Screening of Sceptridium ternatum for antitussive and antiasthmatic activity and associated mechanisms

Objectives Sceptridium ternatum is an expectorant in traditional Chinese medicine and is prescribed for the treatment of asthma. The study aim was to screen Sceptridium ternatum for ingredients with antitussive and antiasthmatic effects and to study their associated mechanisms. Methods Cough in mice was induced using ammonia. Cough latency and the number of coughs within 3 minutes were determined. Airway responsiveness was assessed using ovalbumin as a sensitizer and characteristic asthma indicators were measured. Results Chloroform and ethyl acetate extracts significantly reduced the number of coughs within 3 minutes, tidal volume, and the percentage of eosinophilic granulocytes, lymphocytes and neutrophils. All extracts decreased airway responsiveness in asthmatic mice compared with the untreated group. Petroleum ether, chloroform and n-butanol extracts lowered the Penh values of asthmatic mice. Petroleum ether and ethyl acetate extracts greatly reduced interleukin-4 expression and the interleukin-4/interferon gamma ratio. Compared with the model group, all extracts reduced mRNA expression of the cysteinyl leukotriene receptor-1 (CysLT₁). Conclusions Chloroform extract and ethyl acetate extract displayed obvious antitussive effects and reduced airway inflammation. Thus, these two extracts contain the effective ingredients of Sceptridium ternatum. The active mechanism was ascribed to inhibition of mRNA expression of the CysLT₁ receptor in mice with bronchial asthma.