Synthesis, biological evaluation and molecular docking of novel nereistoxin derivatives containing phosphonates as insecticidal/AChE inhibitory agents

Abstract

In continuation of our program aimed at the discovery and development of natural product-based insecticidal agents, a series of novel nereistoxin derivatives containing phosphonate were synthesized and characterized by ³¹P, ¹H, ¹³C NMR and HRMS. The bioactivities of the derivatives were evaluated for the acetylcholinesterase (AChE) inhibition potency and insecticidal activity. The AChE inhibitory effects of the derivatives were investigated using the in vitro Ellman method. Half of the compounds exhibited excellent inhibition of AChE. All the compounds were assessed for insecticidal activities against Mythimna separate (Walker) and Rhopalosiphum padi in vivo. Some derivatives displayed promising insecticidal activity against Rhopalosiphum padi. Compounds 5b and 6a displayed the highest activity against R. padi, showing LC₅₀ values of 17.14 and 18.28 μg mL⁻¹, respectively, close to that of commercial insecticide flunicotamid (LC₅₀ = 17.13 μg mL⁻¹). Compound 9g also showed notable insecticidal activity, with an LC₅₀ value of 23.98 μg mL⁻¹. Additionally, the binding modes of the active compounds 5b, 6a and 9g with AChE were analyzed in-depth though molecular docking and the intrinsic reasons for the differences in the strength of the compound's activities were elucidated. In summary, our findings demonstrate the potential of these nereistoxin derivatives as promising candidates for the development of novel pesticides.