7. Extractives

Abstract

The term wood extractives covers a large number of different compounds which can be extracted from wood by means of polar and non-polar solvents. In a narrow sense extractives are those compounds which are soluble in organic solvents, and in this sense the term extractives is used in wood analysis (-» 3.2.4.). But watersoluble carbohydrates and inorganic compounds also belong to the extractable substances.The portion soluble in organic solvents amounts to only few percent in the wood of trees from temperate zones, but the concentration can be much higher in certain parts of a tree, e.g. in branch bases, heartwood, roots, areas of sore irritation. Relatively high amounts of extractives are found in certain tropical and subtropical woods (Table 3-6). Various studies are concerned with the artificial induction of a high extractive production (up to 15%) in pines. In the case of treatment with the herbicide paraquat or similar compounds before harvest, areas soaked with resin (lightwood) are formed within the stem (Conner et al. 1977; Zinkel, McKibben 1978) (-» 18.7.).

Analysis of the Chemical Constituents of Kiln-dry Condensate and its Technological Recovery – Part 2: Semi-volatile and Volatile Extractives

“…Extractives represent a minor fraction in the wood structure and consist of a wide range of hydrophilic and hydrophobic components (Amidon et al 2011). The extractives consist of short-chain carboxylic acids, aldehydes, terpenoids (mono-as for instance α-pinene, β-pinene, Δ3-carene and limonene, sesqui-and diterpenoids), sugars (primarily mono-and disaccharides) and sugar alcohols (glycerol, inositol), fatty acids, resin acids, phenolic substances (like simple phenols, lignans, stilbenes, flavonoids, and hydrolysable tannins) sterols and sterol esters, glycerides, glycosides, and proteins (Fengel and Wegener 1983;Amidon et al 2011). The described extractives (if purified) can be easily used as raw materials in the chemical industry.…”