Purification, preliminary characterization and bioactivity of polysaccharides from Grateloupia livida (GL) were investigated. Three water-soluble sulfated polysaccharide fractions (GLP-1, GLP-2 and GLP-3) were isolated and purified from the edible and medicinal red seaweed, Grateloupia livida (Harv.) Yamada by DEAE Sepharose CL–6B and Sephadex G-100 column chromatography, and chemical characterization was performed by HPGPC, GC–MS, FT-IR and SEM. In addition, anticoagulant activities were determined by activated partial thromboplastin time (APTT), thrombin time (TT) and prothrombin time (PT) using normal human plasma in vitro . The antioxidant activities against DPPH and ABTS + radicals were evaluated and compared. The molecular weights of GLP-1, GLP-2 and GLP-3 were 39.5, 60.4 and 3.36 kDa, respectively. Monosaccharide analysis revealed that three polysaccharide fractions were homopolysaccharides and comprised of galactose only. Anticoagulant assays indicated that crude GLP, and purified GLP-1 and GLP-2 effectively prolonged APTT and TT, but not PT. All polysaccharide fractions exhibited significant in vitro antioxidant activities in a dose-dependent manner. GLP-2 showed consistently better anticoagulant and antioxidant activities compared with GLP, GLP-1 and GLP-3. These results demonstrate that sulfated polysaccharides isolated from Grateloupia livida can serve as readily available alternative natural sources of anticoagulant and antioxidant agents. [ABSTRACT FROM AUTHOR]