Chitosan nanoparticles loaded with Cosmos bipinnatus essential oil for sustainable management of plant parasitic nematodes

The sustainable management of plant-parasitic nematodes is a growing concern in agriculture due to the limitations of synthetic nematicides, such as environmental toxicity and resistance development. This study reports, for the first time, the encapsulation of Cosmos bipinnatus essential oil (CAO) into chitosan nanoparticles (CSNPs) for nematicidal application against Meloidogyne incognita. GC-MS analysis identified cis-β-ocimene, cosmene, germacrene D, sabinene, and β-pinene as the dominant constituents. The resulting CSNPs exhibited favourable physicochemical characteristics (mean diameter: 91.2 nm; encapsulation efficiency: 83%) and a pH-responsive controlled release profile. In vitro assays revealed that at the highest concentration (1000 µg/mL), CSNPs demonstrated significantly higher nematode mortality (100%) and egg hatching inhibition (100%) than CAO (77% mortality and 89.04% egg hatching inhibition) and comparable to the commercial nematicide Nimitz at 96 h. Enhanced acetylcholinesterase (AChE) inhibition by CSNPs (IC₅₀ = 16.14 ± 0.05 µg/mL) was observed, with IC₅₀ value approaching that of the standard physostigmine (IC₅₀ = 8.57 ± 0.08 µg/mL). Docking studies confirmed favorable interactions of germacrene D (- 6.8 kcal/mol), sabinene (-6.3 kcal/mol), caryophyllene (- 6.2 kcal/mol), β-pinene - 6.1 kcal/mol), and endo-arbozol (- 5.6 kcal/mol) with AChE's active site, suggesting a neurotoxic mode of action.The study also evaluated ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) properties of major terpenoids, confirming favorable pharmacokinetic profiles for potential agrochemical development. These results highlight the efficacy and mechanistic relevance of chitosan-based nanoformulations of C. bipinnatus EO as a promising biopesticide alternative for integrated nematode control.