pharmacognosy lecture # 1 (glycosides) [by, sir tanveer khan]

8/4/2019 Pharmacognosy Lecture # 1 (Glycosides) [By, Sir Tanveer Khan]

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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

pharmacognosy lecture # 1 (glycosides) [by, sir tanveer khan]

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