Abstract

Background: Boswellia serrata (family Burseraceae) has been traditionally used for the treatment of a wide variety of diseases as arthritis, inflammatory bowel diseases, and airway diseases. However, the direct bronchodilator efficacy of Boswellia serrata hasn’t been explored yet.

Objective: We aimed at the present study to evaluate the direct effect of Boswellia serrata extract (BSE) on isolated rat tracheal preparations precontracted with either Acetylcholine (ACh) or potassium chloride (KCl).

Methods: Tracheal rings were prepared from male Wistar rats (200-250 g). BSE (1-200 μg/ml) was added to tracheal strips precontracted with either ACh or KCl and the response was observed. We also investigated the consequences of epithelial denudation, indomethacin, and N-Nitro-L-arginine on the relaxant effect of BSE as compared to that of the β-adrenoceptor agonist isoprenaline, or the bitter taste receptor (TAS2R) agonist denatonium benzoate. Finally, the possible additive effects of BSE to isoprenaline or denatonium-induced relaxation were evaluated.

Results: By using a set of serial dosing and washout experiments with tracheal rings, results showed that exposure to BSE resulted into a significant and concentration-dependent inhibitory effect on airway smooth muscle contractions precontracted with either ACh or KCl. Epithelial denudation, indomethacin, or N-Nitro-L-arginine had no significant effect on the obtained relaxation. Furthermore, BSE potentiated the relaxant effect of isoprenaline on rat trachea.

Conclusion: BSE exerts a direct concentration-dependent relaxant effect on precontracted tracheal strips. These results could contribute towards validation of the traditional use of BSE in the treatment of airway diseases.

Keywords: Airway diseases, asthma, Boswellia serrata, bronchodilation, denatonium, tracheal contraction.

Graphical Abstract