In vivo antitussive activity of a pectic arabinogalactan isolated from Solanum virginianum L. in Guinea pigs.

Solanum virginianum L. is used for the management of fever, bronchial asthma and cough for thousands of years. While the link to a particular indication has been established in human, the active principle of the formulation remains unknown. Herein, we have investigated a polysaccharide isolated from its leaves. Utilizing traditional aqueous extraction protocol and using chemical, chromatographic, spectroscopic and biological methods we have analysed an antitussive pectic arabinogalactan isolated from its leaves. The water extracted polymer (WEP) is a highly branched arabinogalactan containing, inter alia, (1,3)-, (1,6)- and (1,3,6)-linked β-Galp residues, terminal-, (1,5)- and (1,3,5)-linked units of α-Araf together with (1,2)- and (1,2,4)-linked Rhap. In vivo investigation on the citric-acid induced cough efforts in guinea pigs shows that the antitussive activity of the orally administered pectic arabinogalactan is greater than codeine phosphate. Remarkably, this macromolecule neither altered specific airway smooth muscle reactivity significantly nor it induced considerable change on levels of NO in expiratory flow in guinea pigs. Thus, traditional aqueous extraction method provides a molecular entity, which induces antitussive activity without addiction: this could represent an attractive approach in phytotherapeutic management.