International Journal of Aquaculture, 2025, Vol.15, No.5, 248-254 http://www.aquapublisher.com/index.php/ija 250 3.3 Sulfate polysaccharide and other secondary metabolites Sulfate polysaccharide is the core of the functional ingredients of seaweed, among which seaweed polysaccharide (Porphyran) is the most popular. Seaweed polysaccharides have significant antioxidant, immunomodulatory and other biological activities, which can enhance the body's anti-infection and anti-tumor ability (Pradhan et al., 2022). Studies have found that the oligomers obtained by degradation of seaweed polysaccharides are more active in antitumor and antioxidant aspects (Figure 1). In addition, seaweed also contains secondary metabolites such as betaine and phytosterol, which have the effects of protecting the liver and regulating lipids (Kim et al., 2024). Overall, the sulfate polysaccharides and a variety of secondary metabolites rich in seaweed provide them with diverse biological functions, making seaweed not only a food, but also a marine resource with multiple health benefits (Huang and Li, 2024). Figure 1 Representative images of CV staining in the hippocampus (upper panels) and its CA1 subregion (lower panels) of the sham (a, b), vehicle–IR (c,d), 25 mg/kg (e, f), and 50 mg/kg Porphyran-IR (g,h) groups at 4 days after IR. Strong CV stainability is observed in the stratum pyramidale (SP, asterisks) consisting of pyramidal cells in the CA1 subregion of the 50 mg/kg Porphyran–IR group in comparison with that in the vehicle–IR and 25 mg/kg Porphyran–IR groups, showing damaged pyramidal cells (arrows). CA, cornu ammonis; DG, dentate gyrus; SO, stratum oriens; SR, stratum radiatum. Scale bar = 400 µm (a, c, e, g) and 50 µm (b, d, f, h) (Adopted from Kim et al., 2024) 4 Antioxidant Properties of Seaweed 4.1 Study on the in vitro free radical scavenging activity A large number of in vitro antioxidant experiments have proved that seaweed extract (including proteolytic products, polyphenols, etc.) can effectively eliminate free radicals such as DPPH and ABTS, and its scavenging rate increases significantly with the increase of concentration. The antioxidant peptide obtained by proteolysis of nori showed a good dose-effect relationship in DPPH free radical scavenging experiments; the nori polyphenol extract also showed excellent antioxidant ability in ABTS free radical and reducing force tests (Yang et al., 2024). These results demonstrate the free radical removal potential of seaweed from an experimental level, providing a scientific basis for its antioxidant and health care effects. 4.2 Antioxidant mechanism: enzymatic and non-enzymatic pathways The antioxidant mechanisms of seaweed include non-enzymatic pathways (its active substances directly eliminate free radicals, chelate metal ions, etc.) and enzymatic pathways (intake of seaweed can improve the activity of antioxidant enzymes in the body and reduce peroxidative damage indicators) (Zhong, 2024). Non-enzymatic effects mainly rely on the polyphenols in the seaweed to eliminate excess free radicals through hydrogen supply and chelation, while enzymatic effects indirectly reduce oxidative damage by upregulating the expression of endogenous antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) through the active ingredients of seaweed to indirectly reduce oxidative damage (Wu et al., 2020). The two pathways complement each other, allowing seaweed to play an antioxidant protective role at the cellular level and overall body level. 4.3 Comparison with other seaweed antioxidant capacity Compared with green algae and brown algae, red algae, seaweed, is rich in substances such as bromine polyphenols, and its antioxidant activity has been outstanding in many tests. The study compared the antioxidant
RkJQdWJsaXNoZXIy MjQ4ODYzNA==