A Novel Insect Short Neuropeptide sNPF Peptidomimetic Insecticide: Rational Design, Synthesis, and Aphicidal Activity Study

Short neuropeptide F (sNPF) is an insect-specific neuropeptide named for its C-terminal phenylalanine. It consists of 6-19 amino acids with a conserved RLRFa structure, regulating feeding, growth, circadian rhythms, and water-salt balance in insects. Its receptor belongs to GPCR-As and binds sNPF to regulate the insect nervous system. Many research groups are evaluating sNPF for plant protection and pest control. In this study, the natural sNPF from the pea aphid (Acyrthosiphon pisum) was used as a lead compound. Five novel sNPF analogs were designed and synthesized through molecular docking and peptidomimetics, altering the N-terminal amino acid to Ser, Thr, Tyr, Leu, or Gln. Aphid bioassays showed that the analog I-3 (YLRLRFa, LC50 = 1.820 mg/L) was more active than the natural Acypi-sNPF-1 and pymetrozine. The structure-activity relationship analysis indicated that N-terminal tyrosine incorporation, combined with increased ClogP and TPSA, enhanced aphidicidal activity. Furthermore, Toxtree's toxicity predictions suggest a low risk for all compounds, and a toxicity assay conducted on the honeybee (Apis mellifera) for I-3, which exhibits high aphidicidal activity, indicates that I-3 does not pose a toxicity risk to non-target organisms. Thus, I-3 can be utilized as a selective and environmentally friendly insecticide to manage pea aphids.