An introduction to glycosides By KNS & PDV

AN INTRODUCTIONAN INTRODUCTION
TOTO GLYCOSIDESGLYCOSIDES
Prepared By
Ms. Khyati N. Shah
Assistant Professor, Government College of Pharmacy, Gandhinagar
&
Dr. Preeti D. Verma
Lecturer, L. M. College of Pharmacy, Ahmedabad

CONTENTSCONTENTS
Definition
General properties
Occurrence and Distribution
Importance
Classification
General method of isolation and purification
Different types of glycosides including properties,
examples, uses and chemical tests
Ms. Khyati N. Shah (GCP) & Dr. Preeti D. Verma (LMCP)
2

DEFINITION
A glycoside is an organic compound, usually of plant
origin, and comprising of a sugar moiety and a non-
sugar moiety attached through a glycosidic linkage.
Non-sugar part is known as aglycone or genin.
Sugar/s part is known as glycone.
So, glycosides upon hydrolysis yields a sugar &
non-sugar portion.
3

GENERAL PROPERTIES OF GLYCOSIDES
PHYSICAL PROPERTIES :
State : Amorphous or crystalline solid substances.
Colour : Usually colourless.
Except: Anthraquinone glycosides are orange/red coloured.
Flavone glycosides are yellow coloured.
Solubility :
Glycosides are soluble in H2O and alcohol, insoluble in
organic solvents.
While aglycones are soluble in organic solvents.
Except: Resin glycosides are insol. In H2O and sol. in
organic solvents.
Optical activity: Optically active & usually laevorotatory.
They are easily hydrolysed by water, enzymes or mineral
acids.
4

GENERAL PROPERTIES OF GLYCOSIDES
CHEMICAL PROPERTIES :
One –OH group of sugar condenses with –OH group of
aglycone through a glycosidic linkage & second –OH group
of sugar within the sugar molecule to form an oxide ring.
So chemically they are ‘acetals’ or ‘sugar ethers’.
All glycosides gives positive Molisch’s test, after hydrolysis.
5

OCCURANCEOCCURANCE
Part of the
plant
Examples
Leaf Aloe, Senna, Digitalis
Aerial
parts/stem
Chirata, Kalmegh
Fruits Senna pod, Ammi, Thevetia
Seed Strophanthus, Almond, Mustard, Linseed
Bark Cascara, Wild cherry bark, Quillaia, Arjuna
Roots and
rhizomes
Rhubarb, Gentian, Picrorrhiza, Dioscorea,
Glycyrrhiza, Senega, Ginseng.
Wood Quassia wood
6

DISTRIBUTIONDISTRIBUTION
Families Examples
Liliaceae Aloe, Squill
Dioscoriaceae Dioscorea
Polygonaceae Rhubarb
Scrophulariaceae Digitalis, Picrorrhiza
Apocynaceae Strophanthus, Thevetia
Gentianaceae Gentian, Chirata
Rosaceae Bitter almond, Wild cherry
bark
Leguminosae Senna, Liquorice
Rhamnaceae Cascara
7

ROLEROLE OF GLYCOSIDES
FOR PLANT ITSELF
• Serve as reservoir of sugar
• By forming glycosides they increases solubility of aglycone
and thus help (facilitate) transport of such compound.
• Glycosides formation decreases toxicity and reactivity and
therefore allow such compounds to restore or transported
without any harm to the plant.
• They are involved in regulatory and protective processes of
the plant.
8

THERAPEUTIC IMPORTANCE FOR
LIVING ANIMALS
THERAPEUTIC
USE
EXAMPLES
Laxatives Senna, Aloe, Rhubarb, Cascara
Cardiotonics Digitalis, Squill, Strophanthus,
Thevetia
Hepatic
disorders
Picrorrhiza, Kalmegh
Stomachic Gentian, Picrorrhiza, Quassia
Expectorant Senega, Liquorice
Flavouring
agents
Wild cherry bark, Vanilla
9

CLASSIFICATION OF GLYCOSIDES
They can be classified according to
1.Nature of sugar
2.No. of sugar
3.Physical or physical property and pharmacological
action
4.Glycosidic linkage
5.Nature or chemical nature of aglycone
10

CLASSIFICATION OF GLYCOSIDES
1. According to chemical nature of sugar.
Disadvantage: If rare sugar is present & if structure
is not known, it will be difficult to name that
glycoside,
Sugar present Glycoside
Glucose Glucoside
Rhamnose Rhamnoside
Galactose Galactoside
Fructose Fructoside
Ribose Riboside
11

2. According to No. of sugar
No. of sugar Glycoside
One Monoside
Two Bioside
Three Trioside
12

3. According to physical or pharmacological action:
According to physical property
According to pharmacological action
Disadvantage: This classification does not include many other compounds
pharmacognostic interest.
Glycoside P’cological action
Cardiac Cardiotonic
Anthraquinone Purgative
Bitter Bitter tonic
Glycoside Physical property
Saponin With water when shaken they gives
foam
Bitter They have intensly bitter taste
Cyanogenetic Upon hydrolysis they produce HCN
13

4. According to Glycosidic linkage :
It is one of the modern method of classification.
According to linkage between Sugar (R) & Aglycone (X) the
glycosides are classified as follow:
1.O-glycosides:
R is attached to X through O.
X is having free phenolic or alcoholic group.
They can be easily hydrolysed.
X – OH + HO – R X-O-R + H2O
Eg. AQ glycosides, Cardiac glycosides, Cyanogenetic
glycosides, Flavone glycosides
. Ms. Khyati N. Shah (GCP) & Dr. Preeti D. Verma (LMCP)
14

2.C-glycosides:
R is attached to X through C.
They are not hydrolysed by heating with dilute acids/alkali.
They are hydrolysed by oxidative hydrolysis with FeCl3.
X-CH + HO-R X-C-R + H2O
Eg.
Aloin present in aloe, Cascaroside (cascaroside contain both
‘O’ & ‘C’-glycosides.
. Ms. Khyati N. Shah (GCP) & Dr. Preeti D. Verma (LMCP)
15

3. S-glycosides :
R is attached to X through S.
X-SH + HO-R X-S-R + H2O
Eg. Isothiocynate glycosides
4 . N-glycosides :
R is attached to X through N.
N-H + HO-R N-R
Eg. D-ribose, Deoxyribose.
16

5. According to chemical nature of aglycone
1. Anthraquinone glycosides
2. Cardiac (Sterol) glycosides
3. Saponin glycosides
4. Bitter glycosides
5. Cyanogenetic glycosides
6. Isothiocyanate glycosides
7. Coumarin glycosides
8. Flavonoid glycosides
17

TYPES OF GLYCOSIDES
1.ANTHRAQUINONE GLYCOSIDES
They have basic ring structure- Anthracene.
Distribution in families – Mainly in dicot families like
Leguminosae, Rhamnaceae, Polygonaceae,
Euphorbiaceae etc…
and in monocot families like Liliaceae.
Anthracene basic ring
18

ANTHRAQUINONE GLYCOSIDES (contd.)
In reduced form, anthraquinones are present as either
anthrone, anthranol or dianthrone.
Reduced forms are more active than the parent
anthraquinones.
Most of them are present as 1,8-dihydroxy derivatives
i.e chrysophanol, aloe-emodin or rhein derivatives.
Ex : Chrysophanol anthrone, Chrysophanol anthranol,
Rhein anthrone etc…
19

O
O O
H OH
O OH
Anthraquinone Oxanthrone
H H H H
AnthranolAnthrone
O
O
Dianthrone
Reduced forms of
Anthraquinone
20

O
O OHHO
R
1,8-dihydroxy anthraquinone derivative
R = -CH3 Chrysophanol
R = -CH2OH Aloe-emodin
R = -COOH Rhein
21

Anthrone Anthranol
• Pale yellow
• Alkali insoluble
• Non-fluorescent
• Brownish yellow
• Alkali soluble
• Fluorescent
Oxanthrone
They are intermediate of Anthrone to Anthraquinone
Dianthrones
They are anthrone diamer, which are therapeutically
more active.
22

USE AND MECHANISM OF ACTION:
 Majorly used as purgatives.
 They act on large intestine.
A.Q glycosides
Get absorbed from small intenstine in blood
It carries them to large intenstine
Where they get hydrolysed by intestinal bacteria to
aglycone & sugar
This induces action because of aglycone
Ms. Khyati N. Shah (GCP) & Dr. Preeti D. Verma (LMCP) 23

Two things are observed:
(1)They irritate mucosal membrane.
So increases motility (peristalsis).
So, we get action.
(2) Act on mucosal cells.
Results in opening of Cl- channel.
Stimulate active secretion of Cl-.
Results in net reduction of water & electrolyte absorption.
Results in increase in volume of content.
This increased volume leads to pressure & subsequently
increases peristalsis.
Which gives laxative action.
24

CHEMICAL TESTS :
Simple Borntrager’s Test: Can be applied directly to Aglycone
Aglycone + Alkali
Pink to red colour depending on concentration of the aglycones
Due to phenolate ions.
If crude drug powder is there
Drug pwd + Extract with organic solvent
Separate organic layer + Alkali
Pink colour
25
For ‘O’ glycosides – hydrolysis with acid or alkali
Add alkali or acid, Boil, Cool & Shake with organic solvent
Pink colour

For ‘C’ glycosides – oxidative hydrolysis is needed
Add FeCl3 + HCl , Shake with organic solvent
Pink colour
26
Modified borntrager’s test :

Reduced derivatives : They must be converted to A.Q first.
For Anthrones/Anthranols :
Anthrones/Anthranols + HNO3 A.Q +Alkali
pink colour
Anthranols + Alkali (KOH) + H2O
Strong Yellowish green flourescence
Anthrones gives this test negative.
For Oxanthrones :
Add H2O2 A.Q. +Alkali
Pink colour
For Dianthrones :
Add FeCl3 + HCl/H2SO4 Add Alkali
Pink colour
27

2.STEROL OR CARDIAC GLYCOSIDES
• In these glycosides the aglycone moiety is steroidal
structure, which is having Cyclopentanoperhydro
phenanthrene nucleus. So they are also known as
‘Sterol glycosides’.
• Distribution in families- Present in monocot family like
Liliaceae and dicot families like Scrophulariaceae,
Apocynaceae, Leguminosae etc…
28

2.STEROL OR CARDIAC GLYCOSIDES (contd.)
CARDIAC GLYCOSIDES
Cardenolides Bufadienolides
C-23 glycosides C-24 glycosides
5-membered lactone ring 6-membered lactone ring
with one double bond with two double bond
Eg- Glycosides of Digitalis, eg- glycosides of squill
Strophanthus, Thevetia
In both sugar is attached to C-3 position.
29

O
O
OH
Osugar
O
OH
Osugar
O
Cardenolides Bufadienolides
30

SUGAR PRESENT IN CARDIAC GLYCOSIDES :
They characteristically contains Deoxy sugars.
1. 2,6-dideoxy sugar. Eg- Digitoxose.
2. 3-OCH3 dvt of 2,6-dideoxy sugars.
E. g. Cymarose, Oleandrose.
3. 6-deoxy hexose. Eg- Rhamnose.
4. 2-OCH3 dvt of 6-deoxy gexose
5. Cyclic sugars
6. Amino & acetylated sugars
31

Chemical tests :
Test for sterols:
Liebermann Burchardt’s test :
Glycosides + Acetic anhydride + H2SO4
Red or violet colour, converts to green colour
Both cardenolides and bufadenolides gives this test
positive.
32

Test for Cardenolides :
• Kedde’s test :
Alcoholic extract of drug + 2,4-Dinitrobenzoic acid + KOH
Red-Violet colour.
• Legal test :
Drug extract + Pyridine +Na nitroprusside + KOH
Pink to Red colour
• Baljet test :It is the localization test
Drug extract + Na picrate
Yellow to orange colour
33

Test for Bufadienolide :
• Tollen’s test
Drug extract + Tollen’s reagent (ammoniacal AgNO3)
Black ppts
Test for Deoxy sugars :
• Keller Killiani’s Test
Drug extract + Glacial HAC + FeCl3(drop)+H2SO4 slowly
from side of the t.t.
Reddish-brown ring at junction of two layer & Upper layer
slowly becomes bluish green.
34

THERAPEUTIC USES AND MECHANISM OF ACTION :
 Especially digitalis is used in Congestive Cardiac Failure.
 Used in CCF, atrial flutter, atrial fibrillation.
Mechanism of action :
• Cardiac glycosides inhibit enzyme Na+ K+ ATPase. So
increases force of systolic contraction.
• Na+ is retained, so Ca+ is accumulated, which causes
increase in contraction of heart muscles. Thus useful in
CCF.
• K+ is lost , so decreases in systolic length, so heart muscles
get more time to relax & arrythmias are avoided.
Ms. Khyati N. Shah (GCP) &
Dr. Preeti D. Verma (LMCP)
35

3.SAPONIN GLYCOSIDES
PROPERTIES OF SAPONIN GLYCOSIDES :
Saponins are non-crystalline & with water they forms colloidal solutions.
They are soluble in alcohol but insol. in non-polar organic solvents.
Saponin upon hydrolysis gives Sapogenin (aglycone) & Sugar.
They are having high molecular weight.
With water they produces soapy lather (Foam/ Froth). They
decrease surface tension, emulsify oil & water, so useful as emulsifying
agent.
They give ppts with higher alcohol (cholesterol).
They have bitter acrid taste & drugs containing them are usually irritant
to mucous membrane.
They have haemolytic property i.e causes haemolysis of RBC & are
highly toxic if injected in to blood stream. However if taken by
mouth they are quite harmless.
Many saponins are used as fish poison, as they interfer with
breathing mechanism.
36

Classification based on aglycone
Steroidal saponins Triterpenoidal saponins
E.g.- Diosgenin,
Hecogenin
Sarsasapogenin Tetracyclic Pentacyclic
Eg-Dammarendiol
Lupeol β-amyrin α-amyrin
E.g. Glycyrrhitinic acid E.g. Asiatic acid
Oleanolic acid
37

Importance of saponin glycosides:
Importance of steroidal saponins:
Used commercially for production of
• Corticosteroids like Beta-methasone.
• Sex-hormones like Progesterone, Testosterone.
• Oral contraceptive like mestranol.
• Steroidal diuretics like spiranolactone.
• Different steroids like Vitamine-D, Cardiac glycosides.
38

Importance of triterpenoidal saponins:
Drugs Uses
Glycyrrhiza Expectorant, Sweetening agent, As
anti-inflammatory
Senega Expectorant, Stimulant
Ginseng Adaptogen, Tonic, Stimulant.
Quillaia Expectorant
39

Chemical tests :
1.Froth test:
Take 0.1 gm poweder in a test-tube. Shake vigorously with
distilled water for 30 seconds
Leave undisturbed for 20 minutes
If persistent froth, saponin present
2. Haemolytic zone:
0.5 ml blood + 1% gelatin solution prepared in 0.85% NaCl
solution. Mix them on a glass slide
Place a thick transverse section (T.S.) of drug on it
Clear haemolytic zone formed around the section indicates
presence of the saponin in the drug.
40

4. BITTER GLYCOSIDES
Properties of bitter glycosides :
• They are extremely bitter in taste.
• They are soluble in water.
• Characteristically present in the family Gentianaceae.
• Chemically they are not same, but prominent drugs among
them contains glycosides of monoterpene irridoids with pyran
cyclopentane ring.
• They are taken before or during meal, otherwise they
causes digestive disturbances like diarrhoea, vomiting, pain
in stomach.
Examples : Gentian, Picrorrhiza, Chirata, Kalmegh, Quassia.
Importance : Used as bitter tonic, digestive, stomachic.
41

5. CYANOGENETIC GLYCOSIDES
Properties :
• Upon hydrolysis these glycosides gives HCN (hydrocyanic
acid in gaseous form).
• Chemically they are derivatives of mandelonitrile.
• They hydrolyse in presence of enzyme & give HCN,
benzaldehyde and sugar.
• Characteristically present in family Rosaceae.
Examples: Amygdalin, Prunasin.
Uses :
Bitter almond – Sedative, Demulcent.
Wild cherry bark – Flavouring agent, Expectorant.
42

5. CYANOGENETIC GLYCOSIDES (contd.)
Chemical tests :
Grignard reaction OR Sodium picrate paper test :
Take drug powder in a test tube/flask + moisten with water,
hold sodium picrate paper on the neck of test tube.
Warm the test tube
Yellow color of the paper turns to red
(due to liberation of gaseous HCN & formation of Sodium
isopurpurate)
43

6. ISOTHIOCYANATE GLYCOSIDES
• They are also known as ‘Glucosinolate glycosides’.
• Here aglycone contains isothiocyanate, as it contains sulfur
& nitrogen.
• Characteristically present in family Cruciferae.
• In plants, they are found as thiocyanate which upon
hydrolysis by enzyme myrosinase & H2O gives
isothiocyanate.
Example: Mustard
Uses: Counter irritant (rubefacient), emetic, condiment,
digestive.
Chemical test : Powder + alkali Bright yellow colour.
44

7. COUMARIN GLYCOSIDES :
Properties :
• They are derivative of Benzo-α-pyrone.
• They are volatile and colourless in nature & have aromatic
smell.
• Their alcoholic solutions when made alkaline shows blue
or green fluorescence.
• Coumarins may be present in either free form or glycosidic
form, free form being most common.
Distribution in Families : Umbelliferae, Leguminosae,
Solanaceae, Rubiaceae, etc…
Examples: Psoralea, Ammi visnag, Ammi majus.
45

46
COUMARINS FLAVONOIDS

COUMARIN GLYCOSIDES: (contd.)
COUMARINS
Simple coumarin Condensed coumarin
E.g.Aseculetin,
Scopoletin, Furano coumarin Pyrano coumarin
Umbelliferone. E.g. Psoralen, E.g. Visnadin
Xanthotoxin
Linear furanocoumarin Angular furanocoumarin
47

O O
3
45
6
7
8
1
SIMPLE COUMARINS
If, 6= -OH , 7= -OH Aesculetin
6= -OCH3 , 7= -OH Scopoletin
7= -OH Umbelliferone
CONDENSED COUMARINS
OO
O
O
O
O
Linear furanocoumarins
Angular furanocoumarins
48

Uses :
Drug Uses
Psoralea Psoriasis, Leucoderma, Leprosy
Ammi In leucoderma & vitiligo
Visnaga Coronary dilator, Asthma
Chemical tests :
• Alcoholic extract + Alkali
Blue green fluorescence
• Test with Hydroxylamine HCl
Take ethereal extract+1 drop sated. Alcoholic Hydroxylamine HCl
+ drop of alcoholic KOH
Heat, cool, acidify with 0.5N HCl & Add drop of 1% FeCl3
Violet colour coumarin present
49

8. FLAVONOID GLYCOSIDES
Properties:
• Flavones are Benzo-γ-pyrone derivatives.
• They are mostly polyphenolic colored substances (pigments ,
mostly yellow).
• They are found mainly in dicots, although also present in
monocot & gymnosperm.
• Chemically, they have 15 ‘C’ skeleton, which consist of 2
phenyl rings connected by 3’C’ bridge.
• In chalcone & dihydrochalcone, the bridge is open. But in
other classes 3’C’ bridge is part of heterocyclic ring.
• They occurs as flavone, flavonol,f lavonone, Isoflavone &
chalcone.
50

FLAVONOID GLYCOSIDES (contd.)
Uses:
Drugs Uses
Silymarin In liver diseases
Gingko In vascular diseases
Buckwheat Treatment of capillary bleeding (Rutin-
Vit-P)
Citrus
fruits
In capillary fragility
51

O
O
Chalcone
Dihydrochalcone
Flavanoids/ glycosides
52

O
O
O
O
OH
O
O
Flavone Isoflavone
Flavonol
O
O
OH
Dihydroflavonol
53

O
O
Flavanone
O
O
CH
Aurone
O
OHO
OH
OH
OH
OH
Quercetin (aglycone of Rutin)
54

Chemical tests :
Shinoda test :
Ethanolic extract + Small piece of Mg ribbon
+3-4 drops of conc. H2SO4
Formation of red colour
Flavanones present
55

Chemical tests :
56
Fluorescence test:
Take 15 ml of methanolic extract in a porcelain dish and evaporate
to dryness on water bath. To the residue, add 0.3 ml 3% w/v boric
acid solution (aqueous) and 1 ml 10% w/v oxalic acid solution
(aqueous). Mix and evaporate the mixture to dryness. Allow the
residue to cool at room temperature and then dissolve it in 10 ml
diethyl ether. Take the ether layer in a clean, dry test tube and
observe fluorescence under U.V. light. A greenish coloured
fluorescence is seen.

Chemical tests :
57
Test with neutral lead acetate solution
Take 1 ml of methanolic extract and add neutral lead acetate
solution (prepared in distilled water). Coloured precipitates are seen.
(Difference between flavonoids and tannin on basis of this test:
Tannins give bulky white ppt with neutral lead acetate solution,
While flavonoids give colored ppt)
Test with alkali: (Because of Chalcones)
Take the powder or 1 ml of methanolic extract and add dilute
ammonia solution. Yellow to reddish colour is seen. Now, add dilute
H2SO4. The yellow-reddish colour disappears.
Palash- slight orange colour
Liquorice- red to orange.

Chemical tests :
58
Test with acid: (Because of leucoanthocyanidins)
Take the powder or 1 ml of methanolic extract and add 1 ml of
80%v/v H2SO4. Following colours are observed in case of different
types of flavonoids:
Orange – Flavone
Pink – Flavonol
Red-purple – Flavanol and Xanthone
Orange to red - Flavonone

59
Practice question
Write the classification of glycosides based upon the chemical nature of its
aglycone (in a tabular form):
Sr.
No
Name Basic moiety/ ring
structure
Example of
drugs
Therape
utic
use
1 Anthraquin
one
glycosides
2
3
4
5
6
7
8

GENERAL METHOD OF ISOLATION AND PURIFICATION
Stas-otto method:
Drug containing glycoside is powdered
Powder is extracted by continious hot percolation
with alcohol using soxhlet apparatus.
Extract is treated with lead acetate to ppt tannins
Excess lead acetate is ppted as lead sulfide by passing H2S gas
Extract is filtered & concentrated
Purification is done by fractional solubility,fractional crystallization
Or chromatographic techniques such as TLC.
Identification is done by IR,NMR,U.V.VISIBLE,MASS spectroscopy.
60

References :
•Trease & Evans : Pharmacognosy,15th edition 2002
• C.K.Kokate : Pharmacognosy,19th edition 2002
• Shah & Quadry : Pharmacognosy,12th edition
Revised 2004-2005.
•Tyler & Brady : Pharmacognosy, 8th edition.
• SIM : Medicinal plant glycosides.1968.
61

62

An introduction to glycosides By KNS & PDV

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