Pycnocycla spinosa extract is a more potent relaxant of ileum than uterus smooth muscle

Sadraei H., Asghari G., Andishah M. Department of Pharmacology, School of Pharmacy and Pharmaceutical Sciences, Isfahan University of Medical Sciences, Isfahan, Iran.

Hydroalcoholic extract of Pycnocycla spinosa is a relaxant of rat ileum and with a dose of 1mg/kg inhibits diarrhoea in mice (Sadraei et al., 2003). As P. spinosa extract has spamolytic activity on ileum, it may also affects other smooth muscles like uterus. In this study we have compared the inhibitory effect of P. spinosa extract on rat isolated ileum and uterus.

Hydroalcoholic extract was prepared from aerial part of P. spinosa by percolation method (Samuelsson, 1999 ). Uterine horns or ileum were obtained from non-pregnant female Wistar rats (200-230g)) and cut into longitudinal strips. In the case of uterus, the rats were pretreated a day before with 17-β-estradiol (100µg/kg). Strips were mounted for isotonic recording under 1g tension in Tyrode’s solution, maintained at 37 °C and gassed with O2. Relaxant effect of the extract was examined on tonic contraction induced by KCl (80mM) on both tissues and on phasic spasm induced by oxytocin (0.002iu/ml) on the uterus. After equilibration, the extract was added in a cumulative manner to the bath at 15min intervals for KCl and 10min intervals for oxytocin. All experiments were conducted in parallel with time-matched controls adding an equivalent volume of vehicle. The relaxant effect was assessed by expressing the tension during 5-10min after addition of each extract concentration, as a percentage of the tension in 5min period before extract addition. Mean ± s.e.mean values were calculated for each group of results and significance of differences between the means were calculated by two-tailed paired Student's t-test.

Hydroalcoholic extract of P. spinosa in a concentration-dependent manner inhibited rat ileum contraction induced by 80mM KCl. Relaxation of the ileum began with 10µg/ml, reduced to 10 ± 5% with 80µg/ml extract in the bath and complete inhibition was achieved at 160 µg/ml bath concentration (n=6). This result is similar to the previous studies on the ileum ( Sadraei et al., 2003). On the other hand, inhibitory effect of P. spinosa extract on KCl induced contraction in the uterus began with 80 µg/ml extract in the bath and at 1.28mg/ml bath concentration was still 19 ± 7% of the initial response remained (n=6). No significant changes were observed in the KCl time matched control tissues treated with the vehicle.

Hydroalcoholic extract of P. spinosa (30-640 µg/ml) also reduced the evoked phasic response of uterus by oxytocin. With 640 µg/ml extract in the bath, the response to oxytocin was reduced to 4 ± 1% (n=6). However, in the time matched control tissues, smaller but significant reduction occurred in the oxytocin induced uterus contraction over the course of study (maximum of 40 ± 4%; n=6). Therefore, the actual inhibitory effect on phasic contractile response of the uterus is less than what was seen (56%).

In conclusion this study shows that P. spinosa extract more selectively inhibits ileum contraction than uterus spasm in rat isolated tissues.

Sadraei , H. et al., (2003). Phytother. Res., 17(6), 645-649.
Samuelsson, G. (1999). Drugs of Natural origin. 4 th ed. Stockholm.