Relaxant effects of Ocimum basilicum on guinea pig tracheal chains and its possible mechanism(s)

Therapeutic effects of Ocimum basilicum on respiratory diseases especially dyspnea have been reported in Iranian ancient medical books. In the present study, the relaxant effects of macerated and soxhlet extracts of this plant on tracheal chains of guinea pigs were evaluated. The relaxant effects of 4 cumulative concentrations of macerated and soxhlet extracts (0.25, 0.5, 0.75 and 1.0 W/V) in comparison with saline as negative control and 4 cumulative concentrations of theophylline (0.25, 0.5, 0.75, and 1.0 mM) as positive control were examined on precontracted tracheal chains of two groups of 6 guinea pig by 60 mM KCl (group 1) and 10 μM methacholine (group 2). Decrease in contractile tone of tracheal chains was considered as relaxant effect. In group 1 experiments only the last two higher concentrations of theophylline showed significant relaxant effect compared to that of saline (p<0.001 for both concentrations), which were significantly greater than those of macerated and soxhlet extracts (p<0.001 for all cases) and in group 2 experiments both macerated and soxhlet extracts showed concentrationdependent relaxant effects compared to that of saline (p<0.05 to p<0.001 for both extracts). There were significant differences between the relaxant effects of both extracts with those of theophylline in group 2 experiments (p<0.01 to p<0.001). The relaxant effects of macerated and soxhlet extracts in group 1 were significantly lower than those of groups 2. These results showed a potent relaxant effect of Ocimum basilicum on tracheal chains of guinea pigs which were lower than theophylline at concentrations used.