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Glycosides
Muhammad Tanveer Khan
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Introduction
A glycoside is an organic compound, usually of plant
origin, that is composed of a sugar portion linked to a
non-sugar moiety.
Sugar portion .. Glycone
Non-sugar portion... Aglycone / Genin
Linkage between sugar and non-sugar is
usually an oxygen linkage
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Types
Based on atoms involved in glycosidic
linkage
O- glycosides
C- glycosides
S- glycosidesN- glycosides
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Types
According to Sugar moiety
GlucosidesRibosides
Rhamnosides
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Classification
)a Cardioactive glycosides: Digitalis, Strophanthus andwhite squill
)b Anthraquinone glycosides: Cascara, Aloe, Rhubarb,
Cochineal and Senna)c Saponin glycosides: Glycyrrhiza, Sarsaparilla
)d Cyanophore glycosides: Wild cherry
)e Isothiocyanate glycosides: Black Mustard
)f Lactone glycosides: Cantharide)g Aldehyde glycosides: Vanilla
)h Miscellaneous glycosides: Gentian, Quassia, Dioscorea
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Cardioactive Glycosides
Used in treatment of CHF
Mechanism:These glycosides;
Increase the force of systolic contractionShorten length of systole
As a result
Heart have more time to rest between contraction.
Therapeutic activity depends upon;
1.Chemical nature of aglycone
2.Number of sugars
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Aglycone is steroidal.
Aglycone may be;
Cardenolide (5-membered lactone at place of R
Bufanolide (6-membered lactone at place of R
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a DigitalisBotanical Origin:
Digitalis purpurea
Digitalis lanata
Family:
Plantigenaceae
Part used:Dried leaves
Collection:Leaves collected from 2nd year growth ofplant in June before opening of flower.
Drying is done by applying artificial heat(temperature not more than 65C.
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Chemistry:
Four aglycons in Digitalis
Digitoxigenin
Gitoxigenin
Gitatoxigenin
Digoxigenin (only in Digitalis lanata
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Derivatives D. purpurea D. lanata
Digitoxigenin Digitoxin
Glucodigitoxin(Digitoxin + 1 glucose
Acetyl digitoxin
Lanatoside A(Acetyl digitoxin + 1 glucose
Gitoxigenin Gitoxin
Glucogitoxin
(Gitoxin + 1 glucose
Lanatoside B
(Acetyl gitoxin + 1 glucose
Gitatoxigenin Gitatoxin Lanatoside E
(Acetyl Gitatoxin + 1 glucose
Digoxigenin Digoxin
Acetyl digoxinLanatoside C
(Acetyl digoxin + 1 glucose
Deslanoside
(Digoxin + 1 glucose
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b Strophanthus
Botanical Origin:Strophanthus kombe
Strophanthus hispidus
Family:Apocynaceae
Part used:
Dried ripe seeds
Collection:
Fruits are collected when fully ripen i.e. in
June and July
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Chemistry: Active constituent is Strophanthin.
Upon hydrolysis it yields;
Strophanthidin
Sugars (alpha D-glucose + beta D-glucose + beta D-cymarose
Apart from Strophanthin, there are;
30%fixed oils
Resin / Mucilage
Nitrogenous bases ( Trigonellin, Choline
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Uses:
Cardiac stimulant
Diuretic
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c White squill
Botanical Origin:Urginea maritima
Family:Liliaceae
Part used:Dried fleshy scales of bulb
Collection:Bulbs are collected in August. Outer scaleis removed and inner scale is dividedinto pieces and dried in sunlight.
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Chemistry:
Active constituent is Scillaren.Upon hydrolysis it yields;
Scillarenin
Sugars (1 molecule of glucose + 1 molecule of rhamnose
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Uses:
Emetic
ExpectorantCardiac tonic
Diuretic