2. 2
• Primary metabolites: Molecules that are essential for
growth and development of an organism.
Examples:
1.Carbohydrates 2.Proteins 3.Lipids
4.Nucleic acids 5.Hormones
• Secondary metabolites: molecules that are not
essential for growth and development of an organism.
Metabolites
4. 4
Why secondary metabolites?
• are biosynthetically derived from primary metabolites. They
are more limited in distribution being found usually in specifi
c families.
• Chemical warfare to protect plants from the attacks
by predators, pathogens, or competitors
• Attract pollinators or seed dispersal agents
• Important for abiotic stresses
• Medicine
• Industrial additives
5. 5
• Possibly over 250,000 secondary metabolites in
plants
• Classified based on common biosynthetic pathw
ays where a chemical is derived.
• Four major classes: Alkaloids, glycosides, phen
olics, terpenoids
Secondary metabolites
6. 6
Alkaloids
• Most are derived from a few common amino
acids (i.e., tyrosine, tryptophan, ornithine or
argenine, and lysine)
• Compounds have a ring structure and a nitro
gen residue.
• Indole alkaloids is the largest group in this fa
mily, derived from tryptophan
• Widely used as medicine
7. 7
Terpenoids
• Terpenes are generally polymers of 5-carbon unit
called isoprene
• Give scent, flavors, colors, medicine...
• Three plant hormones are derived from the terpen
oid pathway.
9. WHAT ARE ALKALOIDS?
• These are commonly applied to basic nitrogenous comp
ounds of plant origin that are physiologically active.
• Organic nitrogenous compounds with a limited distribut
ion in native nature.
10. Characteristics:
• They are bitter in taste.
• Derived from amino acids.The amino acids that are most often serve
as alkaloidal precursors are: phenylalanine, tyrosine, tryptophan, h
istidine, anthranilic acid, lysine and ornithine.
• Alkaloids form double salts with compounds of mercury, gold, platin
um and other heavy metals. These salts are obtained as precipitate w
hich are microcrystals.
11. • Insoluble or sparingly soluble in water, but the
salts formed on reaction with acids are usually
freely soluble.
• Most are crystalline solids although a few are a
morphous.
12. • Free alkaloids are usually soluble in polar solvents
like ether, chloroform
• Some alkaloids are liquid because of lacking of ox
ygen in their molecules. (e.g coniine, nicotine, spa
rtenine)
13. Sources and Occurrence of Alkaloids
• Alkaloids can occur in plant kingdoms; among the angiospe
rms,
• Leguminosae,
• Papaveraceae,
• Ranunculaceae,
• Rubiaceae,
• Solanaceae,
• Berberidaceae are outstanding alkaloid-yielding plants.
14. Uses of Alkaloids in Plants:
• Poisonous agents which protect plants against insects and
herbivores
• End products of detoxification reactions representing a metab
olic locking-up of compounds otherwise harmful to the plants
.
• For regulatory growth factors
• Reserve substance capable of supplying nitrogen or other ele
ments necessary to the plant’s economy
15. Naming for alkaloids
• From the generic name or the genus of the p
lant yielding them (e.g vinblastine and vincristi
ne. atropine)
• The specific name or species of the plant yie
lding alkaloids ( e.g belladonnine)
16. • From their physiologic activity (e.g emetine,
morphine)
• From the discoverer (e.g pelletierine)
~ All names of alkaloids should end in “-ine”.
~ A prefix or suffix is added to the name of a principal
alkaloid from the same source. (quinine, quinidine,
hydroquinine)
17. Pharmacologic action of Alkaloids:
• Analgesic (morphine, codeine)
• Narcotics (strychnine, brucine which are central
stimulant)
• Anti malarial ( quinine)
• Anti pyretic
• Anti cancer (vincristine)
• Mydriatics (atropine)
• Anti inflammatory
• Miotics (physostigmine, pilocarpine)
• Ephedrine (rises in blood pressure, bronchodilator)
• Reserpine (produce fall in excessive hypertension)
25. Quinine
• Dia-stereo-isomer of quinidine
• It occurs as white, odourless, bulky crystals or as
a crystalline powder.
• It darkens when exposed to light and effloresces i
n dry air.
• It is freely soluble in alcohol, ether and chlorofor
m but slightly soluble in water.
26. Uses
• Antimalarial
• For treating of chloroquinine resistant falciparum mal
aria combination with pyrimethamine and sulfadoxine
or tetracycline or clindamycin.
• It has a skeletal muscle relaxant effect.
• It is widely used for the prevention and treatment of n
octurnal recumbency leg cramps.
34. PSEUDO ALKALOIDS
DITERPENES
e.g. Aconitine, aconine, hypoaconitine
PROTO OR NON HETERO CYCLIC
ALKALOIDS
ALKYLAMINES
e.g. Ephedrine,pseudoephedrine, colchicine
35. • C17H19NO3
• a component of blackpepper (Piper nigrum)
• has been used in various traditional medicin
e preparations
• an insecticide.
has various effects on human drug met
abolizing enzymes, and is marketed und
er the brand name, Bioperine,
PIPERINE
36. Quinine,
1. molecular formula C20H24N2O2
2. is a white crystalline quinoline alkaloid.
3. Quinine is extremely bitter, and also possesses anti
pyretic, analgesic and anti-inflammatory properties.
4. has strong anti malarial properties,
5. quinine in therapeutic doses can cause various side-
effects, e.g. nausea, vomiting and cinchonism, and i
n some patients pulmonary oedema.
6. It may also cause paralysis if accidentally injected int
o a nerve.
7. Non-medicinal uses of quinine include its uses as a f
lavouring agent in tonic water and bitter lemon.
38. Vinca alkaloids
The Vinca alkaloids are a subset of drugs that are deriv
ed from the periwinkle plant, Catharanthus roseus.
N
N
OH
C2H5
H3
COOC
N
N
R
OAc
OH COOCH3
H
H
MeO
Vinblastine R=-CH3
Vincristine R=-CHO
40. Serpentine
• Molecular Formula: C21H22N2O3
• Isolated from Rauwolfia serpentina
• To treat High blood pressure
• to treat insect stings and the bites of venomous reptiles
43. TERPENES
The chemist Leopold Ruzicka ( born 1887) showed that many compounds
found in nature were formed from multiples of five carbons arranged in
the same pattern as an isoprene molecule (obtained by pyrolysis of
natural rubber).
He called these compounds “terpenes”.
C C
C
C C
.
isoprene
natural
rubber
D
isoprene
unit
head
tail
C C
C C
C
44. The Biological Isoprene Unit
• The isoprene units in terpenes do not come from
isoprene.
• They come from isopentenyl pyrophosphate.
• Isopentenyl pyrophosphate (5 carbons) comes
from acetate (2 carbons) via mevalonate
(6 carbons).
45. Terpenes
• Terpenes are natural products that are
structurally related to isoprene.
H2C C
CH3
CH CH2
or
Isoprene
(2-methyl-1,3-butadiene)
46. The Biological Isoprene Unit
CH3COH
O
3 HOCCH2CCH2CH2OH
CH3
OH
O
Mevalonic acid
H2C CCH2CH2OPOPOH
CH3 O O
Isopentenyl pyrophosphate
48. Isopentenyl and Dimethylallyl Pyrophosphate
Isopentenyl pyrophosphate is interconvertible with
2-methylallyl pyrophosphate.
OPPOPP
• Dimethylallyl pyrophosphate has a leaving group
(pyrophosphate) at an allylic carbon; it is reactive toward
nucleophilic substitution at this position.
Isopentenyl pyrophosphate Dimethylallyl pyrophosphate
49. Carbon-Carbon Bond Formation
• The key process involves the double bond of
isopentenyl pyrophosphate acting as a nucleophile
toward the allylic carbon of dimethylallyl pyroph
osphate.
+
OPP
OPP
50. After C—C Bond Formation...
+
OPP
• The carbocation
can lose a proton
to give a double
bond.
51. After C—C Bond Formation...
+
OPP
OPP
• The carbocatio
n can lose a pro
ton to give a do
uble bond.
H–
+
52. After C—C Bond Formation...
OPP
• This compound is called geranyl pyrophosphate. I
t can undergo hydrolysis of its pyrophosphate to gi
ve geraniol (rose oil).
56. From 10 Carbons to 15
OPP
• This compound is called farnesyl pyrophosphate
.
• Hydrolysis of the pyrophosphate ester gives the
alcohol farnesol.
57. Cyclization
• Rings form by intramolecular carbon-carbon b
ond formation.
OPP
OPP
+
E double b
ond
Z double b
ond
58. CLASSIFICATION OF TERPENES
58
TYPE OF NUMBER OF ISOPRENE
TERPENE CARBON ATOMS UNITS
hemiterpene
terpene
sesquiterpene
diterpene
triterpene
tetraterpene
C5
C10
C15
C20
C30
C40
one
two
three
four
six
eight
hemi = half di = two
Sesqui = one and a half tri = three
tetra = four
NOTE:
59. • Hemiterpenes consist of a single isoprene unit. Isoprene itself is considered
the only hemiterpene, but oxygen-containing derivatives such as prenol and iso
valeric acid are hemiterpenoids.
• Monoterpenes consist of two isoprene units and have the molecular formula
C10H16. Examples of monoterpenes are: geraniol,limonene and terpineol.
• Sesquiterpenes consist of three isoprene units and have the molecular formula
C15H24. Examples of sesquiterpenes are: humulene,farnesenes, farnesol.
• Diterpenes are composed of four isoprene units and have the molecular formu
la C20H32. They derive from geranylgeranyl pyrophosphate. Examples of diterp
enes are cafestol, kahweol, cembrene and taxadiene (precursor of taxol).
CLASSIFICATION OF TERPENES
60. • Sesterterpenes, terpenes having 25 carbons and five isoprene units,
are rare relative to the other sizes, example: geranylfarnesol.
• Triterpenes consist of six isoprene units and have the molecular form
ula C30H48. The linear triterpene squalene, the major constituent of shar
k liver oil, is derived from the reductive coupling of two molecules
of farnesyl pyrophosphate. Squalene is then processed biosynthetically
to generate either lanosterol or cycloartenol , the structural precursors
to all the steroids.
• Sesquarterpenes are composed of seven isoprene units and have the
molecular formula C35H56. Sesquarterpenes are typically microbial in
their origin. Examples of sesquarterpenes are ferrugicadiol and tetrapre
nylcurcumene.
CLASSIFICATION OF TERPENES
61. • Tetraterpenes contain eight isoprene units and have the molecular
formula C40H64. Biologically important tetraterpenes include the
acyclic lycopene, the monocyclic gamma-carotene, and the
bicyclic alpha- and beta-carotenes.
• Polyterpenes consist of long chains of many isoprene units,eg, Natural
rubber .
• Norisoprenoids,eg: C13-norisoprenoids 3-oxo-α-ionol present in
Muscat of Alexandria leaves and 7,8-dihydroiononederivatives, such
as megastigmane-3,9-diol and 3-oxo-7,8-dihydro-α-ionol found in
Shiraz leaves (both grapes in the species Vitis vinifera)
CLASSIFICATION OF TERPENES
62. TERPENES
1. The number of C atoms is a multiple of 5, C5
C10 C15 C20 C25 C30 C35 C40
2. Each group of 5 C is an isoprene subunit
3. They can be saturated or unsaturated
4. Many contain O atoms as well.
5. What they all have in common is 1 & 2 above.
63. 63
JOINING ISOPRENE UNITS
The terms head-to-tail and
tail-to-tail are often used to
describe how the isoprene
units are joined.
C C
C
C C
.
an extra
bond
Head-to-Tail
Head-to-Tail
Tail-to-Tail
78. β-carotene – a linear terpene
8 isoprene units
40 carbon atoms
CH2
CH2
CH2
C
C
C
CH3CH3
CH
CH
C
CH
CH
CH
C
CH
CH
CH
CH
C
CH
CH
CH
C
CH
CH
C
C
CH2
CH2
CH2
C
CH3
CH3 CH3
CH3 CH3
CH3
CH3
CH3
-carotene
79. 79
• Taxol is a terpenoid
• "the best anti-cancer agent” by National Canc
er Institute
• Has remarkable activity against advanced ovari
an and breast cancer, and has been approved
for clinical use.
Taxol
Taxus brevifolia Nutt.
80. 80
• Camptothecin is an indole alkaloid, derived from
tryptophan.
• Has anticancer and antiviral activity
• Two CPT analogues have been used in cancer c
hemotherapy, topotecan and irinotecan.
81. Phenolics
• Derived from aromatic amino acids, such as phenylalanine, tyrosin,
and trytophan.
• All contain structures derived from phenol
• Some examples:
Coumarins: antimicrobial agents, feeding deterrents, and germinati
on inhibitors.
Lignin: abundant in secondary cell wall, rigid and resistant to extraction o
r many degradation reagents
Anthocyanins
Flavones
Flavnols
Phenols are present in every plant they attract pollinators to the plant an
d even impact how these plants act with one another.
82. 82
Glycosides
• Compounds that contain a carbonhydrate and a noncarbohy
drate
• Glycosides are present in vacuoles in inactive form
• Glucosinolates: found primarily in the mustard family to give
the pungent taste
There are four type of linkages present between glycone and aglyc
one:
C-linkage/glycosidic bond,
O-linkage/glycosidic bond
N-linkage/glycosidic bond
S-linkage/glycosidic bond
• .
83. Cyanogenic glycosides
All of these plants have these glycosides stored in the vacuole,
but, if the plant is attacked, they are released and become
activated by enzymes in the cytoplasm.
These remove the sugar part of the molecule and release
toxic hydrogen cyanide.
An example of these is amygdalin from bitter almonds
Cyanogenic glycosides can also be found in the fruit seeds (and
wilting leaves) of many members of the rose
family (including cherries, apples, plums, bitter
almonds, peaches, apricots,raspberries, and crabapples
84. Sources
Plant resins[
A liquid compounds found inside plants or exuded by plants,
But not saps, latex, or mucilage,
The resin produced by most plants is a viscous liquid, composed mainly of
volatile fluid terpenes
resins do not serve a nutritive function.
The toxic resinous compounds may confound a wide range of herbivores,
insects, and pathogens; while the volatile phenolic compounds may attract
benefactors such as parasitoids or predators of the herbivores that attack
the plants
85. Latex
latex as found in nature is a milky fluid found in 10% of all flowering plants
(angiosperms).
It is a complex emulsion consisting of
proteins, alkaloids, starches, sugars, oils, tannins, resins, and gums that
coagulate on exposure to air. It is usually exuded after tissue injury. In most
plants, latex is white, but some have yellow, orange, or scarlet latex.
It serves mainly as defense against herbivorous insects.
Natural rubber is the most important product obtained from latex
This latex is used to make many other products as well, including
mattresses, gloves, swim caps, catheters and balloons
In chewing gum, and glues
86. Sources
Plant sterol;
The richest naturally occurring sources of phytosterols are vegetable oils
and products made from them.
They can be present in the free form and as esters of fatty acid/cinnamic
acid or as glycosides,
Phytosterols, which encompass plant sterols and stanols,
are steroid compounds similar to cholesterol which occur in plants and vary
only in carbon side chains and/or presence or absence of a double bond.
Stanols are saturated sterols, having no double bonds in the sterol ring
structure.
87. Sources
Sapogenins
sapogenins are the aglycones, or non-saccharide, portions of the
family of natural products known as saponins. Sapogenins contain
steroid or other triterpene frameworks as their key organic featu
re. For example, steroidal sapogenins like tiggenin, neogitogenin, a
nd tokorogenin have been isolated from the tubers of Chlorophytu
m arundinacelum. Some steroidal sapogenins can serve as a prac
tical starting point for the semisynthesis of particular steroid hor
mones.
88. Essential Oil
An essential oil is a concentrated hydrophob
ic liquid containing volatile aroma compound
s from plants.
Essential oils are also known as volatile oils
, ethereal oils, aetherolea,
They are used in perfumes, cosmetics, soaps
and other products, for flavoring food and dri
nk, and for adding scents to incense and hous
ehold cleaning products
Oil Tonnes
Sweet orange 12,000
Mentha arvensis 4,800
Peppermint 3,200
Cedarwood 2,600
Lemon 2,300
Eucalyptus globulus 2,070
Litsea cubeba 2,000
Clove 2,000
Spearmint 1,300
89. Phenylpropanoids
The phenylpropanoids are a diverse family of organic compounds that are
synthesized by plants from the amino acid phenylalanine
Phenylpropanoids are found throughout the plant kingdom, where they serve
as essential components of a number of structural polymers, provide
protection from ultraviolet light, defend against herbivores and pathogens,
and mediate plant-pollinator interactions as floral pigments and scent
compounds.
91. Outline: Plant-Derived Insecticides
Important insecticides from plants
-rotenoids - New World and Asia
-pyrethrins - Near Eastern center
-tobacco - New World
Ryania speciosa, Flacourtiaceae
Antifeedants
-neem, Azadirichta indica, Meliaceae
92. Introduction
• Many insecticidal compounds are known from plants. Most plant
s make defensive compounds called allomones. Only a few are i
mportant commercially.
• Plant-derived insecticides have largely been replaced by synthe
tic materials, but there are some advantages to the naturally oc
curring materials. For example, these substances are biodegrad
able.
• Selectivity is needed. Compounds that are toxic to insects, but n
ot toxic to mammals, are preferable, of course.
93. Rotenoids
• A series of compounds found in members of the genera Derris,
Lonchocarpus, Tephrosia are known as rotenones.
• Commercially, rotenoids are isolated mostly from the roots of
Derris elliptica in Indonesia and from Lonchocarpus
• These compounds are isolated by grinding the plant and extracti
ng with solvents such as hexane or petroleum ether or chlorofo
rm.
• The compounds are oil soluble or lipids. They make up 1-20% of
the dry weight of the roots.
97. Pyrethrins
• Another major series of compounds, the pyrethri
ns, come from species of the genus Chrysanthem
um (some people put these species in Pyrethrum)
(Asteraceae or Compositae).
• These were used as far back as the 1st century B.
C. by the Chinese. Insecticidal plants mostly are g
rown in countries with inexpensive labor and hig
h elevations such as Kenya and New Guinea.
100. • Ryania speciosa (Flacourtiaceae) is also used occ
asionally and an insecticide.
• A mixture of diterpene, alkaloids is isolated and us
ed for specialty insecticide uses.
• Because the extract is expensive, it is not commo
nly used.
Other plant-derived insecticides
102. Tobacco, Nicotiana tabacum, Solanaceae
• Tobacco (which contains nicotine) is another
major source of insecticides. Tobacco wastes
are often extracted and used as a source of n
icotine. Nicotine especially effective against
aphids.
104. Calabar bean
• Calabar bean (Physostigma venenosa, Fabacea
e) is (or has been) a trial-by-ordeal drug in the
Calabar coast of Nigeria. The active compone
nt is physostigmine, an acetyl choline esterase
inhibitor.
• The structure of several commercial carbamate
insecticides is patterned after the structure of th
e plant alkaloid.
106. Antifeedants
• Antifeedants are compounds that prevent insect fe
eding. Although many are toxic, the insects usuall
y don’t consume enough to be poisoned.
• Only one of these, neem, Azadirachta indica, Meli
aceae, is commercially available. The active comp
ound, azadirachtin, is a structurally modified triter
pene.
107. Neem, Azadirachta indi
ca, Meliaceae
Courtesy Dr. Ramesh Pandey
William M. Ciesla, Forest Health Management
International, United States