Environmentally‐Friendly Pesticidal Activities ofCallicarpaandKaromiaEssential Oils from Vietnam and Their Microemulsions

Abstract

AbstractThere is an ongoing interest to identify alternative pesticidal agents to avoid the chronic problems associated with synthetic pesticides. Essential oils have shown promise as botanical pest control agents. In the present study, the essential oils of four members of the Lamiaceae (Callicarpa candicans,C. erioclona,C. macrophylla, andKaromia fragrans; Vietnamese names: Nàng nàng, Tu châu lông mem, Tu châu lá to and Cà diện, respectively), obtained from wild populations in Vietnam, have been obtained by hydrodistillation and analyzed by gas chromatography‐mass spectrometry. The essential oils were formulated into microemulsions and the essential oils and their microemulsions were screened for mosquito larvicidal activity againstAedes aegypti,Aedes albopictus,Culex quinquefasciatus, and for molluscicidal activity againstPomacea canaliculata. Atractylone and (E)‐caryophyllene dominated the volatiles ofC. candicans(CCEO) andC. erioclona(CEEO), while the major component inC. macrophylla(CMEO) andK. fragrans(KFEO) was (E)‐caryophyllene. The essential oils and microemulsions of bothC. candicansandC. erioclonaexhibited excellent larvicidal activity against all three mosquito species (Ae. aegypti,Ae. albopictus, andCx. quinquefasciatus) with LC50values <10 μg/mL. Additionally, the larvicidal activity of the microemulsions were significantly improved compared with their free essential oils, especially forC. candicansandC. erioclona. All four essential oils and their microemulsions showed excellent molluscicidal activity with LC50<10 μg/mL. In most cases, the essential oils and microemulsions showed greater pesticidal activity against target organisms than the non‐target freshwater fish,Oreochromis niloticus. Thein silicostudies on physicochemical and ADMET properties of the major components in the studied essential oils were also investigated and most of the compounds possessed a favorable ADMET profile. Computational modeling studies of the studied compounds demonstrated a favorable binding interaction with the mosquito odorant‐binding protein target and support atractylone, β‐selinene, and caryophyllene oxide as potential inhibitors. Based on the observed pesticidal activities of the essential oils and their microemulsions, theCallicarpaspecies andK. fragransshould be considered for potential cultivation and further exploration as botanical pesticidal agents.