Green Nanonization Strategies for Plant-Derived Small-Molecule Pesticides: Supramolecular Self-Assembly and Natural Polymer Carriers

Plant-derived small-molecule pesticides are renewable and rapidly degradable with low residues, but their poor water solubility, photodegradation, and volatility limit field application. Nanotechnology can improve stability and delivery, yet conventional synthetic or inorganic carriers may increase the costs and ecological risks. Supramolecular self-assembly using active ingredients themselves as building units and biodegradable natural polymer carriers offers two promising green formulation pathways. Aromatic rings, phenolic hydroxyl groups, carbonyl groups, and amino groups in plant metabolites provide a structural basis for the self-assembly. This review summarizes nanonization and self-assembly strategies for phenolics and flavonoids, terpenoids and essential oils, alkaloids, saponins, coumarins, quinones, and sulfur-containing compounds, examining structural features, assembly driving forces, representative examples, and their limitations. The roles of natural polymers are also discussed. Finally, environmental and health benefits, challenges, and future directions are considered, and a structure-guided approach is proposed to integrate green active ingredients with a green delivery.