The structure of fucoidan isolated from Laminaria hyperborea was elucidated and chemically tailored in order to obtain a clear structure-function relationship on bioactive properties with a minimal amount of variations among the tested molecules. Analysis revealed a sugar composition of 97.8% fucose and 2.2% galactose. Analysis of the glycosidic linkages showed (1→3)-α-l-fuco-pyranose (31.9%) to be the dominant residue, followed by 1→2-linked (13.2%) and 1→4-linked (7.7%) fuco-pyranose as well as a high degree of branching (22.4%). Inductively coupled plasma mass spectrometry (ICP-MS) revealed a sulfate content of 53.8% (degree of sulfation (DS) = 1.7). Raman spectroscopy determined SO4 located axial at 4C and equatorial at 2C as well as an absence of acetylation. SEC-MALS analysis determined a high molecular weight (Mw = 469 kDa), suggesting a highly flexible main chain with short side chains. Both chemical shifts of the fucoidan, proton, and carbon were assigned by NMR and revealed a highly heterogeneous structure in terms of glycosidic linkages. Bioactivity was assessed using a lepirudin-based whole blood model. The immediate responses by coagulation and complement cascades were measured by prothrombine factor 1 and 2 (PTF1.2) and the terminal complement complex (TCC). Cytokines involved in inflammation were detected in a 27-plex cytokine assay. Fucoidan with a high Mw and DS inhibited coagulation, complement, and the cytokines PDGF-BB, RANTES, and IP-10, while activating MCP-1. These effects were obtained at the concentration of 1000 ug/mL and partly at 100 ug/mL. In low concentrations (10 ug/mL), a coagulation stimulating effect of highly sulfated fucoidans (DS = 1.7, Mw = 469 kDa or 20.3) was obtained. These data point to a multitude of effects linked to the sulfation degree that needs further mechanistic exploration.
Keywords: NMR; Raman; SEC-MALS; desulfation; inflammation; sulfated fucans.