Digitalis glycoside

1. DIGITALIS GLYCOSIDE
Kratika Daniel (Ph.D)
Assistant professor
MANDSAUR INSTITUTE OF PHARMACY,
Mandsaur

2. INTRODUCTION
•The genins of all cardiac glycosides are steroidal in nature, that act as cardio tonic agents.
•They are characterized by their highly specific action cardiac muscle, increasing tone,
excitability and contractility of this muscle, thus allowing the weakened heart to function more
efficiently.
O
R
OH
CH
3
Sugar
Lactone ring
1
2
3
4
5
10
6
7
8
9
11
12
13
14
15
16
17
All cardio active glycosides are characterized by the following structural features:
1.The presence of β-OH at position C-3, which is always involved in a glycosidic linkage to a
mono, di, tri, OR tetra saccharide.
2.The presence of another β-OH group at C-14.
3.The presence of unsaturated 5 or 6- membered lactone ring at position C-17, also in the β
configuration.
4.The A/B ring junction is usually (cis), while the B/C ring junction is always (trans) and the
C/D ring junction is in all cases (cis).
5.Additional OH groups may be present at C-5, C-11 and C-16.
Kratika Daniel (Ph.D)
Assistant professor
MANDSAUR INSTITUTE OF PHARMACY,
Mandsaur

3. 1- Cardiac glycosides that α-β unsaturated 5-membered lactose ring in position C-17 are
known as cardenolides. These are represented by the digitalis and straphanthus group.
2- Digitalis glycosides contain angular methyl group at C-10, while strophanthus glycoside are
characterized by presence of either an aldehydic (CHO) or primary alcoholic (C`H
2
OH) group
at C-10.
O
R
OH
CH
3
OH
Sugar
1
2
3
4
5
10
6
7
8
9
11
12
13
14
15
16
17
O O
Cardenolides
Digitalis glycosides R=CH
3
Strophanthus glycosides R=CHO OR CH
2
OH
3- Cardiac agents that have doubly unsaturated 6-membered lactone ring in position C-17
are referred to as Bufadienolides.
4- This group includes the squill glycosides and the toad venom, Bufotoxin.
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

4. 5- The glycone portion at position C-3 of cardiac glycosides may contain four monosaccharide
molecules linked in series. Thus, from a single genin one may have a monoside, a bioside, a
trioside or a tetroside.
6- With the exception of D-glucose and L-rhamnose, all the other sugars that are found in cardiac
glycosides are uncommon deoxy-sugars e.g., Digitoxose, Cymarose, Thevetose.
C
CHO
C
C
C
CH
3
OH
OH
OH
H
2
C
CHO
C
C
CH
3
OH
OH
H
2
CHO
C
C
CH OH
H
COCH
3
OH
HCH
3O
COHH
CH
3
Digitoxose Cyamarose Thevetose
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

5. SOURCE
O
OH
R
1
R
2
H
1
2
3
4
5
10
6
7
8
9
11
13
14
15
17
O O
12
16
D. purpurea, D. lanata, D. lutea and D. thapsi. Family – Scrophularaceae.
The structures of the common aglycones of the digitalis group are: -
Compounds R1 R2
Digitoxigenin H H
Gitoxigenin H OH
Digoxigenin OH H
kratika
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

6. 1- Glycosides derived from Digitoxigenin:
a- Lanatoside A = Digitoxigenin---DX---DX----DX(AC)---G.
b- Acetyl-digitoxin = Digitoxigenin---DX---DX----DX---(AC).
c- Digitoxin = Digitoxigenin------DX---DX----DX.
d- Purpurea gly A = Digitoxigenin---DX---DX----DX---G
2- Glycosides derived from Gitoxigenin:
a- Lanatoside B = Gitoxigenin---DX---DX----DX(AC)---G.
b- Acetyl-gitoxin = Gitoxigenin---DX---DX----DX---(AC).
c- Gitoxin = Gitoxigenin------DX---DX----DX.
d- Purpurea gly B = Gitoxigenin---DX---DX----DX---G
3- Glycosides derived from Digoxigenin:
a- Lanatoside C = Digoxigenin---DX---DX----DX(AC)---G.
b- Acetyl-digoxin = Digoxigenin---DX---DX----DX---(AC).
c- Digoxin = Digoxigenin------DX---DX----DX.
d- Deslanoside = Digoxigenin---DX---DX----DX---G
DX = Digitoxose, DX (AC)=Acetyldigitoxose,G = Glucose.
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

7. Lanatoside A
Alkaline
hydrolysis
Specific
enzyme
Acetyldigitoxin
Specific
enzyme
Alkaline
hydrolysis
Digitoxin
Digitoxigenin + 3 digitoxose
Acidhydrolysis
purpurea gly. A
1.The primary glycosides Lanatoside A, Lanatoside B, Lanatoside C are acted by specific
enzyme which split the terminal glucose, give the secondary glycosides acetyldigitoxin,
acetylgitoxin and acetyldigoxin respectively.
2.The deacetyl-lanatosides A, B and C can be obtained by the alkaline hydrolysis of the
corresponding lanatosides.
3.Digitoxin, gitoxin and digoxin are obtained by the action of alkali on their acetyl-
derivatives.
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

8. ISOLATION
Digitalis powder
Removal of fatty material by extraction with petroleum ether
Digestion of defatted material with water
Liquid discard Extracted more with several water and ethanol mixture
Concentrate to small volume
Distillation in vaccum
Precipitation of tannin by lead hydroxide
Super gel filtration
Glycoside with low
Solubility in water &
High solubility in
chloroform
Glycoside with low
Solubility in water &
High solubility in
chloroform
Removal of alcohol by
Vaccum distillation
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

9. Aqueous solution
Extraction with
chloroform
Washing with chloroform with water
2N HCl, 2N Na
2
CO
3
.
Discard washing
Separation of glycoside by
chromatography
Elution with chloroform
& chloroform containing graded
proportion of methanol
Adjust filtrate to pH 6
Successive washing with chloroform
Ether. ethanol
Discard washing
Into aqueous phase add
Sodium sulfate to saturation
Extraction with chloroform ethanol mixture
Acetylation/ benzoylation
of more polar glycoside
KHCO
3
Separation of individual glycoside
By chromatography
Less polar
glycoside
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

10. CHEMICAL TESTS
1.Raymond test: - A small quantity of glycoside is dissolved in 1ml of 50% ethanol followed
by addition of 0.1 ml of 1% solution of dinitrobenzene in methanol. To this solution 2 – 3
drops of 20% sodium hydroxide solution is added. Appearance of violet color changes to blue
color.
2.Legal test : - glycoside + few drops of pyridine and 1 drop of 2% sodium nitroprusside and a
drop of 20% NaOH is added. Deep red color occur
3.Tollens test: - mixture of pyridine & ammonical silver nitrate gives silver mirror on wall of
test tube.
4.Keller killani test: - drug + 10ml of 70% alcohol for few minute and filtered. To 5ml filtrate
10ml of hydrogen peroxide and 0.5 ml of strong solution of lead acetate is added. To this
mixture 1 or 2 drop of concentrated sulphuric acid is added. Appearance of blue color
confirms presence of deoxy sugar.
5.Baljet test: - section of digitalis + add sodium picrate solution yellow to orange color.
6.Antimony trichloride test: - solution of glycoside is heated with antimony trichloride and
trichloroacetic acid to obtain blue or violet color.
7.Liebermann test: - solution of glycoside in chloroform is added in acetic anhydride followed
by conc. sulfuric acid gives violet to blue color. This test is for conformation of steroidal
nucleus.
8.Xanthohydral test: - a red color is produced by deoxy sugar when they are heated with
0.125% solution of xanthohydral in glacial acetic acid.
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

11. TLC
Solvent system: - ethyl acetate : chloroform : ethanol (9 : 5 : 0.5)
cyclohexane : acetone : acetic acid (49 : 49 : 2)
Detecting reagent: - antimony tri chloride.
PROPERTIES
SOLUBILITY: -
•The different cardiac glycosides show different solubilities in aqueous and organic solvents.
They are usually soluble in water or aqueous alcohol and insoluble in the fat solvents with
exception of chloroform and ethylacetate.
•The higher number of sugar units in the molecule, the greater solubility in water but lower
soluble in chloroform.
•Alcohols are good solvents for both the glycosides and the aglycones.
•pet.ether and ether are used for defatting process of drug.
STABILITY: -
•Acid hydrolysis cleavage of the glycosides into aglycones and sugar residues.
•Specific enzyme usually coexist with CG in plants, which may split the primary G into G with
less sugar units. Thus, CG deteriorate during drying and storage. These drugs should be stored
in sealed containers over dehydrating agents.
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

12. •It is recommended to heat stabilize these CG, by destroying the enzymes at higher
temperatures. At higher temperature, the tertiary OH gp at C-14 may split off as water,
leading to formation of an inactive anhydro-form of CG
O
R
OH
CH3
Sugar
1
2
3
4
5
10
6
7
8
9
11
12
13
14
15
16
17
O O
O
R
CH3
Sugar
1
2
3
4
5
10
6
7
8
9
11
12
13
14
15
16
17
O O
-H2O
•The gitoxin has in addition to tertiary OH at C-14 another secondary OH at C-16. Both OH
gps split as water by the action of H
2
SO
4
with the formation of two additional double bonds.
These with the double bond of the lactone ring from a conjugated double bond system that
makes the compound fluorescent in UV light.
•The detection of gitoxin in other digitalis G is based on the above mentioned reaction.
•Molecular formula – C
27
H
44
O
5
•Melting point – 230 – 265
o
C
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

13. BIOSYNTHESIS
OH
cholestrol
NADPH
2
O
2
OH
OH
OH
NADPH
2
O
2
OH
O
O
H
O
PREGNENLONEO
O
PROGESTRONE
O
O
5 -b - Pregnane 3,2 dione
O
PREGNENALONE OH
OH
O
DIOL
OH
OH
O
OH
TRIOL
acetyl CoA
OH
OH
O
O
12 - b - hydroxylation
oxalo acetyl CoA
bufalin
C - 2 - unit
strophanthadin
16 - b - hydroxylation
OH
OH
O
O
H
H
OH
OH
O
O
H
OH
digitoxigenin
gitoxigenin
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

14. SAR
1.The glycone part displays a great influence on the solubility and the rate of
absorption and distribution of the glycosides to the site of action.
2.Small change in the molecules such as a change of the location of the OH gp,
modify the cardiac activity or even eliminate it completely.
3. The saturation and/or cleavage of the lactone ring, destroys the cardiac
activity.Therefore, the closely related CG, differ greatly in the rate of
absorption, duration of action and their cumulative effect.
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur

15. USES & ACTION
Main action on heart. The primary action may be divided into 3 parts
1.+
ive
inotropic effect on heart.
2.Partial blockade of A.V. conduction.
3.Reduction in heart rate.
•Direct stimulation of myocardium & increased contractility with a resultant increase in
cardiac output, reduction in heart size, improved, cardiac efficiency.
•Depression of conduction, especially in A. V. node, which protects the ventricles from
excessive bombardment by auricular impulses in auricular arrythmias. Due to this effect
bradycardia occurs.
•Increased vagal activity, which decrease the auricular refractory period with conversion of
flutter to fibrillation. The delay in A. V. conduction & bradycardia is also vagal origin.
•Increased in cardiac excitability makes heart more vulnerable to arrythmias
•It has direct constrictor action on vascular smooth muscle. It may diminished clotting
time.
•GIT – it causes emetic action due to stimulation of chemoreceptor trigger zone in medulla.
USES• Heart failure with sinus rhythm or atrial fibrilation.
• Atrial flutter.
• Paroxysmal atrial tachcardia.
• Prevention of paroxysmal atrial arrythmias.
• Prophylactically before cardiac surgery.
Kratika Daniel (Ph.D) Assistant
professor MANDSAUR
INSTITUTE OF PHARMACY,
Mandsaur