Relaxant effects of asafoetida extract and its constituent umbelliprenin on guinea-pig tracheal smooth muscle.

Objective: To investigate the relaxant effects of the asafoetida (Ferula Asafoetida Oleo-Gum-Resin) and its coumarin constituent umbelliprenin on tracheal chains of guinea pigs.

Methods: The relaxant effects of three cumulative concentrations of the aqueous extract (2, 5 and 10 mg/mL), umbelliprenin (0.04, 0.2 and 0.4 mg/mL), theophylline (0.05, 0.1 and 0.15 mg/mL) and saline were examined by their relaxant effects on precontracted tracheal chains of guinea pig by 60 mmol/L KCl (group 1), and 10 μ mol/L methacholine (group 2).

Results: In group 1 all concentrations of theophylline and the highest concentration of the extract showed signififi cant relaxant effects compared with that of saline (P<0.01 for theophylline and P<0.05 for extract). In group 2, relaxant effects of all concentrations of theophylline, extract and two higher concentrations of umbelliprenin differed significantly compared with saline [P<0.01 for all cases except low concentration of umbelliprenin (0.04 mg/mL)]. There were no signififi cant differences between relaxant effects of the extract and theophylline in group 2. The relaxant effect of the extract in group 2 was signififi cantly greater than that of group 1 (P<0.01). The relaxant effect of the extract was significantly more potent than umbelliprenin in all groups (P<0.05 or P<0.01).

Conclusion: These results showed a potent relaxant effect for the asafoetida extract on tracheal smooth muscle which is, at least, in part, due to its constituent umbelliprenin. A muscarinic receptor blockade was also suggested for the extract.