Sedative effects of vapor inhalation of the essential oil of Microtoena patchoulii and its related compounds

Abstract

Microtoena patchoulii (Labiatae) is a perennial herb that grows in southern China. In the present study, the sedative activity of the essential oil of the leaves was evaluated using mice when the volatile oil was administered by inhalation. The inhalation of the oil by mice significantly reduced the spontaneous motor activity. Fractionation of the oil revealed that the main constituents in the oil were 1-octen-3-ol, terpinolene, patchouli alcohol, and methyl salicylate. Each 1-octen-3-ol, terpinolene, or patchouli alcohol significantly reduce the locomotor activity when it was administered singly. However, the essential oil fraction containing both patchouli alcohol and methyl salicylate did not exhibit any effects. It is suggested that methyl salicylate might negate the sedative effect of patchouli alcohol, and that the concentration ratios of the compounds in vapor would play important roles as sedatives. In order to clarify the mechanism of action, the effects of these compounds on caffeine-induced excitation and pentobarbital-induced elongation of sleeping time in mice were tested. Each 1-octen-3-ol or terpinolene reduced the locomotor activity excited by caffeine to those of normal levels. Elongation of sleeping time induced by pentobarbital was further elongated by the inhalation of terpinolene, but not by that of 1-octen-3-ol. It is indicated that terpinolene is a potent suppressor of the central nervous system.

Development and evaluation of an inhalation chamber for in vivo tests

“…This constant and unidirectional flow carries body smells, excrement smells, and gases expelled by the animals themselves, preventing them from contaminating the internal environment of the chamber. Constant air renewal into the chamber is an advantage compared to chambers working with controlled pressure (Hemenway and Stedman 1981, Lopes 2004, Pereira 2004, those which do not have unidirectional flow, in which the chamber air outlet is near to the entrance (Bung et al1984, Vincent and Guénette 1997, Schenkel et al 2009), and inhalation boxes (Valença et al 2004, Komyia et al 2006, Bradley et al 2007, Takemoto et al 2008, Ito and Ito 2011.…”

“…These situations are probably not observed in inhalation boxes with cotton or filter-paper moistened with the volatile test material (Komyia et al 2006, Bradley et al 2007, Takemoto et al 2008, Ito and Ito 2011. These require an initial time for saturation of the internal environment and subsequent animal placement since volatilization is a slow process, which is necessary for operation of the apparatus.…”

“…Furthermore, apparatus containing an inhalation box (Valença et al 2004, Komyia et al 2006, Bradley et al 2007, Takemoto et al 2008, Ito and Ito 2011 and those that do not present a unidirectional flow of insufflated material (Hemenway and Stedman 1981, Bung et al 1984, Vincent and Guénette 1997, Lopes 2004, Pereira 2004, Schenkel et al 2009) are prone to the accumulation and deposition of such test materials. This may result in the administration of more than the required dose due to both accumulation inside the chamber and deposition on the animals' bodies.…”

“…Since then, new models have emerged to evaluate the effect of inhalation of different types of materials (Rihn et al 1996, Matthew et al 2001. Recently, inhalation boxes were used, which contained pieces of cotton moistened with the studied material, and these were fixed at the top of the walls of the flask (Komyia et al 2006); alternatively, filter-paper discs were moistened with these materials and secured to the flask walls (Takemoto et al 2008, Ito and Ito 2011. Tests were also conducted on square chambers with electronic vaporizers (Bradley et al 2007), chambers with evaporators connected to an oxygen feeder (Shaw et al 2007), and glass cylindrical chambers containing four animal holders fixed to the sides with two tubes for adapting electronic nebulizers (Linck et al 2010).…”

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“…Spikenard oil was isolated from the dried plant material by hydrodistillation for 3 h using a Clevenger-type apparatus according to previously reported methods [11].…”