Gas chromatography-mass spectrometry demonstration of sterols glycosides in eucalypt wood, kraft pulp and process liquids.

Abstract

The occurrence of steryl glycosides (SG) and acyl steryl glycosides (ASG) in eucalypt (Eucalyptus globulus) wood has been investigated. These compounds were analyzed as their trimethylsilyl ethers by gas chromatography-mass spectrometry (GC/MS) using a 15 m-length high-temperature capillary column with thin film, and identified on basis of their mass spectra and relative retention times comparing with those of authentic standards. Significant amounts of SG were identified in eucalypt wood whilst only traces of ASG could be detected. Eucalypt SG and ASG occur in the pyranoside form, which is readily distinguishable from the furanoside configuration by the mass spectra of their trimethylsilyl derivatives. The sterol part of the SG and ASG consisted of sitosterol, being sitosteryl 3β-D-glucopyranoside and sitosteryl (6´-O-palmitoyl)-3β-D-glucopyranoside the major SG and ASG found in E. globulus wood. The presence of SG and ASG was also investigated after kraft cooking by analyzing unbleached pulp and process water samples. The GC/MS results also revealed the presence of sitosteryl 3β-D-glucopyranoside in these samples. By contrast, no ASG could be detected. Therefore, we have shown that SG survive the kraft cooking and can be found at least partly intact after pulping being a possible cause for pitch deposits together with free and esterified sterols.