An exopolysaccharide isolated from a coral-associated fungus and its sulfated derivative activates macrophages

A coral-associated fungus Penicillium sp.gxwz446 that produced exopolysaccharde was isolated from the coral Echinogorgia flora in South China. Two neutral exopolysaccharides GX1-1 and GX2-1 were obtained from the fermented broth of the fungus and purified by anion-exchange and gel-permeation chromatography. Chemical and spectroscopic analyses showed that GX1-1 was a glucan, primarily composed of glucose, with a molecular weight of 5.0 kDa. GX1-1 mainly consists of (1→4)-linked α-d-glucopyranose units as the backbone, substituted at C-2 with a single α-d-glucopyranose on every sixth sugar residues. GX2-1 was a galactofuranose-containing mannogalactoglucan with a molecular weight of 9.5 kDa. The main linkages were composed of (1→4)-β-d-Glcp, (1→5)-β-d-Galf, (1→3,5)-β-d-Galf, (1→6)-α-d-Manp and (1→2, 6)-α-d-Manp. GX1-1 showed RAW264.7 macrophage activation activity. After subjecting GX1-1 to sulfated modification, there was about one sulfate substitution on every sugar ring, primarily at O-6. The sulfated derivative of GX1-1 exhibited a more significant ability to promote the pinocytic activity of RAW264.7 cells and induce the production of NO.