Biocidal Valorization of Essential Oils and Hydrolate-Derived Extracts from a Domesticated Spanish Satureja montana: Chemical Composition, Nematicidal, Ixodicidal and Insect Antifeedant Activities

The domestication of aromatic plants and the valorization of distillation by-products offer promising strategies for the development of sustainable botanical pesticides. This study evaluated the chemical composition and biocidal activities of essential oils (EOs) and hydrolate-derived extracts obtained from mother (CMSAMO1) and domesticated (SAMO1) populations of Satureja montana selected from Spanish germplasm. Chemical characterization by GC-MS revealed carvacrol and thymol as the dominant constituents in EOs and dichloromethane-extracted hydrolate organic fractions (WRD), while an activated-charcoal hydrolate extract was enriched in thymoquinone (WRC). Biological activities were assessed against the root-knot nematode Meloidogyne javanica, the tick Hyalomma lusitanicum, and the insect pests Spodoptera littoralis and Myzus persicae. All extracts showed strong nematicidal activity, with LD50 values ranging from 0.079 to 0.323 μg μL−1, and significantly reduced nematode reproduction in tomato plants under greenhouse conditions. Hydrolate-derived fractions displayed sustained inhibition of egg hatching compared with EOs. Against H. lusitanicum, extracts from the domesticated population were more active than those from the mother plant, with the WRD fraction exhibiting the highest ixodicidal activity and persistent repellency. Antifeedant assays revealed stronger effects against M. persicae than S. littoralis, particularly for hydrolate-derived fractions. Carvacrol, thymol, and thymoquinone were identified as the principal bioactive metabolites, with principal component analysis confirming their association with biological activity. Cytotoxicity assays demonstrated a favorable selectivity of carvacrol and thymol toward tick cells. These findings demonstrate that S. montana domestication and hydrolate valorization enhance the production of chemically stable, bioactive extracts suitable for sustainable biopesticide development within circular-economy frameworks.