Biological activities and structural characterization of sulfated polysaccharide extracted from a newly Mediterranean Sea record Grateloupia gibbesii Harvey

Grateloupia gibbesii Harvey (family; Halymeniaceae) is a newly recorded red alga in the Egyptian Mediterranean Sea. In the present study, Grateloupia gibbesii polysaccharide was isolated by hot aqueous extraction and then precipitated by cold ethanol. The yield of crude polysaccharides was 6.4% (w/w), which increased to 17% (w/w) after deproteinization. Preliminary structural characterization and bioactivity of the deproteinized polysaccharide (DGP) were investigated. The monosaccharides' contents were identified by TLC and HPLC. Preliminary structural estimation was carried out by FT-IR and 1H NMR. Moreover, in-vitro exploration of anticoagulant activity by prothrombin time (PT) and fibrinolytic activity of the polysaccharide was determined. The antioxidant activity was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, and the prebiotic activity was assessed against Lactobacillus spp. bacteria. The molecular weight of DGP was 286 kDa and galactose was the most abundant monomer with traces of xylose and glucuronic acid. Anticoagulant tests of DGP revealed prolonged clotting and prothrombin times (20 &14 s at a concentration of 2 mg/mL), respectively, showing moderate anticoagulant activity. DGP exhibited significant fibrinolytic activity (50%), relatively high antioxidant activity (86% at a concentration of 10 mg/mL) and positive prebiotic activity (2.27–2.67). DGP extracted and purified from Grateloupia gibbesii Harvey can be considered as a natural source contestant in the treatment of thrombosis and as an antioxidant and prebiotic supplement in the drug and food industries.