Salicylic acid functionalized chitosan nanocomposite increases bioactive components and insect resistance of Agastache rugosa

The abundance of monoterpenoids and phenolic compounds determines the medicinal quality and anti-insect properties of Agastache rugosa , which can be compromised by biotic stress such as herbivore attacks. The traditional use of chemical pesticides to mitigate herbivore interference is increasingly incompatible with sustainable agriculture. In response, nanotechnology-based biostimulants, which can activate metabolic processes to enhance plant growth and stress resistance, offer a more cost-effective and environmentally-friendly alternative. However, to date, it remains unknown how nano-biostimulants improve the therapeutic value and insect resistance of medicinal plants simultaneously. This study investigates the effect of 0–1000 mg/L of a nano-biostimulant salicylic acid functionalized chitosan nanocomposite (SCN) on the pharmacological and anti-herbivore properties of medicinal plant A. rugosa . Results showed that 100 mg/L SCN significantly inhibited Spodoptera litura growth by 62.9 %, and increased plant shoot and root biomass by 107.2 % and 77.6 %, respectively. Moreover, 100 mg/L SCN significantly upregulated the expression of the key genes ( e.g. , LS , L3OH , and CHS ) involved in monoterpene and phenolic compounds biosynthesis by 1.4–10.1 folds, thus boosting the production of active compounds such as pulegone, β-myrcene, and chlorogenic acid by 1.5–24.4 folds. These enhancements were superior to salicylic acid or chitosan alone. Altogether, our findings promote the sustainable and eco-friendly application of nano-biostimulant in improving the quality of medicinal plants and green pest control in agroecosystems.