About Secondary metabolite

1. Secondary metabolites
BPY 602- Principle of Plant Physiology
Present by,
Name: ARAVINDHARAJAN S T M
I D No. 55478
Degree: II M Sc (Agri. Microbiology)

2. Secondary metabolites
Carbohydrate, proteins, fats, membrane lipids, nucleic acids, chlorophyll and heme –
Primary metabolite
Apart from these substances, certain organic compounds which weren't involve
mainstream of metabolism (i.e.) Plant growth and development – secondary metabolite
These are numerous and chemically diverse in nature – Alkaloids, terpenes, tannins,
flavonoids etc.

3. • According to Street and Cockburn (1972), “secondary plant products are
compounds which have not so far been shown to be involved in primary
metabolism; as far as their functions can at present be assessed they are accessory
rather than central to the physiology of the plants in which they occur”
Three type of secondary metabolites
a) Isoprenoid compounds or terpenes – essential oils, steroids, rubber etc.
b) Nitrogen containing secondary metabolites – alkaloids, non-protein amino acids
etc.
c) Phenolic compounds or phenolics – Lignin, tannins, flavonoids etc.

4. Overview of secondary metabolites
biosynthesis
a)Isoprenoid compounds or terpenes
produced from acetyl Co A through
mevalonic acid pathways
b) Phenolics synthesized through
either i) acetyl CoA via malonic acid
pathway or ii) erythrose 4 PO4- and
PEP
c) Nitrogen containing compounds
such as alkaloids are synthesized from
amino acids.

5. Isoprenoids or Terpenes or Terpenoids
• Largest group of secondary metabolites
• Shows properties of lipids
• Insoluble in water and derives from 5C unit called
isoperene which as derived from isopentane
compound
Monoterpenes – 10 C (two isoperene) Triterpenes – 30 C (6 isoperene)
Sesquiterpenes – 15 C (three isoperene) Tetraterpenes – 40 C (8 isoperene)
Diterpenes – 20 C (four isoperene) Polyterpenes – n C (n isoperene)
Classification of terpenes

6. Monoterpenes
• 10 C compounds and built up of two isoprene units.
• These structures may be i) acyclic, ii) cyclohexanoid (mono, di or tricyclic) and
iii) cyclopentanoid
• Chiefly found in resin ducts in leaves, twigs and trunks of conifers such as pines
• Monoterpenes of conifer resins such as α-pinene, β-pinene, limonene and
myrcene which are toxic to large number of insects
• Some of imp. Monoterpens such as essential oils (insect repellents), menthol
(peppermint), pyrethroids.

7. Sesquiterpene and diterpenes
Sesquiterpene Diterpenes
• Total carbon number – 15
• 3 isoprenoid compounds
• Largest group of isoprenoids
• Many Sesquiterpene coexist with
monoterpenes found in essential oils of
higher plant
Uses
• Costunolide (Sesquiterpene lactones)-
deterrents to herbivore found in glandular
hairs of sage brush and sunflower
• Gossypol (Aromatic sesquiterpenes) –
provide insect resistance
• Total carbon number – 20
• 4 isoprenoid compounds
Uses
• Abietic acid – obtained from plant resin
such as pines and leguminous tree
(Hymenaea courbrail)
• Function – Deterrents to predators and
help in healing the wounds caused by
insect bites

9. Triterpenes
Its derivatives such as steroids, has usually tetracyclic or pentacyclic molecular
structure and some of them modified into lesser than 30 CC
• Sitosterol
• Phyto ecdysones (Ecdysteroids)
• Limnoids (Bitter principle of citrus fruit)
• Azadirachtin
• Cardenolides – Steroid glycoside; Glycoside part contain as digitoxose and
acetyl digitoxose
• Sapogenins (Saponin)
• Steroid alkaloids
• Steroid hormones – Progesterone (Holarrhena floribunda) and
deoxycorticosterone (Digitalis lanata)

11. Polyterpenes
• High molecular weight
• Defense against herbivores and wound healers
• E.g. – Rubber, Gutta and Chicle
• Rubber – large number of isopentenyl units (1,500-60,000) exist as carbon-carbon
double have cis (Z) configuration . Molecular weight is ~1 x 105 to ~ 4 x 106

12. Gutta – Polymer of isoprene residues with low molecular weight than rubber
• C-C double bond have trans (E) configuration. Its obtained from genus Palaquium
(Saptoaceae) and guayule (Parthenium argenatum)
Chicle – mixture of low molecular weight cis and trans isopentenyl units along with
resins that are soluble in acetone
• Obtained from sapodilla (Manilkara zapota) of family sapotaceae and used for
chewing gum base.

13. Many terpenoids plays a important role in growth and development of plant
• Gibberellins are diterpenes
• ABA is a sesquiterpenes and its degradation product of carotenoid precursor
• Sterols used as essential components of cell membranes
• Carotenoids are tetraterpenes and have a photooxidative properties
• Phytol side chains of chlorophylls are diterpene derivates. Bacteriochlorophylls
also have terpenoid side chains

14. Biosynthesis of
terpenes

15. Nitrogen containing secondary plant products
These group can be divided into three main components
a) Alkaloids
b) Cyanogenic glycosides and glucosinolates
c) Non protein amino acids
Alkaloids
• Extremely heterogenous group called secondary metabolites containing one or
more nitrogen atoms, usually in a heterocyclic ring.
• However, all compounds with heterocyclic ring and containing nitrogen are not
alkaloids e.g. Purines, thiamine's etc.

16. • Literally, alkaloids indicates ‘alkali like’ and its properties should be following
point
I. Colorless,
II. Crystalline,
III. Non volatile solids but Coniine and Nicotine are liquid at room temperature.
IV. Bitter In Taste
V. Insoluble In Water, Soluble In Organic Solvent
VI. Most of them levorotatory, coniine are dextrorotatory and papaverine are
optically inactive
VII.Many of them exhibit pharmacological properties.

17. Distribution and classification of alkaloids
• Alkaloids commonly found in Magnoliaceae, Solanaceae, Papaveraceae,
Leguminosae, Ranunculaceae, Rubiacae, Apocyanceae
• Name of some alkaloids are Morphine from Opium poppy, nicotine from
tobacco, quinine from cinchona, atropine from Atropa, colchicine from meadow
saffron, strychnine and brucine from Strychnos nux vomica, cocaine from coca
and cannabidiol from hemp
Three types of alkaloids
• Protoalkaloides
• True alkaloids
• Pseudoalkaloids – Terpenoids containing alkaloids
Directly derived from amino acids

18. Protoalkaloids Truealkaloids Pseudoalkaloids
Do not contain heterocyclic ring
and amines
Contain heterocyclic ring
Eg-
• Terpenoid containing alkaloids
– Glycosides. Mostly, aglycone
(non carbohydrate part of
glycoside) in tomatine is
tomatidine while in solanine the
aglycone is solanidine
• Phenanthrene alkaloids –
Morphine, Codine and thebaine
• Tropolone alkaloids -
Colchicine
eg –
• Hordenine and
• Ephedrine
Eg-
• Pyridine alkaloids- Nicotine
• Pyrrolidine alkaloids –
Stachydrine
• Piperidine alkaloids – Coniine
• Tropane alkaloids – Atropine
• Quinoline alkaloids – Quinine
• Isoquinoline alkaloids –
Papaverine, Narcotine and
Berberine
• Quinolizidine alkaloids –
Lupinine
• Indole alkaloids – Reserpine,
Ergatomine
• Pyrrolizidine alkaloids –
Heliotridine
• Imidazol alkaloids - Pilocarpine

19. Physiological role of Alkaloides
• Protection against predators
• Act as Nitrogen reserves, but this has not been established
• Act as growth regulators; especially germination inhibitors
• they may help to maintain ionic balance due to their chelating power
• (Robert Robinson – Nobel laureate 1947 in chemistry has done more work in
alkaloids)

20. Different types
of Alkaloids

21. Cyanogenic glycosides and glucosinolates
• Widely distributed in grasses, legumes and members of family Rosaceae.
• Cyanogenic glycosides released the Hydrogen Cyanide (HCN) when plant containing
them are crushed and they come in contact with enzymes glycosidase and hydroxy
nitrile lyase released from other parts of the plants
• Plays a defensive role in plants
• Eg:- Amygdalin from Cotoneaster and many species of Prunus , Linamarin from
Phaseoulus lunatus, Lotaustralin from Lotus tenuis, Dhurrin from sorghum and
Heterodendria from African Acacia.
Glucosinolates
• Benzylglucosinolate contains nitrogen and Sulphur, mainly found in Cruciferae family
• When such plant are crushed and they come in contact with enzymes thiogulcosidase
released from other parts of the plants, gives pungent volatile compound such as
isothiocyanates and nitrile

22. Non Protein amino acids
• Many non protein amino acids found in freely without binding the protein and
closely resemble the structure of protein amino acids.
• More than 200 non protein amino acid is there
• Function – inhibit the synthesis and uptake of amino acids and wrongly
incorporate into protein became non functional

24. Plant Phenolics
Functional hydroxyl group with phenolics produced by plant called plant phenolics
SIMPLE
PHENOL
ICS

25. Shikimic acid
Pathway

26. Simple Phenolics
• Caffeic acid, ferulic acid, coumarins such as umbelliferon; furanocoumarins such
as psoralen (phototoxic); benzoic acid derivatives such as salicylic acid and
methyl ester salicylate (SAR activity)

27. Lignin
• Highly complex and branched polymer of simple phenolic compounds with C6-C3
basic carbon skeleton
• Its structure is obscure. 3 Phenyl proponoid compound as building block such as
coniferyl alcohol, sinapyl alcohol and p-coumaryl alcohol
Advantage –
• a) Mechanical strengthening of plant (Secondary cell wall). And, it contains 15-20
% dry matter of plants.
• b)Secondary wall thickening in the xylem vessels and tracheid's

29. Flavonoids
• 15 C Phenolic compounds, consists of C6-C3-C6 basic carbon skeleton
• Two aromatic rings present right and left side of
flavonoid molecule, designated ring A and B
• 2nd ring B and 3rd carbon from middle ring derived
from shikimic acid pathway
• Whereas, ring A and oxygen from middle ring
derived from malonic acid pathway
• Flavonoids usually as glycosides and soluble in
water, it gives colour like red, crimson, purple, blue
and yellow
Flavonoids contains OH groups
usually at position 3’,4’ of ring B
or 5th and 7th of ring A or 3rd of
middle ring

30. • Based upon the degree of oxidation of various position in central ring, it as classified
a) Anthocyanin b) Flavonoids and flavones c) isoflavones (isoflavonoids)
Anthocyanins:
• Coloured pigment (blue, purple
and red)
• Main role – Pigmentation to
attract the bees for pollination
• Common difference – presence
of sugar molecules (i.e.)
Anthocyanin – contains
sugar; and anthocyanidin –
does not contain sugar

31. Pelargonidin
-OH

32. Delphinidin
-OH

33. Cyanidin
(deep red)
-OH

34. Peonidin
(Rosy red)
-OH
-OCH3

35. Petunidin
(Purple)
-OH
-OCH3
-OH

36. Malvidin
(Purplish)
-OH
-OCH3
-OCH3

38. Anthocyanidins

39. Flavones & Flavonols
• Mostly, yellowish or ivory colored
pigments
• Main difference, presence of
alcohol groups
• Some of these pigment gives
colorless, white or creamy colour
• Main role – Absorb UV radiation,
give protection to cell
• Feeding deterrent against
herbivores

40. Anthocyanins, Carotenoids, Chlorophylls

41. Isoflavonoid
• Ring B is shifted and attached the 3rd
position of central ring
Act as
a) Rotenone
b) Phytoalexin compound
c) Looks similar like of estrogen such as
estradiol causses the infertility to
mammals (sheep)

42. Tannins
• Group of compounds occurs in some plant used to tan the animal skin
• Tannin binds collagen protein of animal skin makes more resistant to
heat, water and microbial attack
• Present in mostly barks, wood, leaves and unripe fruits
• Mol. Wt. – 500-3000 and containing more phenolic hydroxyl group
• It was extract from oak bark (Querus spp.), a common tanning agent
Tannin
Condensed tannin - not easily hydrolysable; if we try to hydrolyses in acid, instead of
hydrolyzed products form the complex amorphous red pigment- Phlobaphene's
Hydrolysable tannin –easily hydrolysable; heterogenous polymer contain phenolic acids
particularly gallic acid and glucose. Simplest e.g. – Chinease tannin from
Sumac(Rhus sp.) yields 8 gallic acid and 1 glucose. Hydrolysable tannin which contain
gallic acid as phenolic residues , are also called as GALLOTANIN

43. Condensed tannin
Role
• Feeding deterrents; cause
astringency
• Give protection against microbial
attack
• Many Gallo tannin have
allelopathic properties

44. Thank you