Characterization of lyso-galactolipids, C-2 and C-3 O-acyl trigalactosylglycerol isomers, obtained from the lichenized fungus Dictyonema glabratum.
A mixture of two lyso isomers of a galactolipid was obtained from Dictyonema glabratum. Aqueous hydrolysis gave rise to galactose and glycerol in a 3:1 molar ratio. ESI-MS spectroscopy gave, in the positive-ion mode, a pseudomolecular ion at m/z 839 and daughter ions with m/z 677, 600, 515 and 353, suggesting three galactosyl units linked to a glycerol moiety, substituted by one O-acyl group. 1D and 2D NMR experiments were used to characterize the glycolipid, and HMQC examination showed three anomeric signals, corresponding to two alpha-Galp and one beta-Galp residue liked to glycerol. The glycolipid structure was shown to be O-alpha-D-Galp-(1-->6)-O-alpha-D-Galp-(1-->6)-O-beta-D-Galp-(1<-->1)-2- and -3-monoacyl-D-glycerol, the latter structures not having been previously found in nature. The fatty acid composition was determined by GC-MS of derived methyl esters: that of palmitic acid C(16:0) was the most abundant, although the presence of C(12:0), C(14:0), C(16:1) and C(18:0) esters was observed.
Sassaki
G L
GL
Departamento de Bioquímica, Universidade Federal do Paraná, CP 19046, 81531-990, PR, Curitiba, Brazil.
Gorin
P A
PA
Iacomini
M
M
D002240:Carbohydrate Sequence; D038983:Galactolipids; D006017:Glycolipids / Q000737:chemistry / Q000302:isolation & purification*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D020072:Polyporales / Q000737:chemistry*
D038983:Galactolipids; D006017:Glycolipids