Wood Chemistry PSE 406
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Transcript of Wood Chemistry PSE 406
PSE 406: Lecture 15 1
Wood ChemistryPSE 406
Lecture 15Stilbenes, Flavonoids, Condensed and
Hydrolysable Tannins, other Miscellaneous Extractives and
Inorganic Compounds
PSE 406: Lecture 15 2
Stilbenes Phenolic extractive found in the heartwood of
softwoods» Particularly prevalent in Pinus
Most often 2 aromatic rings: occasionally more Presence of double bond linkage
» Naturally present most often in trans form
CH CH
HO
4-Hydroxystilbene
CH CH
OH
HO
Pinosylvin
CH CHHO
Glu O
Piceid
PSE 406: Lecture 15 3
Flavonoids
Serve many roles in plants:» Protection» Coloration» Other unique roles.
(Western Hemlock)
O
OH
OH
OH
OH
HO
Catechin
PSE 406: Lecture 15 4
FlavonoidsGeneral Structural
Information
Polyphenolic compounds found in softwoods and hardwoods
Composed of diphenylpropane units C6-C3-C6
Eight structural classifications Flavonoids differ through
substitution on the rings» Typically OH or OCH3 groups» Typical to have OH on positions:
– 5 and 7– 3’, 4’ and 5’
Are also present as gylcosides
O
A
B
C2
3
456
7
8
2'3'
4'
5'6'
PSE 406: Lecture 15 5
Representative Structures of Flavonoid Classes
O
OOH
HO
Chrysin
O
OH O
OH
OH
OH
HO
Taxifolin
O
OOH
HO
Pinocembrin
O
O
OH
OH
HO
Pinobanskin
O
OH O
OH
OH
OH
HO
Quercitin
O
OH
OH
OH
OH
HO
Catechin
(Douglas Fir)
(Western Hemlock) (Oak)
PSE 406: Lecture 15 6
FlavonoidsBiological Significance
Not all flavonoids have same function in plants
Anti-fungal Antioxidant Color: bright colors in plants
PSE 406: Lecture 15 7
FlavonoidsLocation 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
PSE 406: Lecture 15 8
FlavonoidsMedicinal 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
PSE 406: Lecture 15 9
Condensed Tannins
Condensed tannins are formed through the polymerization of flavan-3-ol (catechin) and flavan–3,4-diols (leucoanthocyanidins)» 2-50 units
– Typically 2-8
» Linkages can be through a variety of sites
O
OH
OH
Flavan-3,4-diols(Leucoanthocyanidins)
O
OH
Flavan-3-ols(Catechins)
PSE 406: Lecture 15 10
Condensed Tannins
Typical Structure of Condensed Tannins
O
OH
O OH
OH
OH
OH
OH
OOH
OH
OH
HO HO
HO
HO
O
OH
OH
Leucoanthocyanidins (flavan-3,4-diols)
O
OH
Catechins(flavan-3-ols)
PSE 406: Lecture 15 11
Condensed TanninsLocation in the Tree
Western hemlock» Bark: 18% tannins» Wood: 2% tannins
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Condensed TanninsBiological Significance
Protection of plants against insects/animals» Bad Taste (bitter taste)
Toxic to bacteria Pine calluses: created by fungal invasion
» Tree forms calluses as protective tissue» Calluses contain high levels of tannins
Uses of condensed tannins» Leather tanning: 10,000+ year old industry» Adhesives
PSE 406: Lecture 15 13
Hydrolyzable TanninsStructure
Polymers (esters) of a sugar (usually glucose) with one or more polyphenolic carboxylic acids.
Gallotannins: Gallic acid polymer Ellagitannins: Ellagic Acid polymer
COOH
OH
OHHO
Gallic Acid
OH
OH
CO
OH
OHC
HO
O
HOO
Digallic Acid
OH
C
O
OH
OH
O
C
HO
O
O
Ellagic Acid
PSE 406: Lecture 15 14
Hydrolyzable TanninsPolymer Structure Example
O
O
O
OH
O
O
HO
HO
OH
O
HO
HO
O
OH
OHO
OH
OH
OH
O
OH
OH
OH
O
O
OH
OH
O
O n
Sugar
PSE 406: Lecture 15 15
Hydrolyzable TanninsGeneral Information
Rare to nonexistent in softwoods. Hardwoods which contain large amounts:
» Oak (gallic and ellagic tannins)» Eucalyptus (Ellagitannins)» Chestnut (gallic tannins)
Hydrolyzable tannins located in heartwood. Pulp and paper problems:
» Increased consumption of bleaching chemicals.» Coloration problems.
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Tetraterpenes
Polymers of isoprene containing 40 carbons (8 isoprene units)
Most common are the carotenoids» Generally derivatives of lycopene
– This is a carontenoid which is in high concentration in red fruits (gives color): tomatoes, watermelon, guava, etc.
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Carotene
Tetraterpene carotenoid found in dark green and orange yellow vegetables.
In the human body, it is converted to vitamin A Has been shown to be have many health
related benefits.
PSE 406: Lecture 15 18
Alkaloids (1) These nitrogen containing
compounds are found in a variety of different plants.» Located in the leaves, fruits, and bark.
Quinine» Used to treat malaria» Isolated from bark of cinchonas (South
American Hardwood) – some eucalyptus species
» Causes pulping problems Strychnine
» Found in seeds of tree Strychnos nux-vomica (Tropical hardwood)
N
NCH3
O O
+OH-
Strychnine
N
N
CH2
HO
H3CO
Quinine
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Alkaloids (2)
You are all aware of the alkaloids shown on this page you probably have never seen their structures. These are typically found in small amounts in plants but are worth large sums of cash.
NO
O
N
N
N
N
O
O
N
O
O
Nicotine Caffeine
Cocaine
PSE 406: Lecture 15 20
Inorganic Materials
Inorganic materials » Plants contains small amounts of most metals.
– Some are used by living cells– Some present as contaminants
Ash content gives a rough idea of the amounts of metals present.» Sugar cane: 1.7-3.8% ash» Corn Cobs: 2% ash
Temperate woods contain 0.1-1% ash while tropical and subtropical species contain up to 5% ash.» Main components Ca (50%), potassium and
magnesium.
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Inorganics in Grasses
Grasses contain high levels of inorganics particularly silica.
Wheat straw: Reported values 4-12+% ash» Leaves: 14-19% ash, 10-14% silica» Nodes: 8-14% ash, 5-7% silica» Internodes: 3+% ash, 2+% silica