What are secondary metabolites? Why they are produced? Compartment of synthesis Classes of secondary metabolites Applications Conclusion References

1. By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

3. Secondary metabolites are organic compounds that are
not directly involved in the normal growth, development,
or reproduction of an organism. Unlike primary
metabolites, absence of secondary metabolites does not
result in immediate death, but rather in long-term
impairment of the organism's survivability, fecundity, or
aesthetics, or perhaps in no significant change at all.

4. WHY THEY ARE PRODUCED?
Secondary Metabolites are produced in plants is
mainly for:
1.Disease resistance (from fungus, bacteria, viral, and
pests),
2.For pollination and
3.To combat in extreme conditions of stress.
The stress may be biotic or abiotic [Drought, Cold,
Temperature, etc.]

6. Main Groups of Secondary Metabolites-
-29,000 terpenes derived from the C5 terpenes- alkaloids.
-8,000 phenolics shikimate pathway or phenolics-
malonate/acetate pathway in Plants precursor isopentenyl
diphosphate (IPP).
-12,000 alkaloids - derived from amino acids.
Main secondary metabolite-
Nitrogen containing compound-
•Alkaloids(12,000)
•Non protein amino acid(600)
•Amines(100)
•Cynogenic glycosides(100)
Glucosinolates(100)

7. Main secondary metabolites-
Non nitrogen containing
Terpenoids(29,000)-
Mono(1,000)
Sesquiterpene(3,000)
Diterpines(1,000)
Triterpines,Steroids,saponines(4,000)

8. Compartmentation of SMs biosynthesis-
Mostly in the Cytosol-hydrophilic compounds
Chloroplasts-alkaloids (caffeine) and terpenoids (monoterpenes)
Mitochondria-some amines, alkaloids
Vesicles-alkaloids (protoberberines)
Endoplamic reticulum-hydroxylation steps, lipophilic compounds
Water soluble compounds-
alkaloids, NPAAs,cyanogenic glucosides, glucosinolates,
saponines, anthocyanines, flavonoids,cardenolides.

9. Example-
Anthocyanines-
-Blue-red flavonoid pigments
- They are stabilized in the vacuole
-Oxidation in cytosole
-The sequestration is a
detoxification process SMs
sequestration in to Vacuoles SMs

10. SMs Vacuoles-
Anthocyanin exampleAnthocyanin example-Bz2 mutant an9
mutant
-When the BRONZE2gene is not active, anthocyanines
accumulate in the cytosol and a tan bronze phenotype of
tissue is obtained
-BRONZE2is a Glutathione-S-transferase
-Glutathionation of anthocyanines is a pre-requisite for the
targeting to the vacuole through a GST-x-pump in the
tonoplast membrane.

11. Anthocyanin example-bz2& the an9 mutant& mutant
Bz an9

12. Biosynthetic Pathway-
• Nucleoside diphosphate sugar pathway: cellulose, hemicellulose,
glycosides.
• Shikimate-cinnamate pathway: lignin, lignans, hydrolyzed tannins.
• Mixed pathways of 3 and 4: some prenylflavonoids, quinones and
stilbenes.

13. The Classes of Secondary Metabolites-
The majority of secondary metabolites belong to one of a
number of families, each of which have particular
structural characteristics arising from the way in which
they are built up in nature (biosynthesis).
The classes of secondary metabolites are:
– Polyketides and fatty acids
– Terpenoids and steroids
– Phenylpropanoids
– Alkaloids

14. Terpenes-
Isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate
(DMAPP) combined to yield geranyl pyrophosphate (GPP), leading to
monoterpenes. Similarly, compounds derived from farnesyl
pyrophosphate (IPP) lead to sesquiterpenes, and triterpenes are formed
from two equivalents of FPP, and triterpenes are formed from two
equivalents of FPP.
The function of terpenes in plants is generally considered to be both
ecological and physiological
– Allelophathy
– Insecticidal
– Insect pollinators
– Plant hormone (Abscisic acid, gibberlellin)

15. Myrcene is found in the essential oil of bay leaves as well as hops. It is
used as an intermediate in the manufacture of perfumes.
Hops (Humulus lupulus) Greek Bay (Laurus nobilis)

16. Geraniol is isomeric with linalool, constitutes the major part of the oil of
roses and is also found in essential oils of citronella, lemon grass, and others.
Geraniol Linalool
Menthol is a well-known monoterpene which is found in the essential oil
of peppermint and other members of the mint family.

17. Sesquiterpenoids-
• More than 10000 sesquiterpenoids have been identified, representing a
wide variety compounds of different skeletal types from acyclic to tetra
cyclic systems.
-Farnesol is widely distributed in many essential oils such as
citronella, neroli, cyclamen, lemon grass, tuberose, rose, musk, and
balsam. It is used in perfumery to emphasize the odors of perfumes.
The presence of farnesol prevents the yeast-to-mycelium conversion,
resulting in actively budding yeasts without influencing cellular
growth rates.

18. -Nerolidol is present in neroli, ginger, jasmine, lavender, tea tree
and lemon grass. The aroma of nerolidol is woody and
reminiscent of fresh bark. It is used as a flavoring agent and in
perfumery. It was also shown to be produced by the leaves of a
large number of plant species in response to herbivory insects and
then to be transformed into a C11-homoterpene (4,8-dimethyl-
1,3,7-nonatriene)
which attracts predatory insects.

19. -Abscisic acid plays a key role in plants in the regulation of stomatal
closure by regulating ion channel activities and water exchanges
across the plasma membrane of guard cells. Abscisic acid has also a
variety of roles in plant development, bud and seed dormancy,
germination, cell division and movement. It induces also storage
protein synthesis in seeds and may be involved in defense against
insect attack

20. Phenolic Constituents-
-Heartwood and bark contain a large variety of complex aromatic
extractives. Most of them are phenolic compounds, and many are
derived from the phenylpropanoid structure.
-Vanillin is a phenolic aldehyde, an organic compound with the
molecular formula C8H8O3. Its functional
groups include aldehyde, ether, and phenol. It is the primary
component of the extract of the vanilla bean. Synthetic vanillin,
instead of natural vanilla extract, is sometimes used as a flavoring
agent in foods, beverages, and pharmaceuticals.

21. -Eugenol is a phenylpropene, an allyl chain-
substituted guaiacol. Eugenol is a member of
the phenylpropanoids class of chemical compounds. It is a
clear to pale yellow oily liquid extracted from certain essential
oils especially from clove oil, nutmeg, cinnamon, basil and bay
leaf. It is slightly soluble in water and soluble in
organic solvents. It has a spicy, clove-like aroma.

22. The Most Important Classes of Phenolic Compounds in Plants
number of C-atoms basic skeleton Class
6 C6 simple phenols, benzoquinones
7 C6 - C1 phenolic acids
8 C6 - C2 acetophenone, phenylacetic acid
9 C6 - C3
hydroxycinnamic acid, polypropene,
coumarin, isocoumarin
10 C6 - C4 Naphtoquinone
13 C6 - C1 - C6 Xanthone
14 C6 - C2 - C6 stilbene, anthrachinone
15 C6 - C3 - C6 flavonoids, isoflavonoids
18 (C6 - C3)2 lignans, neolignans
30 (C6 - C3 - C6)2 Biflavonoids
N
(C6 - C3)n
(C6)n
(C6 - C3 - C6)n
lignins
catecholmelanine
(condensed tannins)

23. The basic structure of flavonoids is derived from the C15 body of
flavone. They differ from other phenolic substances in the degree
of oxidation of their central pyran ring. And, very fundamentally,
also in their biological properties. While some classes (the
flavonones, for example) are colourless, the members of other
classes (the anthocyanes, for example) are always coloured and
known as pigments of flowers or other plant parts.

24. The Most Important Classes of Flavonoids and their Biological Significance
Class
number of known
members
biological significance (so far as known)
anthocyanin(s) 250 red and blue pigments
Chalcons 60 yellow pigments
Aurones 20 yellow pigments
Flavones 350 cream-coloured pigments of flowers
Flavonols 350 feeding repellents (?) in leaves
Dihydrochalcons 10 some taste bitter
Proanthocyanidins 50 astringent substances
Catechins 40
some have properties
like those of tannins
biflavonoids ? 65 ?
Isoflavonoids 15 oestrogen effect, toxic for fungi

25. The lignans are a group of chemical compounds found in plants. Lignans are one of the
major classes of phytoestrogens, which are estrogen-like chemicals and also act as
antioxidants. The other classes of phytoestrogens are the isoflavones and coumestans. Plant
lignans are polyphenolic substances derived from phenylalanine via dimerization of
substituted cinnamic alcohols (see cinnamic acid), known as monolignols, to
a dibenzylbutane skeleton 2. This reaction is catalysed by oxidative enzymes and is often
controlled bydirigent proteins.
Carbohydrates --> Shikimic acid pathway --> Aromatic a.a.'s --> Cinnamic acids --> Lignans (Steganes)

26. Alkaloids-
Alkaloids are a group of nitrogen-containing bases. Most of them
are drugs. Only a few (like caffeine) are derived from purines or
pyrimidines, while the large majority is produced from amino
acids.
Ornithine derivatives- Ornithine is a precursor of the cyclic
pyrrolidines that occur in the alkaloids of tobacco (nicotine,
nornicotine) and other Solanaceae. Nicotine is a starting
compound of numerous further tobacco alkaloids. During the
biosynthesis of tropane, intermediates are produced that are at
the same time starting compounds for cocaine and hyoscamine.

28. Derivatives of phenylalanine:
The most important are:
Ephedra-alkaloids:ephedrine, pseudoephedrine,
alkaloids gained from micro-organisms: cytochalasine B and D,
the Taxus-alkaloids: taxine,
the Lunaria-alkaloids: lunarine and lunaridine,
alkaloids of the Lythraceae.

29. Tyrosine derivates- Synthesis of Benzylisoquinolines, Starting with Two
Mol Tyrosine
Colchicine, an alkaloid of the naked ladies (Colchicum autumnale and
the related species C. byzanthinum) belongs also to this class. It is a
poison best-known as an inhibitor of mitosis. It prevents the aggregation
of tubuline dimers so that no micotubuli are formed.

30. Plant products Plant species Industry Industrial uses
Codeine (alkaloid) Papaver sominifera Pharmaceutical Analgesic
Diosgenin (steroid) Dioscorea deltoidea Pharmaceutical Antifertility agent
Quinine (alkaloid) Cinchona leitgeriana Pharmaceutical Antimalaria
Digoxin (glycoside) Digitalis lanata Pharmaceutical Cardiactonic
Scopolamine
(alkaloid)
Dhatura
stramonium
Pharmaceutical Antihypersensitive
Vincristine (alkaloid) Catharanthus roseus Pharmaceutical Antileukaemic
Taxol Taxus brevifolia Pharmaceutical Ovarian and
breast cancer
Pyrethrin Chrysanthemum
cinerariaefolium
Agrochemical Insecticide
Quinine (alkaloid) C. ledgeriana Food & drink Bittering agent
Jasmine Jasmium sp. Cosmetics Perfume
Application-

31. Conclusion
Secondary metabolites are not involve in main biosynthetic
pathway but it useful for plants. They responsible for
protection of plant from stress, help in pollination and gives
disease resistivity. They also useful for human in many way like
production of drugs, essential oil, flavoring substance and
pigments.

32. Reference-
Books:
•Introduction to plant tissue culture By M. K. Razdan 1st edition 1997
•Plant biotechnology: By H. S. Chawla
Internet:
www.wikipedia.com
http://www.biologie.uni-hamburg.de/b-online/e20/20a.htm