چكيده لاتين :
In the previous studies the relaxant, anti-cholinergic (functional antagonism) and anti-histaminic effects of Nigella sativa have been demonstrated on guinea pig tracheal chains. To elucidate the main
substance responsible for the relaxant effect of this plant, the effect of thymoquinone, one of the main constituent of Nigella sativa was examined in this study. The bronchodilatory effects of three
cumulative concentrations (40, 80, and 120 moM) of thymoquinone were examined by their relaxant effects on precontracted tracheal chains of guinea pigs using (1) 10 JiM methacholine and (2) 60 mM
KCI. The results were compared with the effects of saline, theophylline, and extracts (macerated and aqueous) of Nigella sativa (n = 5 for each group). The results showed significant relaxant effects of
theophylline and extracts from Nigella sativa as compared to saline in group 1 experiments (P<0.05 and P<0.005). There were no significant differences between the effects of two higher concentrations of
extracts with those of theophylline. However, none of the three thymoquinone concentrations showed any relaxant effect in both groups. There were also significant differences between the relaxant effect
of theophylline and extracts with those of thymoquinone concentrations (P<0.05 and P<0.001). In group 2, only theophylline showed .a significant relaxant effect (P<0.05 and P<0.001). The effects of
two higher concentrations of both extracts and thymoquinone were significantly lower than those of theophylline in group 2 (P<0.05 to P<0.001). These results indicated that the relaxant effect of Nigella
sativa is not due to its constituent thymoquinone.
