Pharmacognosy Lecture No.1
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Transcript of Pharmacognosy Lecture No.1
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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- glycosides
N- glycosides
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Types
According to Sugar moiety
Glucosides
Ribosides
Rhamnosides
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Classification
(a )Cardioactive glycosides: Digitalis, Strophanthus and white 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 GlycosidesUsed in treatment of CHF
Mechanism:These glycosides;
Increase the force of systolic contraction
Shorten 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 purpureaDigitalis lanata
Family:Plantigenaceae
Part used:Dried leaves
Collection:Leaves collected from 2nd year growth of plant in June before opening of flower.
Drying is done by applying artificial heat (temperature not more than 65°C).
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Chemistry: Four aglycons in Digitalis
Digitoxigenin
Gitoxigenin
Gitatoxigenin
Digoxigenin (only in Digitalis lanata)
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DerivativesD. purpureaD. lanata
DigitoxigeninDigitoxin
Glucodigitoxin
)Digitoxin + 1 glucose(
Acetyl digitoxin
Lanatoside A)Acetyl digitoxin + 1 glucose(
GitoxigeninGitoxin
Glucogitoxin)Gitoxin + 1 glucose(
Lanatoside B)Acetyl gitoxin + 1 glucose (
GitatoxigeninGitatoxinLanatoside E)Acetyl Gitatoxin + 1 glucose(
DigoxigeninDigoxin
Acetyl digoxin
Lanatoside C)Acetyl digoxin + 1 glucose(
Deslanoside)Digoxin + 1 glucose(
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b( StrophanthusBotanical 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 squillBotanical Origin:
Urginea maritima
Family:Liliaceae
Part used:Dried fleshy scales of bulb
Collection:Bulbs are collected in August. Outer scale is removed and inner scale is divided into 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
Expectorant
Cardiac tonic
Diuretic