Objective To investigate the effects of the different ingredients separated from the
Algal Polysaccharide Sulfate (Aps) against
the
Platelet Activating Factor (Paf) and explore the relationship between their structures and activities. Methods The APS from brown algae were separated by alkali extraction and ethanol precipitation. The effects against PAF were cheched with the method of rabbit platelet aggregation. The assay of sulfuric acid-carbazole was used to determine the contents of the glucuronic acid, the method of sedimentation by barium chloride for the contents of sulfate radical and the assay of sulfuric acid-cysteine for the fucose. Results All the ingredients of APS showed a certain activity against PAF. The contents of the fucose were kept nearly consistent while the contents of sulfate and glucur-onate changed greatly. The results revealed that the lower level for the glucuronate and the higher level for the sulfate, the stronger anti-PAF activity the had . Conclusion The ingredients from APS had definite anti-PAF activities which was increased along with the decrease of the glucuronate level and the increase of the sulfate contents.