Abstract:

Polysaccharide from Laminaria japonica (LPA-P) was isolated by using aqueous citric acid solution. After
the removal of protein and salt, LPA-P was purified by DEAE Sepharose fast flow chromatography to obtain LPA-P1,
LPA-P2, and LPA-P3. The respective relationships of bile salt adsorption capacity and antioxidant activity with molecular
weight, sulfated group content and monosaccharide composition for LPA-P and its fractions were investigated. The results
indicated that all LPA-P and its purified fractions contained sulfated group. LPA-P3 had the highest sulfated group content
of 5.36%, while LPA-P1 had the lowest of only 1.22%. The major monosaccharide composition consisted of fucose,
galactose and mannose. Galactose was the major monosaccharide in both LPA-P and LPA-P3, whereas mannose dominated
the monosaccharide composition of both LPA-P1 and LPA-P2. LPA-P3 was the highest in fucose. The average molecular
weights of LPA-P, LPA-P1, LPA-P2 and LPA-P3 were estimated to be 20.13, 17.55, 28.71, and 17.14 kD, respectively.
LPA-P3 exhibited the strongest antioxidant capacity but LPA-P1 the weakest; the antioxidant capacity of LPA-P was a little
stronger than that of LPA-P2. LPA-P3 had the strongest bile salt adsorption capacity, followed by LPA-P and LPA-P2.
LPA-P1 had substantially no bile salt adsorption capacity. According to the structure-activity relationship of polysacchrides
from Laminaria japonica, it is speculated that the higher the contents of sulfated group as well as fucose and galactose, the
stronger bile salt adsorption capacity and antioxidant activity of the polysaccharides.

Key words: Laminaria japonica, polysaccharides, bile salt adsorption capacity, antioxidant activity