An unusual juxtaposition of polysaccharide components of Collema leptosporum
1999
Prado, S.R.T. | Gorin, P.A.J. | Stuelp, P.M. | Honda, N.K. | Iacomini, M.
The lichenised ascomycete, Collema leptosporum Malme, was extracted with aqueous methanol to give traces of mannitol and 3-O-beta-D-glucopyranosyl-D-mannitol (2.7% yield). The residue was consecutively extracted with hot water to give a complex uronic acid-containing polysaccharide, and then with hot aqueous alkali which provided a mixture of polysaccharides. This was fractionated with Cetavlon to give a branched galactomannan, which had the lowest content of galactose yet reported for such a lichen polysaccharide. It has a main chain of (1 leads to 6)-linked alpha-Manp units partly substituted at O-2,4 by non-reducing end-units of Manp and Galp, shown by NMR spectroscopy to have alpha- and beta-configurations, respectively. The other polysaccharide component was unexpectedly a branched (1 leads to 3), (1 leads to 6)-linked beta-glucan, which is typical of a basidiomycete, whereas those of ascomycetes contain similar linkages but in linear glucans.
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