The Relaxant Effects of Different Methanolic Fractions of Nigella sativa on Guinea Pig Tracheal Chains

  Objective(s): In regard to the high incidence of asthma and the side-effects of the drugs used, finding novel treatments for this disease is necessary. Our previous studies demonstrated the preventive effect of Nigella sativa extract on ovalbumin-induced asthma. In addition, water-soluble substances of N. sativa extract and methanol fraction of this plant were responsible for the relaxant effect of this plant on tracheal chains of guinea pigs. Therefore, for the first time, in the present study, in order to identify main constituents of the methanolic extract, the relaxant effects of five different methanolic fractions (۲۰%, ۴۰%, ۶۰%, ۸۰%, and ۱۰۰%) of N. sativa   on tracheal chains of guinea pigs were examined.     Materials and Methods:     The relaxant effects of four cumulative concentrations of each fraction (۰.۸, ۱.۲, ۱.۶, and ۲.۰ g%) in comparison with saline as negative control and four cumulative concentrations of theophylline (۰.۲, ۰.۴, ۰.۶, and ۰.۸ mM) were examined by their relaxant effects on precontracted tracheal chains of guinea pig by ۶۰ mM KCl (group ۱) and ۱۰ μM methacholine (group ۲).     Results: In group ۱, all concentrations of only theophylline showed significant relaxant effects but all concentrations of these methanolic fractions showed significant contractile effects compared with that of saline (P<۰.۰۰۱ to P<۰.۰۵). However, in group ۲, all concentrations of theophylline and these methanolic fractions showed significant relaxant effects compared with that of saline (P<۰.۰۰۱ to P<   ۰.۰۵).     Conclusion: These results showed a potent relaxant effect of ۲۰% methanolic fractions from N. sativa   on tracheal chains of guinea pigs that were higher than that of theophylline at the used concentrations