The isolation, structure characterizations and anti-photoaging activities of sulfated polysaccharides isolated from Sargassum fusiforme

Background Our previous study found that crude polysaccharide extracted from Sargassum fusiforme (PSF) exhibited excellent anti-photoaging activity, but the composition responsible for this activity remained unknown. Results In this study, three fractions (P1, P2 and P3) obtained by hot water extraction and column chromatographic separation from PSF were structurally characterized. The anti-photoaging activities of these isolated polysaccharides were evaluated using HaCaT cells. The results showed that P1, P2 and P3 were acidic polysaccharides with 42.94%, 40.75% and 2.21% uronic acid. In addition, the contents of sulfate groups were 3.01%, 10.05% and 7.44%, respectively. Moreover, their content of reducing sugar was low, and none of the fractions had a triple-stranded helical structure. P1 had the largest average molecular weight of 208.89 kDa, while P2 and P3 had a relatively lower molecular weight of 154.09 and 151.71 kDa, respectively. Treatment with P2 effectively safeguarded the viability of HaCaT cells exposed to UVB irradiation. Additionally, it inhibited the secretion of MMP-1 and MMP-3 while elevating the content of hydroxyproline (HYP) in the cell supernatant. Methylation and NMR analysis suggested the main structure of P2 might be -> [4)-beta-ManA-(1]23 -> 4)-beta-ManA-(1 -> 3)-beta-d-Glcp-(1 -> 4)-beta-d-Glcp-(1 -> 4)-beta-d-Glcp-(1 -> . The two terminal groups of beta-ManA-(1 -> and beta-d-Glcp-(1 -> were connected via the glycosidic bonds of -> 3, 4)-O-3 in beta-ManA-(1 -> and O-6 in -> 4, 6)-beta-d-Glcp-(1 -> , respectively. Conclusions These findings will open new avenues for exploring the potential use of Sargassum fusiforme polysaccharide, particularly P2, as a functional ingredient with anti-photoaging activity.