Pharmacognosy Lecture # 1 (Glycosides) [By, Sir Tanveer Khan]

Glycosides : 

Glycosides Muhammad Tanveer Khan

Introduction : 

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”

Types : 

Types Based on atoms involved in glycosidic linkage O- glycosides C- glycosides S- glycosides N- glycosides

Types : 

Types According to Sugar moiety Glucosides Ribosides Rhamnosides

Classification : 

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

Cardioactive Glycosides : 

Cardioactive Glycosides Used 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

Slide 8: 

Aglycone is steroidal. Aglycone may be; Cardenolide (5-membered lactone at place of R) Bufanolide (6-membered lactone at place of R)

a) Digitalis : 

a) Digitalis Botanical Origin: Digitalis purpurea Digitalis 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).

Slide 10: 

Chemistry: Four aglycons in Digitalis Digitoxigenin Gitoxigenin Gitatoxigenin Digoxigenin (only in Digitalis lanata)

b) Strophanthus : 

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

Slide 14: 

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 )

Slide 15: 

Uses: Cardiac stimulant Diuretic

c) White squill : 

c) White squill Botanical 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.

Slide 17: 

Chemistry: Active constituent is Scillaren. Upon hydrolysis it yields; Scillarenin Sugars (1 molecule of glucose + 1 molecule of rhamnose)

Slide 18: 

Uses: Emetic Expectorant Cardiac tonic Diuretic