Evaluation of antitussive and anti-asthmatic activity of Tabernaemontana divaricata (L.) R. Br. Ex Roem. and Schult.

Background: The study was aimed to investigate the antitussive and anti-asthmatic activities of ethanolic extract of Tabernaemontana divaricata (TDEE) leaves by in vivo and in vitro models. Recently, indole alkaloids (monoterpenoid indole alkaloids) have been approved as investigational new drug for clinical trial in respiratory diseases, and T. divaricata has already proven its potential for the presence of indole alkaloids.

Materials and Methods: Acute toxicity studies of TDEE were performed in accordance with the Organization for Economic Cooperation and Development guidelines no. 425. The sensitized guinea pigs were screened out and divided into control, standard, and TDEE-treated groups. Anti-asthmatic activity of TDEE was assessed by in vitro guinea pig tracheal chain method and in vivo bronchoprotective test method using aminophylline as a standard drug. Taken codeine as standard, antitussive activity was evaluated by in vivo citric acid-induced tussive response.

Results: TDEE was found to be safe up to 2000 mg/kg, body weight. TDEE exhibits maximum bronchi relaxation of 91.66% and 92.83% against acetylcholine and histamine-induced contraction, respectively. TDEE exhibited maximum and significant ( P < 0.001) bronchoprotection of 42.28% at the dose level of 200 mg/kg, body weight. TDEE at aerosolic dose of 6% (w/v) exhibited decreased average cough frequency (4.83 ± 0.30) which is quite significant ( P < 0.001) and effective as compared to standard drug codeine. Based on the histopathological evidences, TDEE-treated groups showed reduced inflammatory cell infiltration and had restored epithelial damage.

Conclusion: The results of the study revealed the potent antitussive and anti-asthmatic activities of T. divaricata , which support its further implication for the treatment of cough-associated complications such as cough variant asthma.