Sargassum hornery fucoidan oligosaccharide: Purification, characterization, and antioxidant effects targeting the MAPK and KEAP1-NRF2 signaling pathways

The current research looked into the inhibitory effect of a purified component of Sargassum hornery fucoidan oligosaccharide (F2) with a sulfate content of 16.35 %, which showed substantial protective effects on H₂O₂-induced oxidative damage in RAW 264.7 cells and zebrafish. The chemical and structural characteristics were examined by GC, FTIR, MS, and NMR spectroscopy, revealing that F2 was composed of not only a mixed oligosaccharide with 1–4 degrees of polymerization but also had a main chain consisting of (1 → 3) linked α-L-Fucp and (1 → 3,4) linked α-L-Fucp, sulfated groups mainly at C2 position. It was found that F2 could activate the MAPK and Keap1-Nrf2 signaling pathways through the dissociation of the Keap1-Nrf2 complex in RAW 264.7 cells. Then Nrf2 entered the cell and bound to the antioxidant response element (ARE), resulting in activating the expression of downstream antioxidant genes. F2 was also found to have a strong protective effect on oxidative stress in zebrafish induced by H₂O₂, which can reduce the heart rate of zebrafish and prevent the generation of intracellular ROS and cell death. Therefore, S. hornery fucoidan oligosaccharide (F2) could be a potential ingredient for functional foods, cosmetics, and pharmaceuticals because of its antioxidant activity.