Immune-enhancing activity of polysaccharides from Hibiscus sabdariffa Linn. via MAPK and NF-κB signaling pathways in RAW264.7 cells

Four novel heteropolysaccharides (HSP-I, HSP-II, HSP-III, HSP-IV) were isolated from blossoms of Hibiscus sabdariffa. Average molecular weights of the four polysaccharides were 8.7 x 10(3) Da, 1.4 x 10(4) Da, 4.4 x 10(4) Da and 1.4 x 10(5) Da, respectively. Glucuronic acid, rhamnose, mannose, glucose and galactose composed the main components of HSP-II at an approximate molar ratio of 1:9.89:4.64:1.99:7.65. (1 -> 3)-linked glycosidic bond formed the main linkage type of HSP-II and its branch linkage types were (1 ->), (1 -> 6), and (1 -> 2)-linked glycosidic bonds. All fractions could significantly promote the proliferation of spleen cells induced by Con A and LPS. HSP-II showed greater immune enhancement potential than other fractions based on production of NO in RAW264.7 cells. HSP-II also dramatically increased secretion of INF-alpha and IL-6, as well as mRNA expression of iNOS, IL-beta and IL-6 through activating phosphorylation of ERIC, JNK, p38 and p65. HSP-II might be a novel immunomodulator by activating macrophages through MAPK5 and NF-kappa B signaling pathway. (C) 2017 Published by Elsevier Ltd.