Chapter 9 tanins

1. Tannins

2. Objectives
– Definition of Tannins
– Introduction
– Classification
– Test for tests
– Tannin from plant source
– Pharmacognostic features of tannins source

3. – Complex organic, non-nitrogenous plant products.
– Derivatives of polyhydroxy benzoic acid (polyphenols).
– Ability to precipitate proteins
– Having high molecular weight (500 to > 20000).
– Historically, tannin containing drugs are related to their
tanning property i.e. their ability to transform fresh hides
into imputrescible leather.

4. – The consequence of tanning is the formation of bonds between the
collagen fibers in the hide, which imparts resistance to water, heat, and
abrasion.
– This capability of tannins to combine with macromolecules explains why
they precipitate cellulose, pectins, and proteins
– It also explains their characteristic astringency and tartness: by
precipitating the glycoproteins contained in saliva, tannins make the latter
lose its lubricating power.

5. Classification of tannins
– based on Goldbeaters skin test
positive
tanning test
negative
tanning test
True tannin Psedutannin

6. True tannins
Hydrolysable
tannins
Non Hydrolysable
tannins

7. Hydrolysable tannins
– These are ester of sugars and phenolic acid molecules
– Mineral acids
– Tannase
Sugar
part
Phenolic acid

8. – Phenolic acid either
– Gallic acid or Ellagic acid
Gallotannins
Ellagitanninse.g:
• rhubarb
• Gall
• Clove
e.g:
• pomegranate
• eucalyptus

9. – on dry distillation are converted to pyrogallol derivatives.
– The hydrolysable tannins are soluble in water and their solution produces
blue color with ferric chloride.

10. Condensed tannins
– Proanthocyanidins
– They consist of flavan-3-ol units
linked together by carbon-carbon
bonds
– most often 4 8 or 4 6

12. – Condensed tannins occur due to polymerization
(condensation) reactions between flavonoids.
– The polymers may include up to 50 monomer units.
– On treatment with acids or enzymes condensed tannins are
converted into red insoluble compounds known as
phlobaphenes.
– Phlobaphenes give the characteristic red colour to many drugs
such as red cinnamon bark.

13. – On dry distillation, they yield catechol derivatives.
– Condensed tannins are also soluble in water and produces green color with
ferric chloride.

14. Pseudotannins
– They are compounds of lower molecular weight than true tannins and they do not
respond to the goldbeater's skin test.
– Examples of drugs containing Pseudotannins are:
Gallic acid: Rhubarb
Catechins: Guarana, Cocoa
Chlorogenic acid: Mate, Coffee
Ipecacuanhic acid: ipecacuanha

15. Gallic acid
COOH
OH
OH
HO
Catechin
OHO
OH
OH
OH
OH
Chlorogenic acid
O
O
OH
HO
OHHOOC
OH
OH

16. Properties and tests of tannins
– Tannins are soluble in water, dilute alkalis, alcohol, glycerol and acetone, but
generally only sparingly soluble in other organic solvents.
– Solutions precipitate heavy metals, alkaloids, glycosides and gelatin.
– With ferric salts, gallitannins and ellagitannins give blue-black precipitates and
condensed tannins brownish-green ones.

17. 1. Goldbeater's skin test
Soak a small piece of goldbeater's skin in 2% hydrochloric acid;
rinse with distilled water and place in the solution to be tested
for 5 min. Wash with distilled water and transfer to a 1%
solution of ferrous sulphate. A brown or black colour on the skin
denotes the presence of tannins.
 Goldbeater's skin is a membrane prepared from the intestine of
the ox and behaves similarly to an untanned hide.

18. – 2- Phenazone Test:
– To 5 ml of aqueous solution of tannin containing drug, add 0.5
g of sodium acid phosphate. Warm the solution, cool and filter.
Add 2 % phenazone solution to the filtrate. All tannins are
precipitated as bulky, colored precipitate.
– 3- Gelatin Test:
– To a 1 % gelatin solution, add little 10 % sodium chloride. If a 1
% solution of tannin is added to the gelatin solution, tannins
cause precipitation of gelatin from solution.
– 4- Bromine water:
– only condensed tannin gives ppt. with bromine water

19. Uses of Tannins
– Industrially; in leather tanning, ink manufacture.
– Medicinally; astringent, haemostatic, antidiarrheal, antidote in alkaloid and
heavy metals toxicity.
– In labs; reagent for detection of proteins, alkaloids and heavy metals
because of their precipitating properties.

20. Biosynthesis of
tannin

21. – A general schematic diagram of the flavonoid biosynthetic
pathway. CHI, chalcone isomerase; CHS, chalcone synthase;
F3H, flavonoid 3-hydroxylase; F3′H, flavonoid 3′-
hydroxylase; FLS, flavonol synthase; DFR or BAN,
dihydroflavonol reductase; LAR, leucoanthocyanidin
reductase; ANS, anthocyanidin synthase; ANR,
anthocyanidin reductase; UFGT, glucose transferase.

22. Kino
Kino is the name of the plant gum produced by various plants and trees,
particularly Eucalyptus, in reaction to mechanical damage, and which can be
tapped by incisions made in the trunk or stalk.

23. – Its red colour, together with the tendency of some species
to ooze large amounts of it from wounds, is the source of
the common names "red gum" and "bloodwood". The word
“kino” is of West African origin.

24. Chemical composition
– Astringent tannin compounds are a major active
component of kinos.
– The chief constituent of kino is kinotannic acid, of which it
contains 70 to 80 per cent. It also contains kino red,
a phlobaphene produced from kinotannic acid by oxidation.
– Kino also yields kinoin, a crystalline neutral principle.

25. – In cold water it is only partially dissolved, leaving a
pale flocculent residue which is soluble in boiling water but
deposited again upon cooling.
– It is soluble in alcohol and caustic alkalis, but not in ether.

26. – When exuding from the tree, it resembles red-currant jelly,
but hardens in a few hours after exposure to the air and
sun
– Kinos typically dry to an amber-like material.

27. – It consists of dark red angular fragments, rarely larger than
a pea.
– Of the small angular glistening fragments, the smaller are
reddish, and the larger are almost black; thin pieces are
ruby red.
– a It is brittle and easily powdered. It has no smell, but a
very astringent taste.[

28. Application
– Kinos are used in medicine, tanning, and as dyes
– Kino is not absorbed at all from the stomach and only very
slowly from the intestine.
– The drug was frequently used in diarrhoea, its value being
due to the relative insolubility of kinotannic acid, which
enabled it to affect the lower part of the intestine.

29. Myrobalan
– ‫رڑ‬َ‫ہ‬ ‫۔‬ ‫ہڑ‬ ‫۔‬ ‫ہلیلہ‬

30. Introduction
– Terminalia chebula, commonly known as black- or chebulic
myrobalan,is a species of Terminalia, native to South
Asia from India and Nepal east to southwest
China (Yunnan), and south to Sri Lanka, Malaysia,
and Vietnam.

31. Chemical compositon
– triterpenes arjunglucosid I, arjungenin, and
the chebulosides I
– Other constituents include a coumarin conjugated with
gallic acids called chebulin, as well as other phenolic
compounds including ellagic acid, 2,4-chebulyl-β-D-
glucopyranose, chebulinic acid, gallic acid, ethyl
gallate, punicalagin, terflavin A, terchebin, luteolin,
and tannic acid

32. Application
– Asthma
– Acid reflux
– Aphthous stomatitis is a common condition characterized
by the repeated formation of benign and non-
contagious mouth ulcers (aphthae) in otherwise healthy
individuals. The informal term canker sores is also used,
mainly in North America, although this may also refer to
any mouth ulcer.

33. Catechu
– Catechu is an extract of acacia trees used variously as a
food additive, astringent, tannin, and dye.
– It is extracted from several species of Acacia, but
especially Senegalia catechu (Acacia catechu), by boiling
the wood in water and evaporating the resulting brew.
‫کتھا‬

35. Chemicals and its uses
– As an astringent it has been used since ancient times
in Ayurvedic medicine as well as in breath-freshening spice
mixtures—for example in France and Italy it is used in
some licorice pastilles.
– It is also an important ingredient in South Asian
cooking paan mixtures, such as ready-made paan
masala and gutka.

36. Cont..
– The catechu mixture is high in natural
vegetable tannins (which accounts for its astringent effect),
and may be used for the tanning of animal hides.

37. Nutgall ‫گٹھی‬ ‫ماجو‬

38. Intro of Nutgall
– Quercus infectoria (Aleppo oak) is a species of oak, bearing galls that
have been traditionally used for centuries in Asia medicinally.
– Chemical constituents The main constituents found in the galls of
Quercus infectoria are
– tannin (50-70%) and
– small amount of free gallic acid and ellagic acid.

39. Uses
– astringent, antidiabetic,
– antitremorine, local anaesthetic,
– antiviral, antibacterial,
– antifungal, larvicidal
– anti-inflammatory activities.

40. – Tremorine is a drug which is used in scientific research to
produce tremor in animals.
– This is used for the development of drugs for the treatment
of Parkinson's disease, as tremor is a major symptom which
is treated by anti-Parkinson's drugs.
– Beta blockers are also effective in counteracting the effects
of tremorine.

41. Uses of nutgall
– antiamoebic,
– anticariogenic
– anti-inflammatory activities,
– to treat skin infections
– gastrointestinal disorders.

42. Castanea or Chestnut
– The chestnut group is a genus (Castanea) of eight
or nine species of deciduous trees and shrubs in
the beech family Fagaceae, native
to temperate regions of the Northern
Hemisphere.

43. Chemical constituents
– starch
– sugars, mainly sucrose, glucose, fructose,
and, in a lesser
amount, stachyose and raffinose
– Tannins
– Vitamine
– Minerals

44. Uses
– The fruit can be peeled and eaten raw, but it can
be somewhat astringent, especially if the pellicle
is not removed
– Chestnuts can be dried and milled into flour,
which can then be used to prepare
breads, cakes, pies, pancakes, pastas, polenta

45. Krameria
– Krameria is the only genus in the Krameriaceae family, of
which any of the approximately 18 species are commonly
known as Rhatany, ratany or rattany.
– The biological action of rhatany is caused by
the astringent rhataniatannic acid, which is similar to tannic
acid. Infusions have been used as a gargle, a lozenge,
especially when mixed with cocaine, as a
local hemostatic and remedy for diarrhea.

46. – When finely powdered, the dried roots furnished a
frequent constituent of tooth powders.
– The powdered roots have also served, especially
in Portugal, to color wines ruby red.
– The root bark contains an almost insoluble free red
substance called ratanhia red.

47. – Add 10 of alcohol to the drug, to moisten it, and complete
the percolation process.
– Tincture of krameria is used internally as an astringent, and
externally to make a mouth wash or gargle by adding one
teaspoonful to a wineglassful of water, for inflamed and
spongy gums.