Plants produce secondary metabolites that serve as communication signals and defense weapons. Secondary metabolites are not directly involved in primary growth and reproduction but play roles in defense, protection, attracting pollinators, and taxonomy. They are produced for fitness in harsh environments, communication by attracting pollinators and beneficial microbes, attracting predators to protect against harmful insects and pathogens, and signaling to other plants about herbivore attacks. Major groups of secondary metabolites include terpenoids, alkaloids, and phenolic compounds, which have various functions for the plant and human uses such as medicines, perfumes, pesticides, and food colorings/flavors.

1. Secondary Metabolites: Untold Language & Weapons of Plants
What are secondary metabolites?
Secondary metabolites are the language of
communication as well as the defense weapons of
plants. They are bio-molecules that are not directly
involved in primary growth, development &
reproduction but involves in defense mechanism,
protection , & attraction of pollinators and can also be
used for taxonomic classification.
Plants produce diverse array
of secondary metabolites in
their cells for –
For Fitness – Plants are
known as “Sitting Ducks ”
in harsh environment so they
have to defend
themselves from different
biotic / abiotic
stresses to remain fit in the
ecosystem.
For Communication – When
flowers are blossomed they
use secondary metabolites to
produce aroma or color to
invite pollinators as well as
beneficial microbes like
Rhizobia
For Attracting Predators –
Plants also attract predators
to
protect them from the attack
of harmful insects or
pathogens. Predators are like
“ Friend of Enemies Enemy.”
For Signaling – Plants use WiFi
signals through volatile
substances produced by them
to communicate & give
message to other plants that
they are attacked by
herbivores.
Why plants produce secondary metabolites?
Wax
Lignification
Phytoalexins
Defense Mechanism
Department of Genetic
Engineering & Biotechnology
Tabina Ruzbitun Nesa
Major Groups of secondary Metabolites
Terpenoids – compounds composed of one or more C5 units. The simplest terpenoid is
isoprene, volatile gas emitted during photosynthesis in large quantities by leaves that
may protect cell membranes from damage caused by high temperature or light.
Alkaloids- compounds composed of nitrogen.
Phenolic compounds - The phenols consist of a hydroxyl group (–OH) attached to an
aromatic ring.
Contributions of Terpenoid
* Yellow color of Sunflower
*Flavor of ginger
*Flavor of cinnamon
*Flavor of cloves
*Red color of Tomato
*Artemisinin and Taxol as malaria and cancer
medicines
*Bioactive terpenoids have potential to ameliorate
metabolic disorders via activation of peroxisome
proliferator-activated receptors (PPARs).
*Citrus derived terpenoids have anticarcinogenic,
antihypertension, & anticardiovascular disease
effects
Role of Terpenoid in Human
Taxol
Artemisinin
Industrial use of
terpenoid
•Perfume production
•Production of
Antibacterial pesticide
•Production of
antineoplastic
•Pharmaceuticals uses
Perfume
Drugs
Use of Phenolics in
Agriculture
Furanoflavonoids like karanjin
or rotenoids can be used as
insecticidesPhenolics in Human Food6
The more colorful they are , the
more phenolics!
e.g.:grapes, pomegranate,green
vegetables, chocolate, green tea,
legumes,honey, berries etc.
Karanjin
insecticide
Juglone
fungicide
Catechin
herbicide
Production of caffeine,
c cocaine, nicotine, insecticides
& also in production of drugs
like Morphine, Quinine
Do you know?
Changing flower
color & making
rare colored
flowers are
possible by
introducing
Phenolic
compounds
pathway in a
plant knowing
the gene
responsible for
the color.
Nilmoni BushraShamarthee Monjur Muna Rahaman
Biosynthetic Pathway