Sassaki GL, Gorin PAJ, Reis RA, Serrato RV, Elífio SL, Iacomini M. Carbohydrate, glycolipid, and lipid components from the photobiont (Scytonema sp.) of the lichen, Dictyomema glabratum.
Carbohydr Res 2005;
340:1808-17. [PMID:
15963960 DOI:
10.1016/j.carres.2005.05.004]
[Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Accepted: 05/11/2005] [Indexed: 11/20/2022]
Abstract
The photobiont of the lichen, Dictyonema glabratum (Scytonema sp.), was isolated and cultivated in a soil-extract medium and submitted to chemical analysis. Successive extractions with CHCl3-MeOH, aqueous MeOH, and H2O gave rise to solutions of lipids (25%), low-molecular-weight carbohydrates (22%), and polysaccharides (4%), respectively. TLC of the lipid extract showed the presence of glycolipids, which were further purified and examined by NMR spectroscopy and GC-MS. Monogalactosyldiacylglycerol (1%), digalactosyldiacylglycerol (0.8%), trigalactosyldiacylglycerol (0.4%), and sulfoquinovosyldiacylglycerol (0.5%) were identified. The most abundant fatty acid ester in each fraction was palmitic (C16:0), but a great variation of the ester composition from one to another was found. Others present were those of C12:0, C14:0, C15:0, C16:1, C17:0, C18:0, C18:1, C18:2, C18:3, C22:0, C22:2, and C24:0. The lipid extract was also subjected to acid methanolysis, which gave rise to dodecane, 2-Me-heptadecane, 2,6-Me2-octadecane, and 8-Me-octadecane, methyl esters of C14:0, C15:0, C16:0, C16:1, C17:0, C18:0, C18:1, C18:2, C20:0, and C24:0 fatty acids, and the dimethyl ester of decanedioic acid. The polysaccharide had mainly Glc, Gal, and Man, with small amounts of 3-O-methylrhamnose and 2-O-methylxylose, both found in plants, and unexpectedly, some of the units were beta-galactofuranose, typical of fungal, but not cyanobacterial polysaccharides. The low-molecular-weight carbohydrates showed mannose as the main free reducing sugar, which differs from Nostoc sp. and Trebouxia sp. photobionts.
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