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Red seaweeds synthesize a great variety of sulfated galactans. Sulfated polysaccharides (PLSs) from seaweed are comprised of substances with pharmaceutical and biomedical potential. The aim of the present study was to evaluate the protective effect of the PLS fraction extracted from the seaweed Gracilaria birdiae in rats with naproxen-induced gastrointestinal damage. Male Wistar rats were pretreated with 0.5% carboxymethylcellulose (control group—vehicle) or PLS (10, 30, and 90 mg/kg, p.o.) twice daily (at 09:00 and 21:00) for 2 days. After 1 h, naproxen (80 mg/kg, p.o.) was administered. The rats were killed on day two, 4 h after naproxen treatment. The stomachs were promptly excised, opened along the greater curvature, and measured using digital calipers. Furthermore, the guts of the animals were removed, and a 5-cm portion of the small intestine (jejunum and ileum) was used for the evaluation of macroscopic scores. Samples of the stomach and the small intestine were used for histological evaluation, morphometric analysis and in assays for glutathione (GSH) levels, malonyldialdehyde (MDA) concentration, and myeloperoxidase (MPO) activity. PLS treatment reduced the macroscopic and microscopic naproxen-induced gastrointestinal damage in a dose-dependent manner. Our results suggest that the PLS fraction has a protective effect against gastrointestinal damage through mechanisms that involve the inhibition of inflammatory cell infiltration and lipid peroxidation.

The sulfated polysaccharide (PLS) fraction of Agardhiella ramosissima was characterized by microanalysis, infrared spectroscopy, NMR and gas-liquid-chromatography-mass-spectrometry. The main constituent of PLS was the ι carrageenan. The monosaccharide composition of the PLS showed galactose, 3,6-anhydrogalactose and 6-O-methylgalactose. The PLS (30 mg kg(-1)) significantly reduced the paw oedema induced by carrageenan, dextran, histamine and serotonin and also was able to significantly inhibit leucocyte migration into the peritoneal cavity and decrease the concentration of myeloperoxidase (MPO) in paw tissue. In the antinociceptive tests, the pre-treatment with PLS reduced the number of writhes, the licking time but did not increase the latency time of response. This study demonstrates for the first time the anti-inflammatory and anti-nociceptive effects of PLS from A. ramosissima. Thus, we concluded that PLS could be a new natural tool in pain and acute inflammatory conditions.

Our results suggest that the PLS fraction has a protective effect against intestinal damage through mechanisms that involve the inhibition of inflammatory cell infiltration, cytokine releasing and lipid peroxidation.

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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.Seaweeds (marine macroalgae) are excellent sources of pharmacologically active compounds, and the number of substances isolated from seaweed sources has been generating a great deal of interest [1]. The structures of most isolated compounds have been determined, and the therapeutic potentials of these substances are currently being examined [2,3]. Investigations into the precise phytochemical composition of different seaweeds have revealed that they are principally composed of different types of sulphated polysaccharides and other potentially useful chemical biomolecules [4].Over the past several decades, it has become clear that sulphated polysaccharides are involved in numerous cellular processes and possess a range of pharmacological activities; therefore, they have attracted the attention of numerous research groups [5]. Sulphated polysaccharides are complex macromolecular compounds found in the extracellular matrix, and these polysaccharides are known to have anticoagulant, antiviral and anti-inflammatory activities that have potential applications as nutraceuticals, cosmetics and pharmaceuticals [6].In Brazil, several species of the genus Gracilaria, including Gracilaria caudata, thrive in coastal regions. We showed that G. caudata produces an agaran consisting of alternating residues of 3-linked-b-D-galactopyranose connected to either 4-linked-3,6-anhydro-a-L-galactopyr...