Gastric Protective Activities of Sea Cucumber Fucoidans with Different Molecular Weight and Chain Conformations: A Structure–Activity Relationship Investigation

A variety of bioactivities has been established for fucoidan extracted from sea cucumber, whereas its structure-activity relationships have been seldom investigated. In this study, sea cucumber ( Thelenota ananas) fucoidans with different molecular weights were prepared with enzymatic degradation. The chain stiffness and molecular size decreased with the decreasing of molecular weight. Fucoidans with molecular weight of 1380.0, 828.7, and 483.0 kDa exhibited random coil conformations, while fucoidan molecular weight of 215.0 kDa existed as sphere in solution. All examined fucoidans could effectively prevent the ethanol-induced gastric ulcer, of which mechanism involved antioxidation and anti-inflammation. Within the range of the study, the performance of fucoidans adopted random coil conformations declined with the decreasing of molecular weight, and the performance recovered when the chain conformation transited from coil to sphere, indicating the subtle influences of molecular weight and chain conformation on the gastric protective activity of sea cucumber fucoidan.