Exploring the Insecticidal Potential of Boldo () Essential Oil: Toxicity to Pests and Vectors and Non-target Impact on the Microcrustacean .

Every year Chile exports about 2000 tons of boldo folium (), which is used around the world as a traditional herbal medicinal product (THMP), mostly to relieve gastrointestinal disorders. This biomass may be a resource for the agrochemical industry to manufacture botanical insecticides. In this regard, the insecticidal potential of boldo has been poorly investigated. In the present work, hydrodistillation of a commercial boldo folium gave 1.5% (/) of a yellowish essential oil (boldo essential oil, BEO) containing 1,8-cineole (20.7%), -cymene (18.5%), limonene (9.1%), ascaridole (9.1%) and β-phellandrene (6.4%) as the main constituents, as determined by gas chromatography-mass spectrometry (GC-MS). NMR analysis allowed us to determine that ascaridole was mainly represented by the -isomer. BEO was toxic to larvae of the filariasis vector and adults of the housefly , showing LC/LD values of 67.9 mgL and 98.5 µgadult, respectively. On the other hand, lower insecticidal activity was observed against larvae of the moth pest (LD of 268.9 µglarva). It is worth noting that, when tested at LC concentration, BEO was significantly less toxic to aquatic microcrustacean than the conventional insecticide α-cypermethrin. Finally, in the attempt to explore the BEO mode of action, we tested it for acetylcholinesterase (AChE) inhibitory properties using the Ellman method, obtaining negligible effects (IC = 0.45 mg·mL). Taken together, these results gave new insights into the potential of BEO as a future ingredient of botanical insecticides.