Abstract: After removal of resin and gutta percha under petroleum ether reflux, Eucommia ulmoides Leaves were decocted with distilled water and the extract was concentrated and fractionally precipitated by adding the one-fold,two-fold and three-fold volumes of alcohol to obtain three groups of crude polysaccharides, PsEUL1, PsEUL2, and PsEUL3. Of them, the group of polysaccharides, PsEUL1, was decolourized on a macro-porous resin (S-8) column and deproteinized using Sevag reagent.After dialysis,the refined PsEUL3 was applied to a diethylaminoethyl (DEAE)-cellulose anion exchange column and isolated into three monomeric polysaccharides, PsEUL11, PsEUL12, and PsEUL13. The assays of anti-complement activities indicated many fractions of polysaccharides have different extent of inhibitory activities with dose-effect relationships. PsEUL13 was demonstrated to be an acidic polysaccharide by reacting with sulfuric acid and carbazole, containing 21.2% of uronic acid. The gas chromatography revealed that it was composed of L-rhamnose, D-fucose, D-arabinose, D-xylose, D-glucose and D-galactose besides uronic acid, their percentage composition being 11.8, 1.6, 37.7, 4.2, 10.7 and 12.8, respectively.

Key words: Eucommia ulmoides Leaf, polysaccharide, isolation, anti-complement activities, molecular structures