Insecticidal activity and biochemical responses of novel natural pyrethroid derivatives from pyrethrum residues

Plant-derived substances have long been valued as eco-friendly pesticides, with pyrethrum flowers recognized for their insecticidal properties since the nineteenth century. Over time, pyrethrum extracts became widely adopted as a natural, effective, and relatively safe green pesticide. However, the high production costs of these natural compounds prompted the development of synthetic pyrethroids, such as cypermethrin, which dominate the market today. While these synthetic alternatives offer effectiveness in pest control, they also present environmental concerns, such as pest resistance and toxicity to aquatic organisms. This has led some countries to continue using natural pyrethrins, resulting in large amounts of pyrethrum residue waste. In response to the need for sustainable solutions, we focused on repurposing these residues by isolating and evaluating 11 pyrethroid-related compounds. Among them, pyrethrindreg II, first isolated from natural sources, exhibited the highest insecticidal activity. Morphological observation and molecular docking revealed that pyrethrindreg II acts as a promising voltage-gated sodium channel (VGSC) inhibitor. The quantification of esterase-β, esterase-α, and GST concentrations explains the biochemical responses of pyrethrindreg II in Armigeres subalbatus. Density functional theory (DFT) calculations provide insight into its relatively weaker activity compared to the positive control, cypermethrin. Pyrethrindreg II exhibited significantly lower toxicity, indicating its potential as a safer, greener alternative to synthetic pyrethroids.