Biomass Fundamentals
Modules 6-11: Carbohydrates: a major building block for
biomass
A capstone course for
BioSUCCEED:
Bioproducts Sustainability: a University Cooperative Center
of Excellence in EDucation
The USDA Higher Education Challenge Grants program gratefully
acknowledged for support
This course would not be possible without
support from:
USDA
Higher Education Challenge (HEC) Grants Program
www.csrees.usda.gov/funding/rfas/hep_challenge.html
Emil Fischer:
Father of Carbohydrate Chemistry
• Prof. of Organic
Chemistry University of
Berlin
(1852-1919)
• Known for his
monumental work on
configuration of sugars
• Also worked on
aminoacids, proteins,
indoles &
stereochemistry
• As a Grad. student he
discovered
phenylhydrazine
Nobel prize for Chemistry 1902
What is a carbohydrate?
• Carbohydrates are
polyhydroxyl compounds
general formula
Cn(H2O)n
“Hydrates of
Carbon”
• All contain hydroxyl groups
-OH
primary -CH2OH and
secondary =CHOH
Quiz M6/11.1
1.
What is a saccharide?
• A carbohydrate possessing
the empirical formula,
Cm(H2O)n, or hydrates of
carbon analogous to
inorganic hydrates (e.g., Fe2
(SO4)3*6H2O)
• Shown at left is open chain
form (Fischer Projection
formula) of D-Glucose,
isomer in which the hydroxy
on C5 is RIGHT
D-Glucose is a stereospecific
form of glucose having the
orientation specified by the Fisher
Projection formula shown at left.
Abundance
Quiz M6/11.2
1.
• Carbohydrates are the most
abundant living biomaterial (a
substance derived from living
systems) on the planet
• They comprise the bulk of plants,
while constituting a significant
portion of the cellular membrane
of animals (yet, lesser than
proteins and lipids)
• They are however, a significant
source of stored energy
Typical carbohydrates
• D-glucose, D-fructose
• Sucrose: common table
sugar that is a disaccharide
synthesized from
dehydration of D-glucose &
D-fructose
• Lactose: common milk
sugar that is a disaccharide
of D-glucose & D-galactose
Structure of carbohydrates
Based on glyceraldehyde
Quiz M6/11.1
1.
Common carbohydrates
ESSAY
At this point, describe in a
page or less, how XXX
contributes to your lifestyle
or how you would like it to
Common carbohydrate: sucrose
• Dimer
• Disaccharide
• Indispensable to our
way of life!
• Notice -acetal
linkage
The linkage between glucose and fructose
responsible for the formation of this dimer
known as sucrose is known as a glycosidic
bond.
Nomenclature
Quiz M6/11.4
Monosaccharides - characterized in terms
of the number of carbons
Example
# of Carbons
Name
3
triose
4
tetrose
xylose
5
pentose
glucose
6
hexose
glyceraldehyde
etc
1.
Nomenclature: part II
CHO
H
OH
HO
H
CHO
H
HO
H
OH
H
OH
HO
H
H
OH
HO
H
CH2OH
d-glucose
CH2OH
l-glucose
Shown above are two forms of a generic
amino acid (where R = carbon-containing
groups) that are said to be “enantiomeric.”
Nomenclature: part III
1
CHO
H
OH
2
HO
H
H
3
H
H
OH
4
4
HO
HO
5
OH
6
CH2OH
4
HO
HO
5
H OH
2
3
H
OH
H
O
1
H
D glucose
Fisher Projection
H
OH
6
OH
6
5
2
3
H
H
H O
OH
OH
4
6
HO
HO
OH
1
H
H
Chair Conformation
-D glucopyranose
5
3
H
H
H O
2
H
OH
1
OH
-D glucopyranose
• C1: Anomeric Carbon
• α : Axial configuration (vertical to the seat of the chair)
• β : Equatorial configuration (parallel to the seat of the
chair)
Most Important Chemical Consideration of
Sugars
Consider the anomeric carbon! The aldehyde on the one
position can be nucleophilically attacked by any of the hydroxyls!
Hemiacetalization Concept Key to
Carbohydrate Ring Structures
Nomenclature of Carbohydrates
• D, L Defines the configuration at C5
D has the OH at Right in Fischer projection
L has the OH at Left in Fischer projection
• Gluco defines the configuration of the OH at C2, C4, C5. These OH’s are
on same side while the C3-OH is opposite to others
• α,β defines the configuration of the OH at C1, the anomeric carbon
• Pyran indicates 6 member ring size
• Furan indicates 5 member ring size
Examples follow
In Glucuronic acid C2, C4, C5 OH’s are on same
side
H
C
H
HO
H
H
H
O
OH
C
H
O
OH
H
HO
H
OH
HO
H
OH
H
CO2H
glucuronic acid
OH
CO2H
galacturonic acid
Alditols
• In Mannitol C2, C4,
C5 OH’s are not at
same side in Fisher
Projection
CH2OH
CH2OH
HO
HO
H
H
H
OH
H
OH
H
OH
HO
H
H
OH
CH2OH
CH2OH
Mannitol
Xylitol
Conformations
Anomers
CH2OH
O OH
OH
OH
OH
OH
-D glucopyranose
[a]
25
D
CH2OH
O
OH
-D glucopyranose
+19o
For aged solutions [a]
OH
OH
+112o
25
Rotations of
Fresh Solutions
= +52.7o
D
Reason: Mutarotation is the best evidence for the cyclic
hemiacetal structure of D-(+)-glucose
Monosaccharides,Hemiacetal Formation II
CH2OH
H
C
C
H
OH
HO
CH2OH
O
..
H
H
C
C
C
H
OH
O
H
H
C
C
H
OH
H
C
C
H
OH
HO
O
OH
C
H
C5 OH attacks aldehyde giving a pyranose ring (6 member structure)
CH2OH
C H O
..
C
H
OH
HO
CH2OH
H
H
HO
C
C
C
H
OH
H
O
H
C H O
C
OH
C
OH
H
C
C
H
OH
H
C4 OH attacks aldehyde giving a furanose ring (5 member structure)
-D glucofuranose
CH2OH
HO
O
OH
-D glucopyranose
Mutarotation
CH2OH
O
OH
OH
OH
OH
Ring closure between C1
OH and C4 -OH
CHO
OH
CH2OH
OH
OH
CHO
OH
OH
CH2OH
O OH
HO
OH
H
HO
H
H
OH
H
OH
OH
CH2OH
D glucose
CH2OH
OH
CHO
OH
OH
OH
Ring closure between
C1 and C5 -OH
CH2OH
O OH
OH
OH
OH
-D glucofuranose
OH
-D glucopyranose
Hemiacetalization Concept Key to
Carbohydrate Ring Structures
• Oligosaccharides
– consist of several monosaccharide residues
joined together with glycosidic linkages
– di, tri, tetrasaccharides
(depending on the number of monosaccharides)
– up to 10 - 20 monosaccharides (depending on
analytical techniques i.e GC vs LC/MS)
• Polysaccharides
– refer to polymers composed of a large number of
monosaccharides linked by glycosidic linkages
ex. Cellulose
Cellobiose
CH2OH
HO
HO
O
OH
CH2OH
OH
HO
O
O
CH2OH
anhydroglucopyranose
unit
O
HO
O
OH
OH
HO
O
OH
O
CH2OH
n = 1 -5000
oxygen bridge
(ether-type or
glycosidic bond)
Cellulose
-D-anhydroglucopyranose units linked by
(1,4)-glycosidic bonds
6
HO
HO
OH
CH2OH
O
Non-Reducing
End-Group
CH2OH
4
O
HO
5
3
HO
O
2
OH
OH
3'
O
1
4'
5'
2'
CH2OH O
6'
CH2OH
1'
O
O
HO
n
OH
OH
Reducing
End-Group
(potential aldehyde)
Polysaccharides
Polysaccharides are polymers composed of
many monosaccharide units linked by
glycosidic bonds
The glycosidic bond can can have either the α
or a β-configuration and be joined to any of
the hydroxyl groups at C-2, C-3, C-4 or C-6
The chain can either be Linear or Branched
– branches can be single monosaccharide units,
chains of two or more units, or chains of a
variable number of units
Polysaccharides
Polysaccharides can be divided into two classes
– Homopolysaccharides
• consist of only one kind of monosaccharide
ex cellulose
– Heteropolysaccharides
• consist of two or more kinds of
monosaccharides
ex galactoglucomannans
Homopolysaccharides
Homopolysaccharides can be further divided by the
type(s) of glycosidic linkages
Homolinkages - either an α or a β configuration to
a single position (exclusive of any branch
linkages)
•that is a single kind of monosaccharide linked
by one type of bond α-14, β-14, and so on
Heterolinkages - a mixture of a- and bconfigurations and/or mixture of positions
•usually have a definite pattern for the
arrangement of the linkages
Heteropolysaccharides
Heteropolysaccharides can have the same kind
of linkage diversity as with
homopolysaccharides, but now associated with
one or more of the different kinds of
monosaccharide units
– infinite degree of diversity of structure
Polysaccharides
Polysaccharides can not only have
different sequences of monosaccharide
units, but also different sequences of
glycosidic linkages and different kinds of
branching
– a very high degree of diversity for
polysaccharides and their structurefunction relationships
Plant Polysaccharides
The conformation of individual
monosaccharide residues in a polysaccharide
is relatively fixed, however, joined by
glycosidic linkages, they can rotate to give
different chain conformations.
1,4 glycosidic
linkage
OH
O
HO
O
HO


O
HO
OH
O
HO
HO
OH
HO

HO
O
O
1,6 glycosidic
linkage
HO
HO
O

O
HO
O
Plant Polysaccharides
The different kinds of primary structures that
result in secondary and tertiary structures give
different kinds of properties
– water solubility, aggregation and crystallization,
viscosity, gelation, etc.
Polysaccharides have a variety of functions
– Storage of chemical energy in photosynthesis
– Inducing Structural Integrity in plant cell walls
Starch
Starch is composed completely of D-glucose
– found in the leaves, stems, roots, seeds etc in higher plants
– stores the chemical energy produced by photosynthesis
Most starches are composed of two types of polysaccharides - amylose and amylopectin
– amylose - a mixture of linear polysaccharides of D-glucose units linked -(1-4) to each other
• between 250-5,000 glucose residues
The Components of Starch
O
HO
OH
O
OH
O
HO
OH
O
OH
O
(1-4)
HO
Amylose
OH
HO
O
O
OH
HO
O
OH
O
Amylopectin
– Amylopectin - a mixture of branched polysaccharides of Dglucose units linked -(1-4), with ~ 5% -(1-6) branch linkages
• between 10,000-100,000 glucose residues
OH O
OHO
OH O
HO
OH O
OH
O
OH O
OH O HO
O HO
OHO
HO
(1-4)
OH
O (1-6)
O
OH
O
HO
OH
O
HO
O
Starch Polymer Components
Amylose
Amylopectin (1 residue in every 20 is 16 linked to branch off)
The Components of Starch
Amylose
O
HO
Amylopectin
OH
O
OH O
OH
O
HO
OHO
OH
O
OH O
HO
OH O
OH O
OHO
HO
OH O HO
OH
O
(1-4)
HO
OH
HO
O HO
(1-4)
O
OH
O (1-6)
O
OH
O
HO
OH
O
O
OH
HO
O
OH
O
HO
O
OH
O
Starch tertiary structure (Helix)
Building Blocks of Life
Hemiacetalization Concept Key to
Carbohydrate Ring Structures
Fructose is Bane of Our Civilization
•
•
•
•
•
•
Glycoproteins (biomaterial) from food
sugars are sticky – adhere to teeth enamel
Streptococcus mutans also adhere to
biomaterial
The glucose of the sucrose is polymerized
by glucosyl transferase (enzyme of
bacteria) to form plaque
Fructose from the above hydrolysis is
released
Bacteria needs anaerobic conditions
which are partially supprted by plaque to
hydrolyze fructose for energy
Ca3(PO4)2 + CH3CH2(OH)COOH 
CaHPO4 + Ca+2  loss of enamel
Alditols: Reduction Products
Reduced aldehyde
end-group
D-Mannitol
Aldaric Acids: Oxidation Products
• Above is oxidation product of D-galactose
• Galactaric acid
• Why is it not labeled as “D- ?”
Sorbitol (D-Glucitol)
It is a polyol discovered in the berries of the mountain ash in 1872
commercially produced by the hydrogenation (reduction) of glucose).
It does not lead to tooth decay. WHY?
60% as sweet as sucrose with 1/3 fewer calories
Good sugar substitute
Relative Sweetness
COMPOUND
RELATIVE SWEETNESS
Lactose
D-Galactose
Maltose
D-Glucose
Sucrose
D-Fructose
Sodium cyclamate (procarcinogen)
Aspartame
Sodium saccharin (possible carcinogen)
Sucralose (brand name = Splenda)
Neohespiridin dihydrochalcone
5-nitro-2-propoxyaniline
0.2
0.3
0.3
0.7
1.0 (Standard)
1.7
30
190
500
600
1,000
4,000
Glucose Derivative Spotlight: Glucosamine
Nitrogen
• Found in mucin, a glycoprotein constituent of saliva
• Plays important role in production, maintenance, and repair of cartilage
(prevents bone ends from rubbing)
• Used in Europe since 1980s to “offset” onset of osteoarthritis
• USA is now touting its benefits (perform search – 906K hits)
Most Important Chemical Consideration of
Sugars
Consider the anomeric carbon! The aldehyde on the one
position can be nucleophilically attacked by any of the hydroxyls!
Important Oligosaccharides
• ,-tetrahalose: glucose disaccharide found
in the circulatory systems of insects; energy
for insect eggs, larvae, and pupae. Found in
fungi & yeasts
• Raffinose: widely distributed in plants at low
concentration – 1:1:1 D-galactose:Dglucose:D-fructose (galactose+sucrose in
which it is on C6 of glucose moiety)
Starch (Amylose)
• High MW polyglucoside that is plant energy
• Can be hydrolyzed to specific oligosaccharides
• -Amylase (saliva & pancreatic juice) converts it to
maltose and glucose
• -Amylase (in plants only) converts it to maltose –
NOTE: malt from barley is its common source to
BREW BEER
Starch, Part Deux
• Noncrystalline
• Partially water soluble
• 25% amylose (linear polysaccharide), 75%
amylopectin (branched polysaccharide)
Starch Polymer Components
Amylose
Amylopectin (1 residue in every 20 is 16 linked to branch off)
Homework Questions
• Draw structure of raffinose by only consulting
these notes!
• Provide an explanation for the “sweetness” of
saccharides – you may consult the literature
• Using your explanation, design a molecule that
may compete with commercial sugars for
market share!
Article of Interest for Discussion
•
“Chemically modified chitin and chitosan as biomaterials” – Sashiwa, H.; Aiba, S.-I. Prog.
Polym. Sci. 29 (2204) 887-908.
•
http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6TX2-4CNJ8S2-16&_cdi=5578&_user=290868&_orig=search&_coverDate=09%2F30%2F2004&_qd=1&_sk
=999709990&view=c&wchp=dGLbVzbzSkzS&md5=e9e66537b26f5f36324572d9f01635b8&ie=/sdarticle.pdf
•
Chitosan-derivatized -CD (2-position)
•
Slow radiative iodine release in blood of rats
•
Decontamination of textile dye-laden waters
•
Absorbent matrix
•
Positive cholesterol interaction
Structure of Starch
• Unbranched chains
• 500-20K -(14)-Dglucose units
• Extended shape has
possible 7-22 nm
hydrodynamic radius
• Usually forms stiff lefthanded single helix
Hydrogen Bonding in Amylose
• Single helical amylose has H-bonding between O2 
O6 atoms on outside
• Syneresis (release of water) occurs
• Double-stranded crystallites formed resistant to
amylase
• Fairly hydrophobic & low solubility
• Interior is like cyclodextrins – hydrophobic
Cyclodextrins (CDs)
• Cyclic oligomers of -Dglucopyranose
• Glycosidic bonds
• Discovered in 1891 by
Villiers
• Synthesized by the
enzymatic conversion of
amylose & selective
precipitation
Cavity volume: 0.174, 0.262, & 0.472 nm2 for , , & -CDs, respectively
CD Formation
Precipitating
Agent
Yield (%)
-CD
1-decanol
40
-CD
toluene
50-60
-CD
Cyclohexadec8-en-1-ol
40-50
Interesting Properties
• Formation of inclusion (host/guest) complexes with
lipophilics
– -CD: aliphatic chains
– -CD: small aromatics (toluene)
– -CD: larger molecules
• Low toxicity
• Biodegradable
From Frömming and Szejtli: Cyclodextrins in Pharmacy,
Kluwer, Acad. Press, Dordrecht, 1994.
Cyclodextrin Derivatives of
Pharmaceutical Interest
OR
HO
OH
O
OH
O
O
O
OH
OH
HO
OR
O
RO
HO
O
OH
O
OR
O
HO
O
RO
HO
OH
O
HO
O
O
OH
OH
O
HO
OR
Cyclodextrin
R
DS
HPCD
CH2CHOHCH3
0.6
SBECD
(CH2)4SO3- Na+
0.9
RMCD
CH3
1.8
Also the CD derivative: HPCD
Some cyclodextrin-containing products
Cyclodextrin
Product
Trade name
CD
PEG1 iv infusion
Prostavastin (Eur.), Caverject (USA)
CD
Piroxicam tablets
Brexin (Eur.)
HPCD
Intraconazole oral
solution and iv soln.
Sporanox (Eur. and USA)
SBECD
Ziprasidone maleate
im solution
Zeldox (Eur.), Geodon (USA)
RMCD
Estradiol nasal spray
Aerodiol (Eur.)
OP-1206 tablets
Opalmon (Japan)
Diclofenac sodium
eye drop solution
Voltaren (EUR.)
CD
HPCD
World-wide there are close to 30 cyclodextrin containing pharmaceutical products
on the market and most of them are marketed in more than one country. Almost
half of them contain the natural CD.
What are cyclodextrins used for?
• To increase aqueous solubility of drugs.
• To increase chemical stability of drugs.
• To enhance drug delivery to and through biological membranes.
• To increase physical stability of drugs.
• To convert liquid drugs to microcrystalline powders.
• To prevent drug-drug and drug-excipient interactions.
• To reduce local irritation after topical or oral administration.
• To prevent drug absorption into skin or after oral administration.
And so on.
Cyclodextrin complexation:
conventional wisdom
-Cyclodextrin:
Seven -1,4-linked glucopyranose units form a cone
with a hydrophilic outer
surface and a lipophilic
cavity in the center.
Complex Formation
From Frömming and Szejtli:
Cyclodextrins in Pharmacy
Kluwer Acad. Press,
Dordrecht, 1994.
Cyclodextrin Complexes
Doxorubicin-CD complex
Aspirin-CD complex
Why are cyclodextrins better
than organic solvents?
• Frequently less irritating after iv
and im injection.
• Frequently less toxic.
• The drug does not precipitate after
iv injection.
• Can be used in solid dosage
forms.
Homework Questions
• Describe why CD is in “Fabreeze” (P&G
product) and how you think it works.
• How do K1:3 complexes form? Give an
example.