Antitussive activity of an extracellular Rhodella grisea proteoglycan on the mechanically induced cough reflex

A mucilagineous extracellular proteoglycan (EPG) composed of xylose and its 3-O-and 4-O-methyl-derivates (55%), glucuronic acids (17%), rhamnose (14%), galactose (8%), glucose (4%) and minor amounts of other sugars (∼2%) has been isolated from culture medium of Rhodella grisea. A white fluffy algal biopolymer of molecular mass over 8.1×10⁵ contained protein (13%), methoxyl (6%), acetyl and succinyl groups. EPG was tested in vivo on mechanically induced cough in non-anaesthetized cats as a test system. The biopolymer showed a cough suppressing effect on laryngopharyngeal type of cough while the cough from tracheobronchial mucous area was slightly or not affected. Further, the intensity of maximal cough efforts from laryngopharyngeal and tracheobronchial parts in expirium and inspirium were influenced slightly only indicating that the expectoration effect was not suppressed by biopolymer application.