Program

PO2-12-2

Behavioral pharmacology of plant-derived substances (29): Identification of active constituents of Thyme and tea tree essential oils that promote mouse ambulation

[Speaker] Toyoshi Umezu:1
[Co-author] Tomoharu Sano:2, Junko Hayashi:2, Yasuko Yoshikawa:2
1:Center for Health and Environmental Risk Research, National Institute for Environmental Studies, Japan, 2:Center for Environmental Measurement and Analysis, National Institute for Environmental Studies, Japan

Background: Use of various plant-derived essential oils (EOs) for the treatment of mental illnesses have traditionally been practiced for long time. EOs are mixtures of volatile organic chemicals (VOCs). As VOCs are basically small molecular weights and lipophilic, VOCs are supposed to pass blood-brain barrier and influence central nervous system (CNS) functions. Previous studies have shown that various kinds of EOs and the constituents of EOs produce a variety of behavioral and/or CNS effects after inhalation or peripheral administrations. Thyme is a well-known herb. Tea tree is endemic to Australia and has been used as a traditional medicine. Thyme and tea tree essential oils (THY and TEA, respectively) promote mouse ambulation as well as psychostimulants. This study aimed to identify active constituents for the ambulatory effect of THY and TEA.
Methods: THY and TEA were analyzed using GC/MS. Authentic standards were also analyzed using GC/MS under the same conditions. When the retention time on the total ion chromatogram and the mass spectrum of an authentic standard was identical to one peak in THY or TEA, it was concluded that the peak of THY or TEA was identified to the authentic standard. Ambulatory activity of mouse was measured using a tilt-type ambulometer. After the 30-min adaptation period, doses of THY, TEA, doses of each of identified constituents were administered to mice, and ambulatory activity was continuously measured for 60 min.
Results: GC/MS analyses showed that THY contained 16 kinds of compounds and TEA contained 12 kinds of compounds. By comparing with authentic standards, 13 kinds of compounds including linalool, terpinen-4-ol, alpha-pinene, myrcene, p-cymene, gamma-terpinene were identified as THY constituents. Six kinds of compounds including p-cymene, cineol, gamma-terpinene and terpinen-4-ol were identified as TEA constituents. Effects of these identified constituents on mouse ambulation were examined. Some of the constituents significantly promoted mouse ambulation.
Conclusion: Active constituents for the ambulatory effects of THY and TEA were identified. These constituents probably possess CNS acting effects.
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