Chain structures of glucans from Lentinus edodes and their effects on NO production from RAW 264.7 macrophages

Four glucans (LNT-H, LNT-S, LNT-E, and LNT-B) were successively isolated from the fruiting bodies of Lentinus edodes by hot-water, sonication, enzyme, and NaOH. The chemical structures were characterized by GC, FTIR, and 13C NMR, which demonstrated that the four samples are (1 → 3)-β-d-glucans with (1 → 6)-glucopyranoside side groups having different molecular weight. The results of viscometry and atomic force microscopy (AFM) proved that LNT-H, LNT-S, LNT-E, and LNT-B exist as stiff triple helices in water and random coil in dimethyl sulfoxide (DMSO). The morphology of the original triple helix was almost dominated by linear shape, but the renatured LNT-B contains some branched structures in AFM image. Among the four glucans, LNT-H, LNT-E, and LNT-B are clearly contaminated by endotoxin, while LNT-S significantly exhibits nitric oxide (NO) inhibition effect in LPS-stimulated RAW 264.7 macrophages in a dose-dependent manner. Therefore, LNT-S is probably used as a promising molecule which can be helpful to the diseases associated with NO overproduction. This is the first primary report dealing with the suppression of LPS-induced NO from macrophage RAW 264.7 cells by Lentinan.