Molecular Modification Of Polysaccharide Of Porphyridium Creuntum And Its Antioxidant Activity In Vitro

Polysaccharide of Porphyridium creuntum is a sulfate polysaccharide that synthesised by Porphyridium cruentum. Because of its large molecular weight and complex structure, it is hard to detect through traditional method. Both of its properties of physical and chemical and studies of biological functions are subject to certain restrictions. In this research, through two types modified methods of degradation and derivatization, the molecular weight and sulfate-based content of polysaccharide of Porphyridium creuntum are changed. The relationship between molecular weight and sulfuric acid-based content with its physiological activity are discussed through studying its in vitro antioxidant. The main results are as follows:Firstly, the optimized degradation conditions of oxidativing degradation: 8% of H2O2 concentration, 70℃of temperature and 6h of time. Under this condition, the rate of degradation is about 85%, number average molecular weight stabilizes at about 19.4×104 g·mol-1. Three different molecular weights of polysaccharides PSP1, PSP2, PSP3 are obtained.Secondly, PSP4, PSP5 are obtained after Polysaccharide of Porphyridium cruentum derived by sulfation and acetyl esterification. The sulfuric acid-based content of sulfated polysaccharide PSP4 increased from 17.4% to 31.0%, and derivative degree tatsus reachs 79.0%. Polysaccharide PSP1 is derivatived to get three polysaccharides PSP11, PSP12, PSP13 with different sulfate acid-based contents.Finally, through determinating the scavenging effects of polysaccharide on the hydroxyl radical OH·, superoxide anion O2-·and diphenyl bitter acyl free radical DPPH·, in vitro antioxidant activity of different molecular weight and derivatization of polysaccharide Porphyridium cruentum is investigated .The results show that:(1) Different molecular weight of polysaccharide of Porphyridium cruentum PSP1, PSP2, PSP3, have scavenging effects on OH·, O2-·free radicals. With the reduction of molecular weights, the effects were enhanced. Polysaccharide PSP1 has the effect to clear organic free radical DPPH·, but PSP2, PSP3 have no effects. (2) Derived polysaccharide of Porphyridium cruentum PSP4, PSP4 have scavenging effects on OH·, O2-·free radicals, but have no effect in scavenging of organic free radical DPPH·.(3) The antioxidant capacity with different sulfate acid-based content of polysaccharide of Porphyridium cruentum has obvious differences. With the increasing of sulfate acid-based content, the antioxidant capacity of polysaccharide was improved accordingly. The scavenging effect of sulfated of oxidative degradated polysaccharides PSP11, PSP12, PSP13 on OH·, O2-·and DPPH·free radical are positively correlated with concentration. As the content of sulfate acid-based was higher, the effect showed stronger. At concentration of 4.0 mg·mL-1, scavenging rate of PSP12 on OH·, O2-·and DPPH·free radical are 74.7%, 71.6% and 58.9%.