Antispasmodic effects of Prangos ferulacea acetone extract and its main component osthole on ileum contraction

Prangos ferulacea is a plant found in the Mediterranean and Middle-east regions used as carminative, anti-flatulent, emollient and antibacterial herb. It is believed that the coumarins are responsible for some of known effects of Prangos. In this research the relaxant effects of P. ferulacea coumrin rich extract as well as osthole as its main prenylated coumarins were investigated on rat ileum contraction in vitro. Relaxant effect of osthole and P. ferulacea extract were examined on contraction induced by KCl, acetylcholine (ACh) and electrical field stimulation (EFS) and compared with propantheline and nifedipine. The acetone extract of P. ferulacea concentration-dependently relaxed ileum contraction induced by KCl (IC50=1.3 ± 0.25 μg/ml), ACh (IC50=7.7 ± 1.1 μg/ml) and EFS (IC50=8.8 ± 1.4 μg/ml), while, the extract at lower concentration (4 μg/ml) potentiated the ACh and EFS responses. Unlike the extract, osthole did not potentiate the ileum contraction but concentration-dependently inhibited ileum contractile responses to KCl (IC50=2.2 ± 0.7 μg/ml), ACh (IC50=2.5 ± 0.7 μg/ml) and EFS (IC50=2.8 ± 0.24 μg/ml). Propantheline concentration dependently inhibited the ileum response to ACh, with IC50 value of 0.61 ± 0.09nM without affecting the KCl response. As expected, the EFS response was only partially reduced. Nifedipine (0.2-50 nM) inhibited tonic contraction induced by KCl with IC50 value of 2.5 ± 0.8 nM but only partially inhibited the response to ACh. However, the response to EFS was reduced only by 33%. These results confirmed both potentiatory and inhibitory action of P. ferulacea extract on rat ileum contractile activity. Osthole is responsible for the inhibitory effect but potentiating components are not yet known.