Wood extractives, or wood extracts, are tiny molecules that are extracted from wood using solvents or other extraction methods. The extractives are the waxes, fatty acids, resin acids, and terpenes of a tree. They are classified as phenolic, aliphatic, alicyclic compounds, or other lesser compounds.
The overall composition of the extracts varies dramatically from tree species to tree species. The growth environment that the tree grows within also has an effect on the composition and levels of wood extractives.
Wood extracts are considered to have a low molecular weight, and do not have an effect on the growth rate of the plant. Therefore, they are not vital to plant growth.
Wood extractives must be gathered quickly from a tree because as soon as a tree is felled its extractive levels immediately start to decrease. The exposure of the tree’s inner layers to air causes a chain reaction that generates free radicals rapidly. The free radicals work as oxidants. Light also appears to accelerate the oxidation process, which quickly breaks down the extractives.
The most common types of wood extractives are terpenoids, terpenes, phenolic, and aliphatic extractives. Wood extractives are gathered using solvent and cold/hot water extraction methods. It is important to not use chemical-based solvents because doing so would destroy the extractives, rendering them useless.
Extractives in wood are what give it its color, scent, and other physical and mechanical properties. Wood extracts, or extractives, have been in use for centuries in medicine and are used to make essential oils.