No abstract

The composition of steam-distilled essential oils from the leaves of Alpinia zerumbet (Pers.) B. L. Burtt. et R. M. Sm. cultivated in Okinawa Island was investigated by GC-MS analysis. The seasonal variation of the main volatile constituents was also investigated. Analysis of the essential oil identified 17 compounds. It showed the predominant presence of monoterpenic constituents, representing 95% of the essential oil. p-Cymene was the most abundant compound, followed by 1,8-cineole, terpinen-4-ol, alpha-pinene, beta-pinene and limonene. The amount of sesqiterpenic content of the essential oil was small, mostly represented by beta-caryophyllene and alpha-caryophyllene. One of the phenylpropanoid derivatives, methyl cinnamate, was also detected. The essential oils from the leaves collected at ten different collection periods for over 5 years showed significant differences in their compositions. p-Cymene, terpinen-4-ol and 1,8-cineole were the most predominant constituents over the periods with a few exceptions. The content rates of p-cymene were abundant in summer, still high in late autumn and early winter, and decreased in mid-winter and early spring. In contrast, the contents of terpinen-4-ol and 1,8-cineole were high in winter, but decreased around summer. On enantiomeric distribution, terpinen-4-ol and alpha-pinene were suggested to relate to seasonal transformation. (+)-Terpinen-4-ol had a tendency to decrease in high temperatures and huge precipitations. It was also suggested that (-)-alpha-pinene was more sensitive to climate change than (+)-alpha-pinene.

The use of essential oils is common throughout the world, and clarification of their detailed effects and pharmaceutical potencies is necessary. Additionally, detailed information regarding the pharmacokinetics of essential oils is needed. In this report, GC-MS analysis was used to observe the tissue distribution of the multiple components of Alpinia zerumbet (Pers.) B.L. Burtt. et Sm. Anxiety-related behavior was evaluated by the light and dark box test (LD), open field test (OF), and elevated plus maze test (EPM). GC-MS quantification of the major components of A. zerumbet essential oil (AZEO) (α-pinene, p-cymene, 1,8-cineole, and limonene) was almost identical using either the injection or headspace injection method. All the behavioral assessments indicated that inhalation of AZEO had a positive anxiolytic effect. This was especially evident in the EPM (time spent in the open arms), where anxiolytic effects were clearly observed (P < 0.05). α-Pinene accumulated in the brain at almost the same rate as in the liver. However, the oil components chiefly accumulated in the kidney. Therefore, the essential oil component in the largest proportion will not necessarily be distributed to organs throughout the body in the same quantities and/or ratios. It is necessary to consider tissue distribution for investigating the effects of essential oil inhalation.

Several reports have described the relationship between the quantity of an essential oil (EO), delivered by injection, and the effects on emotional behaviour. However, few studies have examined the relationship between the duration of EO inhalation and effects on emotional behaviour. It is necessary to clarify this relationship to accomplish effective utilization of an EO. Therefore, we aimed to clarify the relationship between EO inhalation time and anxiolytic-like effects. The anxiolytic-like effect of inhaled EO at various administration times was examined in normal healthy mice using the elevated-plus maze (EPM) test. The effect of a dose of 3.5 mg/l air of Alpinia zerumbet EO was assessed using the EPM test. A time-dependent potentiation in the anxiolytic-like effect was observed when the inhalation time was altered from 0 to 120 min. A significant (P < 0.05 compared to time 0) anxiolytic-like effect was observed to peak at inhalation times of 90 and 120 min. However, the anxiolytic-like effect returned to normal with a 150-min exposure. There was an optimal time of EO inhalation for expressing an anxiolytic-like effect.

Essential oils are composed of multiple components. It is thought that the effect of essential oils is due to specific component ratios, which may differ from the original ratio when the essential oil is absorbed. However, very little detailed research exists in this area. We studied the distribution of essential oil components after inhalation of single and mixed components in mice. This research was done using four main components of Alpinia zerumbet (Pers.) B. L. Burtt. and R. M. Sm.: α-pinene, p-cymene, 1,8-cineole, and limonene. After inhalation of single or mixed components for 90 min, component levels in the brain and liver of mice were measured. The results indicated that the amount of α-pinene in the brain and liver was twofold greater after mixed-component inhalation than that after single-component inhalation. In a comparison of the components of the mixed inhalation, the ratio of α-pinene increased to about three times that of 1,8-cineole. It is thought that the absorption via the nasal mucus greatly influences this phenomenon. The results of this investigation of the bodily distribution of essential oil volatile components may provide clues for elucidating their action.