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ANTHRACENE GLYCOSIDES • Contains anthraquinone derivatives as their aglycone component • Anthraquinones present either in their free state or as glycosides • They possess a laxative/cathartic effect

Anthracene glycosides lecture-2012-2013(1)

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Page 1: Anthracene glycosides lecture-2012-2013(1)

ANTHRACENE GLYCOSIDES

• Contains anthraquinone derivatives as their

aglycone component

• Anthraquinones present either in their free

state or as glycosides

• They possess a laxative/cathartic effect

Page 2: Anthracene glycosides lecture-2012-2013(1)
Page 3: Anthracene glycosides lecture-2012-2013(1)

• They are present in:

• Senna /Cassia

• Cascara

• Aloes

Page 4: Anthracene glycosides lecture-2012-2013(1)

DISTRIBUTIONMonocots

• Found in the Liliaceae family

• As C-glycosides

• E.g barbaloin

Page 5: Anthracene glycosides lecture-2012-2013(1)

Dicots

• Occurs in the ff families:

• Rubiaceae

• Leguminosae

• Polygonaceae

• Rhamnaceae

• Ericaceae

• Euphorbiaceae

• Verbenaceae etc

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Mode of Action

• Absorbed first in the small intestines

• Hydrolysed in the colon by enzymes to the

pharmacologically active free aglycones

• Released anthraquinones irritate and

stimulate the colon• This enhances its peristaltic movements

leading to purgation

Page 7: Anthracene glycosides lecture-2012-2013(1)

• This usually produces their action in 8-12

hours after administration

• Causes appreciable griping effect

• Generally administered with carminatives

to counteract undesirable effects

Page 8: Anthracene glycosides lecture-2012-2013(1)

Derivatives of anthraquinones

• Anthranols

• Anthrones

• Oxanthrones

• And dianthrones exist

Page 9: Anthracene glycosides lecture-2012-2013(1)

Anthranols and anthrones

• They are reduced anthraquinone

derivatives

• May occur as free or combined as

glycosides

• The 2 are isomeric

• May be converted to the other in solution

Page 10: Anthracene glycosides lecture-2012-2013(1)
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Oxanthrones

• These are products obtained from

• Anthraquinones

• Present in cascara bark

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• Oxidation of oxanthrones produce

anthraquinones

• Oxidising agents e.g H2O2 may be used

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Test for Anthracene glycosides

Borntrager’s Test

• Boil powdered plant material in dil acid

• Filter hot

• Shake filtrate with organic solvent- e.g

chloroform, Ethylacetate, Ether

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• Separate organic layer

• Shake with dil ammonia

• Rose pink colour in aqueous layer shows

the presence of free anthraquinones

• Borntrager’s test distinguishes

anthraquinones from anthrones and

anthranols

Page 15: Anthracene glycosides lecture-2012-2013(1)

Modified Borntrager’s test

• Some C-glycosides eg Aloin/barbaloin

do not undergo hydrolysis using only acids or

bases

• Hydrolysis may be caused by using Ferric

chloride/HCl due to oxidative hydrolysis

Page 16: Anthracene glycosides lecture-2012-2013(1)

• Heat powdered drug with solutions of

FeCl3 + HCl on water bath

• Filter whilst hot

• Extract liberated anthraquinone with

organic suitable solvent e.g CHCl3 etc

• Shake organic layer with ammonia

solution

• Rose-pink colour confirms its presence

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• Anthrones and anthranols do not give the

test unless they are converted to

anthraquinone

• This is done by oxidation with mild

oxidants such as hydrogen peroxide

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Drugs containing Anthracene derivatives

Senna

• Consists of the dried leaflet of Cassia

senna /Alexandrian senna, (C.acutifolia),

Tinnevelly senna (C.angustifolia)

• Family:Leguminosa

• Contains sennoside A & B, C, D

Page 19: Anthracene glycosides lecture-2012-2013(1)

Cascara• The dried bark of Rhamnus purshiana

• Family Rhamnaceae

• Present as O-glycosides/C-glycoside

• Collection made at least one year before

bark is used

• Fresh bark contains emetic principles

• Possesses drastic cathartic action

Page 20: Anthracene glycosides lecture-2012-2013(1)

i) Cascara contains the ff glycosides:

• Cascarosides A & B = barbaloin

• Cascarosides C & D = chrysaloin

Page 21: Anthracene glycosides lecture-2012-2013(1)

Aloes• E.g Aloe vera, A. barbadensis etc

• Common in the liliaceae family

• Aloins are very resistance to hydrolysis

and are not easily hydrolysed to

corresponding anthraquinones

• Oxidative hydrolysis is employed

Page 22: Anthracene glycosides lecture-2012-2013(1)

Effect of storage on the activities of Anthracene glycosides

• Prolonged storage causes oxidation of

anthranols and anthrones to give the

relatively less drastic anthraquinones

• Thus, the degree of the drastic activity of

drugs decreases with time

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• Thus anthrones and anthranols are more

potent than their corresponding

oxanthrones

• Oxanthrones in turn are more active

than their corresponding anthraquinones

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Activity of Anthraquinone derivatives

• Anthrones and anthranols > Dianthrones >

Anthraquinones