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PLANT SECONDARY
METABOLITES
Dr. Muayad S. Shawkat
University of Baghdad
College of Science
Department of Biotechnology
*Plant secondary metabolites are a diverse group
of molecules that are involved in the adaptation of
plants to their environment but are not part of the
primary biochemical pathways of cell growth and
reproduction.
*These compounds are played many important rules in
plant life such as involved in defense against
herbivores and pathogens, regulation of symbiosis,
control of seed germination, and chemical inhibition
of competing plant species (allelopathy), and
therefore are an integral part of the interactions of
species in plant and animal communities and the
adaptation of plants to their environment.
* In addition, plant secondary metabolites are also
associated with improved nutritive value and may have
beneficial effects on animal health.
* Growing interest in the potential health-promoting
effects of plant secondary metabolites in human foods
has prompted research on their potential to prevent or
treat cancer, circulatory disease, and viral infection.
*
The mechanisms by which these substances have beneficial
effects on health may also be related to their toxic effects,
and the difference between toxicity and beneficial effects
may be dose- and structure-dependent.
The term “plant extract" determines the part/parts of a
plant used for preparing medicine (for example: leaves,
flowers, seeds, roots, barks, stem....etc). Studies on the use
of plant extracts for controlling disease have shown the
importance of natural chemicals (phytochemicals) as possible
sources of non-phytotoxic and easily biodegradable,
alternative fungicides and antibiotics
Preparing the plant Material:
 Plants were dried before extraction.
 freeing of plant under study from
contamination

From other plants
from disease
General methods Extraction:
choosing of the precise method of
extraction depend on texture and
water content of the plant material.
1. Maceration
the whole or coarsely powdered crude drug is
placed in a container with the solvent and
allowed to stand at room temperature for a
period of at least 3 days with frequent agitation
until the soluble matter has dissolved.

In this method, the finely ground crude drug is
placed in a porous bag or “thimble” made of
strong filter paper, which is placed in chamber E
of the Soxhlet apparatus. The extracting solvent
in flask A is heated ,and its vapors condense in
condenser D. The condensed extractant drips
into the thimble containing the crude drug, and
extracts it by contact. When the level of liquid in
chamber E rises to the top of siphon tube C, the
liquid contents of chamber E siphon into flask A.
CO2 
Photosynthesis
Primary carbon metabolism
Pentose phosphate
pathway
Phosphoenol pyruvate
TCA Cycle
pyruvate
Acetyl Co-A
Erythrose-4-phosphate
Aliphatic amino acid
Shikimic acid
Aromatic
amino
acids
Nitrogen
containing
compounds
Malonic acid
Pathway
Phenolic
compounds
Mevalonic acid
Pathway
Terpenes
MAIN GROUPS OF PLANT
SECONDARY METABOLITES
A/ Terpenoids
B/ Nitrogen containing secondary metabolites
C/ Phenolic compounds
THE TERPENOIDS
ISOPRENE C5 is the basic unit of the terpenoids
Production in Plants: * Flowers
* Leaves
* Fruit
Biological Role(volatile and non volatile):
-Flavour, fragrance, scent
-Antibiotics
-Hormones
-Membrane lipids
-Insect attractants
-Insect antifeedants
TERPENOIDS --IMPORTANT MOLECULES !
C5-hemiterpenes -e.g. isoprene
C10-monoterpenes -e.g. limonene
C15-sesquiterpene -e.g. abscisic acid (ABA)
C20-diterpene -e.g. gibberellin
C30-triterpne -e.g. brassinosteroids
C40-tetraterpenes -e.g. carotenoids
> carbons -polyterpenes-e.g. ubiquinones,
rubber
Nitrogen containing compounds!
 Alkaloids (pseudo-, True-, proto-)
 Extremly heterogenous group
 alkali like
 have important pharmacological properties
 further classified in to many groups
- Pyridine alkaloids , e.g. nicotine
- pyrrolidine alkaloids , e.g. stachydrine
- piperidine alkaloids , e.g. coniine
- tropane alkaloids , e.g. atropine
- quinoline alkaloids , e.g. quinine
- Isoquinoline alkaloids , e.g. berberine
- Quinolizidine alkaloids , e.g. lupinine
- Indol alkaloids , e.g. resrpine
- Imidazol alkaloids , e.g. pilocarpine

Phenylalkylamines:
e.g. Ephedrine
CH
2
CH
NH

CH
3
2
Pyridine and piperidine
e.g. lobeline, nicotine
N

N
H
Tropane
e.g. Atropine.
NCH
3
OH

Quinoline
e.g.quinine and quinidine
N

Isoquinoline
e.g. papaverine
N

Phenantheren
e.g. Morphine

Indole
e.g.ergometrine
N
H

Imidazole
N
e.g. pilocarpine
N

Purine
e.g. caffeine
6
1
5
N
7
N
H
8
2
4
N
3
P u rin e
N
9

Steroidal
e.g. Solanum and Veratrum
alkaloids

Terpenoid
e.g. Taxol
 Cyanogenic glycosides
 widely
distributed in plants
volatile poisons
 e.g. Lotustraline
 Glucosinolates
 contain nitrogen and sulpher
 volatile toxins
 strong deterrent
Cyanogenic Glycosides
Non-Protein amino acids
found in plants of the family
leguminosae
 e.g. Canavanine resemble in
structure with arginine
 there are not incorporated in to
protiens

Phenolics
• Plants produce a
variety of compounds
that contain one or
more phenol groups called phenolics
• Thousands of
phenolics occur in
plants
Phenolics
• Large group of diverse compounds
• Many serve as defense compounds against
herbivores and pathogens
• Some function in support – primary cmpd
• Some attract pollinators
• Some absorb UV light
• Some reduce growth of competitors
Tannins
• They are high molecular weight phenolic
compounds
• They are widely distributed in plants.
• capable of precipitation of animal proteins
Classification of Tannins:
True Tannins
Pseudotannins
(High molecular weight compounds)
Low molecular weight compounds
e.g. Gallic acid, Flavan-3,4-diol
Hydrolysable Tannins
(Pyrogallol)
Condensed Tannins
(Catechol)
Not hydrolysable,
no sugar in mol.
Uses of Tannins:
•
•
•
•
•
•
•
1) Antioxidant.
2) Antidiarrheal.
3) Antidote for heavy metals poisoning.
4)Treatment of burns, ulcers, inflammations
4) Astringent to stop bleeding (hemorrhage)
5)Treatment of Hemorrhoids.
6) Tanning industry.
Lignin a complex phenolic
• Primary metabolite - secondary cell wall
component occurs in all vascular plants
• Structural function
• Also protective because deters herbivores
due to its toughness
• Blocks growth of many pathogens because
only small group of fungi can degrade
Flavinoids
• One of the largest classes of phenolics
• Carbon skeleton has 15 carbons with two
benzene rings connected by a 3-C bridge
-C3-
Anthocyanins
• Colored flavinoids red, pink, blue,
purple pigments
• Attract animal
pollinators and
seed dispersers
Anthocyanin
B
- cyanidine
cyanidine 3-glucoside
cyanidine 3-rutinoside
- peonidine
peonidine 3-glucoside
peonidine derivative
Flavones and Flavonols
• Also flower pigments
• Absorb UV not visible light - not visible to
human eye but visible to many insects maybe be attractants, nectar guides
• Also present in leaves where they protect
against UV-B damage
• Appeared to be involved in legume roots in
attracting N-fixing bacteria
Some applications of Important
plants and their compounds in
biotechnology
Green Tea (Camellia sinensis)

Polyphenols from
leaves
 anti-cancer inhibiting
tumor initiation and
cell proliferation
 anti-oxidant
Wine Grape (Vitis vinifera)


Contains over 50 different
flavonoid phenolics
including resveratrol and
catechins
Reduces heart disease by
inhibiting platelet
aggregation, lowering
LDL (low density
lipoproteins) and acting as
antioxidants
Ginger (Zingiber officinale)

from the rhizome
 Over 12 compounds
with anti-oxidant
activities greater than
vitamin E
 anti-tumor
 anti-emetic (inhibits
vomiting)
Garli c (Allium sativum)
Onion (Allium cepa)

Organo-sulfur
compounds from
leaves
 Anti-carcinogenic and
anti-microbial
 Anti-atherosclerosis
and anti-hypertensive
 Toxic in high amounts
Soybeans (Glycine max)

Contains phytoestrogens like isoflavones
 Reduces health risks associated with menopause:
osteoporosis and heart disease in women
 Reduces prostrate, colon and breast cancer
Thank
You
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