Preparation of different molecular weight polysaccharides from Porphyridium cruentum and their antioxidant activities.

Hermetical microwave was used to degrade Porphyridium cruentum polysaccharides from 2918 to 256.2, 60.66 and 6.55kDa. The antioxidant properties of different molecular weight polysaccharides were evaluated by determining the scavenging ability of free radicals, inhibitory effects on lipid peroxidation in liver homogenates and hemolysis of mouse erythrocytes. Analysis of physicochemical properties confirmed that microwave degradation might not markedly change the chemical components of the polysaccharides. High-molecular-weight polysaccharides from P. cruentum had no obvious antioxidant activity, but low-molecular-weight fragments after degradation exerted an inhibitory effect on oxidative damage. The 6.55-kDa fragment had stronger antioxidant activity than the 60.66 and 256-kDa fragments.