Classification of Wood Extractives 1. Resins of softwoods. Basis of tall oil. Old leather and dye industries used hemlock, oak and chestnut. Hydrolyzable tannins built upon glucose and gallic acid.
Condensed tannins are flavonoid-based and found in most woody plants.
Free radical coupling process is controlled. Typically burned for fuel value. Some research into medicinals or use in adhesives has been done. Certain barks cannot be used as mulch due to toxicity or potential pathogen spread. Mostly calcium salts.