Non-specific immune potentiating activity of fucoidan from a tropical brown algae (Phaeophyceae), Sargassum cristaefolium in tilapia (Oreochromis niloticus)

Fucoidan mainly produced by brown algae is a sulfated polysaccharide with fucose as a main molecule backbone. The objective of this research was to evaluate the non-specific immune potentiating activity of fucoidan from a tropical brown alga, Sargassum cristaefolium indigenous to the Gunungkidul coast, Yogyakarta, Indonesia. Fucoidan was extracted by acidic extraction, separated from alginate by CaCl2 precipitation and precipitated with ethanol. To know the component of fucoidan, acid hydrolysis was conducted and analyzed by using silica gel thin layer chromatography. In these analyses, a commercial fucoidan from Fucus vesiculosus was used as a standard fucoidan. Fucoidan isolated from S. cristaefolium was composed by monosaccharide components of fucose and galactose. The result revealed that injection of fucoidan increased phagocytic activity, total plasma protein, leukocrit and leukocyte count significantly (p < 0.05). The immunomodulating activity of fucoidan from S. cristaefolium was comparable to that of fucoidan standard from F. vesiculosus. However, administration of fucoidan did not affect the phagocytic index and leukocyte differentiation. Injection of fucoidan from S. cristaefolium effectively increased innate immunity parameters of tilapia at doses of 0.4-0.6 mg/kg fish suggested that this fucoidan was potential use for immunostimulant to control fish diseases.