Possible mechanism for the relaxant effect of Pimpinella anisum on guinea pig tracheal chains

Abstract

Pimpinella anisum L. is a grassy plant that is believed to have several therapeutic effects including antiasthmatic uses. In a previous study, the relaxant (bronchodilatory) effect of this plant on isolated guinea pig tracheal chains was demonstrated. To study mechanisms responsible for this effect, the inhibitory effect of this plant on contracted tracheal chains of guinea pig was evaluated in the current study. The relaxant effects of aqueous and ethanol extracts and essential oil from P. anisum compared to negative controls (saline for aqueous extract and essential oil and ethanol for ethanol extract) and positive control (diltiazem) were examined on precontracted isolated tracheal chains of the guinea pig by 10 μM methacholine (group 1) and 60 mM KCl (group 2, n = 7 for each group). In group 1 experiments, diltiazem, both extracts, and essential oil from P. anisum showed significant relaxant effect on methacholine-induced contraction of tracheal chains compared to those of negative controls (p < 0.05 to p < 0.001). In addition, the effects of extracts were significantly greater than that of diltiazem (for aqueous and ethanol extracts p < 0.05 and p < 0.01, respectively). However, in group 2 experiments, only diltiazem and ethanol extract showed significant relaxant effects on KCl-induced contraction of tracheal chains (p < 0.05 for ethanol extract and p < 0.001 for diltiazem). Relaxant effects of extracts and essential oil obtained in group 2 experiments were significantly lower than those of group 1 (p < 0.05 to p < 0.001). These results confirm the bronchodilatory effects of extracts and essential oil from P. anisum. However, with regard to the effect of KCl on calcium channels, the results indicated that inhibitory effect of only ethanol extract from P. anisum on calcium channels may contribute to its relaxant (bronchodilatory) effects on guinea pig tracheal chains. In addition, the results suggest a potassium channel opening effect for this plant, which may contribute on its relaxant effect on tracheal chains of guinea pig. © 2004 Taylor & Francis Ltd.