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Wood Chemistry
PSE 406
Lecture 12
Wood Extractives
PSE 406 Lecture 12
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Agenda
 General Extractives Information
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Classes
Chemistry
Occurrence
Uses
PSE 406 Lecture 12
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Tree Extractives (1)
 Besides the big three wood compounds, trees contain
other compounds that serve a variety of functions
including:
» Protection (from insects, animals, and rot).
» Attractants (flowers, fruits)
» Food storage
 The amount of extractives in wood can range from 120% (species, position in the tree, season,
geographical location)
 More in heartwood
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Tree Extractives (2)
 Extractives add
significant properties to
wood:
» Color
» Odor
» Density
 These compounds are
typically present in very
limited amounts but still
affect the wood
properties greatly.
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Protection Chemicals
 Here is a list of the classes of extractives that
can serve to protect the tree.
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Terpenes
Resin Acids
Flavonoids
Lignans
Stilbenes
Tannins
Phenolics
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“Other Extractives”
 These extractives are in the tree typically for
reasons other than protection.
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Fats and fatty acids
Proteins
Flavonoids
Sterols
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The Fragrance of a Tree
 Each tree has a unique fragrance.
» Some have strong fragrances than others like Cedar.
» Some have only light odor.
 The aroma is due to volatile compounds produced by
the tree (the odor chemicals become gases easily).
 These chemicals can be isolated and sold.
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General info
 End use:
» Pine pitch and resins (waterproof boats, in torches and
binders).
» Medicine, etc.
 Monomers, dimers, polymers.
 Softwood have higher extractive content than
hardwood.
 Might be poplar (water) or non-polar solvent
(toluene, ethanol, or ether) soluble.
 More extractives in bark compared to whitewood.
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Pitch Chemicals
 When you grab a softwood tree and your hand
sticks to the tree, you have discovered pitch.
 Pitch consists of about 50/50 terpenes and resin
acids. Resin acids are glassy like chemicals also
made of isoprene units.
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Pitch as a Bandage
 When a softwood tree
is wounded, it releases
pitch to “seal” the
wound.
» Terpenes serve as the
antiseptic and then
evaporate.
» Resin acids serve as the
bandage (and also as an
antiseptic).
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Sterols
Role in Nature
 Sterols are found in plants as both free sterols,
as sterol esters (of fatty acids) and as sterol
glycosides
 Serve as components of membranes
» Work with phospolipids to create membranes
which are only permeable to certain chemicals
 Sterol esters
» Believed to serve as transport agent to get
sterols from site of biosynthesis to membrane
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What are Fats and Oils?
 Fat and oils are energy
storage material.
 Fats and oils are similar
chemically: the difference
is that fats are solids at
room temperature and
oils are liquids.
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Chemical Composition of
Fat/Oils
 Esters of long chain fatty acids
» Most often with glycerol
 Trigylcerides, diglycerides, & monoglycerides
 Similar structures in all plants. What varies is the fatty acids
attached to the glycerol and the percentage of tri, di, and
monoglycerides
H2C O CO R1
H2C O CO R1
H2C O CO R1
H 2C O CO R2
H2C O CO R2
H
H
H2C OH
H2C O CO R3
H2C OH
H2C OH
Diglyceride
Triglyceride
Monoglyceride
O
H2C O C
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Chemical Composition of Fatty
Acids
 Fatty acids are long chained carboxylic acids
» Mostly even numbered chains
– 16-18 carbons most common
– 20-22 less common
» 80% unsaturated: 1, 2 or 3 double bonds
Secondary Fatty Acids
Major Fatty Acids
COOH
COOH
Palmitic acid (C16)
Oleic acid (C18)
COOH
COOH
Linolenic acid (C18)
COOH
Linoleic acid (C18)
Eicosadienoic acid (C20)
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Fat (Oil) Content
 There are high levels of fats in seeds.
» Corn and soybeans contain 10-20% oils.
» Canola and sunflower contain up almost 50%
oils.
» Nuts 50-70% oils
 In agricultural crops the majority of the oils
are triglycerides.
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Fats in Trees
 Fats are found in living cells - parenchyma
» Very low content (1-2%) in oleoresin.
» More present in sapwood than heartwood.
» High content in many nuts.
 Function
» Fats role in trees is the same as in your waist
line: serves as a storage material.
» The amount of fat in the tree is seasonally
dependent.
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Waxes
 Wax is the water
resistant protective
coatings of leaves, fruits,
and trees (bark). Wax is
a mixture of a variety of
different chemicals.
» Waxes consist mainly of
very long chained (C12-38)
fatty acid esters of long
chained alcohols.
Waxes
CH3 (CH2)n O CO (CH2)m CH3
C20H41OH
C24H49OH
PSE 406 Lecture 12
Arachidic Alcohol
Lignoceric Alcohol
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Flavonoids
OH
OH
 Serve many roles in
plants:
O
HO
OH
» Protection
» Coloration
» Other unique roles.
OH
Catechin
(Western Hemlock)
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Flavonoids
Location in Tree
 Found in the heartwood of most tress
» Often responsible for coloration
 Found in lesser amounts in the sapwood
 Are found in large amounts in bark and roots
 Leaves: green tea can contain up to 30%
flavonoids
 Flowers: color is often due to flavonoids
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Flavonoids
Medicinal Uses
 Higher flavonoid content in diet reduces
chance of:
» Heart Disease
– Strengthen capillaries
– Dilates blood vessels
» Stroke
» Cancer: all types reduced
– Finnish study = ½ rate of cancer
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Condensed Tannins
Biological Significance
 Western hemlock
» Bark: 18% tannins, wood: 2% tannins
» Chestnut and oak
 Protection of plants against insects/animals
» Bad Taste (bitter taste)
 Toxic to bacteria
 Uses of condensed tannins
» Leather tanning: 10,000+ year old industry
» Adhesives
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Alkaloids
 These nitrogen containing
compounds are found in a
variety of different plants.
» Located in the leaves, fruits, and
bark.
O
N
N
O
N
N
 You are all aware of the
Nicotine
alkaloids shown on this
N
page you probably have
never seen their structures.
These are typically found in
small amounts in plants but
Cocaine
are worth large sums of
cash.
PSE 406 Lecture 12
N
Caffeine
O
O
O
O
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