A water-soluble low molecular–weight polysaccharide named UP2-1 was isolated and purified from the marine green algae Ulothrix flacca using ion-exchange and size-exclusion chromatography. Composition and characteristics analyses showed that UP2-1 was a sulfated glucuronorhamnan consisting of rhamnose and glucuronic acid in a ratio of 2:1 with 21% sulfate content and a molecular weight of 5.0 kDa. Structural properties were determined using desulfation and methylation analyses combined with infrared spectrum (IR), gas chromatography-mass spectrometer (GC-MS) and nuclear magnetic resonance (NMR). The results showed that UP2-1 was a type of ulvan composed of alternate 4-linked-α-L-rhamnose residues (→4)-α-L-Rha(1→) and 4-linked-β-D-glucouronoc acid residues. The sulfate groups were mainly present in the O-3 position of →4)-α-L-Rha(1→. Most (70%) of the rhamnose was sulfated. UP2-1 also had a small amount of →4)-α-L-Rha(1→ branch at the O-2 position of the →4)-α-L-Rha(1→. UP2-1 exhibited significant anticoagulant and immunomodulating activity in vitro. This study demonstrated that the green algae Ulothrix flacca, which is used as a food and traditional marine herb in China, could also be considered as a source of bioactive ulvan.

To explore bioactive polysaccharides from the byproducts of squid processing, a heteropolysaccharide, named SV2-1, was isolated from the viscera of squid Ommastrephes bartrami by autolysis, anion-exchange and gel-permeation chromatography and measured for its neuroprotective activity. It was a homogeneous polysaccharide with a molecular weight of 2.3 kDa by HPSEC analysis. SV2-1 contained glucuronic acid, galactosamine and fucose in the ratio of 1.0:1.1:1.2. Its structural characteristics were elucidated by methylation analysis, gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR). The backbone of SV2-1 was composed of alternant →4)-α-l-Fucp-(1→ and →3)-β-d-GlcUA-(1→ Most of →4)-α-l-Fucp-(1→ (90%) was substituted by single α-d-GlcNAc as the branches. SV2-1 can protect against the death of PC12 induced by 6-OHDA, and effectively improves cell viability and reduces extracellular LDH release in PC12 cells after injury. Moreover, SV2-1 significantly increases SOD activity but decreases MDA levels.

A water-soluble sulfated polysaccharide, F2-1, was obtained from the marine green alga, Codium isthmocladum, using ion-exchange and size-exclusion chromatography. Structure analysis showed that the F2-1 was a sulfated arabinan comprising Ara, Rha, Man, Gal, and Xyl with an 18% sulfate content and a molecular weight of 100 kDa. Methylation analysis combined with desulfation, GC-MS, IR, and NMR spectroscopy showed that the backbone of F2-1 was →4)-β-L-Arap(1→ residue. Its 2-O and/or 3-O positions showed sulfate modification; additionally, the 2-O or 3-O position showed branch points. The side chains were composed of →5)-β-D-Galf, (1→2,6)-β-D-Galf(1→, (1→2)-β-L-Rhap4S, →4)-α-D-Glcp(1→, and terminal α-D-Galp(1→ and β-D-Xylp(1→. Polysaccharides containing β-D-galactofuranose are rarely found in seaweed. F2-1 exhibited significant anticoagulant activity in vitro. Our findings suggested that the green-tide alga, Codium isthmocladum, can be considered as a useful resource for bioactive polysaccharides.