Indole-diterpenoids from an endophytic Penicillium brefeldianum F4a and their antifeedant and insecticidal activities against Spodoptera frugiperda.

BACKGROUND

Spodoptera frugiperda (Lepidoptera: Noctuidae) is one of the world's major agriculture pests, causing significant crop damage and serious economic losses. As S. frugiperda has developed widespread resistance, environmentally friendly insecticides are urgently needed. Therefore, searching for natural antifeedant or insecticidal lead compounds has become imperative.

RESULTS

Three new indole diterpenoids, paspamine A (1), paspamine B (2), and paspalitrem D (3), along with nine known ones (compounds 4-12), were isolated from an endophytic Penicillium brefeldianum F4a. Their structures were identified through comprehensive spectroscopic data analysis [one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), ultraviolet (UV), infrared (IR)], and electronic circular dichroism (ECD) calculations. Furthermore, plausible biosynthetic pathways of these compounds were deduced. The bioassay results indicated that compound 8 displayed more significant antifeedant activity against S. frugiperda larvae than azadirachtin and compounds 5-7 demonstrated superior insecticidal activities compared to abamectin. Moreover, comparative transcriptome analysis revealed that compound 6 exerted a distinct insecticidal mechanism. In the early stages, it regulated the expression of genes associated with peptidases and chitinases. Subsequently, this regulation influenced the expression of genes related to cuticle proteins and other relevant genes, ultimately resulting in S. frugiperda larval death. These results were further confirmed by real-time quantitative polymerase chain reaction (RT-qPCR) experiments.

CONCLUSION

This research will provide valuable information for the development of indole diterpenoids as novel microbial insecticides for the management of S. frugiperda. © 2025 Society of Chemical Industry.