Antitussive activity of a glucuronoxylan from Rudbeckia fulgida compared to the potency of two polysaccharide complexes from the same herb.

An alkali-extracted low-molecular glucuronoxylan and two water-extractable polysaccharide complexes isolated from various parts of Rudbeckia fulgida were tested for antitussive activity on mechanically induced cough in nonanaesthetized cats. Glucuronoxylan consisted of a (1-->4)-linked beta-D-xylopyranosyl backbone with about 18% of 4-0-methyl-D-glucuronic acid attached to 0-2 of the chain xylose residues. The polysaccharide complexes differed from each the other regarding the in qualitative and quantitative composition of the sugar components. It was found that peroral administration of all the compounds led to a significant suppression of the cough reflex without negative influence on expectoration. Glucuronoxylan and the complex from the aerial parts of the herb exhibited much higher antitussive activity than the complex from the roots which did not contain any uronic acid component. Their activity (48.2% and 46.5%, respectively) highly surpassed the activity of the complex from the roots (23.5%) as well as that of the peripherally acting drugs dropropizine (28.3%) and prenoxdiazine (24.7%).