Enhancing effect of polysaccharides from an edible brown alga, Hijikia fusiforme (Hijiki), on release of tumor necrosis factor-alpha from macrophages of endotoxin-nonresponder C3H/HeJ mice.

An enhancing activity for the release of tumor necrosis factor-alpha from macrophages of C3H/HeJ mice was detected in the hot water-soluble extract of an edible brown alga, Hijikia fusiforme (Hijiki in Japanese). This activity was divided into the polysaccharide and nonpolysaccharide fractions, with the former showing much higher activity than the latter. The active components in the polysaccharide fraction were further purified by ion-exchange column chromatography and gel permeation system of high-performance liquid chromatography; they were identified as polysaccharides with apparent molecular mass of about 2,000 and 70 kDa and were designated Hijiki-derived polysaccharides I and II (HPS-I and HPS-II), respectively. They also enhanced macrophage-dependent suppression against the growth of EL-4 tumor cells in an in vitro culture experiment, with HPS-I exhibiting much higher immunologic activity than HPS-II. Furthermore, other comparative experiments confirmed that the immunoenhancing activities of polysaccharides from H. fusiforme are associated with the functions of polysaccharides themselves, but not with the artificial activity induced by contaminated endotoxins. Some biochemical properties of immunoenhancing polysaccharides were partially characterized, and the significance of this finding is discussed from the viewpoint of the protective role of edible seaweeds against carcinogenesis.