Organized Meeting
Junho Yoon
Ph.D. Candidate
Seoul National University
Seoul, Seoul-t'ukpyolsi, Republic of Korea
Jun-Hyung Tak
Assistant Professor
Seoul National University
Seoul, Seoul-t'ukpyolsi, Republic of Korea
To reduce the chemical input in pest management practices, the use of synergists has been widely explored. Among them, plant essential oils have been acknowledged for their insecticidal activities, but also as the synergist conventional insecticides. However, the mechanism by which essential oils synergize the respiratory blocker, chlorfenapyr, have not been explored. In this study, electrophysiological screenings on the larval central motor nerves of Drosophila melanogaster and Musca domestica were conducted to identify the potential neuroactive essential oil constituents. Among them, thymol and eugenol (31.1% and 87.2% in thyme and clove bud oils) were inhibitory to nerve firing rate, while t-cinnamaldehyde and terpinen-4-ol (74.6% and 52.0% in cinnamon and teatree oil) were excitatory. The neuronal effects were further confirmed by behavioral assays. Meanwhile, the synergy was only observed in neuroinhibitory compounds, which boosted the ATP depletion induced by chlorfenapyr. However, along with conventional insecticides permethrin and chlorpyrifos, the neuroinhibitory compounds were rather antagonistic to chlorfenapyr and displayed nullifying effects on ATP depletion. Finally, the quantified amount of depleted ATP was artificially injected into the synergistic group (thymol or eugenol + chlorfenapyr). When ATP was compensated, the synergistic interaction was diminished, indicating the bioenergetic effects of neuroinhibitors are responsible for their synergistic interactions.