A novel linear 3-O-methylated galactan isolated from Cantharellus cibarius activates macrophages

Abstract

A novel polysaccharide (WCCP-N-b) with a molecular weight of 18 kDa was isolated and purified from the fruiting bodies of Cantharellus cibarius. Monosaccharide composition, methylation analysis and NMR spectra indicated that WCCP-N-b was a linear α-1,6-galactan, partially methylated at O-3 of galactose. The molar ratio of Gal, 3-methylated-Gal, Glc and Man was 14.4:4.6:1.0:1.2. WCCP-N-b could significantly increase macrophage phagocytosis, release of NO and secretion of TNF-α, IL-6 and IL-1β. On a cellular mechanistic level, WCCP-N-b activated MAPKs and NF-κB signaling pathway via Toll-like receptor 2 (TLR2). To further elucidate the structure-function relationship, WCCP-N-b was hydrolyzed by acid. Four degraded fragments were obtained, with molecular weights of 16.1 kDa, 11.2 kDa, 5 kDa and 3.5 kDa, respectively. Their macrophage activation effects were significantly decreased along with the molecular weight decrease. Collectively, WCCP-N-b could activate RAW264.7 cells, and the activation effect was related to its molecular weight.