Sulfated polysaccharides (SP) are found in various marine organisms and their biological activities have aroused great interest in the medical sciences. The objective of this study was to evaluate the anticoagulant activity of SP isolated from the red marine alga Halymenia pseudofloresia. Initially, the compound was obtained enzymatically during the performance of three consecutive extractions, and then purified by ion-exchange chromatography on DEAE-cellulose column. The obtained fractions were concentrated by lyophilization and submitted to agarose gel electrophoresis. The anticoagulant activity was evaluated by the activated partial thromboplastin time (APTT) using plasma from rabbits and standard heparin (100 IU mg-1). The extractions (47.14%) showed marked differences during the fractionation and in the degree of purification of these macromolecules. The species showed higher activity anticoagulant than that of heparin. However, the fractions’ APTT changed up sharply among the extractions, expressing themselves in dose-dependent manner and decreasing from 464.2 (1st extraction) to 137.1 IU mg-1 (3rd extraction). The results suggest that the anticoagulant activity of SP isolated from H. pseudofloresia be promoted by inhibition intrinsic and/or common pathway the cascade of coagulation. The changes on APTT possibly be justified by differences conformation of these SP and will be elucidated through the mechanisms of action involved on clotting and structural characterization of these compounds.
