Molecular characteristics of partially hydrolyzed fucoidans from sporophyll of Undaria Pinnatifida and their in vitro anticancer activity

The effects of molecular characteristics on the anticancer activity of fucoidans were investigated after hydrolysis by copper acetate and then fractionation with 30 and 5 kDa membranes, which produced three fucoidan fractions: F>30 K, F5–30 K and F<5 K. The F>30 K and F5–30 K consisted of mostly carbohydrate (58.2–61.3%) and sulphate (31.7–35.5%) with small amounts of proteins (1.2–6.4%). However, the major constituents of F<5 K were sulphate (31.8%) and ash (37.5%) with smaller amounts of carbohydrate (15.5%) and protein (1.2%). The molecular weights (Mw) of F>30 K, F5–30 K and F<5 K, obtained by a light scattering technique, were 262, 5.6 and 1.6 kDa, respectively. The observed anticancer activities were 18.0–28.5% for F>30 K, 19.2–57.5% for F5–30 K and 26.5–36.5% for F<5 K, respectively, in the concentration range of 0.2–0.8 mg/mL. The results suggest that the anticancer activity of fucoidans could be considerably improved by lowering their Mw and by improving the binding properties of sulphate groups possibly through changing the molecular conformation.