Squid is too important seafood; which is well for its wide varieties, wide spreading distribution, abundance, and fishing production. Meanwhile, it is representative of the increased waste production in the seafood industry. The resulting byproducts largely consist of the head, fin, wings, and viscera; which contain abundant natural proteins, lipids, and minerals.
The marine bio-processing industry offers great potential to utilize these byproducts. Proteolysis is an efficient way to produce bioactive peptides and free amino acids from the discarded byproducts with high nutritive value and functional properties, which can use in the food and medicine industries. But a heteropolysaccharide, SV2-1 with a molecular weight of 23 kDa was isolated from the viscera autolysates of squid (Ommastrephes bartrami); as the major polysaccharide component.
Therefore the structures of SV2-1 was found to be a backbone consisting of alternate →4)-α-l-Fucp-(1→ and →3)-β-d-GlcUA-(1→ at a molar ratio of 1:1, and with a single branch of α-N-acetylgalactosamine at the C-3 position of the 90% of the fucose according to chemical analysis and NMR analysis. But it is interesting that many examples reveal marine animals; contain abundant fucosylated polysaccharides.

The monosaccharide composition

Those polysaccharides isolated from sea cucumber and cephalopod also have GlcA, GalNAc, and Fuc as the monosaccharide composition could illustrate that fact. However, the structures are different from SV2-1. The heteropolysaccharide from sea cucumber; so which is chondroitin, has a repeating disaccharide unit of GlcA-GalNAc at the backbone with fucose as the branch; rather than Fuc at the backbone with GalNAc as the branch as the SV2-1.

Therefore the polysaccharide isolated from the ink of cuttlefish S. maindroni also has Fuc at the backbone; which is the same as SV2-1. By contrast, the polysaccharide isolated from S. maindroni was composed of Fuc and GalNAc at the backbone with GlcUA as the branch. SV2-1 can protect PC12 cells from the death induced by 6-OHDA. Oxidative stress has considered as a major factor caused by 6-OHDA.

Regulates apoptosis in PC12 cells

Oxygen tension regulates apoptosis in PC12 cells. SOD is a powerful antioxidant that catalyzes redox reactions by converting superoxide radicals into hydrogen peroxide and oxygen; which plays a beneficial role in the response of the brain to oxidative stress and protects brain tissues from further oxidative damage. Meanwhile, SOD reflects the level of ischemic tissue. MDA, a stable end product of lipid peroxidation, is responsible for ROS-mediated oxidative stress and in disease severity.
In the present study, oxidative injury in PC12 was by measuring SOD activity and MDA concentration. SV2-1 significantly reversed the abnormality of SOD and MDA. This result indicated that SV2-1 may normalize the redox status of PC12 cells under 6-OHDA injury and the underlying mechanism may be involved in its antioxidant capacity.