Immunomodulatory effects and antimicrobial activity of heterofucans from Sargassum filipendula

Parasitic diseases are a human health problem mainly in low-income areas. The drugs available for the treatment of these diseases are far from satisfactory due to high costs, toxicity, and drug resistance. Sulfated polysaccharides are a complex group of bioactive polymers and can be obtained from seaweeds. The heterofucans from Sargassum filipendula (SF) present strong antiproliferative and antioxidant activities. However, their immunomodulatory and antimicrobial capacity have not been evaluated until now. In this study, five sulfated fucose-rich fractions were isolated (named SF0.5V, SF0.7V, SF1.0V, SF1.5V, and SF2.0V). The chemical composition showed slight differences among polysaccharides and, consequently, biological activity of these polymers. Three fractions (SF0.5V, SF0.7V, and SF1.0V) showed a strong immunomodulatory activity enhancing the release of nitric oxide (NO) by murine macrophages (RAW 264.7), though only SF0.5V was able to induce interleukin-6 (IL-6) and TNF-alpha release from RAW cells. The sugar to sulfate ratio was not correlated with these activities. Meanwhile, the contents of xylose (P = 0.98 for NO; P = 0.98 for IL-6; P = 0.96 for TNF-alpha) and glucuronic acid (P = 0.91 for NO; P = 0.9190 for IL-6; P = 0.79 for TNF-alpha) were strongly positively correlated. SF0.7V and SF1.0V inhibited biofilm formation by Klebsiella pneumoniae (4.2 and 6.8%, respectively), whereas SF0.5V showed inhibitory effect (similar to 50%) on biofilm formation by Staphylococcus epidermidis. Furthermore, SF0.7V and SF1.0V showed high inhibition capacity on the survival of the protozoan Trichomonas vaginalis. The sugar to sulfate ratio was positively correlated (P = 0.60) with this activity. The results demonstrate the spectrum of action of these sulfated polysaccharides obtained from SF and show their potential as immunomodulatory and microbicidal agents.