Zhien Li

Antioxidant activity of different molecular weight sulfated polysaccharides from Ulva pertusa Kjellm (Chlorophyta)

Polysaccharides extracted from Ulva pertusa Kjellm (Chlorophyta) are a group of sulfated heteropolysaccharides, the ulvans. In this study, different molecular weight ulvans were prepared by H2O2 degradation and their antioxidant activities investigated including superoxide and hydroxyl radical scavenging activity, reducing power and metal chelating ability. The molecular weights of natural and degraded ulvans were 151.7, 64.5, 58.0, and 28.2 kDa, respectively, as determined by high performance gel permeation chromatography. Among the four samples, U3 (the lowest molecular weight sample) showed significant inhibitory effects on superoxide and hydroxyl radicals with IC50 values of 22.1 μ g mL−1 and 2.8 mg mL−1; its reducing power and metal chelating ability were also the strongest among the four samples. All the other samples also demonstrated strong activity against superoxide radicals. The results indicated that molecular weight had a significant effect on the antioxidant activity of ulvan with low molecular weight ulvan having stronger antioxidant activity.

In vivo antioxidant activity of polysaccharide fraction from Porphyra haitanesis (Rhodephyta) in aging mice.

Sulfated polysaccharide fraction F2 from Porphyra haitanesis (Rhodephyta) showed inhibitory effect on the in vitro lipid peroxidation. In the present study, the age-related changes in the antioxidant enzyme activity, lipid peroxidation, and total antioxidant capacity (TAOC) in different organs in mice were investigated and the in vivo antioxidant effect of F2 in aging mice was checked. Increased endogenous lipid peroxidation and decreased TAOC were observed in aging mice. Intraperitoneal administration of F2 significantly decreased the lipid peroxidation in a dose-dependent manner. F2 treatment increased TAOC and the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in all the organs tested in aging mice. It is concluded that the sulfated polysaccharide fraction F2 can be used in compensating the decline in TAOC and the activities of antioxidant enzymes and thereby reduces the risks of lipid peroxidation.

Antioxidant activities of sulfated polysaccharide fractions from Porphyra haitanesis

Three sulfated polysaccharide fractions (F1, F2, and F3) were isolated from Porphyra haitanesis, an important economic alga in China, through anion-exchange column chromatography and their in vitro antioxidant activities were investigated in this study. Galactose was the main sugar unit of the three fractions. The analytical results indicated that polysaccharide fractions from P. haitanesis had similar chemical components to porphyran from other species, but differed in their high sulfate content. The sulfate content of F1, F2 and F3 was 17.4%, 20.5% and 33.5% respectively. All three polysaccharide fractions showed antioxidant activities. They had strong scavenging effect on superoxide radical, and much weaker effect on hydroxyl free radical. Lipid peroxide in rat liver microsome was significantly inhibited, and H2O2 induced hemolysis of rat erythrocyte was partly inhibited by F1, F2 and F3. Among them, F3 showed strongest scavenging effect on superoxide radical; F2 had strongest effect on hydroxyl radical and lipid peroxide.

Extension of life span and improvement of vitality of Drosophila melanogaster by long-term supplementation with different molecular weight polysaccharides from Porphyra haitanensis

Polysaccharides isolated from Porphyra (porphyran) have been known to have diverse biological activities, including immunomodulatory and antioxidant activities. The molecular weight-antiaging activity relationship of degraded porphyrans was examined in this study. Natural porphyran was extracted from P. haitanensis, and then was degraded into different molecular weight fractions, P1 molecular weight 49 kDa, P2 molecular weight 30 kDa, P3 molecular weight 8.2 kDa, by free radical. The influence on life span and vitality of porphyrans were carried out on Drosophila melanogaster. We found that all the degraded porphyrans and natural porphyran (P), added daily to the diet, can significantly increase the life span of D. melanogaster, except for P3. Among them, P1 exhibited the most prolonging life span activity. Furthermore, vitality of middle-aged flies (assessed by measuring their mating capacity) receiving porphyrans was increased considerably in comparison with the controls. Finally, in the heat-stress test, we observed a remarkable increase in survival time, especially in P3-diet groups. These results suggest that porphyrans may be effective in reducing the rate of the aging process and molecular weight has important influence on the effects. It seems that P1 and P2, possessed higher molecular weight, may be more useful in normal metabolic condition and P3, possessed the lowest molecular weight, may be more beneficial for D. melanogaster in stress condition.

In vitro antioxidant activity of acetylated derivatives of polysaccharide extracted from Ulva pertusa (Cholorophta)

Polysaccharides obtained from Ulva pertusa (Chlorophyta) contained a group of sulfated heteropolysaccharide referred to as ulvan in this paper. In this study, the acetylated ulvans with different substitution degree were prepared with acetic anhydride/ p-toluenesulfonyl chloride in N, N-dimethylacetamide, and their antioxidant activities were investigated including scavenging activity on superoxide, hydroxyl radicals and reducing power. The natural ulvan and its derivatives exhibited much higher scavenging activity on superoxide radical than vitamin C. Compared with natural ulvan, the acetylated ulvans exhibited stronger reducing power. The antioxidant activity of acetylated ulvans did not increase with increasing substitution degree. Interestingly, the ulvan (AU4) with highest degree of substitution showed weakest scavenging effect on hydroxyl radical.