PhCol semis

• Tannins


  Used in aromatherapy and insect repellent
• The term tannin was first applied by Seguin


  1796
• Qualitative test for tannins

  Tanning test (goldbeater's skin test)
• Tannins


  Used in the leather industry
• The two main groups of tannins

  • Hydrolysable tannins
  • Condensed tannins (proanthocyanidins)
• True tannin


  Molecular weight of 1000 to 5000
• Most tannins are glycoside
• Modern authors treat tannins not as a specific phytochemical group but as an example of polyphenols
• Value of tannins


  • Important in leather industry
  • Physiological activity of herbal medicines
  • Taste of foodstuffs and beverages
  • Nutritional value of feeds for herbivores
• Properties of tannins


  • Soluble in water, dilute alkalis, alcohol, glycerol and acetone
  • Sparingly soluble in other organic solvents
  • Solutions precipitate heavy metals, alkaloids, glycosides and gelatin
  • With ferric salts, gallotannins and ellagitannins give blue-black ppt and condensed tannins brownish-green ppt
• Uses of tannins


  • Styptics and protection of inflamed surfaces of mouth and throat (astringent)
  • Possess antidiarrheal property
  • Antidote for heavy metal, alkaloids and glycosides poisoning
  • Treatment of burns (antiseptic and astringent property)
  • Preservative
• Tannin usage decline after world war
• Il-absorbed tannic acid-causing severe central necrosis of the liver
• Recent study concentrated on the anti tumor activity of tannins (green and black tea)
• Other Form of Tannin

  • Complex mixture of polyphenols difficult to isolate because they do not crystallize

  Complex Tannin

  • Applied for newly discovered group of tannins which are biosynthesined from both hydrolysable ( a-C-gluconide ellagitannin] and condensed tannin

  • Union occur throuh a C-C bond between the C of the glucose unit of the ellagitannin and the C or C. of the flavan-3-ol derivatives

  • Identified in plants like quercus, castanea, rheum and camelia
• Tannins


  The term tannin was first applied by Seguin in 1796
• Tannins


  • Qualitative test; tanning test (goldbeater's skin test)
  • Used in leather industry
  • The two main groups are hydrolysable tannins and condensed tannins (proanthocyanidins)
  • True tannin has a molecular weight of 1000 to 5000
  • Most tannins are glycoside
  • Modern authors treat tannins not as a specific phytochemical group but as an example of polyphenols
• Value of tannins


  • Important in leather industry
  • Physiological activity of herbal medicines
  • Taste of foodstuffs and beverages
  • Nutritional value of feeds for herbivores
• Properties of tannins


  • Soluble in water,dilute alkalis, alcohol, glycerol and acetone
  • Sparingly soluble in other organic solvents
  • Solutions precipitate heavy metals, alkaloids, glycosides and gelatin
  • With ferric salts, gallotannins and ellagitannins give blue-black ppt and condensed tannins brownish-green ppt
• Uses of tannins


  • Styptics and protection of inflamed surfaces of mouth and throat (astringent)
  • Possess antidiarrheal property
  • Antidote for heavy metal, alkaloids and glycosides poisoning
  • Treatment of burns (antiseptic and astringent property)
  • Preservative
• Tannin usage declined after World War II - absorbed tannic acid causing severe central necrosis of the liver
• Recent study concentrated on the anti-tumor activity of tannins (green and black tea)
• Complex tannins


  A newly discovered group of tannins which are biosynthesised from both hydrolysable (a-C-gluconide ellagitannin) and condensed tannin. The union occurs through a C-C bond between the C of the glucose unit of the ellagitannin and the C or C of the flavan-3-ol derivatives.
• Pseudotannins


  Compounds of low molecular weight, do not respond to gold beater skin test, found in dying or dead cells (large quantity), contribute a protective function in barks and heartwoods, exert inhibitory effect on many enzymes due to protein precipitation
• Tests for tannins


  • Gold Beater's Test
  • Gelatin Test
  • Ferric Chloride Test
  • Catechin Test
• Hydrolysable tannins


  Hydrolyzed by enzymes such as tannase, form from several molecules of phenolic acids such as gallic and hexahydroxydiphenic acids
• Condensed tannins


  Not readily hydrolysed to simpler molecules, do not contain sugar moiety, content: cathecin and leucoanthocyanidins, on treatment with acids or enzymes are converted into red insoluble compounds known as phlobaphenes
• Commercial tannins used in leather industry

  • Quebracho
  • Wattle
  • Chestnut
  • Myrobalans trees
• Pharmaceutical tannins


  • Oak galls (yields glucose and gallic acid)
• Gallitannins


  • Rhubarb
  • Cloves
  • Red rose petals
  • Bearberry leaves
  • Chinese galls
  • Turkish galls
  • Hammamelis
  • Chestnut
  • Maple
• Ellagitannins


  • Pomegranate rind
  • Pomegranate bark
  • Myrobalans
  • Eucalyptus leaves
  • Kousso
  • Some Australian kinos
  • Chestnut (Castanea spp.)
  • Oak bark
• Plants containing proanthocyanidins (condensed tannins)

  • Barks: cinnamon, wild cherry, cinchona, willow, acacia (wattle, mimosa) oak and hammamelis
  • Roots and rhizomes: krameria (rhatany) and male fern
  • Flowers: lime and hawthorn
  • Seeds: cocoa guarana, kola and areca
  • Fruits: cranberries, grapes (red wines), hawthorn
  • Leaves: hamamelis, hawthorn and tea, esp. green tea
  • Extracts and dried juices: catechu, acacia and mangrove cutches, East Indian kino, butea gum and eucalyptus kino
• Pseudotannin constituents


  • Gallic acid: rhubarb and most materials which contain gallitannins
  • Catechins: catechu, acacia cutch, many Australian kinos, cocoa, guarana and many other drugs containing condensed tannins
  • Chlorogenic acid: mate, coffee (particularly unroasted) and nux vomica (small quantity)
  • Ipecacuanhic acid: ipecacuanha
• Tannin-containing plants and their uses

  • Turkish galls (Quercus infectoria) - constituent: gallotannic acid, tannic acid, uses: astringent and styptic
  • Hammamelis leaf (witch hazel leaves from Hammamelis virginiana) - contents: gallitannins, ellagitannins, free gallic acid, proanthocyanidins, bitter principles and traces of volatile oil
  • Hawthorn (Crataegus monogyna and C. laevigata) - content: procyanidins, uses: mild cardiac tonic, can be used as cardiac glycosides
  • Alchemilla (Alchemilla xanthochlora) - content: pyrogallol, uses: astringent against bleeding and diarrhea, use for menorrhagia
  • Rhatany (Krameria triandra) - constituent: phlobaphenes, uses: astringent
  • Pomegranate rind - constituent: ellagitannins, uses: treatment for non-specific diarrhea, astringent, colorant
  • Catechu (from Uncaria gambir) - constituent: catechin, uses: astringent
• Coumarins and glycosides


  Derivatives of benzo-a-pyrone such as coumarin (the lactone of O-hydrocinnamic acid), aesculin, umbelliferone, and scopoletin are common in plants both in the free state and as glycosides
• Plants containing coumarins


  • Tonco seed (Dipteryx odorata) - content: coumarin, uses: used in perfumery
  • Celery fruit (Apium graveolens) - content: terpenes, coumarins, uses: treatment for rheumatic diseases
• Anthraquinones and glycosides


  Rhubarb, aloes, senna and cascara were recognized as forming a natural group of purgative drugs, with 2 close identical structures: emodin and alizarin
• Anthraquinone derivatives


  May be dihydroxy phenols such as chrysophanol, trihydroxy phenols such as carminic acid
• Anthranols and anthrones


  Reduced anthraquinone derivatives that occur either free or combined as glycosides, are the main constituents of chrysarobin
• Oxanthrones


  Give anthraquinones on oxidation, an oxanthrone has been reported as a constituent of cascara bark