Carbohydrates

DEFINITION
The term “carbohydrates” was originated from the belief that these are
hydrates of carbon as they have the same ratio of hydrogen and oxygen
as in water e.g. glucose (C6H12O6) and sucrose (C12H22O11).
“A carbohydrate is an organic compound which consists only
of carbon, hydrogen, and oxygen, with a hydrogen: oxygen atom ratio of
2:1.”
A carbohydrate has an empirical formula Cm(H2O)n (where m could be
different from n) but all the organic compounds in which hydrogen and
oxygen are in same ratio are not carbohydrates e.g. formaldehyde HCHO,
acetic acid CH3COOH and Lactic acid CH3CHOHCOOH

 Some carbohydrates such as cymarose, rhamnose and
digitoxose also don not follow the same definition where as
some of the carbohydrates also have nitrogen or Sulphur in
their formulas.
 So the new chemical definition of carbohydrates described as “
polyhydroxy aldehydes or polyhydroxy ketones or the
compounds that upon hydrolysis produce either of the above”
 Carbohydrates are the first product that arise as a result of
photosynthesis

FUNCTIONS IN PLANT
Plants store starch in roots, tubers, and leafy parts, mainly
during photosynthetic activity; some plants, such as sugar
beets and sugarcane, also store sucrose.
Carbohydrates serve as storage products of energy. The
principal forms are starch in plants which are polymers of
glucose; they are deposited in cells in the form of granules
when a surplus of glucose is available. In times of metabolic
need, when the body is exerting itself, the polymers are broken
down by enzymatic action and become fuel.
Carbohydrates function as the main rigid structural elements
in plants, in two forms: cellulose and hemicelluloses.

 Pharmacognostic importance of carbohydrates also increase when sugar
unites with a variety of compounds to form glycosides and other secondary
metabolites e.g. mucilages as water retaining vehicle
 Gums and mucilages are similar in composition and properties i.e.
composed of uronic acid components but mucilages are physiological
products while gums are pathological products.
 Low molecular weight carbohydrtaes are crystalline, soluble in water and
sweet in taste e.g. glucose, sucrose and fructose while high molecular weight
carbohydrtaes are amorphous, tasteless and relatively less soluble e.g.
starch, cellulose and inulin

Types
carbohydrate
saccharides
monosaccharides Bioses,trioses, tetroses
Disaccharides Sucrose, maltose, lactose
Trisaccharides Raffinose
Tetrasaccharides stachyose
polysaccharides

Monosaccharides
 Monosaccharides upon hydrolysis yield no further suagrs, having general
formula CnH2nOn.
 These are subdivided as bioses,trioses, tetroses, pentoses, hexoses,
heptoses depending the number of carbon atom they possess.
 Bioses contain two carbon atoms and they do not exist free in nature,
trioses contain three carbon atoms in the form of phosphoric esters e.g.
glyceraldehyde
 Tetroses contain four carbon atoms e.g. erythrose and thresoe

 Pentoses with five carbon atoms are the products of hydrolysis of polysaccharides
e.g.gums, mucilages and hemicellulose commonly available in plants e.g.
ribose,arabinose and xylose
 Hexoses are the monosaccharides of six carbon atoms which are further divided
into two types i.e. aldoses like glucose, mannose and galactose and ketoses such
as fructose and sorbose.
 Heptoses contain seven carbon atom and play vital role in photosynthesis

Di,tri & tetra saccharides
 Carbohydrates that upon hydrolysis yield two molecules of monosaccharides are called
disaccharides e.g. sucrose, maltose and galactose
 Trisaccharides liberate three molecules of monosaccharides upon hydrolysis e.g.
Raffinose and gentianose
 Tetrasaccharides yield four monosaccharide molecules upon hydrolysis e.g. stachyose

Polysaccharides
 These upon hydrolysis yield indefinite number of
monosaccharides e.g. cellulose & starch, cellulose is composed
of glucose units linked by β-1,4 linkages while starch aslo
contain glucose units that may be linked by α-1,4 & α-1,6
linkages

Test for carbohydrates
 Fehling solution reduction test: to the solution of carbohydrates
add equal quantity of fehling A & B is added upon heating brick
red precipitates are obtained
 Molisch Test: this test is performed for both soluble and insoluble
carbohydrates. In this test material is treated with α-naphthol
and concentrated sulphuric acid that gives purple colour.
 With soluble carbohydrate it appears in the form of a ring if
sulphuric acid is poured gently whereas in case of insoluble
carbohydrates e.g. cellulose the colour will not appear until
solution is shaken to bring the material in contact with the solvent

 Osazone test : sugar derivatives formed by heating a sugar
solution with phenylhydrazine hydrochloride , sodium acetate
and acetic acid if the yellow crystals are formed that indicate
the presence of certain sugars
 Resorcinol test for ketones : A crystal of resorcinol is added
and warmed on water bath with an equal volume of Conc.HCl ,
a rose colour is produced if a ketone is present e.g. fructose,
honey or inulin
 Tets for pentoses: heat the solution of material in a test tube
with an equal volume of conc.Hcl with little phloroglucinol, the
formation of red colour indicates the presence of pentoses

 Keller killani test for deoxy sugars: deoxy sugars mostly
found in cardiac glycosides dissolved in acetic acid containing a
trace of ferric chloride and transferred to the surface of
concentrated sulphuric acid. At the junction of layers a reddish
brown colour is obtained that gradually becomes blue.
 Furfural test : carbohydrate is treated with a drop of
phosphoric acid to convert it into furfural. A disk of filter paper
moistened with a drop of 10% solution of aniline in 10% acetic
acid is placed over the mouth of the test tube ,the bottom of the
test tube is heated for 30-60sec, a pink or red stain appears on
reagent paper.

Carbohydrates
Sucrose/
sucrose drugs
Sucrose
Dextrose
Liquid
glucose
Fructose
Lactose
Cellulose/Cellulose
derivatives
Purified
cotton
Powdered
cellulose
Microcryst
alline
cellulose
Methyl
cellulose
Sodium
CMC
Gums &
mucilage
Tragacanth
Acacia
Sodium
alginate
Agar
Pectin

Gums & mucilage have similar constitutions and on
hydrolysis yield a mixture of sugars & uronic acids.
Gums are considered to be pathological products,
formed upon injury of the plant or owing to
unfavourable conditions such as drought, by a
breakdown of cell walls, While mucilage is formed by
normal metabolism products formed within the cell
and may represent storage material

Gums are amorphous translucent substances
which are insoluble in alcohol & most organic
solvents. It is soluble in water & gives a viscous,
sticky solution. Other gums are swollen by
absorbing water to form a jelly-like mass.
Mucilage is often found in Epidermal leaf cells of
leaves e.g; (Senna) Seed coats (linseeds, psyllium)
Roots (marshmallow) Barks (Slippery elm)

AGAR
It is also called as vegetable gelatin
Source:
Agar is a gelatinous substance derived from a polysaccharide
that accumulates in the cell walls of agarophyte red algae
primarily from the genera Gelidium and Gracilaria,
or seaweed (Sphaerococcus euchema).
For commercial purpose, it can be obtained from Gelidium
amansii and Gelidium cartilaginum.

Cultivation & Collection:
Red algae grows on rocks in shallow water or it can
be cultivated on bamboos by placing them in
ocean
Algae is collected in the summers (May to
October), beaten with stick to remove sand and
shells, washed with water and bleached in
sunlight at altitude.
agar is extracted by boiling with 50 parts of
acidified water (acetic acid or dil. Sulphuric
acid). Mixture is filtered by cloth and filterate is
transferred to wooden trough, the mucilaginous
liquid is then cooled and jelly like mass is
obtained that is cut into strips. Water from the
jelly is removed by drying it at 35°C . Agar block
is crushed and reduced to fine powder.

Constituents
 Agar consists of a mixture of agarose and
agaropectin.
 Agarose is neutral galactose polymer and is
responsible for gel properties, it consists of D-
galactose and L-galactose units while agaropectin
consists of sulphonated polysaccharides in which
galactose and uronic acid are partially esterified
with sulphuric acid. Agaropectin is responsible for
viscosity of agar solution

Uses:
 Impression material in dentistry
 Suspending and emulsifying agent
 Tablet disintegrant
 Encapsulating substance
 Nutrient media for bacterial cultures
 Laxative
 As tablet excipient, surgical lubricant, gelting agent for
suppositories
 As gelling agent in cosmetics

PECTIN
It is a general group of polysaccharides present
in primary cell wall of all seed bearing plants,
these polysaccharides work with cellulose
and hemicellulose as an intercellular support
Pectin is a purified product obtained from inner
part of rind of citrus fruits e.g. lemon (citrus
lemon) & orange (citrus aurantium)
It may also be
Obtained from;
 Papaya (Carica papaya)
 Guava (Psidium guyava)
 Mangoes (Mangifera indica)
 Carrot (Daucus carota)

Collection
It occurs in the middle lamella of cell wall, in an insoluble form i.e.
protopectin.
Fresh peels are boiled gently with fresh water at 90OC for 30
minutes by maintaining pH at 3.5-4.0 with food grade citric acid
or lactic acid
After boiling peels are squeezed to obtain liquid portion which is
then subjected to centrifuge to obtain clear solution
Proteins and starch contetnts are removed by enzymatic hydrolysis,
then solution is warmed to deactivate the enzymes.
Final solution is decolourized with activated charcoal
Pectin is collected by dissolving water miscible solvents

Constituents
Pectin consists of polysaccharides of variable molecular
weight and may range form 200,00-400,000 depending
upon the number of carbohydrate linkages.
Core Molecule consists of D-polygalactouronate and L-
rhamnose while side chains are formed by D-galactose,
L-arabinose, D-xylose, L-fructose.

Uses:
Gelling agent
 Emulsifying agent
As Thickening agent widely used in sauces, jams and
ketchups
 Acts as hemostatic in case of hemorrhages
 Have tendency to lower blood lipoprotein levels
Also acts as enteroabsorbants
Treatment of diarrhea as it assists the adsorption of toxins
from GIT.

SODIUM ALGINATE
Alginic acid was first isolated in 1883 by an
English chemist Stanford. It is purified
carbohydrate extracted from brown seaweed
by treatment with dil. alkali
Seaweed is found in atlantic and pacific oceans
Sodium alginate is the sodium salt of alginic
acid while alginic acid is a ployuronic acid
composed of reduced mannuronic and
glucoronic acids.
Algae from family Phaeophyceae i.e.
Macrocystis pyrifera, Laminaria
hyperborea, Laminaria digitata by using
dilute alkali.

Preparation
Brown algae is used for the extraction of alginic acid. The colour
is due to carotenoid pigment present in it. The seaweed is a
perennial plant that lives from 8-12 years and mainly found in
pacific oceans, it is harvested , dried, milled and extracted with
dil. sodium carbonate which results in pasty mass.
After washing it is treated with calcium chloride or sulphuric
acid for conversion in calcium alginate or insoluble alginic acid
which is collected and purified by washing alginic acid is treated
with sodium carbonate for neutralization and converted into
sodium salt.
Alginic acid contents on dry solid basis may vary from 22-35%

Constituents:
It consists of alginic acid.
Alginic acid is linear polymer of D-Mannuronic acid and L-gluronic acid
Uses:
 Suspending agent
 Emulsifying agent
 Stabilizing agent
 Tablet binders and disintegrator
 Also used in the preparation of ijellies, ice-creams
 Capsule containing sodium alginate and calcium carbonate are used to
protect inflamed areas near the enterance of the stomach, acidic
environment causes the formation of insoluble alginic acid that rises on the
top of stomach and results in the formation of protective layer

ACACIA
Sources:
Acacia arabica
Acacia senegal
Family:
Leguminosae
Part used:
Dried gummy exudates from
stem
 According to USP acacia is dried gummy
exaudation obtained from the stem and
branches of the plant

Collection:
Gum is collected from 6-8 years old tree twice a year in dry
weather in November or February- March.
On the bark, a transverse incision is made by an axe and
cambium and xylem is exposed by avoiding injury. If xylem is
exposed, white ant enters the plant and gum is not produced.
The formation of gum may be caused by bacterial action. Gum
is scraped off, collected in leather bags.
For bleaching, gum is exposed to sun for 3-4 months. Cracks
are formed on the outer surface of gum tears. Finally tears
are graded on the basis of external appearance and packed.

Constituents:
 It consists of arabin which is a Calcium, magnesium and potassium salts of arabic acid.
 Arabic acid is
 Arabic acid is a branched polysaccharides that yield L-arabinose, L-rhamnose, D-galactose and D-
glucoronic acid
 12-15 % of water
 Gum also contain some occluded enzymes such as oxidases, peroxidases, pectinases
Uses:
 Demulcent
 Emollient
 Tablet binder
 Suspending agent
 Emulsifying agent
 As granulating agent
 Gum acacia solution has consistency similar to blood so used in haemodialysis after iv administration

TRAGACANTH
Sources:
Astragalus gummifer,
Family:
Leguminosae
Part used:
Dried gummy exudate obtained from a wedge
shape incision from the base of plant,
Gum is obtained from 2 years old plant
because gum from one year old plant is
not considered suitable for commercial use

Collection:
Gum is produced in the plant cell by a process called gummosis. It is a
process in which pith and medullary rays of cell walls are converted
into gum.
Incision is made on stem and gum is obtained as a soft solid mass.
When exposed to air and sunlight, water in the gum evaporates, and
gum is dried.

Constituents:
 Water soluble component is “tragacanthin” Water insoluble component is
“bassorin”
 Bassorin swells up to form a gel while tragacanthin forms an instant
colloidal solution
 Tragacanthin does not contain any methoxy group whereas bassorin
contain approximately 5.38% of methoxyl moieties
 Tragcanthin is composed of Polysaccharides (Arabinose & galactose) and
uronic acid units, tragacanthnic acid on hydrolysis yields galactose,
xylose, and galacturonic acid

Uses:
 As demulcent in cough and cold preparation
 Thickening, Suspending and emulsifying agent
 Emollient in cosmetics
 Mucilage of traganth is used as binding agent and also as an excepient
in pills
 used as stabilizer in ice creams and sausages.
 Tragacanth also possesses anti cancer activities

CELLULOSE AND
CELLULOSE DERIVATIVES

CELLULOSE
Source:
Cellulose is the structural component of the primary cell
wall of green plants, many forms of algae and
the oomycetes. Some species of bacteria also secrete it
to form a biofilms. About 33% of all plant matter is
cellulose (the cellulose content of cotton is 90% and that
of wood is 40–50%).
For industrial use, cellulose is mainly obtained
from wood pulp and cotton.

Constituents:
Cellulose is a polysaccharide
consisting of a linear chain of
several hundred to over ten
thousand β(1→4) linked D-
glucose units.

METHYL CELLULOSE
Methyl cellulose is a derivative of cellulose.
It is a hydrophilic white powder in pure form and dissolves in
cold water, forming a clear viscous solution or gel.
It is used as;
Lubricant
Thickener
Emulsifier

CARBOXY METHYL CELLULOSE
Carboxy methyl cellulose (CMC) also
called cellulose gum, is a cellulose derivative.
It contains carboxy methyl groups (-CH2-
COOH) bounded to hydroxyl groups of
the glucopyranose monomers that make up
the cellulose backbone.
It is often used as its sodium salt,
sodium carboxy methyl cellulose.

Synthesis:
It is synthesized by the alkali-catalyzed reaction of cellulose
with chloroacetic acid.
Uses:
It is used as;
 Viscosity modifier
 Stabilizer
 Cation exchange resin in ion exchange chromatography

CELLULOSE MICROCRYSTALLINE
Microcrystalline cellulose refers to refined wood pulp.
It is used as;
 An anti-caking agent, an extender, bulking
agent in food production.
 The most common form is used in vitamin
supplements or tablets.
 It is also used in plaque assays for counting viruses,
as an alternative to carboxy methyl cellulose.
It is used as diluent in pharmaceutical preparations.

SUCROSE AND
SUCROSE DERIVATIVES

CARAMEL
Source:
Sugar
Preparation:
Caramel is obtained by heating glucose or sugar with
alkali, alkaline carbonate or a trace of mineral acid until
sweet taste of sugar is destroyed and uniform dark
brown mass is formed.
Uses:
Coloring agent & sweetening agent

XYLOSE
Source:
Straws
Corn cobs
Preparation:
Xylose is obtained by boiling corn cobs,
straws or other such material with dilute
acid i.e. HCl , to hydrolyze the xylan
polymer which is broken down to yield
xylose.

Structure:
Uses:
Diagnostic agent in disorders due to intestinal malabsorption.
For example;
 Crohn’s disease
 Radiation enteritis
 Pellagra

LIQUID GLUCOSE
Botanical origin: Zea mays
Family: Gramineae
Preparation:
Liquid glucose is prepared by controlled hydrolysis of starch.

Constituents:
Dextrose
Dextrin
Maltose
Water
Uses:
 Sweetening agent
 Tablet binder
 Tablet coating agent
 Diluent

FRUCTOSE
Source:
Fructose can be obtained from;
 Honey
 Sweet fruits
 Inulin
Structure:

Uses:
 Electrolyte replenisher
 Fluid nutrient

Preparation:
It is obtained by inversion of aqueous solution of sucrose and
subsequent separation of fructose from glucose. When
sucrose is hydrolyzed, glucose and fructose are obtained in
equal quantities.

SUCROSE
Sucrose, a non-reducing sugar, is major product of plant
photosynthesis.
Sources:
Sugar cane (Saccharum officinarum)
Sugar beet (Beta vulgaris)
Sugar maple (Acer saccharum)

Preparation:
(i) Sugar beets
Beets are dug, washed and sliced into small, limp slices
known as “cossettes”. Sucrose and other soluble
constituents are extracted from plant material with hot
water. Crude sugar containing solution is subjected to
purification purpose.
(ii) Sugar cane
stems of sugar cane are crushed between series of heavy
iron rollers. It is boiled with lime to neutralize plant acid.
Boiling is done to coagulate albumin.

Coagulated albumin rises to the top as scum and is removed.
Juice is filtered. It is sometimes decolorized with sulphur
dioxide, concentrated and crystallized.
Structure:

Uses:
 Preservative
 Demulcent
 Nutrient
 Anti- oxidant
 Coating agent

LACTOSE
Source: Milk of Bos Taurus
Family : Bovidae
Preparation:
Whey is source of lactose. Lactose is crystallized from whey.
Impure crystals are redissolved in water. Charcoal is added
to decolorize and after Recrystallization lactose is obtained.

Structure:
Uses:
 Tablet diluent
 Tablet binder
 Nutrient

DEXTROSE
Source:
 Grapes and other fruits
 It can be obtained by hydrolysis of certain
natural glycosides.
Preparation:
Commercially, dextrose is obtained by
controlled hydrolysis of starch.

Structure:
Uses:
 Nutrient
 Part of anti-coagulant solution
 Tablet binder
 Coating agent

INULIN
Sources:
 Taraxacum officinale
 Dioscorea spp
 Helianthus tuberosus
 Allium cepa
Uses:
 Fermentative identifying agent for bacteria
 Lab evaluation of renal function

DEXTRIN
Sources:
 Maize
 Potato starch
Preparation:
Uses:
 Nutrient
 Adhesive for surgical dressing
 Binder
 Thickening agent

STARCH
Sources:
Maize (Zea mays)
Wheat (Triticum turgidum)
Potato (Solanum tuberosum)
Rice (Oryza sativa)

Preparation:
 Rice starch: prepared from broken pieces of rice by macerating with
0.5% caustic soda solution to dissolve gluten. Rice pieces are
separated and milky starch liquid is allowed to settle down and
starch is separated by centrifuge, washed, dried and powdered.
 Wheat Starch: dough is made from wheat flour by adding water and
kept for one hour for swelling gluten, lumps or balls are made and
passed through a grooved roller moving to and fro, water is poured
simultaneously . Milky liquid falling down contains starch in it.
starch is separated by centrifuge, washed and dried

Constituents
 Starch consists of amylose and amylopectin,
 Amylose contain straight chain α1-4 glycosidic bonds with higher
molecular weights and it helps in solubility of starch, amylose
undergoes hydrolysis with beta amylase and yield maltose.
 Amylopectin contain both straight and branched chain of glucose
unit. It has α1-4 linkage in straight chain and α1-6 in branched
chain. It is insoluble in water and swells up when comes in contact
with water. It is responsible for gelatinizing properties of starch

Structure:
Uses:
 Tablet disintegrant
 Absorbent
 Binder
 Emollient
 Antidote in codeine poisoning

Carbohydrates

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