Structural features and anticancer activity in vitro of fucoidan derivatives from brown alga Saccharina cichorioides.

A fucoidan ScF from brown alga Saccharina cichorioides was extracted, purified and partially depolymerized by autohydrolysis at 37°C for 24, 48 and 72h. Supernatant (SN) and pellet (PL) fractions were obtained by ethanol precipitation of each sample. Unlike spectral data of ScF, NMR of PL derivatives clearly suggested the structure: 1,3-linked α-l-Fucp-4-OSO3- repeating unit. Molecular weights (MWs) of PL fractions were 30, 26 and 18kDa for 24, 48 and 72h of autohydrolyis, respectively. MALDI-TOFMS, size-exclusion HPLC and carbohydrate polyacrylamide-gel electrophoresis (C-PAGE) indicated a similarity of SN mixtures. They consisted mainly of a polysaccharide part (MW 6kDa, C-PAGE data) with a structure similar to PL components (NMR data) and monosaccharides α-l-Fucp-4-OSO3-, α-l-Fucp-2,4-di-OSO3-. PL fractions exhibited almost identical antiproliferative activity in vitro as native fucoidan, while an SN sample for 72h of autohydrolysis was slightly more active against colony formation of colorectal carcinoma cells HT-29.