Ginger oil and its active ingredient, citral, relax rat airway smooth muscle by calcium channel blockade

Ginger, the rhizome of Zingiber officinale Roscoe (Zingiberaceae) which is a common constituent of diets around the world, exhibits several pharmacological activities such as anti-diarrheal, anti-nausea related to motion sickness, pregnancy, surgery or chemotherapy, and blood pressure lowering effects [1 – 6]. Our group has reported the in vitro bronchodilatory activity of ginger oil and identified citral as its major active ingredient. We have also proposed that ginger oil relaxes airway smooth muscle through β₂-adrenergic receptor stimulation as its mechanism of action [7]. In this study, the possible involvement of Ca²⁺ channel in the relaxing effect of ginger oil was investigated. The effect of ginger oil (112.5 µg/ml), citral (70 µg/ml), and verapamil (10µM) on concentration-response curve for Ca²⁺ in rat isolated trachea contracted by the muscarinic agonist carbachol (1µM) was examined in Ca²⁺-free medium. The results showed that both ginger oil and citral shifted concentration-response curve of Ca²⁺ in carbachol-induced tracheal smooth muscle contraction to the right similar to verapamil, an L-type calcium channel blocker. We conclude that in addition to β₂-adrenergic receptor stimulation, Ca²⁺ channel blockade also contributes to the relaxing effect of ginger oil.

Acknowledgements: This research project was funded by Suranaree University of Technology.

Keywords: Ginger oil, Zingiber officinale, citral; bronchodilation, calcium channel.

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