An immune-enhancing water-soluble α-glucan from Chlorella vulgaris and structural characteristics

Water-extractable polysaccharides obtained from Chlorella vulgaris were fractionated using anion-exchange chromatography to investigate molecular characteristics and biological activities. Crude and fractionated polysaccharides F-1, F-2, and F-3 mostly consisted of carbohydrates (40.0-64.7%), proteins (18.3-31.0%), ash (4.10-16.6%), and uronic acids (1.02-7.30%). Monosaccharide constituents were predominantly glucose (83.9-100%) with small amounts of xylose (10.8-16.1%). Crude polysaccharide and fractions contained 1 or 2 sub-fractions with average M-w values ranging from 19.7 to 1,145x10(3) g/mol. Fractions F-1, F-2, and F-3 stimulated RAW264.7 cells, inducing release of NO, PGE(2), and the inflammatory cytokines TNF-alpha, IL-6, and IL-10. The biologically active part of the immune-enhancing fraction (F-3) was mainly connected via 1,6-linked glucose with branches at C-3 positions.