Resin canals main components

The oleoresin present in the resin canals of certain conifers, especially pine, is secreted as a viscous fluid when the tree is wounded. Pine oleoresin contains about 25% volatile components known as "volatile oil" (or turpentine) the nonvolatile residue consists mainly of resin acids. 

The lipophilic fraction, extractable with nonpolar solvents (ethyl ether, dichloromethane, etc.) consists mainly of fats, waxes, terpenes and terpenoids, and higher aliphatic alcohols (cf. Sections 5.3.1 and 5.3.2). Terpenes, resin acids, and sterols are located in the resin canals present in the bark and also occur in the cork cells and in the pathological exudate (oleore-sin) of wounded bark. Triterpenoids are abundant in bark /3-sitosterol occurs in waxes, as an alcohol component, and the cork cells in the outer bark (periderm) of birch contain large amounts of betulinol (cf. Fig. 5-6). 

Figure 2.16. Some important extractives of softwoods, (a) A mixture of resin acids in turpentine is present in resin canals of Pinus radiata. (b) Ray parenchyma resin of Pinus radiata consists mainly of fatty acid esters and unsaponifiable materials (a major component of which is 3-sitosterol). (c) Polyphenolics found in Pinus radiata heartwood. (d) Some polyphenols that are significant in certain other softwoods.

The four main components of wood resin from most species are the resin acids, free fatty acids, combined fatty acids (esters), and unsaponifiable sterols, alcohols, terpenes, and waxes. (The resins from tropical hardwoods (e.g., Shorea spp.) can be mainly terpenoid and steroid compounds (e.g., 88, 89, 156, 157, 184, 187) and the cause of color reversion and resin spots (156, 157) (see Sect. 9.3.7.2).) As mentioned, the composition of canal and parenchyma resins differ, and in living Picea and Pinus spp. woods, levopimaric acid predominates in the canal resin over abietic, neoabietic, and palustric acids. The resin acids are the most brittle or hardest, whereas the others range between the fluid and solid state. Consequently, variations in composition will affect the plasticity or stickiness of the resultant pitch (30). Deposits at different points in a paper mill processing ther-... 

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