GC-MS and SPME Techniques Highlighted Contrasting Chemical Behaviour in the Water Extractives of Modified Castanea sativa Mill. and Fagus sylvatica L. Wood

Abstract

The sweet chestnut (Castanea sativa Mill.) and European beech (Fagus sylvatica L.) are wood species largely present in the European forest area. The composition and relative variation of the secondary metabolites of chestnut and European beech wood under thermal effect is a little-explored area. The wood material was thermally modified at 170 °C for 3 h using a thermo-vacuum technology. Raw and modified wood extracts were obtained with aqueous extraction techniques in an autoclave, subsequently lyophilized, solubilized in ethyl acetate, and determined by Gas Chromatographic-Mass Spectrometric Analyses (GC-MS). In addition, the volatile compounds were determined by Solid-Phase Micro Extraction (SPME) analyses. As a general statement, the extraction in an autoclave produced a higher number of compounds in the modified chestnut and beech wood compared to unmodified wood material. Beech wood showed low degradation in the compounds after modification. Notably, squalene and ar-tumerone were the main bioactive compounds present in beech wood extractives. Chestnut, conversely, showed a greater degradation after thermo-modification. However, a reduction in chemical compounds in the modified samples was also observed. In this case, the main biologically active compounds detected only in the chestnut control samples were apocynin and ar-tumerone. The recovery of this residual wood material, before energy consumption, could provide a sustainable and environmentally friendly means of obtaining natural chemicals suitable for various industrial applications.