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Bioactive Molecules from Plants IIPhenolic Botanicals and Alkaloids

Plant alcohols
• Plant alcohols exist in free or combined states as sugars
ethers or esters
...

• Others include erythritol, sorbitol, and mannitol, which may
be inter-convertible to sugars in nature
...

O H

O H

O H
H O

O H

H O
O H

O H

E r u th r ito l

O H

S o r b ito l

O

O H

H O
O H
O H
G lu c o s e

O H

O H

O H H O

G ly c e r o l

O H

O H

O H
O H

H O
O H
D -m a n n ito l

O H

O H
o r g lu c ito l

Plant alcohols
• Glycerol is a by product of saponification of fats and oils to
make soap
...

• It is also a component in glycerine soap
...


Saponification of fats

Phenols
• Phenolics occur as esters and as glycosides
...

• They are in the classes of simple phenols,
tannins, coumarins, anthraquinones, flavonoids
and anthocyanins
...

• Examples are phenol, catechol, phloroglucinol,
eugenol, vanillin, salicylic acid and their
derivatives
...
Vanillin may be
synthesized from eugenol or guaiacol
...

• Caffeic acid is an analgesic and an antiinflammatory
...

• Salicyl alcohol just like aspirin has analgesic and
anti-inflammatory activity
...

• It can also be made from salicyl alcohol and
salicyl aldehyde both of which are found in
plants
...

They need two equivalents of base to
neutralise
...
They need three
equivalents of base to neutralise
...

• They exhibit anti-microbiol activity
• Typical examples are aesculetin and psoralen
• Aesculetin derivative is used for treatment of varicose veins
...
It also has carcinogenic effect and
can cause skin cancer
...

• Warfarin , a synthetic coumarin is rat poison or rodenticide
...

H
O

OO O

OO

H
O
P
s
o
r
a
l
e
n

A
e
s
c
u
l
e
t
i
n

HO

O

O

O

O

HO

O

OH

O

OH
OH
D ic o u m a r o l

OH

OH
W a r fa r in

O

Anti-oxidant effect of phenols
•
...


...

• They are found in tree barks, galls, leaves and
stems of certain plants
...
Complexing with proteins of
hides and skins cause animal skins not to
putrefy and therefore changed to leather
...

• Tannins are high molecular weight glycosides which are
either hydrolysable or condensed
...

• Hydrolysable tannins are hyrolysed by acids
...

• Hydrolysable tannins are readily soluble in water and their
solutions are used to prevent bleeding of wounds, and
reduce inflammation and swellings
...


Gallic acid, ellagic acid, tannin
O H
H O

C O O H

H O

O

O

O H
O

O H
G a llic a c id

O

O H
O H

E lla g ic a c id

O H

H O
H O

O H

O

O

O
H O
H O

H O

O H

O

O H

O

O

O

O H

O H

O
O
H O

H y d r o ly s a b le ta n n in

O H

Condensed tannins
• Condensed tannins are also known as phlobotannins
...

• Oligomeric procyanidins are condensed tannins which
have two or three catechin molecules linked together
by carbon-carbon bonds
...

• Grape seed extract is a strong anti-oxidant which is 20
times more effective than vitamin C
...


Condensed tannin monomers
O H

O H

O H

O H
H O

O
H O

H O

O

H O
O

H O

O H

C h r y s in
C a te c h in

O

H O

O H

E p ic a te c h in

Other oxidising reagents
•
•
•
•

Hydroxyl radical
Peroxide radical
Chain reactions in destruction of tissues
...


Flavonoids
• Flavonoids are wide spread in nature being found in at least 60%
of higher plants
...

• They are typically yellow in color and concentrate in flowers and
also found in other plant tissues
...

• Flavonoids find application as anti-oxidants even though this is
more pronounced in vitro than in vivo
...

• Principal sources of flavonoids in human diet are tea, onions,
vegetables and fruits
...
These
are due to compounds called anthocyanins
...

OH

OH

+
HO

O

O g lu c o s e
OH

C y a n in

Origin of anthocyanins
O H

•
...

• In this country the Rumex species are used as
ethno-anthelmintics because of their purgative
activity
...
25- 2
...

• Such compounds are also found in rhubarb, Senna
and Aloes
...

• Alkaloids may also be produced by microorganisms- fungi
and bacteria
• Many alkaloids are toxic to other organisms
• They often have pharmacological effects and are used as
medications, recreational drugs and in ethneogenic rituals
...


Alkaloid examples
O

C H

N

H 3C

3

O H

O
O

N

H N

O

C o c a in

P s ilo c in

C H

3

N

N

H

O

N
N

N
H 3C

C H

3

O

C H
N

3

N ic o tin e

C a ffe in

O

H O

O
O

H
N

H

C H

H O
3

N

H 3C O

H O
M o r p h in e

+

N
O

O C H 3
B e r b e r in e
N

Q u in in e

Alkaloid examples contd
...
But borderline
cases exist , for example, quinine( pyridine
and piperidine)

Grouping of alkaloids
• “True alkaloids” – they contain heterocyclic nitrogen and
originate from amino acids e
...
atropine, morphine, nicotine
• “Protoalkaloids” they contain non heterocyclic nitrogen but
also originate from amino acids
...
g
...

• Peptide and cyclopeptide alkaloids
...
These are human
hormones produced during stress
...

• Its biosynthetic origin can be traced from
dopamine, dopa, noradrenaline
...
It has antiasthmatic effect and is also used to treat
coughs
...

• Caffeine is found in coffee and tea while
theobromine is found in cocoa
...

• They include hygrine, tropinone and atropine
• Atropine from Atropa belladona has eye
pupil dilatory effect
...

Thebaine provides another source for the derivation of the analgesic
codeine
...

Morphine has euphoric and analgesic effects
...
It produces euphoria and dependency
in some people but sometimes causes anxiety
...

Papaverine is cerebral and coronary vasodilator
...


Isoquinoline alkaloid structures

H
C
O
3
H
C
O
H
O
3
N
O
H
O
C
H
O
C
H
H
C
H
3
3
3
N
H
C
H
O N
3
HH
O
o
d
e
i
n
e
H
O C
O
C
H
3
H
C
O
3
O
O
O
C
H
3
N
H
N
H
C
OH
3
C
O
3
T
h
e
b
a
i
n
e
O
C
H
3
P
a
p
a
v
e
r
i
n
e

M
o
r
p
h
i
n
e

+

B
e
r
b
e
r
i
n
e

Quinoline alkaloids
• The principal source is Cinchona bark which contains about
25 related alkaloids with quinoline core structure
...

• Quinine is used as anti-malarial drug as well as a skeletal
muscle relaxant
...


H
O
H
O
N
N
O
O
N
N
N
Q
u
i
n
i
n
e

Q
u
i
o
l
i
n
e

Q
u
i
n
i
d
i
n
e

Tropane alkaloids
• These alkaloids are usually found in the Solanaceae
spp
...
They include
hyoscyamine, hyoscine or scopolamine, atropine,
and cocaine
N
O
H
H
C
N
O
H
H
C
3
3
O
O

H
y
o
s
c
y
a
m
i
n
e

O
O

A
t
r
o
p
i
n
e

O
N
C
H
N
O
H
H
C
H
C
3
3
3
O
O
O
O
O
O
C
o
c
a
i
n
e

H
y
o
s
c
i
n
e
o
r
s
c
o
p
o
l
a
m
i
n
e

Tropane alkaloids contd
• Datura stramonium contains both hyoscine and
hyoscyamine with the former being more in young plants
...

• Hyoscyamine has anti-diarrhea effects
• The roots of Atropa belladona contains 0
...
8% of
hyoscyamine
...
Its
hydrochloride is the anaesthetic called novacaine and stops
nerve transmission when topically applied-it is a tranquilizer
• It is rapidly absorbed in the lungs, heart, and brain leading to
psychic dependence and tolerance
...

• They are based on indole system
...
All these
compounds find application
...

• Catharanthus roseus contains many of such alkaloids in low
concentrations
...

• These compounds are dimeric alkaloids as seen from the structure
of vinblastine
...
Most of them are found in the
Solanaceae and occur as glycosides
...
Unripe potatoes also produce glycoalkaloids
such as solanine
...

• Solasodine is a also a poison found along with solanine
...

• There are two of them in tea and coffee-caffeine and
theophyline
...

• Caffeine is a CNS stimulant, enhancing alertness and
reducing fatigue
...

• Theophyline has similar effects but more pronounced
...


Xanthine, Caffeine, Theophyline,
Theobromine

O
O
O
C
H
H
3C
3H
H
C
H
C
3
3
N
N
N
H
N
N
N

N
N
N
O
N
O
N
O
N
H
H
H
X
a
n
t
h
i
n
e C
a
f
f
e
i
n
e
T
h
e
o
p
h
y
l
i
n
e

O
C
H
3
H
C
3
N
N

N
O
N
H
T
h
e
o
b
r
o
m
i
n
e

Amino sugars
• Amino sugars contain NH2 group instead of OH group at non
anomeric carbon
...

Although it is not classified as a drug it is available in many
over the counter drugs used against osteoarthritis
...

• Acetylation of glucosamine forms N-acetylglucosamine
(NAG) or chitin
...

• Chitin forms the exoskeleton of insects, lobsters, crabs and
shrimps
...

• They belong to the groups, prostaglandins, leukotrienes, thromboxanes
and prostacyclines
...
They are synthesized in the prostate gland
and found in human seminal fluid
...
Prostaglandins are not hormones which are produced in a gland
and then circulate in the blood and influence activity elsewhere
...

• They participate in transient events such as inflammation, blood clotting,
fertilization and immune responses
...

• Dinoprostone or PGE2 is used to relax the smooth muscle of the uterus
when labor is induced and causes abortion in early stages
...

• Prostaglandins inhibit blood platelet
aggregation
• Lower gastric secretions
• Stimulate uterine contractions
• Relax smooth muscle of the uterus

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