Abstract: The scavenging effects of polysaccharides from the mycelia (intracellular) and culture supernatant (extracellular) of Cordyceps sinensis after 6 days of cultivation were determined against hydroxyl free radicals generated in a Fenton reaction system, superoxide anion free radicals (by pyrogallol auto-oxidation method) and hydrogen peroxide. The extracellular polysaccharides from Se-rich Cordyceps sinensis had the strongest ability to scavenge superoxide anion free radicals and hydrogen peroxide, followed by the intracellular polysaccharides from Se-rich Cordyceps sinensis as well as the extracellular and the intracellular polysaccharides from common Cordyceps sinensis. By the scavenging effect against hydroxyl free radicals, the four polysaccharides could be ranked in the following order: the extracellular polysaccharides from Se-rich Cordyceps sinensis, the extracellular polysaccharides from common Cordyceps sinensis, the intracellular polysaccharides from Se-rich Cordyceps sinensis and the intracellular polysaccharides from common Cordyceps sinensis. Adding each of the four polysaccharide solutions (100 mg/L) at a level of no less than 80, 40μL and 90μL had a scavenging rate of over 50% against hydroxyl and superoxide anion free radicals as well as hydrogen peroxide, respectively.

Key words: polysaccharides from Cordyceps sinensis, Se-rich Cordyceps sinensis, radicals, antioxidation in vitro