Chemical Composition of Herbal and Medicinal Plants

Role of medicinal Plants

Medicinal Plants have been used for health and medical purposes
for several thousands years .A majority of the World population in
developing countries still relies on herbal medicine to meet its
health needs. Medicinal plants are important sources for
pharmaceutical manufacturing.
To promote the proper use of medicinal plants a comprehensive
studied required :
Medicinal Plants identification, Extraction of phytochemicals,
Quality Control of herbal products, Pharmaceutical
evaluation,preparation,cultivation/good agricultural practices(GAP)
, post harvest processing, good manufacturing practices(GMP) to
includes herbal medicine in National and International standard or
pharmacopeia.
Some Indian Medicinal Plants and their potential
as Drugs
Brahmi (Bocoppa monnieri)

Memory enhancer
Contains potent
antioxidants,enthanolic
extract contains bacoside A
and B,cucurbitacins and
betulinic acid.
Cucurbitacins reported for
their antitumor and anti-
proliferative activity
 Shatavari

Immunomodulator and galactogogue ,alleviate

axiety,reduced fatigue, enhance overall well-being.
 Giloy (Tinospora cordifolia)

Immuno–Modulator and Hepatoprotective,

antitumor properties
Some Medicinal Plants and their potential

Malaria, jaundice and Anemia, to support /improve

the immune system, aid digestion, used in Fevers and
infection
 Bhumi Amala(Phyllanthus niruri)

Skin diseases, Wounds and Ulcers and Blood purifier, liver

disorder/ to support liver function
 Plant metabolites

Metabolites are organic compounds synthesized by plant using

enzyme-mediated chemical reactions called metabolic pathways.
Functions of metabolites:
a) Basic or essential: Growth and development (Primary
metabolites)
b) Specific : Pollinator attraction, defense against herbivory
etc.(Secondary metabolites)
 CO2 + H2O

hn PRIMARY METABOLISM

Photosynthesis Glucose Carbohydrates

SECONDARY SECONDARY
METABOLISM G METABOLISM
L
Building Blocks Y
C
O
Phenyl- L
propanoids Y
Amino Acids S Fatty Acids
Flavonoids I Lipids
Proteins S
Alkaloids synthesis
enzymes Acetyl CoA
regulation Acetogenins
Nucleic
Terpenes
Acids Citric Acid Steroids
reproduction Cycle

RNA DNA CO2 + H2O + ATP

 Active Principles in Plants (Secondary metabolites)

Green plants synthesize and preserve a variety of biochemical

products, many of which are extractable and used as chemical
feed stocks or as raw material for various scientific investigations.
Many secondary metabolites of plant are commercially important
and find use in a number of pharmaceutical compounds.

Medicinal Plants are those plants rich in secondary

metabolites and potential source of drugs. These secondary
metabolites includes alkaloids, glycosides, tannins, terpene,
lipids, vitamins, saponnin etc.
The medicinal effects of plants are due to metabolites
especially secondary compounds produced by plant species.
Secondary Metabolites
 Major Groups of Secondary Metabolites
Alkaloids: Many different compounds, found in many plants. They all
contain nitrogen atoms, are alkaline (basic), and taste bitter. Structures
vary widely
Glycosides: A sugar is attached to the active component. This makes them
non-toxic until an enzyme removes the sugar, which happens in the
digestive system. Glycosides are non-reducing organic compounds that on
hydrolysis with acids, alkalis or enzymes yield:

– A sugar part (or glycone, formed of one or more sugar units).

– A non-sugar part (or aglycone, also called genin).

Steroids: Steroids have a particular ring structure and are used to make
hormones in animals. Two main type
Cardio active (meaning that they affect your heart).
Saponins are soapy and very toxic: they work especially well as fish poisons
because they dissolve easily in water. The steroid found in yams (Dioscorea)
is a saponin.
 Phenolic Group of secondary Metabolites
Phenolic are products or compounds composed of a hydroxyl group attached to an
aromatic ring . A broad range of compounds - found in all components of plants:
leaves, flowers, fruit etc.
Comprised of many groups: Tannins, Flavonoids, Lignin etc.
• The phenolic or ‘polyphenols’ which compounds commonly occurs in food
materials are classified in three groups:
• Simple phenols and phenolic acids(Vanillic, gallic,ellagic)
• Hydroxy cinnamic acids(caffeic, ferulic,sinapic)
• Flavonoids
• Tannins : are "phenolic natural products that precipitate proteins from their
aqueous solutions".

Tannins are one of the most widely occurring group of natural substances in different
families of higher plants. These secondary metabolites are preset in solution form in
the cell sap. They have been known since long time as astrigent substances.

Classification of Tannins:

1- Hydrolysable tannin (pyrogallol tannin):

Classified into gallotannin and ellagitannin

2- Condensed tannin (catechol tannin).

 Major plant drugs for which no synthetic one is currently available
Active Principle Plant Use Treatment
Vinblastine Catharanthus roseus Anticancer
Vinblastine Catharanthus roseus Anticancer
Ajmalacine Catharanthus roseus Anticancer,
Rescinnamine Rauvolfia serpentina Tranquilizer
Reserpine Rauvolfia serpentine Tranquilizer
Quinine Cinchona sp. Antimalarial,
Cocaine Erythroxylum coca Topical anaesthetic
Morphine Papaver somniferum Painkiller
Codeine Papaver somniferum Anti cough
Atropine Atropa belladonna Spasmolytic, cold
Cardiac glycosides Digitalis sp. For congestive heart
failure
Artemisinin Artemesia annua Antimalarial,
Taxol Taxus baccata Anticancer
Emetine Cephaelis ipecacuanha Amoebiasis
Glycyrrhizin Glycyrrhizia glabra Antiulcer
Nimbidin Azadirachta indica Antiulcer
Catechin Acacia catechu Antiulcer
Forskolin Coleus forskohlii Hypotensive
Ecological role of Secondary Metabolites
Plant Primary Metabolites
 Primary Metabolites

• Primary metabolites are compounds that are

commonly produced by all plants and that are
directly used in plant growth and
development.
• The main primary metabolites are
carbohydrates, proteins, lipids and nucleic
acids.
Building blocks of Primary Metabolites Molecules
 Carbohydrates
(Most abundant biomolecules on earth)

The Carbohydrates are very important plant constituents and

occupy central position in plant metabolism.
The Carbohydrates are group of organic compounds
Containing Carbon, Hydrogen & Oxygen . (CH2 O)n
 Carbohydrates

Basic mechanism of Photo synthesis

➢The most important chemical reaction in nature is

photosynthesis.
➢End Product: Glucose (Cellulose and starch)
➢Energy derived from: Sun, water, and carbon dioxide.
➢Essential Plant pigment: Chlorophyll

➢This provides the plant food for animals and humans.

 Glucose
hn CH2OH (6 carbons) CH2OH CH2OH CH2OH
O O O O
OH OH OH OH
HO OH HO O O O
CO2 OH OH OH OH
photosynthesis starch n
glycolysis
CHO
CH OH CHO CH2OH
CH OH HC OH C O
polyketides
CH2OP CH2OP CH2OP
erythrose- acetogenins
4-phosphate
CH2
phosphoenol O O lipids
C OP
pyruvate (PEP) H3C C CH2 C CH2 fatty acids
COOH
COOH shikimic (3 carbons)
acid anthanilic
acid
HO OH
acetyl-
COOH O
OH
coenzymeA
H3C C SCoA
(2 carbons)
NH2 HO CH3
mevalonic
phenylpropanes
lysine oxalo- acid
O O
phenylalanine ornithine acetate citric
energy (ATP)
tyrosine acid
tryptophan + CO2 + H2O
cycle
terpenes
NH3 steroids
nicotinic aspartic
alkaloids acid acid carotenoids
glutamic acid
Glucose gives rise to most of the mono-saccharides in
cell wall
 General characteristics of carbohydrates
• The term carbohydrate is derived from the French: hydrate de Carbone
compounds composed of C, H, and O

• Basic formula: (CH2O)n ; Form= 5, C5H10O5 )

• Not all carbohydrates have this empirical formula: deoxysugars,

amino sugars

• Carbohydrates are the most abundant compounds found in nature (cellulose: 100
billion tons annually)

Most carbohydrates are found naturally in bound form rather than as simple sugars

• Polysaccharides (starch, cellulose, inulin, gums)

• Glycoprotein and proteoglycans (hormones, blood group substances,
antibodies)
• Glycolipids (cerebrosides, gangliosides)
• Glycosides
• Mucopolysaccharides (hyaluronic acid)
• Nucleic acids
 Role of Carbohydrate in plants:

Major source of respiratory Energy

Plant and animal interaction (Honey bees)
Storing Energy (starch)
Building block (cellulose, Hemi cellulose)
Protection of plants from wound & infection (gums)
 Carbohydrates and Related Drugs
S.NO Name of Drug & Biological sources Constituents Uses
Synonym
1. Acacia (Indian gum) Acacia arabica Aranin oxidase Emulsifying and suspending agent
(Leguminosae)
2. Guar gum Cyamopsis tetragonolobus guaran Binding agent, emollient,
(Leguminosae) disintegrating agent
3 Honey Apis species (Apitae) Natural invert sugar Demulcent, sweetening agent

4. Algin (Alginic acid) Macrocystis pyrifera, Alginic acid Thickening and suspending agent
Laminaria hyperborsea
5. Tragacanth Astragalus gummifer Tragacanthin, Traganthic acid, Thickening agent, demulcent
(Leguminosae) bassorin
6. Pectin Citrus limon, C.aurantium D-galactouronic acid Adsorbent and thickening agent
(Rutaceae) Pectric acid
7. Gum ghatti Anogeissus latifolia Two distict polysaccharide, Emollient, pharmaceutical aid
(Combretaceae) osidase
8. Gum karaya Sterculia urens A polysacchairide containing Thickening agent, Emollient
(Sterculiaceae) 8% acetyl and 37% uronic acid
residues and no methoxyl
group
9. Isabgol Plantago ovata Pentosan mucilage, Aldobionic Demulcent, laxative,
(Plantaginaceae) acid pharmaceutical aid
10. Bael Aegle marnelos Marnelosin and furocoumarin Digestive, Antidiarrheal

11. Carrageenan (Irish moss) Chondrus cryspus Gigartina Kappa- Carrageenan Demulcent, Antidiarrheal,
sps. (Gigarginaceae) Lamda carrageenan pharmaceutical aid
12. Arrow root Maranta Pharmaceutical aid
Arundinaceae
 Classification of Carbohydrates

➢Monosaccharide/ simple sugars(monoses or glycoses) (Trioses, tetroses,

pentoses, hexoses)
➢Disaccharides (Most important sugars)
➢Oligosaccharides (tri, tetra, penta, up to 9 or 10 )
➢ Poly saccharides (glycans)
•Homopolysaccharides
•Heteropolysaccharides
•Complex carbohydrates
 Monosaccharide

➢Also known as simple sugars

➢Classified by
1. the number of carbons and
2. whether aldoses or ketoses

➢Most (99%) are straight chain compounds

➢D-glyceraldehyde is the simplest of the aldoses (aldotriose)

➢All other sugars have the ending ose (glucose, galactose, ribose,
lactose, etc.)
Structure of a simple aldose and a simple ketose
Monosaccharide rich in Honey
COMPOSITION OF HONEY
Chemical composition of honey is very complex. Honey mainly contains:
➢Water
➢Sugar (glucose, fructose, maltose, Oligosaccharides, sucrose, etc)
➢Organic Acids ( Tartaric, citric, malic, gluconic acid)
➢Minerals ( K, Ca, P, Na, Fe, Au, Ag)
➢Vitamins ( B1, B2, nicotinic acids, K, B- carotene)
➢Enzymes ( Diastase, Catalase, glucose oxidase, glucosidase, Saccharase)
➢Antibiotic Substances
➢Pollen, Protein, Amino acids
➢Flavors & Aromas , Pigments( Carotene, Xanthophyll, chlorophyll)

North India Honey have lesser moisture content (20%)

Western & Eastern ghat Honey have more moisture (23%)
Carbohydrates – Structural diversity
Disaccharides
Disaccharides(Palm gur, Coconut gur )
 Oligosaccharides
Oligosaccharides are polymers containing 2-10 simple sugars linked
together.

Sucrose, lactose, and maltose

Maltose hydrolyzes to 2 molecules of D-glucose

Lactose hydrolyzes to a molecule of glucose and a

molecule of galactose

Sucrose hydrolyzes to a molecule of glucose and a

molecule of fructose
 Tri-saccharides

Raffinose /Melitose: found in beans, cabbage, brussels

sprouts, and broccoli.
Humans cannot digest this saccharide and it is fermented
in the large intestine by gas-producing bacteria.
 Polysaccharides
Polysaccharides are long carbohydrate molecules of
repeated monomer units joined together by glycosidic bonds. They range in
structure from linear to highly branched.
Function: Usually either structure- or storage-related.
 Classification of Polysaccharides
Structural Polysaccharide:
Cellulose, Arabino xylans, Chitin and Pectin

Storage Polysaccharide:
Starch, Glycogen
Structural Composition of Plants Cell
Structural Composition of Plants Cell
 Structural Polysaccharide

Cellulose:
Are linear molecules empherical formula (C6H10O5)n
• It is the main constituent of the cell walls of plant.
• Cellulose is a colorless solid, insoluble in water and organic solvent.
• Soluble in strong hydrochloric acid (40%) strong Sulphuric acid(72%)
• Cellulose are polymer of a single sugar (Glc.Pyranose) with ß-1-4 linkage
• Value for the degree of polymerization (DP) ranges from 7000 to 10,000
for wood and 15,000 for cotton.
• Cellulose constitutes the principal structural element in the plant cell
wall. It constitutes ~ 1/3 of annual plant and ½ perennial plants.
Structure of Cellulose
 Properties of Cellulose

➢ Polymer of beta-D-glucose attached by β (1-4) linkages

➢ Yields glucose upon complete hydrolysis

➢ Partial hydrolysis yields cellobiose

➢ Most abundant of all carbohydrates

➢ Cotton, flax: 97-99% cellulose
➢ Wood: ~ 50% cellulose

➢ Gives no color with iodine

➢ Held together with lignin in woody plant tissues

Hemi cellulose: are closely associated with the skeletal polysaccharide
cellulose in the cell wall.
Hemi cellulose have a variety of sugar components and fall into three main
types: the Xylans, glucomanns and arabinogalactans
• are those polysaccharides extractable from plant parts by strong alkali
• Are structurally complex (branched) with degree of polymerization (DP)
ranging from less than 100 to about 200 units.
• Soft wood contain ~ 25% Hemi cellulose
• Hard wood ~ 30% Hemi cellulose
Soft wood Hemi cellulose: mannose, galactose, xylose, glucose
Hard wood Hemi cellulose: Xylose, galactose, mannose and minor amount of
rhamnose and arabinose.
Difference between cellulose and Hemi cellulose:
(1) Cellulose have a higher degree of Polymerization (
more monosaccharide units) per molecule than hemi
cellulose.
(2) Cellulose are less soluble in alkali and less readily
hydrolyzed by dilute acids than hemi cellulose.
(3) Cellulose are fibrous, while hemi cellulose are non
fibrous.
(4) Cellulose yield D- glucose on hydrolysis, while hemi
celluloses yield predominately D- Xylose and other
monosaccharide.
(5) Cellulose have a higher ignition temp. than hemi
celluloses.
LIGNINS
• Lignins are phenolic polymers present in the cell walls of plants,
which are responsible with cellulose for stiffness and rigidity of
plant stems.

• Lignin acts as binding material between cellulose and

Hemicellulose to form wood structure

• It is not a polysaccharide. It is a polymer with three different

monomers.

• In mature wood tissues the amount of lignin is vary between 18% - 38%

• Lignin is extracted with 95% alcohol containing 3% HCl

Structure of Lignin
 Uses of Lignin
• Feed and pellet binders
• Dust suspension and road stabilizers
• Plant micronutrients
• Emulsifier
• Oil well drilling
• Dye and pigment dispersant
• Concrete admixtures
• Phenolic resins
• Phenol formal dehyde resins
• Panel board adhesive
• As antioxidants in Rubber,Lubricant and animal feed
Arabinoxylans
Arabinoxylans are found in both the primary and secondary cell walls of plants
and are the copolymers of two pentose sugars: arabinose and xylose.

Chitin
Chitin is one of many naturally occurring polymers. It forms a structural
component of many animals, such as exoskeletons. Over time it is bio-
degradable in the natural environment. Its breakdown may be catalyzed
by enzymes called chitinases, secreted by microorganisms such
as bacteria and fungi, and produced by some plants.
 Pectin
Pectin are a family of complex polysaccharides that contain
1,4-linked α-D-galactosyluronic acid residues. They are
present in most primary cell walls and in the non-woody
parts of terrestrial plants.

• Pectin are heteropolysaccharides found in the pulp of fruits

(citrus, apples)
• on hydrolysis pectin yield galacturonic acid, galactose,
arabinose, methanol and acetic acid
• Pectin are composed of galactans and arabans
used as gelling agents (to make jellies)
Pectin Substances:
These consist of a group of carbohydrates which are considerable interest in foods of plant origin. They comprise
not only those substances (pectin) in fruit and vegetables which are capable of forming gels with sugar and acids
but a number of otherCOOH
compounds as well. COOCH 3
H OH H
OH O
H

H OH H
OH OH
H H
OH H
H OH

a  galacturonic acid Methy- a- galacturonic acid

The peptic substances are polysaccharide of galacturonic acid or of its methyl ester.
COOCH3
COOCH3 H
H OH H
H O
O O H
H OH
O H O H O
H OH
OH O
H OH
H OH COOH

Poly galacturonic acid molecule

Pectic Substances is a group designation for those complex, colloidal carbohydrate substance
which occurs in plants and contain a large proposition of an hydra glacturonic acid units.
Fruits such as apples, lemon, Tamarind pulp. Fruits of Annona squamosa contains appreciable
quantities of pectin.
 Starch

• Most common storage polysaccharide in plants

• Composed of 10 – 30% alpha -amylose and 70-90%

amylo pectin depending on the source.

• The chains are of varying length, having molecular

weights from several thousands to half a million
 Storage Polysaccharides
Starches
➢Starches are glucose polymers in which glucopyranose units are bonded
by alpha-linkages.
➢It is made up of a mixture of amylose (15–20%) and amylopectin (80–85%).

➢Amylose consists of a linear chain of several hundred glucose molecules and

Amylopectin is a branched molecule made of several thousand glucose units
(every chain of 24–30 glucose units is one unit of Amylopectin).

➢Starches are insoluble in water.

➢They can be digested by hydrolysis, catalyzed by enzymes called amylases,

which can break the alpha-linkages (glycosidic bonds).

➢Humans and other animals have amylases, so they can digest starches.
➢Potato, rice, wheat and maize are major sources of starch in the human diet.
➢ The formations of starches are the ways that plants store glucose.
Amylose and amylopectin are the 2 forms of starch. Amylopectin
is a highly branched structure, with branches occurring every 12
to 30 residues
 Iodine Solution Test of Starch

Suspensions of amylose
in water adopt a helical
conformation

Iodine (I2) can insert in

the middle of the amylose
helix to give a blue color
that is characteristic and
diagnostic for starch
Chemical structures from a selection of the
carbohydrates
 Inulin
• Beta -(1,2) linked fructofuranoses
• linear only; no branching
• lower molecular weight than starch
• colors yellow with iodine Jerusalem artichokes
• hydrolysis yields fructose
• Plants containing large quantities of inulin are Jerusalem artichoke,
chicory root, garlic, asparagus root and dandelion root
• Inulin is widely applied in the food industry and it serves many
purposes. It has been used as a (low calorie) sweetener, to form gels,
to increase viscosity, to improve organoleptic properties, and as a
non-digestible fiber. Mostly it is used as a sugar and fat replacer in
dairy products and as a prebiotic.
• used as diagnostic agent for the evaluation of glomerular filtration
rate (renal function test)
• Inulin is a natural storage carbohydrate present in more than 36,000
species of such as : agave, wheat, onion, bananas,.
 Inulin content of different crops
Source Inulin content (% of fresh Range of DP
weight)
Banana (Musa cavendishii) 0.3–0.7 2–5

Barley (Hordeum vulgare) 0.5–1.5 No data

Chicory (Cichorium intybus) 15–20 2–60

Garlic (Allium sativum) 9–16 2–50

Globe artichoke (Cynara 2–3 2–250

scolymus)
Jerusalem artichoke 3–10 2–50
(Helianthus tuberosus)

Leek (Allium ampeloprasum) 16–20 No data

Onion (Allium cepa) 1–8 2–12

Wheat (Triticum aestivum) 1–4 2–8

 Some tubers of Indian origin

Colocasia esculenta Yams Amorphophallus

Sweet Potato Canna Arrowroot

 Tubers Starch Properties
Tubers Starch % Viscosity Clarity Stability

Cassava 25-35 High High Medium

Sweet 20-25 Medium- High Medium

potato high
Yams 15-33 Medium- High High
high

Low
Aroids 10-20 Low- High
medium
Canna 15-25 High High High

Arrowroot 16-28 Medium- Medium Medium

high
Industrial Importance of Carbohydrates
Syrups, such as corn syrup made from corn starch, have
DE (dextrose equivalent) values from 20 to 91.

Commercial dextrose has DE values from 92 to 99.

High fructose corn syrup (HFCS), commonly used to

sweeten soft drinks, is made by treating corn syrup with
enzymes to convert a portion of the glucose into
fructose.
Relative sweetness of various carbohydrates
Fructose 173
HFCS (42% fructose) 120
Sucrose 100
Invert Sugar* 120
Glucose 74
Sorbitol 55
Xylitol 100
Regular corn syrup 40
Lactose 15
Galactose, Maltose 32
high-DE corn syrup 70
Mannitol 50
Invert sugar is a mixture of glucose and fructose
found in fruits
Sugar Alcohols
are the hydrogenated forms of the aldoses or
ketoses. For example,
glucitol, also known as sorbitol, has the same
linear structure as the chain form
of glucose, but the aldehyde
group is replaced with
a -CH2OH group.
 Sugar Alcohols
Sugar Alcohols are the hydrogenated forms of the aldoses or
ketoses.
For example, sorbitol, has the same linear structure as the
chain form of glucose, but the aldehyd group is replaced with
a -CH2OH group.
Other common sugar alcohols include the monosaccharides
erythritol and xylitol
Sugar alcohols have about half the calories of sugar
and are frequently used in low-calorie or "sugar-free"
products.
Xylitol, which has the hydroxyl groups oriented like xylose, is a
very common ingredient in "sugar-free" candies and gums
because it is approximately as sweet as sucrose, but contains
40% less food energy.