Laminaran and three fractions of fucoidan were isolated from brown alga Alaria angusta. The laminaran AaL was characterized as a typical 1,3;1,6-β-D-glucan (ratio of bonds 1,3:1,6 = 10:1). Fucoidans AaF1 and AaF2 are sulfated heteropolysaccharides, containing fucose, galactose, mannose and xylose. The fraction AaF3 is sulfated and acetylated galactofucan with the main chain represented by a repeating unit → 3)-α-L-Fucp-(2,4-SO3(-))-(1 →. According the data of methylation analysis, AaF3 contains mainly 1,3-linked fucose, less 1,4-linked and 1,4,6-linked galactose residues. The autohydrolysis (37 °C) of fucoidan AaF3 allowed to obtain selectively 2-desulfaled polysaccharide fraction, built up of fucose only, and low molecular weight (LMW) fraction. The negative-ion tandem mass spectrometry of LMW fraction, further hydrolyzed by acid hydrolysis identified the following fragments: Gal-2-SO3(-)-(1 → 4)-Gal, Gal-4-SO3(-)-(1 → 4)-Gal, Gal-(1 → 2)-Gal-4-SO3(-), Fuc-2-SO3(-)-(1 → 4)-Gal, Gal-2-SO3(-)-(1 → 3)-Fuc-(1 → 3)-Fuc, Fuc-2-SO3(-)-(1 → 3)-Fuc-(1 → 4)-Gal. The laminaran AaL and the fucoidan AaF3 exhibited no cytotoxicity in vitro for HT 29, T-47D, and SK-MEL-28 cell lines. The AaF3 fraction suppressed colony formation of HT 29 and T-47D cells, AaL-only HT 29 cells.
Keywords: Anticancer activity; Brown alga; Depolymerization; Fucoidan; Structure.
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