Structural characterization of a distinct fucan sulfate from Pattalus mollis through an oligosaccharide mapping approach

The elucidation of the precise structure of fucan sulfate is essential for understanding the structure -activity relationship and promoting potential biomedical applications. In this work, the structure of a distinct fucan sulfate fraction V (PmFS in Ref 15 and FSV in Ref 16 -> PFV) from Pattalus mollis was investigated using an oligosaccharide mapping approach. Six size -homogeneous fractions were purified from the mild acid hydrolyzed PFV and identified as fucitols, disaccharides and trisaccharides by 1D/2D NMR and MS analysis. Significantly, the sulfation pattern, glycosidic linkages, and sequences of all the oligosaccharides were unambiguously identified. The common 2-desulfation of the reducing end residue of the oligosaccharides was observed. Overall, the backbone of PFV was composed of L-Fuc2S (major) and L-Fuc3S (minor) linked by alpha 1,4 glycosidic bonds. Importantly, the branches contain both monosaccharide and disaccharide linked to the backbone by alpha 1,3 glycosidic linkages. Thus, the tentative structure of natural PFV was shown to be {-(R-alpha 1,3)-L-Fuc2S-alpha 1,4-(L- Fuc2S/3S-alpha 1,4)x-}n, where R is L-Fuc(2S)4S-alpha 1,3/4-L-Fuc4S(0S)- or L-Fuc(2S)4S-. Our results provide insight into the heterogeneous structure of the fucan sulfate found in sea cucumbers. Additionally, PFV and its fractions showed strong anticoagulant and anti-iXase activities, which may be related to the distinct structure of PFV.