While the signalling and biochemical processes of heartwood formation are still poorly understood, the net result of heartwood formation is the deposition of relatively large quantities of secondary metabolites, the types and amounts of which are species and site dependent. Natural restriction to wood decay in many species is due to the secondary metabolites broadly classified as tannins. Generalized Biosynthetic Pathway. Aromatic Biosynthetic Pathway. Terpenes and Resin Acids.
Extractive contents are variable within individual species and are site specific.
Values also depend on the method of extraction, time of extraction vs. date of felling, amount of heartwood, etc.