Structure, chemical and enzymatic modification, and anticancer activity of polysaccharides from the brown alga Turbinaria ornata

In this study, water-soluble polysaccharides from the brown alga Turbinaria ornata (laminaran ToL, fucoidans ToF1 and ToF2) were obtained. The anticancer activity of these polysaccharides and modified derivatives of fucoidan ToF2 against several cancer cell lines was studied. The structure of fucoidan ToF2 was thoroughly investigated using methylation analysis of polysaccharides and mass spectrometry of low molecular weight derivatives of fucoidan, released by fucoidanase from the marine mollusk Patinopecten yessoensis. Fucoidan ToF2 contained a main chain, built up of (1 -> 3)-linked fucose residues with branches of single residues or short chains, consisting of fucose and galactose at C2 and C4, and single HexA residues at C2. The following fragments were identified in the structure of fucoidan: Fuc-2,4-SO3--(1 -> 2)-Fuc, Fuc-2-SO3--(1 -> 4)-Fuc-2-SO3-, Gal-2-SO3--(1 -> 3)-2-SO3--Fuc, Fuc-4-SO3--(1 -> 4)-Gal-3SO(3)(-), Fuc-2-SO3--(1 -> 4)-Gal-3-SO3--(1 -> 4)-Fuc, Gal-4SO3 --(1 -> 4)-, Fuc-4-SO3--(1 -> 3)-Fuc, and HexA-(1 -> 2)Fuc- 4-SO3-. Sulfate groups occupied the positions at C2 and/or at C4 of fucose and C2, C3, and C4/C6 of galactose residues. The fucoidan ToF2 and its derivative obtained by enzymatic hydrolysis inhibited colony formation of human colorectal, breast adenocarcinoma, and malignant melanoma cell lines in vitro.