Anthraquinone and Aglycones Overview

### Anthraquinone Glycosides

• Oxygenated derivatives with pharmacological importance used as laxatives, cathartics, anti-inflammatory agents, antibacterial, antifungal, and natural dyes.
• Present in drugs like cascara sagrada, frangula, aloe, rhubarb, and senna.
• Activity decreases as oxidation level increases.

Aglycones

• Anthracene derivatives found in plants.

Dimeric Anthracene Derivatives

• Formed from two anthracene units connected by a covalent C-C bond through C-10.

Homo-Dianthrones

• Two anthrone moieties are similar.
• Examples: Sennidins A&B and their corresponding glycosides Sennosides A&B.
• Formed of two Rhein monomers.
• A group is (l)-form while the B group is meso compounds with zero optical rotation.

Hetero-Dianthrones

• Two anthrone moieties are different.

• Examples: Sennidins C&D and their corresponding glycosides Sennosides C&D.

• Formed of one Rhein and one Aloe-emodin monomers.

• C group is (l)-form while the D group is meso compounds with zero optical rotation.

• Free anthraquinones without sugar moiety exhibit little therapeutic activity.

• Sugar is essential for transporting the aglycone to the site of action in the large intestine.

• Anthraquinone group can be interchanged by oxidation or reduction.

Mechanism of Action

• Anthraquinone and related glycosides are stimulant cathartics.
• Action: Increase the tone of smooth muscle in the colon wall and stimulate secretion of water and electrolytes into the large intestine.
• Cascara sagrada, frangula, and senna are the preferred drugs.
• Aloe and rhubarb are not recommended due to their irritant properties.

Numbering System and Nomenclature

• Numbering can start from any corner, ensuring substituents have the smallest number.

Plants Containing Anthraquinone Glycosides

Senna

• Dried leaves of Cassia acutifolia, known as Alexandria senna.
• Active constituents: Dimeric glycosides whose aglycons are composed of aloe-emodin and/or rhein.
• Sennosides A and B are major constituents, stereoisomers whose aglycones are rhein dianthrone.
• Sennosides C and D are minor constituents, composed of one molecule of rhein and one of aloe-emodin.
• C-C bond protects the anthrone from oxidation.
• Use: As cathartics.

Cascara Sagrada Bark

• Dried bark of Rhamnus purshianus.
• Aged for one year to lose griping properties.
• Stored to change the reduced form (drastic griping) into the oxidized form (less griping).
• Active Constituents:
  • Cascarosides A&B (glycosides of barbaloin)
  • Cascarosides C&D (glycosides of chrysaloin which is deoxy barbaloin)

Frangula

• Dried bark of Rhamnus frangula.
• Laxative effect due to anthraquinone glycosides.
• Aged for one year before use in medicinal preparations.
• Consists of:
  • Frangulin (frangula emodin rhamnoside)
  • Glucofrangulin (frangula emodin glucorhamnoside)

Aloe

• Dried juice of the leaves of Aloe barbadensis.
• Active constituents: Anthraquinone glycosides, the principal ones being aloins A and B (Barbaloin).
• C-linked glucose at C-10 protects anthrones from oxidation.
• Active constituents vary between species.
• Uses:
  • As a cathartic
  • Fresh juice for treating burns and skin irritations.
  • Extracted gel for sunburn, deep thermal burns, and radiation burns.
  • Provides pain relief, reduces itching, minimizes keratosis and ulceration.

Rhubarb

• Dried rhizome and root of Rheum officinale.
• Active constituents: Rhein anthrones.
• Uses: As cathartics.

Anthraquinone Glycosides

• Are oxygenated derivatives of pharmacological importance.
• Used as laxatives, cathartics, anti-inflammatory, antibacterial, and antifungal agents.
• Also act as natural dyes.
• Present in drugs like cascara sagrada, frangula, aloe, rhubarb, and senna.

Anthraquinone Aglycones

• Anthracene derivatives found in plants.
• Activity decreases as oxidation levels increase.

Dimeric Anthracene Derivatives

• Derived from two anthracene units connected by a covalent C-C bond through C-10.

Homo-Dianthrones

• The two anthrone moieties are similar.
• Examples include:
  • Sennidins A&B
  • Sennosides A&B
• All formed of two Rhein monomers.
• Group A are (l)-form.
• Group B are meso compounds with zero optical rotation.

Hetero-Dianthrones

• The two anthrone moieties are different.
• Examples include:
  • Sennidins C&D
  • Sennosides C&D
• All formed of one Rhein and one Aloe-emodin monomer.
• Group C are (l)-form.
• Group D are meso compounds with zero optical rotation.
• Free anthraquinones exhibit little therapeutic activity without the sugar moiety.
• The sugar is essential for transporting the aglycone to the site of action in the large intestine.

Anthraquinone Group Interchangeability

• Anthraquinone group members can be interconverted by oxidation or reduction.

Mechanism of Action

• Anthraquinone glycosides are stimulant cathartics.
• Exert their action by increasing colon smooth muscle tone.
• Stimulate water and electrolyte secretion into the large intestine.
• Cascara sagrada, frangula, and senna are the preferred drugs.
• Aloe and rhubarb are not recommended due to their irritant properties.

Numbering System and Nomenclature

• Numbering starts from any corner.
• Substituents are given the smallest number.

Plants Containing Anthraquinone Glycosides

Senna

• Dried leaves of Cassia acutifolia (Alexandria senna).
• Active constituents are dimeric glycosides with aglycones composed of aloe-emodin and/or rhein.
• Major constituents:
  • Sennosides A and B (stereoisomers with rhein dianthrone aglycones).
• Minor constituents:
  • Sennosides C and D (one molecule of rhein and one of aloe-emodin).
• The C-C bond protects the anthrone from oxidation.
• Uses: Cathartics.
• Sennosides A, B, C, and D contain glucose.

Cascara Sagrada Bark

• Dried bark of Rhamnus purshianus.
• Aged for at least one year before use to lose griping properties.
• Storage allows conversion of the reduced form (drastic griping action) to the oxidized form (less griping action).
• Active constituents include:
  • Cascarosides A&B (glycosides of barbaloin).
  • Cascarosides C&D (glycosides of chrysaloin, a deoxy barbaloin).

Frangula

• Dried bark of Rhamnus frangula.
• Laxative effects are due to the presence of anthraquinone glycosides.
• Aged for a year or more before medicinal use.
• Consists of:
  • Frangulin (frangula emodin rhamnoside).
  • Glucofrangulin (frangula emodin glucorhamnoside).

Aloe

• Dried juice of Aloe barbadensis leaves.
• Contains multiple anthraquinone glycosides.
• Principal ones include:
  • (Barbaloin) aloins A and B.
• C-linked glucose at C-10 protects anthrones from oxidation.
• Active constituents vary qualitatively and quantitatively based on species.
• Uses:
  • Cathartic by acting on the large intestine.
  • Fresh juice for burns and skin irritations.
  • Extracted gel blended with lanolin base as ointment for sunburn, deep burns, and radiation burns.
  • Relieves pain, itching, and minimizes keratosis and ulceration.

Rhubarb

• Dried rhizome and root of Rheum officinale.
• Active constituents:
  • Rhein anthrones.
• Uses: Cathartics.