Pharmacological evaluation of Alstonia scholaris: anti-tussive, anti-asthmatic and expectorant activities.

ETHNOPHARMACOLOGICAL RELEVANCE: Alstonia scholaris (Apocynaceae) was documented as an effective herb for the treatment of chronic respiratory diseases in "dai" ethnopharmacy historically, and its leaf crude extract, used for releasing tracheitis and cold symptom, was approved to be a commercial formulation by State Food and Drugs Administration of China (SFDA).

AIM OF THE STUDY: The investigation evaluates the anti-tussive and anti-asthmatic activities of the ethanolic extract, fractions and main alkaloids of Alstonia scholaris leaf to provide experimental evidence for its traditional and modern clinical use. For our most interesting, is to reveal the active components for further new drug development.

MATERIALS AND METHODS: The leaf of Alstonia scholaris was extracted with ethanol and then separated into different fractions. Furthermore, alkaloids were isolated by phytochemical method. The anti-tussive activity was evaluated using three different models including ammonia or sulfur dioxide induced mice coughing, and citric acid induced guinea pigs coughing. The anti-asthmatic activity was investigated on guinea pigs bronchoconstraction induced by histamine. The expectorant activity was evaluated by volume of phenol red in mice's tracheas.

RESULTS: The alkaloids fraction significantly inhibited mice's frequency of cough induced by ammonia, increased mice's latent period of cough induced by sulfur dioxide, and increased guinea pigs' latent period of cough and inhibited frequency of cough. Besides, the alkaloids fraction increased delitescence of convulsion, and tumble of guinea pigs in anti-asthmatic test, and enhanced tracheal phenol red output in expectorant evaluation. Moreover, the main alkaloid, picrinine exhibited anti-tussive and anti-asthmatic activities in vivo.

CONCLUSIONS: The alkaloids fraction was anti-tussive, anti-asthmatic and expectorant activities component of Alstonia scholaris leaf, and it may also be a valuable lead material for respiratory diseases drug development. Picrinine, the main anti-tussive and anti-asthmatic compound, could be applied in quality control of products from Alstonia scholaris leaf.