Fumigant Toxicity of Oriental Sweetgum (Liquidambar orientalis) and Valerian (Valeriana wallichii) Essential Oils and Their Components, Including Their Acetylcholinesterase Inhibitory Activity, against Japanese Termites (Reticulitermes speratus)

This study investigated the fumigant toxicity of oriental sweetgum (Liquidambar orientalis) and valerian (Valeriana wallichii) essential oils and their components against the Japanese termite (Reticulitermes speratus). The fumigant toxicity of oriental sweetgum and valerian oil differed significantly according to exposure time. Oriental sweetgum showed toxicity at short exposure times (2 days), and the toxicity of valerian oil was high 7 days after treatment. The main constituents of oriental sweetgum and valerian oils were tested individually for their fumigant toxicity against Japanese termites. Among the test compounds, benzyl alcohol, acetophenone, 1-phenyl-1-ethanol, hydrocinnamyl alcohol, trans-cinnamyl aldehyde, trans-cinnamyl alcohol, cis-asarone, styrene, and cis-ocimene showed toxicity against Japanese termites 7 days after treatment. Hydrocinnamyl alcohol and trans-cinnamyl alcohol were found to be the major contributors to the fumigant antitermitic toxicity of oriental sweetgum oil. The acetylcholinesterase (AChE) inhibition activity of two oils and their constituents was tested to determine their mode of action. Only cis-ocimene showed strong AChE inhibition activity with an IC(50) value of 0.131 mg/mL. Further studies are warranted to determine the potential of these essential oils and their constituents as fumigants for termite control.