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Anthracene (Anthraquinone) Glycosides

Anthracene (Anthraquinone) Glycosides. Anthracene glycosides are oxygenated derivatives of pharmacological importance that are used as laxatives or cathartics, anti-inflammatory, antibacterial, antifungal and also as natural dyes. Forms of Anthracene derivatives in Plants: A- Aglycones :.

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Anthracene (Anthraquinone) Glycosides

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  1. Anthracene (Anthraquinone) Glycosides • Anthracene glycosides are oxygenated derivatives of pharmacological importance that are used as laxatives or cathartics, anti-inflammatory, antibacterial, antifungal and also as natural dyes.

  2. Forms of Anthracene derivatives in Plants: A- Aglycones: The activity decreases as oxidation level increase.

  3. B- Dimeric Anthracene derivatives: • They are derived from two anthracene units connected by covalent C-C bond through C-10. 1) Homo-Dianthrones: The two anthrone moieties are similar. e.g. Sennidins A&B and their corresponding glycosides Sennosides A&B. They are all formed of two Rhein monomers. The A group are (l)-form while the B group are meso compounds with zero optical rotation.

  4. 2) Hetero-Dianthrones: The two anthrone moieties are different. e.g. Sennidins C&D and their corresponding glycosides Sennosides C&D. They are all formed of one Rhein and one Aloe-emodin monomers. The C group are (l)-form while the D group are meso compounds with zero optical rotation.

  5. O-glycosides: e.g. Cascarosides A & B. They are both O- and C-glycosides. Each one contain two sugar unites. • C-glycosides: e.g. Barbaloin it is formed from the removal of one sugar from Cascarosides.

  6. Structure-Activity Relationship: • Glycosylation is essential for activity. • Hydroxylation at C-1 and C-8 is essential for activity. • Oxidation level at C-9 and C-10 is important: • Highest level of oxidation (anthraquinones) have the lowest activity. • Oxanthrones are less active than anthrones. • Complete reduction of C-9 and C-10 eliminates the activity. • Substitution at C-3 have great impact on activity: CH2OH > CH3 > COOH

  7. Some Drugs containing Anthracene derivatives: • Senna: • Leaves and pods contain Sennosides A-D. • The C-C bond protect the anthrone from oxidation.

  8. Cascara bark: • Contain Cascarosides A- D. • Barbaloin present as a secondary glycoside in Cascara. • They are O- and C-glycosides. • The C-linked glucose at C-10 protect anthrones from oxidation. • Frangula bark: • Contain anthraquinone derivatives the most oxidized and least active.

  9. Aloes: • The major glycoside in Aloes is the C-glycoside Barbaloin. • Barbaloin is primary glycoside in Aloes. • The C-linked glucose at C-10 protect anthrones from oxidation. Barbaloin (aloin)

  10. Rhubarb (Rhei): • It is purgative only in large doses. • It contains high amount of tannins that have astringent effect.

  11. Mechanism of Action: • The glycosides are absorbed from the small intestine and re-excreted in the large intestine where they cause irritation of colon mucosa increase the motility so produce laxation. • Aglycones produce gripping effect so it is recommended to prescribe antispasmodic with them. • Side effects: Urinary tract irritation, vomiting, diarrhea, uterine pain

  12. Chemical test:Borntrager’s and Modified Borntrager’s test: • For Aglycones: • Extract plant material with organic solvent. • Shake with NH4OH OR KOH. • For O-Glycosides: • Boil plant material with dil. HCl for 10 min, filter and shake with organic solvent (Ether or Benzene). • Separate the organic solvent. • Shake with NH4OH OR KOH. • For C-Glycosides: • Boil plant material with dil. HCl/FeCl3, filter and shake with organic solvent (Ether or Benzene). • Separate the organic solvent. • Shake with NH4OH OR KOH. • Positive result indicated by Rose Red colour in the aqueous alkaline layer.

  13. Hypericin • Sources:Dried flowering tops of Hypericumperforatum. • Structure:Aromatic polycyclic dianthrones. • Uses: Tranquilizer, mild antidepressant (MAO inhibitor) • it has antiviral (anti-HIV) activity (in vitro). Side effects: allergic reaction in sensitive individuals

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