1002/ps.6056. Epub 2020 Sep 9.

Abstract

Background: In order to discover natural-product-based pesticidal candidates, a series of coumarin-like derivatives containing oxime ester fragments at the C-8 position were prepared by structural modification of osthole, a natural plant product isolated from Cnidium monnieri. Their pesticidal activities were evaluated against two typically fruit trees/crop-threatening agricultural pests, Mythimna separata Walker and Tetranychus cinnabarinus Boisduval.

Results: Osthole was regioselectively oxidized by selenium dioxide to give the E-isomer, (2'E)-3'-formaldehydylosthole (2). Four key steric structures of 2, (2'E, 4'E)-(o-chloropyrid-3-ylcarbonyl)oximinylosthole (4o), (2'E, 4'E)-(styrylcarbonyl)oximinylosthole (4t), and (2'E, 4'E)-(acetyl)oximinylosthole (4w) were undoubtedly confirmed by X-ray crystallography. Against T. cinnabarinus, it is noteworthy that (2'E, 4'E)-(p-chlorophenylcarbonyl)oximinylosthole (4c) exhibited over three-fold more potent acaricidal activity of the precursor osthole, with especially good control efficiency observed in the glasshouse. Against M. separata, compounds 4c and (2'E, 4'E)-(p-nitrophenylcarbonyl)oximinylosthole (4f) showed the most pronounced growth inhibitory activity. The relationships between their structures and agricultural activities also were studied.

Conclusion: These results demonstrate that compound 4c could be further structurally modified as pesticidal agents. It will lay the foundation for future application of osthole derivatives as pesticides. © 2020 Society of Chemical Industry.

Keywords: agricultural activity; natural product; osthole; oxime esters; structural modification.

MeSH terms

  • Animals
  • Cnidium*
  • Coumarins / pharmacology
  • Molecular Structure
  • Oximes / pharmacology

Substances

  • Coumarins
  • Oximes
  • osthol