Structural elucidation of bioactive fungi-derived polymers

Chemical composition and molecular structure of exopolysaccharides (EPS) from three strains of fungi, Akanthomyces pistillariiformis BCC2694, Cordyceps dipterigena BCC2073, and Phytocordyceps sp. BCC2744, which can promote the production of IL-8 (a cytokine enhancing wound healing), were elucidated. The results from HPLC after acid hydrolysis revealed that the EPS were mainly composed of glucose indicating the presence of glucan. Galactose, mannose and arabinose were also found as minor monosaccharides. In addition, the protein content in the EPS was determined to be approximately 6–7% with the exception of Phytocordyceps sp. BCC2744 (21%). To identify the linkages between the monosaccharides and the molecular structure of the EPS, methylation followed by reductive cleavage and 13C-NMR analyses were performed. They were shown to be composed of a (1→3)-β-d-glucan backbone substituted at O-6 with side chains of (1→6)-β-d-glucopyranosyl units. The highest branching structure was shown in the EPS from A. pistillariiformis BCC2694, followed by C. dipterigena BCC2073 and Phytocordyceps sp. BCC2744, respectively. Apart from the highly branched at O-6 of (1→3)-β-d-glucan, (1→2) mannan and (1→3) galactan were also found in C. dipterigena BCC2073.