Influence of viscous Rhodella grisea (Rhodophyceae) proteoglycan on chemically induced cough reflex

An algal extracellular biopolymer (over 8.5×105Da) composed of carbohydrates (52%) and protein (∼13%) has been isolated from a red alga Rhodella grisea growing in natural conditions by concentration of water medium, alcohol precipitation, dialysis and freeze-drying. This mucilagineous biopolymer contained xylose and its 3-O- and 4-O-methyl derivatives (∼63%), galactose (∼12%), glucuronic acid (11–12%), glucose (∼5%), rhamnose (∼4%), fucose (∼3–4%) and low content of others accompaning sugars. When tested on the citric acid-induced cough and reactivity of airways smooth muscle in vivo in the test system guinea pigs, this biopolymer assigned a significant cough suppressing effect. The reactivity of airways smooth muscle was not affected indicating that expectoration effect was not suppressed by biopolymer application, which is important from the pharmacological point of view.