This presentation summarizes the basics to chemistry of carbohydrates for pharmacy graduates.

1. CHEMISTRY OF CARBOHYDRATES
PREPARED BY: K V NANDA KUMAR
ASSOCIATE PROFESSOR
KRISHNA TEJA PAHRMACY COLLEGE, TIRUPATHI-517506

2. CONTENTS
INTRODUCTION
CLASSIFICATION
NOMENCLATURE
CHEMISTRY OF
GLUCOSE
OTHER SUGARS
GLYCOSIDES

3. INTRODUCTION
Carbohydrates (also called saccharides) are molecular compounds made from just three elements: carbon, hydrogen and oxygen.
Monosaccharides (e.g. glucose) and disaccharides (e.g. sucrose) are relatively small molecules.
They are often called sugars.
Other carbohydrate molecules are very large (polysaccharides such as starch and cellulose).

4. IMPORTANCE
a source of energy for the body e.g.
glucose and a store of energy, e.g.
starch in plants
building blocks for polysaccharides
(giant carbohydrates), e.g. cellulose
in plants and glycogen in the human
body
components of other molecules eg
DNA, RNA, glycolipids,
glycoproteins, ATP

5. DEFINITION OF CARBOHYDRATES
“Saccharide” comes from the word for “sugar” in several early languages (sarkara in Sanskrit,
sakcharon in Greek, and saccharum in Latin).
The terms “carbohydrate,” “saccharide,” and “sugar” are often used interchangeably.
The general formula for carbohydrates is Cx(H2O)y.
Chemically, carbohydrates are defined as “optically active polyhydroxy aldehydes or ketones or
the compounds which produce units of such type on hydrolysis”.

6. CLASSIFICATION OF CARBOHYDRATES

7. SIMPLE CLASSIFICATION
There are two classes of carbohydrates: simple carbohydrates and complex
carbohydrates.
Simple carbohydrates are monosaccharides (single sugars), whereas complex
carbohydrates contain two or more sugar subunits linked together.
Disaccharides have two sugar subunits linked together, oligosaccharides have three
to 10 sugar subunits (oligos is Greek for “few”) linked together, and polysaccharides

8. MONOSACCHARIDES
 A monosaccharide can be a polyhydroxy aldehyde such as D-glucose or a polyhydroxy ketone such as D-
fructose.
 Polyhydroxy aldehydes are called aldoses (“ald” is for aldehyde; “ose” is the suffix for a sugar), whereas
polyhydroxy ketones are called ketoses
 Monosaccharides have the general molecular formula (CH2O)n, where n can be 3, 5 or 6.
 They can be classified according to the number of carbon atoms in a molecule:
n = 3 trioses, e.g. glyceraldehyde
n = 4 tetroses, e.g. threose(‘tetr' indicates 4)
n = 5 pentoses, e.g. ribose and deoxyribose ('pent' indicates 5)
n = 6 hexoses, e.g. fructose, glucose and galactose ('hex' indicates 6)

9. D-Aldoses

10. D-Ketoses

12. DISACCHARIDES
 Monosaccharides are rare in nature.
 Most sugars found in nature are disaccharides.
 These form when two monosaccharides react.
 A condensation reaction takes place releasing water.
 This process requires energy.
 A glycosidic bond forms and holds the two monosaccharide units
together.
 The three most important disaccharides are sucrose, lactose and
maltose.
 They are formed from the a forms of the appropriate
monosaccharides.
 Sucrose is a non-reducing sugar.
 Lactose and maltose are reducing sugars.

14. POLYSACCHARIDES
 Monosaccharides can undergo a series of condensation reactions, adding one unit after another to the
chain until very large molecules (polysaccharides) are formed.
 This is called condensation polymerisation, and the building blocks are called monomers.
 They are again sub-divided into two types.
 They are homopolysaccharides and heteropolysaccharides.
 Homopolysaccharides: They possess only a single type of monosaccharide units.
Examples: Starch, cellulose, and glycogen.
 Heteropolysaccharides: They possess two or more types of monosaccharide units.
Examples: Heparin and chondroitin sulfate.

16. NOMENCLATURE OF CARBOHYDRATES

17. HOW TO NAME ACYCLIC MONOSACCHARIDE?
Acyclic monosaccharides have three different characteristics:
1. the number of carbon atoms it contains,
2. its D or L configuration, and
3. the placement of its carbonyl group (aldehyde or ketone).

19. Putting all the concepts together

20. HOW TO NAME CYCLIC MONOSACCHARIDE ?
 Cyclic monosaccharides mostly consist of 5 or 6 carbon ring.
 5 carbon rings have the suffix fruscose and 6 carbon rings have the suffix pyranose.
 Also, when acyclic molecules are turned into cyclic molecule, it creates a chiral
center at the anomeric carbon and this gives rise to α and β anomers.
 α means that the anomeric OH and CH2OH groups are trans whereas β means
anomeric OH and CH2OH groups are cis

22. HOW TO NAME CYCLIC DISACCHARIDES?
 A disaccharide is two monosaccharide units linked by a glycosidic bond.
 The linkage between these two bonds is labeled by the carbon that they are attached to.
 For example, in maltose the glucose units are 1-4 linked, meaning that the C-1 of one glucose
is linked by a glycosidic bond to the C-4 oxygen of the other glucose

23. STRUCTURE OF GLUCOSE

24. GLUCOSE
 Glucose is a group of carbohydrates which is a simple sugar with a chemical formula C6H12O6.
 It is made of six carbon atoms and an aldehyde group.
 Therefore, it is referred to as an aldohexose.
 It exists in two forms viz open-chain (acyclic) form or ring (cyclic) form.

25. MUTAROTATION
 Glucose crystallized from methanol has a melting point of 147 °C.
 When dissolved in water, it has an initial specific rotation of +113°, which falls
after several hours to +52.5°.
 Glucose crystallized from water at a high temperature (> 50 °C) has a melting
point of 150 °C.
 Its initial specific rotation is +19° and rises gradually to the value of +52.5°.
 The change in optical rotation on standing is called mutarotation.
 This is explained by the fact that glucose gives rise to a cyclic ‘internal’
hemiacetal with the formation of a bond between carbon atom 5 (carrying an
OH group) and carbon atom 1 (the aldehyde carbonyl group)
 During ring closure, a new chiral center is formed (carbon atom 1), and the
hydroxyl group will assume either the α- or the β-configuration (right or left
respectively of the projection formula).
 The new chiral center is known as the anomeric carbon, and the resulting two
structures as the α- and β-anomers.
 Anomers are not enantiomers and have different specific rotations.

26. REACTIONS OF GLUCOSE

27. INTRODUCTION
 Because monosaccharides contain alcohol functional groups and aldehyde
(or ketone) functional groups the reactions of monosaccharides are an
extension of the reactions of alcohols, aldehydes, and ketones
 For example, an aldehyde group in a monosaccharide can be oxidized or
reduced and can react with nucleophiles to form imines, hemiacetals, and
acetals.

28. OXIDATION
 Aldoses can be distinguished from ketoses by observing what happens to the color of an aqueous solution of bromine
when it is added to the sugar. is a mild oxidizing agent and easily oxidizes the aldehyde group, but it cannot oxidize
ketones or alcohols.
 Consequently, if a small amount of an aqueous solution of is added to an unknown monosaccharide, the reddish-brown
color of will disappear if the monosaccharide is an aldose, but will persist if the monosaccharide is a ketose.
 The product of the oxidation reaction is an aldonic acid.

29. REDUCTION
 The carbonyl group of aldoses and ketoses can be
reduced by the usual carbonyl-group reducing agents.
 The product of the reduction is a polyalcohol, known as
an alditol.
 Reduction of an aldose forms one alditol.
 Reduction of a ketose forms two alditols because the
reaction creates a new asymmetric carbon in the product.

30. OSAZONE
 Emil Fischer found that when phenylhydrazine is added to an aldose or a ketose, a yellow
crystalline solid that is insoluble in water is formed.
 He called this derivative an osazone (“ose” for sugar; “azone” for hydrazone).
 Osazones are easily isolated and purified and were once used extensively to identify
monosaccharides.

31. CHAIN ELONGATION: THE KILIANI–FISCHER SYNTHESIS
 The carbon chain of an aldose can be increased by one carbon in a Kiliani–Fischer
synthesis.
 In other words, tetroses can be converted into pentoses, and pentoses can be
converted into hexoses.

32. CHAIN SHORTENING: THE RUFF DEGRADATION
 The Ruff degradation is the opposite of the Kiliani–Fischer synthesis.
 Thus, the Ruff degradation shortens an aldose chain by one carbon: Hexoses are converted
into pentoses, and pentoses are converted into tetroses.

33. OTHER IMPORTANT SUGARS

34. SUCROSE
 Sucrose (C12H22O11) is the chemical name of table sugar.
 Sucrose is a disaccharide; each molecule consists of two "simple"
sugars (a glucose and a fructose), called monosaccharides.
 The sucrose molecule is a disaccharide composed of one molecule of
glucose connected via an glycosidic bond to one molecule of fructose.
 In sucrose, the components glucose and fructose are linked via an
acetal bond between C1 on the glucosyl subunit and C2 on the
fructosyl unit. The bond is called a glycosidic linkage.

35. STARCH
 Starch is the most important source of carbohydrates in
the human diet and accounts for more than 50% of our
carbohydrate intake.
 Starch is a mixture of two polymers: amylose and
amylopectin
 Amylose is an unbranched homopolysaccharide formed
by about 5-600 glucose units, linked by α-(1→4)
glycosidic bonds. It has a helix structure with six glucose
units for turn, is soluble in water and places in the core of
the starch granules.
 Amylopectin represents about 80% of polysaccharides
taken up with diet.
 It is a branched molecule formed by thousands of
glucose units, up to 50000, that, in main chain, are joined
by α-(1→4) glycosidic bonds.

36. CELLULOSE
 Cellulose, a fibrous carbohydrate found in all plants, is the
structural component of plant cell walls
 Like amylose, cellulose is a linear polymer of glucose. It differs,
however, in that the glucose units are joined by β-1,4-glycosidic
linkages, producing a more extended structure than amylose
 This extreme linearity allows a great deal of hydrogen bonding
between OH groups on adjacent chains, causing them to pack
closely into fibers.

37. REDUCING AND NON REDUCING SUGARS

38. REDUCING AND NONREDUCING SUGARS
 An anomeric carbon is the first stereocenter of the molecule.
 If that stereocenter has an OH group coming off of it then it is a reducing sugar.
 This is because when the sugar is in the open configuration, that alcohol becomes a ketone or aldehyde
which is able to reduce other compounds.
 All monosaccharides are reducing sugars.
 A monosaccharide is the simplest form of a sugar.
 Disaccharides are two monosaccharides combined.
 Common disacccharides are maltose, lactose, and sucrose.
 These can either be reducing or non-reducing sugars.

40. PHARMACEUTICAL IMPORTANCE OF CARBOHYDRATES

41. STARCH
 Starches are typically derived from corn or potato.
 Starches are used in the pharmaceutical industry for a wide variety of reasons, such as an
excipient, a tablet and capsule diluent, a tablet and capsule disintegrant, a glidant, or as
binder.
 Disintegrants enable tablets and capsules to break down into smaller fragments (dissolve) so
that the drug can be released for absorption.
 Starches also absorb water rapidly, allowing tablets to disintegrate appropriately.

42. CELLULOSE
 Microcrystalline cellulose is a commonly used excipient in the pharmaceutical industry.
 It has excellent compressibility properties and is used in solid dose forms, such as tablets.
 Tablets can be formed that are hard, but dissolve quickly.
 Microcrystalline cellulose is the same as cellulose, except that it meets USP standards.

43. SUCROSE
 Sucrose (C12H22O11) is sugar, often referred to as table sugar or saccharose.
 Commercial sugar is usually produced from either beet or cane sugar.
 Sucrose has been used since antiquity for its sweetness. It is often used in medications to
impart a more pleasant taste to often unpalatable chemicals.
 Sucrose can be found in many medical dosage forms such as chewable tablets, syrups,
lozenges, or gums.
 Sugar-free formulations of many of these dosage forms exist as well.
 While sugar is essentially non-toxic, it can be associated with dental caries, exacerbation of
diabetes, and weight gain

44. LACTOSE
 Lactose (C12H22O11) is milk sugar. It is a disaccharide composed of one galactose and one
glucose molecule.
 In the pharmaceutical industry, lactose is used to help form tablets because it has excellent
compressibility properties.
 It is also used to form a diluent powder for dry-powder inhalations.
 Lactose may be listed as lactose hydrous, lactose anhydrous, lactose monohydrate, or lactose
spray-dried.

45. MANNITOL
 Mannitol is a polyol (sugar alcohol) and an isomer of sorbitol.
 Mannitol (C6H8(OH)6) is used in pharmaceutical products as a sweeting agent, tablet and capsule
diluent, excipient for chewable tablets, a tonicity agent, and as a vehicle (bulking agent) for lyophilized
preparations.
 Mannitol is industrially derived from the sugar fructose, and is roughly half as sweet as sucrose.
 Mannitol has a cooling effect often used to mask bitter tastes, and may be used in gums and candies.

46. SORBITOL
 Sorbitol (C6H14O6) is a sugar alcohol (polyol) used in the pharmaceutical, cosmetic and
food industry as a sweetener or humectant (for protection against loss of moisture content).
 It is produced by hydrogenation of glucose and is available in liquid and crystalline form. It
also occurs naturally in many fresh fruits and berries.
 Sorbitol is also found commonly in "sugar-free" chewing gum, and may be used to sweeten
pharmaceutical dosage forms such as syrups or chewable tablets.

47. GLYCOSIDES

48. GLYCOSIDES
 A glycoside is any molecule in which a sugar group is bonded through its anomeric carbon to another
group via glycosidic bond.
 A glycosidic bond is a certain type of chemical bond that joins a sugar molecule to another molecule.
 Specifically, a glycosidic bond is formed between the hemiacetal group of a saccharide (or a molecule
derived from a saccharide) and the hydroxyl group of an alcohol.
 A substance containing a glycosidic bond is a glycoside.
 The glycone and aglycone portions can be chemically separated by hydrolysis in the presence of acid.
 There are also numerous enzymes that can form and break glycosidic bonds.
 The sugar group is known as the glycone and the nonsugar group as the aglycone or genin part of
the glycoside.
 The glycone can consist of a single sugar group (monosaccharide) or several sugar groups
(oligosaccharide).

49. CLASSIFICATION
 The glycosides can be classified by the glycone, by the type of glycosidal linkage, and by the aglycone.
On the Basis of Glycone:
 If the glycone group of a glycoside is glucose, then the molecule is a glucoside; if it is fructose, then the
molecule is a fructoside; if it is glucuronic acid, then the molecule is a glucuronide, etc.
On the Basis of Glycosidic Linkage
 1. O-glycosides: Sugar molecule is combined with phenol or –OH group of aglycon, for example,
Amygdaline, Indesine, Arbutin, Salicin, cardiac glycosides, anthraxquinone glycosides like sennosides etc.
 2. N-glycosides: Sugar molecule is combined with N of the –NH (amino group) of aglycon, for example,
nucleosides
 3. S-glycosides: Sugar molecule is combined with the S or SH (thiol group) of aglycon, for example,
Sinigrin.
 4. C-glycosides: Sugar molecule is directly attached with C—atom of aglycon, for example,
Anthraquinone glycosides like Aloin, Barbaloin, Cascaroside and Flavan glycosides, etc.

50. ON THE BASIS OF AGLYCONE

51. GLYCOSIDIC LINKAGE
 A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar)
molecule to another group, which may or may not be another carbohydrate.
 A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide (or a
molecule derived from a saccharide) and the hydroxyl group of some compound such as an alcohol.
 A substance containing a glycosidic bond is a glycoside.

52. ENZYMATIC HYDROLYSIS OF GLYCOSIDES
 Enzymatic hydrolysis is a process in which enzymes facilitate the cleavage of bonds in molecules with the
addition of the elements of water.
 It plays an important role in the digestion of food.
 Glycoside hydrolases (also called glycosidases or glycosyl hydrolases) catalyze the hydrolysis of glycosidic
bonds in complex sugars.
 They are extremely common enzymes with roles in nature including degradation of biomass such as
cellulose (cellulase), hemicellulose, and starch (amylase), in anti-bacterial defense strategies (e.g.,
lysozyme), in pathogenesis mechanisms (e.g., viral neuraminidases) and in normal cellular function (e.g.,
trimming mannosidases involved in N-linked glycoprotein biosynthesis).
 Together with glycosyltransferases, glycosidases form the major catalytic machinery for the synthesis and
breakage of glycosidic bonds.

53. ANTHRAQUINONE GLYCOSIDES
 Anthraquinones are structurally related to anthracene and possess the
9,10-anthracenedione core.
 They are sometimes referred to as 9,10-dioxoanthracene.
Anthraquinones typically occur in their glycosidic forms.
 The anthraquinone glycosides are the ones whose aglycone component
is a polyhydroxyanthraquinone derivative.
 The drugs having these glycosides possess cathartic activity.
 The polyhydroxyanthraquinone derivatives present in these drugs are
chrysophanic acid (1, 8- dihydroxy- 3- methylanthraquinone), aloe
emodin (1, 8- dihydroxy-3- methyl anthraquinone), Frangula emodin and
rhein (1, 8- dihydroxy anthraquinone -3-carboxylic acid).

54. IMPORTANCE
 The sugar residue facilitates absorption and translocation of the aglycone to the site of action.
 The anthraquinone and related glycosides are stimulant cathartics and exert their action by
increasing the tone of the smooth muscle in wall of the large intestine.
 Anthraquinone glycosides can take 6 to 12 hours or longer to reach the colon, depending on
gut motility and transit time of the patient.
 Once hydrolyzed in the colon, anthraquinones induce water and electrolyte secretion, as well
as peristalsis, including catharsis.

55. Thank
you