Mouse brain concentrations of α‐pinene, limonene, linalool, and 1,8‐cineole following inhalation

The main volatile components of essential oils are monoterpenes. It is known that olfactory receptors recognize monoterpenes as a fragrance, and that they can affect emotions. On the other hand, the components of essential oils may act directly on the central nervous system as well as the olfactory nerve. However, the transport of monoterpenes to the brain following inhalation, which is the main method of administration in aromatherapy, is unclear. In this study, we investigated major monoterpenes of essential oils, such as (+)-α-pinene, (+)-limonene, (-)-linalool, and 1,8-cineole. After the inhalation of each compound, the mice brains were dissected, and brain extracts prepared with n-hexane. The extracts were then subjected to gas chromatography-mass spectrometry analysis. The results revealed that α-pinene was transported to the brain maximally with 30 min inhalation, which may be due to its high volatility. Limonene and linalool showed maximal transport to the brain with 90 min inhalation. Brain concentrations of 1,8-cineole showed minimal level after 30 min inhalation. Moreover, 1,8-cineole was easily transported to the brain following intraperitoneal administration. These results could be applied as one of the indices for the effective use of essential oils in aromatherapy. Copyright © 2016 John Wiley & Sons, Ltd.