Participation of citral in the relaxation of isolated rat tracheal smooth muscle induced by ginger oil

Ginger (Zingiber officinale) Roscoe is a common food plant that has been used as alternative medicine for a number of ailments. The rhizome of this plant is well known for the treatment of gastrointestinal tract disorders, such as dyspepsia, nausea and vomiting, as well as respiratory illnesses [1]. Its hydroethanolic extract has been shown to inhibit airway hyperreactivity and remodelling, and lung inflammation [2–3]. The inhibitory effects of aqueous and methanolic crude extracts of ginger on tracheal smooth muscle were described [4], however, the effects of ginger oil and its active compound on airway smooth muscle have never been reported. The aim of this study is to investigate the effect of ginger oil and its constituents on tracheal smooth muscle in vitro. Chemical compositions of ginger oil were determined by GC-MS. Citral and camphene appeared to be its major components. For the relaxation study, two-cartilage segments of rat trachea were prepared and mounted vertically in an organ bath. The contraction of tracheal smooth muscle was induced by acetylcholine (Ach) before ginger oil, citral or camphene were added. Ginger oil and citral, but not camphene, were found to reverse the Ach-induced airway contraction in concentration-dependent manner. This result indicates that citral is, at least partly, responsible for the myorelaxant effect of ginger oil on rat trachea.

Keywords: Ginger oil, Citral, Tracheal smooth muscle, Relaxation

Acknowledgement: This study is supported by the National Research Council of Thailand.

References: 1. Ghayur MN et al. (2008) Can J Physio Pharmacol 86: 264–271.

2. Kuo PL et al. (2011)J Agric Food Chem (in press).

3. Aimbire F et al. (2007) Prostaglandins Leukot Essent Fatty Acids 77:129–38

4. Ghayur MN, Gilani AH (2007) Eur Food Res Technol 224:477–481.