Chemical profile of a polysaccharide from Psidium guajava leaves and it's in vivo antitussive activity.

Decoction of Psidium guajava leaves has been used as medication for chronic coughs and breathlessness for ages. Despite demonstration of antitussive activity, the specific molecule responsible for this remains unidentified. Herein, we report chemical profile and antitussive activity of its water extract (WE) and a polysaccharide (F1) present therein. This polysaccharide (F1), purified from WE by precipitation with ethanol and then through Cu(II)acetate, contains Ara, Gal, Rha, Glc and GalA residues, and has a molecular mass of 156 kDa. It comprises of terminal-, (1,5)- and (1,3,5)-linked Araf; (1,3)-, (1,6)- and (1,3,6)-linked Galp alongside (1,2)- and (1,2,4)-linked Rhap residues. Oligosaccharides indicating polysaccharide structure have been generated by Smith degradation and characterized. The WE fraction suppressed citric acid induced cough efforts in guinea pigs in the dose of 50 mg kg-1. Assessment of antitussive activity of fractions prepared from WE namely F1 (polysaccharide) and F2 (ethanol soluble fraction) revealed that polysaccharide is the active component. Remarkably, tested samples do not alter the specific airway smooth muscle reactivity in animals significantly. The simple extraction method, prominent activity and favorable reactions profile suggest that this macromolecule could be an antitussive drug candidate.