Carbohydrate, glycolipid, and lipid components from the photobiont (Scytonema sp.) of the lichen, Dictyomema glabratum

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• 作者：Guilherme L. Sassaki ; Philip A.J. Gorin ; Rodrigo A. Reis ; Rodrigo V. Serrato ; Selene L. Elí ; fio and Marcello Iacomini
• 关键词：Scytonema sp. ; Dictyonema glabratum ; Fatty acids ; Glycolipids ; Polysaccharides ; Monosaccharides ; NMR ; GC– ; MS
• 刊名：Carbohydrate Research
• 出版年：2005
• 期刊代码：15_00086215
• 类别：ch
• 出版时间：2005
• 卷：340
• 期：11
• 页码：1808-1817
• 文件大小：295 K

摘要

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 (C_16:0), but a great variation of the ester composition from one to another was found. Others present were those of C_12:0, C_14:0, C_15:0, C_16:1, C_17:0, C_18:0, C_18:1, C_18:2, C_18:3, C_22:0, C_22:2, and C_24:0. 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 C_14:0, C_15:0, C_16:0, C_16:1, C_17:0, C_18:0, C_18:1, C_18:2, C_20:0, and C_24:0 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 β-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.