General notes; they are anionic polysaccharides that are obtained from cell walls of know algae. they act as mucosal protectants by forming viscous gel which flout on the surface of contents of the stomac hence relieve symptoms of gastro intestinal reflux disease. they are mainly used togather with antacids. they nare also known to stimulate the release of prostaglandin E2, epidermal growth factors and gastric mucus.