Extractives of mechanically wounded wood and knots in beech

Abstract

Various types of wound-associated wood, such as discoloured wood including knots of living and dead branches, were sampled from common beech trees (Fagus sylvatica L.), extracted, and the extracts have been analysed by GC and colourimetry assay. Sequential pressurised solvent extraction was applied with cyclohexane and aqueous methanol. The yield of hydrophilic compounds was three to five times higher than that of lipophilic extractives. The fractions differed mainly in their hydrophilic moieties. The lipophilic extractives consisted mainly of free fatty acids, fatty alcohols and free sterols. The yield of fatty acids was slightly higher in reaction zones and knots. The content of free sterols was highest in the reaction zones and in the discoloured wood. The hydrophilic extractives consisted of soluble sugars, various acids and phenolic compounds with catechin as the dominant one. Expectedly, the yield of phenolic extractives and catechin (proanthocyanidins) was highest in knots and woundwood. Discoloured wood gave rise to lower amounts of catechin.

Yield of Stirred Cold Maceration and Extraction of Milled European Black Alder Wood and Bark using Different Solvents

“…Extractions were performed in 300 mL Erlenmeyer flasks equipped with a ground glass stopper. Extractions of 6 hours were conducted by the procedures of Albert et al (2003), and Vek et al (2014). Afterwards, the extracts were filtered through Munktell 388 quantitative ashless filter paper (Ahlstrom Munktell).…”

“…On the other hand, extractives are of great importance in wood technology; they can affect the successful implantation of hydrothermal wood processing (e.g., wood drying), which is necessary in the production of finished wood products. It has been suggested that extractives, especially polyphenols among others, participate in the colour changes of wood during tree growth (Vek et al 2014(Vek et al , 2015 or wood processing (Burtin et al 1998;Kreber et al 1998;Pervan et al 2006;Esteves et al 2008;Straže et al 2008;SandovalTorres et al 2010;Chen et al 2014;Tolvaj et al 2016). Sundqvist and Morén (2002) concluded that the degradation products of wood polymers and extractives participate in wood colour formation during hydrothermal processing.…”

Review on Lipophilic and Hydrophilic Extractives in Tissues of Common Beech

“…In the case of beech wood dust, extracts were characterized by a relatively low amount of lipophilic (Vek et al, 2014). Besides fatty acids, the extracts of beech knots are also characterized by a low concentration of resin acids (Lindberg et al, 2004).…”

“…In addition to simple phenols, the presence of aromatic dimeric structures, i.e. lignin-type compounds, was also proven in beech wood extracts (Koch et al, 2003;Vek et al, 2014). These dimers made up of coniferyl and sinapyl alcohol were referred to as the precursors of a lignin biosynthesis accordingly to Koch et al (2003), but they can represent another group of phenolic extractives, called lignans.…”

“…Furthermore, it can be extracted from these tissues by means of non-polar solvent, i.e. cyclohexane (Vek et al, 2014). Further to the above, vitamin E could be classifi ed as the lipophilic extractive as well.…”