Two galactofuranomannans, Ths-4 and Ths-5, were isolated from the lichen, Thamnolia vermicularis var. subuliformis, using ethanol fractionation and anion-exchange and size-exclusion chromatography. The average molecular weights of Ths-4 and Ths-5 were estimated to be 19 and 200 kDa, respectively. Structural characterisation of Ths-4, Ths-5 and their partially hydrolysed derivatives was performed by methanolysis and methylation analysis. The intact and partially hydrolysed Ths-4 was further analysed using NMR spectroscopy (1D, COSY, NOESY, TOCSY, HSQC and HMBC). According to the data obtained, the heteroglycans Ths-4 and Ths-5 have similar structures, but have large differences in molecular weight. The structure is composed of 3-O-linked and 5-O-linked galactofuranosyl chains linked to a mannan core. The mannan core consists of a main chain of alpha-(1 -> 6)-linked mannopyranosyl residues, substituted at O-2 with either a single alpha-mannopyranosyl unit or an alpha-Manp-(1 -> 2)-alpha-Manp-(1 -> 2)-alpha-Manp group in the ratio of approximately 1:3, respectively. The polysaccharides have idealised repeating blocks as is shown. (c) 2006 Elsevier Ltd. All rights reserved.
Carbohydrate Research, 2006, Vol 341, Issue 14, p. 2449-2455