The relationship between dose-dependent antitussive and bronchodilatory effects of Opilia celtidifolia polysaccharide and nitric oxide in guinea pigs

A crude polysaccharide composed of uronic acids (32%), arabinose (26%), glucose (15%), galactose (11%), rhamnose (7%), mannose (5%), xylose (4%) and small amount of fucose residues has been isolated from the leaves of Opilia celtidifolia by boiled water extraction. Chemical analyses of Opilia polysaccharide revealed the prevalence of a pectin material with high arabinose and galacturonic acid contents. Opilia polysaccharide showed significant biological effects on chemically induced cough reflex and reactivity of airways smooth muscle in vitro and in vivo conditions in guinea pigs test system. Tests confirmed the dose-dependent cough-suppressive effect of Opilia polysaccharide comparable with activity of centrally acting codeine. Further, the bronchodilatory tests resulted in significant decrease in the values of specific airway resistance, which is very sensitive predictor of airway smooth muscle reactivity in vivo conditions regardless of bronchoconstricting mechanism. The results of in vitro experiments confirmed not only the bronchodilatory effect Opilia polysaccharide but revealed that its bronchodilatory mechanism is partially accompanied with enhanced NO production.