Chemical Profile and Bioinsecticidal Nanoemulsion of Haplopappus foliosus Essential Oil: Mechanistic Insights into Pest Management Using a Drosophila Model

The increasing demand for sustainable pest management has positioned essential oils (EOs) as viable bio-based alternatives to synthetic pesticides. This study investigates the insecticidal potential of Haplopappus foliosus EO, a Chilean endemic medicinal plant, against Drosophila melanogaster as a key toxicological model for fruit fly control. Chemical characterization identified 56 compounds, with 4-terpineol (27.27%) and α-bisabolol (10.40%) as the primary constituents, marking the first report of α-bisabolol in this species. To enhance bioavailability and overcome EO volatility, a nanoemulsion was developed, achieving an exceptionally small and stable particle size of 2.10 nm that remained consistent for over 90 days. Nanoencapsulation significantly optimized the EO’s efficacy, reducing the median lethal concentration (LC50) from 120.26 µg/mL to a potent 54.57 µg/mL. While in vitro assays showed the free oil as a more potent acetylcholinesterase (AChE) inhibitor, molecular docking confirmed the high affinity of 4-terpineol and α-bisabolol for the enzyme’s active site, elucidating the neurotoxic mechanism at a molecular level. In silico analysis predicted a favorable human safety profile within GHS classes 4 and 5. Overall, this stable nanoformulation represents a sustainable biotechnological strategy for agricultural pest management, leveraging the synergistic effects and enhanced delivery of natural products.