Chemical structure and biological activity of the (1 → 3)-linked β-D-glucan isolated from marine diatom Conticribra weissflogii

Several polysaccharides are considered to be "biological response modifiers" (BRM) - these refer to biomolecules that augment immune responses and can be derived from a variety of sources. Microalgae produce a diverse range of polysaccharides and could be an excellent source of BRM. Here, we describe the chemical structure and biological activity of water-soluble polysaccharide isolated from the marine diatom Conticribra weissflogii. Using chemical and NMR spectroscopic methods, the polysaccharide was identified as a (1 → 3)-linked β-D-glucan with a low proportion of C-6 substitution by single β-glucose units. The biological activity of this low molecular weight β-glucan (11.7 kDa) was investigated with respect to glioblastoma cell lines (U87 MG and U251) and macrophages (RAW 264.7). We observed that this β-D-glucan did not exhibit cytotoxic activity against glioblastoma cells, but did enhance the phagocytic activity of macrophages, suggesting that it possesses immunomodulatory properties.