Structure Elucidation of Glykenin, Glycosidic Antibiotics from Basidiomycetes sp. VI. Structure Characterization of the GK Components Using Frit-FAB LC/MS

Abstract

The structures of the glycosidic antibiotics, the glykenin (GK) family, produced by Basidiomycetes sp. were characterized using frit-FAB LC/MS. The GK was separated into nine components (GK-I-VII and DG) with differences in the number and positions of the acetyl groups in the sugar moiety. Although each of these components is further composed of three isomers depending on the three aglycones, it was difficult to isolate individual components because of the presence of the labile acetyl groups in the sugar moiety. For this reason, frit-FAB LC/MS in the negative ion mode was used for the structure characterization of each component. Three peaks were found in the mass chromatogram of each GK component monitored for the molecular ion species. The fragment ions related to the aglycone and sugar moieties were observed in each mass spectrum. Their molecular weights, the locations of the acetyl groups and the presence of three aglycones were confirmed using these ions. Furthermore, a profile analysis of the GK mixture was possible using a gradient elution mode.