Mechanisms underlying the antispasmodic and bronchodilatory properties of Terminalia bellerica fruit

Aim of the study: The present investigation was carried out to provide the pharmacological basis for the medicinal use of Terminalia bellerica in hyperactive gastrointestinal and respiratory disorders. Materials and methods: Crude extract of Terminalia bellerica fruit (Tb.Cr) was studied in in vitro and in vivo. Results: Tb.Cr caused relaxation of spontaneous contractions in isolated rabbit jejunum at 0.1-3.0 mg/mL. Tb.Cr inhibited the carbachol (CCh, 1 μM) and K⁺ (80 mM)-induced contractions in a pattern similar to that of dicyclomine, but different from nifedipine and atropine. Tb.Cr shifted the Ca⁺⁺ concentration-response curves to right, like nifedipine and dicyclomine. In guinea-pig ileum, Tb.Cr produced rightward parallel shift of acetylcholine-curves, followed by non-parallel shift at higher concentration with the suppression of maximum response, similar to dicyclomine, but different from nifedipine and atropine. Tb.Cr exhibited protective effect against castor oil-induced diarrhea and carbachol-mediated bronchoconstriction in rodents. In guinea-pig trachea, Tb.Cr relaxed the CCh-induced contractions, shifted CCh-curves to right and inhibited the contractions of K⁺. Anticholinergic effect was distributed both in organic and aqueous fractions, while CCB was present in the aqueous fraction. Conclusions: These results indicate that Terminalia bellerica fruit possess a combination of anticholinergic and Ca⁺⁺ antagonist effects, which explain its folkloric use in the colic, diarrhea and asthma.