Abstract: The effects of reagents and solvents on the sulfation of Acaudina-fucoidan (AFuc) were investigated and AFuc was chemically modified by chlorosulfonic acid-pyridine (CA-Py) and sulfur trioxide-pyridine (SO₃-Py) in two solvents including N,N-dimethyl formamide (DMF) and pyridine (Py).The results indicated that the sulfur content of sulfated Acaudina fucoidan (S-AFuc) reached more than 50% with CA-Py as the reagent,and only reach about 20% with SO₃-Py as the reagent.The reaction temperature can be low with DMF as solvent and Py must be 90 ℃ or more with higher yield.FT-IR analysis suggested that the characteristic absorption peak of sulfate significantly enhanced.Anti-oxidation analysis revealed the ability of S-AFuc on scavenging DPPH· radical was highest,then hydroxyl radical second and superoxide anion radical least.The antioxidatnt activity of S-AFuc with SO₃-Py as the reagent was higher than that of CA-Py,DMF as solvent better than Py.Hence,SO₃-Py in DMF for sulfation of AFuc was comparatively simple and feasible.

Key words: Acaudina fucoidan, sulfation, antioxidant activity