Abstract: Objective:To research the effect of anti-mutation in mice and the free radical scavenging activity of crudepolysaccharide from Gracilaria Lemaneiformis. Methods: The crude polysaccharid was extracted from Gracilaria Lemaneiformisby hot water, alcohol-precipitating and protein-depositing with chlor-acetic acid. The inhibitory effect was studied on mouse bonemarrow micronucleus and abnormal sperm induced by cyclophosphamide (cp) and the scavenging activities on• OH of Fentonreaction and O2•produced by pyrogallic acid of crude polysaccharide. Results:At the dose of 4 g/kg, the inhibitory ratio ofmicronucleus was 89.8%; It can significantly inhibit the aberrance of sperm (p<0.05). At the dose of 1.1 mg, the scavengingability on• OH was close to benzoic acid, while it also had the ability to scavenge O2•. Conclusion: The crude polysaccharidethe ability of anti-mutation and the effects of scavenging free radical oxidated out of the body.

Key words: Gracilaria lemaneiformis, polysaccharide, antimutagenicity, free radical