A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds in Scots pine ( Pinus sylvestris) wood : Part II. Hydrophilic compounds

Abstract

Hydrophilic extracts of Scots pine ( Pinus sylvestris) heartwood and sapwood and a solid Scots pine knotwood sample were studied by UV resonance Raman spectroscopy (UVRRS). In addition, UVRR spectra of two hydrophilic model compounds (pinosylvin and chrysin) were analysed. UV Raman spectra were collected using 244 and 257 nm excitation wavelengths. The chemical composition of the acetone:water (95:5 v/v) extracts were also determined by gas chromatography. The aromatic and oleophilic structures of pinosylvin and chrysin showed three intense resonance enhanced bands in the spectral region of 1649–1548 cm −1. Pinosylvin showed also a relatively intense band in the aromatic substitution region at 996 cm −1. The spectra of the heartwood acetone:water extract showed many bands typical of pinosylvin. In addition, the extract included bands distinctive for resin and fatty acids. The sapwood acetone:water extract showed bands due to oleophilic structures at 1655–1650 cm −1. The extract probably also contained oligomeric lignans because the UVRR spectra were in parts similar to that of guaiacyl lignin. The characteristic band of pinosylvin (996 cm −1) was detected in the UVRR spectrum of the resin rich knotwood. In addition, several other bands typical for wood resin were observed, which indicated that the wood resin in the knotwood was resonance enhanced even more than lignin.