Degraded polysaccharides from Porphyra haitanensis: purification, physico-chemical properties, antioxidant and immunomodulatory activities.

To explore effect of the structural properties of porphyra haitanensis polysaccharide on its biological activity, degraded porphyra polysaccharides were separated and purified by Cellulose DEAE-52 and Sephadex G-100 chromatography, obtaining three purified components (P1, P2 and P3). All the three components were sulfate polysaccharides containing the repeating units of → 3) ß-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →, and → 3) ß-D-galactose (1 → 4) α-L-galactose-6-S (1 →, and → 3) 6-O-methyl-ß-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →. The molecular weight of the three fractions was measured to be 300.3, 130.4 and 115.1 kDa, respectively. Their antioxidant activity was investigated by the determination of the free radical scavenging effect and ferric reducing power. It was found that P1, P2 and P3 possessed marked antioxidant activity. It was also found that they appreciably enhanced the proliferation, phagocytic ability and nitric oxide secretion in RAW264.7 cells. Lower molecular weight and higher sulfate content were beneficial to bioactivities of P. haitanensis polysaccharides. Overall, P2 and P3 possess superior immuno-modulatory activity to that of P1 and PHP. Thus, the current work will provide the basis for the better utilization of P. haitanensis to develop the related functional foods.

Purification, characterization and antioxidant activity of polysaccharides from Porphyra haitanensis.

In order to study the antioxidant activity of Porphyra haitanensis polysaccharides and the effect of their structure on the antioxidant activity, the Porphyra haitanensis polysaccharide (PHP), prepared by hot water extraction and alcohol precipitation, was separated and purified by Cellulose DEAE-52 ion exchange and Sephadex G-100 column chromatography. Three purified components including PHP1, PHP2 and PHP3 were obtained, and chemical composition analysis and structural characterization were performed. The in vitro free radical scavenging activity of the purified polysaccharide fractions and their ability to relieve oxidative stress in macrophage RAW264.7 were investigated. The results indicated that all the three fractions possessed appreciable DPPH radical, superoxide anion radical, and hydroxyl radical scavenging ability and reducing power. They were also found to effectively reduce the MDA content and ROS level, and to improve the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) in H2O2-treated RAW264.7 cells. Among the three polysaccharides, PHP3 possessed the most potent activity. Porphyra haitanensis polysaccharides have potential to develop as natural non-toxic antioxidants and may find application as the ingredients of functional foods.

Improved antioxidant and immunomodulatory activities of enzymatically degraded Porphyra haitanensis polysaccharides.

Porphyra haitanensis polysaccharide (CPH) was degraded by pectinase to improve its biological activities. Box-Behnken response surface design was used to optimize the hydrolysis conditions. The molecular weight of CPH and the degraded P. haitanensis polysaccharide (DCPH) were measured to be 524 and 217 kDa, respectively. GC-MS spectrometry results showed that CPH and DCPH were mainly composed of galactose. In vitro antioxidant assays indicated that DCPH possessed improved radical scavenging activity and ferric iron reducing power when compared to those of CPH. In H2 O2 -treated RAW264.7 cells, DCPH was also found to be more effective in reducing the generation of malondialdehyde and reactive oxygen species than CPH. The immunomodulatory assays demonstrated that DCPH possessed superior activities in enhancing the proliferation, phagocytosis, and NO secretion in a RAW264.7 macrophage cell model to those of CPH. PRACTICAL APPLICATIONS: Polysaccharide is the most abundant bioactive component of an edible red algae Porphyra haitanensis. However, the use of CPH is limited due to its relatively low biological activities. Thus, in order to fully utilize P. haitanensis, it is necessary to enhance the biological activities of CPH for its practical use. An efficient and practical method to enhance the bioactivities of P. haitanensis polysaccharide has been developed in the present work. The DCPH prepared in this work could have potential applications in food and medicinal areas.