Xizhen Niu

Structural studies on a novel fucogalactan sulfate extracted from the brown seaweed Laminaria japonica.

A low molecular weight fucogalactan, obtained from the brown seaweed Laminaria japonica, was separated into three fractions (LF1, LF2 and LF3) by DEAE-Sepharose FF column chromatography. All three fractions contained predominantly fucose, sulfate group and galactose. The results showed that the main fraction LF2 consisted of l-fucose, d-galactose and sulfate at a molar ratio 6:1:9. Structural study on the LF2 was carried out by NMR spectroscopy. The backbone of LF2 was primarily (1-->3)-linked alpha-l-fucopyranose residues (75%) and a few (1-->4)-alpha-l-fucopyranose linkages (25%). The branch points were at C-4 of 3-linked alpha-l-fucopyranose residues by beta-d-galactopyranose unites (35%, molar ratio) or at C-2 of 3-linked alpha-l-fucopyranose residues by non-reducing terminal fucose unites (65%, molar ratio). Sulfate groups occupied at position C-4 or C-2, sometimes C-2, 4 to fucose residues, and C-3 and/or C-4 to galactose residues. The structure of LF2 was supposed as following: .

Preparation of the different derivatives of the low-molecular-weight porphyran from Porphyra haitanensis and their antioxidant activities in vitro

Porphyran extracted from Porphyra haitanensis is a sulfated polysaccharide, which possesses excellent antioxidant activities. In this study, we prepared one low-molecular-weight porphyran and its sulfated, acetylated, phosphorylated and benzoylated derivatives. Their antioxidant activities were investigated including scavenging effect of superoxide, hydroxyl and 1,1-diphenyl-2-picrylhydrazyl radicals. The results of chemical analysis and FT-IR spectrums showed the modification was successful. And in addition, we found that certain derivative exhibited stronger antioxidant activity than low-molecular-weight porphyran. The benzoylated derivative showed the most excellent antioxidant activity in three assays, so this derivative needs to be attended to.

Chemical composition and moisture-absorption/retention ability of polysaccharides extracted from five algae

In this study, we prepared seven polysaccharides extracted from five algae including one brown alga Saccharina japonica, one red alga Porphyra haitanensis and three green algae Codium fragile, Enteromorpha linza and Bryopsis plumose. The chemical composition and capability of moisture-absorption and moisture-retention were investigated in comparison with those of hyaluronic acid (HA). The low molecular weight polysaccharides extracted from brown seaweed exhibited the highest moisture-absorption and moisture-retention abilities of all of the polysaccharides studied and performed better than HA. The relationships between chemical composition (including sulfated groups, monosaccharide, and molecular weight) and the functions of polysaccharides were also studied. We found the sulfated group was a main active site for moisture-absorption and moisture-retention abilities. These abilities were also related to molecular weight; with the exception of the low molecular weight polysaccharide extracted from red seaweed, lower molecular weight improved moisture-absorption and moisture-retention abilities.