Identification of 4,6-O-(1-carboxyyethylidine)-d-galactose in extracellular polysaccharide fromPalmella texensisUTEX 1708

Abstract

Extracellular polysaccharide (EPS) from Palmella texensis UTEX 1708 contained galactose as a sole sugar constituent. 1H-NMR spectroscopy indicated the possibility of the presence of pyruvyl groups. Pyruvyl groups were also supported by the positive result of coloremetric assay. Methylation analysis before and after depyruvylation showed that a 2,3-linked galactose was pyruvylated at the 4,6-positions. Studies of trimethylsilyl (TMS) derivatives of methylglycosides on gas chromatography (GC) supported the 4,6-position and the resulting fragmentation pattern on GC-mass spectroscopy confirmed the presence of the pyruvic acetal, 4,6-O-(1-carboxyethylidine)-d-galactose residue. The occurence of either galactan or pyruvylated galactose in green algae has not yet been reported.