Structural characterisation of a new O-methylated heteroglycan, colleman, from the cyanolichen Collema flaccidum

An alkali-extractable heteroglycan, colleman, was isolated from the cyanolichen Collema flaccidum, using ethanol fractionation and anion-exchange chromatography. The average molecular weight was estimated to be 360 kDa. Structural characterisation of the heteroglycan was performed by high-field NMR spectroscopy (1D proton, 2D-COSY, NOESY, 2D-TOCSY, 1H 13C-HSQC, HMBC, H2BC and HSQC-NOESY).According to the data obtained, the structure of colleman is composed of repeating units of A, B, C and D in approximate molar ratio 5:5:2:1;