The neuroprotective activities of heteropolysaccharides extracted from Saccharina japonica.

Crude fucoidan extracted from Saccharina japonica was separated by anion-exchange chromatography. Then, the neuroprotective activities of the crude fucoidan (J) and its fractions (J0.4, J0.5, J1 and J2) were tested. J, J0.4 and J0.5 were shown to have neuroprotective effects. To simplify the structural features of the compounds, crude fucoidan was degraded to obtain low molecular weight fucoidan (DJ). DJ was further fractionated into DJ0.5, DJ1 and DJ2, and the neuroprotective activities of these fractions were determined. This analysis revealed that DJ and DJ0.5 retained the neuroprotective activity. However, the DJ0.5 fraction remained very complex. Thus, DJ0.5 was further separated into six fractions (F0.1, F0.2, F0.3, F0.4, F0.5 and F1). Finally, it was concluded that the anion-exchange fractions F0.1, F0.2 and F0.3 exhibited neuroprotective activities. These results suggest that heteropolysaccharides might contribute to the neuroprotective activity. Moreover, the neuroprotective heteropolysaccharide fractions contained relatively low fucose (less than 20%) and sulfate (25%), high UA content (more than 10%) and a high molar ratio of all other monosaccharides.