Galactofucoidans from Sargassum fusiforme and their antagonistic effects against the proliferation-inhibition of RAW264.7 macrophage induced by culture supernatants of melanoma cells

Abstract Two purified galactofucoidans, SFA1B-1 and SFA1C-2, with apparent molecular weights of 1.6 × 105 and 8.9 × 104, respectively, were isolated from Sargassum fusiforme via ion-exchange and gel-filtration column chromatography. SFA1B-1 and SFA1C-2 were composed of large amounts of fucose (Fuc), minor amounts of galactose (Gal), and small amounts of xylose and glucuronic acid. The backbone of these galactofucoidans consisted of α-(1→3)-linked Fucp residues sulfated mostly at the C-2 and/or C-4 positions. The backbone was primarily branched at the C-2 and/or C-4 positions probably by side chains comprising t-Fucp residues and (1→4)-Galp residues. Bioactive tests preliminarily showed that SFA1B-1 and SFA1C-2 could strongly not only antagonize against but also reverse the proliferation-inhibition of RAW264.7 cells induced by B16F10-CS. This finding suggests that SFA1B-1 and SFA1C-2 may antagonize the immunosuppressed function of macrophages. However, their possible effects on immunosuppressed peritoneal macrophages from mice or human with tumors and the underlying antagonistic mechanism warrant further investigation.