Sulphated Polysaccharide Isolated from the Seaweed Gracilaria caudata Exerts an Antidiarrhoeal Effect in Rodents.

Diarrhoea is a significant health problem for children in developing countries that causes more than 1 million deaths annually. This study aimed to evaluate the antidiarrhoeal effect of sulphated polysaccharide (PLS) from the alga Gracilaria caudata in rodents. For the evaluation, acute diarrhoea was induced in Wistar rats (150-200 g) by administration of castor oil (10 mg/kg). Then, different parameters, including enteropooling and gastrointestinal transit and its pharmacological modulation by opioid and cholinergic pathways, were assessed using activated charcoal in Swiss Mice (25-30 g). Secretory diarrhoea was examined using cholera toxin (CT) (1 mg/loop)-treated, isolated intestinal loops from Swiss mice (25-30 g), which were also used to examine fluid secretion, loss of chloride ions into the intestinal lumen and absorption. In addition, a GM1-dependent ELISA was used to evaluate the interaction between PLS, CT and the GM1 receptor. Pre-treatment with PLS (10, 30 and 90 mg/kg) reduced faecal mass, diarrhoeal faeces and enteropooling. However, 90 mg/kg more effectively reduced these symptoms; therefore, it was used as the standard dose in subsequent experiments. Gastrointestinal transit was also reduced by PLS treatment via a cholinergic mechanism. Regarding the diarrhoea caused by CT, PLS reduced all study parameters, and the ELISA showed that PLS can interact with both the GM1 receptor and CT. These results show that PLS from G. caudata effectively improved the parameters observed in acute and secretory diarrhoea, which affects millions of people, and may lead to the development of a new alternative therapy for this disease.