Structural Features and Digestive Behavior of Fucosylated Chondroitin Sulfate from Sea Cucumbers <i>Stichopus japonicus</i>

Abstract

Fucosylated chondroitin sulfate from sea cucumber <i>Stichopus japonicus</i> (FCS_SJ) has been demonstrated with various biological activities; however, its precise structure is still controversial, and digestive behavior remains poorly understood. FCS_SJ was purified, and its detailed structure was elucidated mainly based on the NMR spectroscopic methods. Its main chain was characterized as →4)-β-d-GlcA-(1 → 3)-β-d-GalNAc-(1→ with GalNAc4<i>S</i>6<i>S</i>:GalNAc4<i>S</i> in a ratio of 1.5:1, and three types of sulfated fucosyl branches attaching C-3 of GlcA, namely, Fuc<i>p</i>2<i>S</i>4<i>S</i>, Fuc<i>p</i>3<i>S</i>4<i>S</i>, and Fuc<i>p</i>4<i>S</i>, were found in a ratio of 2:1.5:1. The digestibility of FCS_SJ was investigated in vitro, and the unchanged molecular weight and reducing sugar content indicated that FCS_SJ was not broken down under salivary and gastrointestinal digestion. Furthermore, FCS_SJ showed a significant inhibitory impact on pancreatic lipase dose-dependently but not on α-amylase, indicating that the inhibition of pancreatic lipase by FCS_SJ might be a pathway for its hypolipidemic effect. These findings propose a fucosylated chondroitin sulfate and provide insight into the mechanism of its physiological effects in the digestion system.