Tannins

For B.Pharm, 5th Semester

1. Mr. SonamBhutia

4. Introduction
The term tannin was first time coined by
Seguin in 1796.
This term was used to denote substances
present in plant extract which react with
protein of animal hide, prevent their
putrefaction and convert hide and skin
into leather.

5. Definition
“Tanninisanastringents,polyphenolicbiomoleculesthatbinds
to&precipitatesproteins&variousotherorganiccompounds
includingaminoacids&alkaloids.”
OR
“Tannins are polyhydroxy phenolic compounds.”
-Any large polyphenolic compound containing sufficient
hydroxyl & carboxyl to form strong complexes with various
macromolecules.
-the word “tan” & “tanning”-German word which are used
for the treatment of leather.

6. Examples

7. Physical Properties
Color: Dark brown or reddish brown
Taste: Puckering taste
State: Non-crystalline
Solubility: Soluble in water, alcohol, dilute alkalis, glycerols
and acetone.

8. Chemical properties
(i) Precipitation
(ii) Anti-oxidizing properties
(iii) Astringent
(iv) Carcinogenicity
(v) Reaction with salts
(vi) Reaction with potassium ferricyanide and ammonia

9. (i) Precipitation
Tannins have ability to precipitate solutions of;
Gelatin
Alkaloids
Glycosides
Heavy metals
Proteins
(ii) Anti-oxidizing properties
Because of accumulation of OH group on small size nucleus,
these agents have anti-oxidant nature.

10. (iii) Astringent
Tanninshavepropertytoreactwithproteinofmucous
membraneandcauseprecipitation.
(iv) Carcinogenicity
Prolong use of tannin containing plant material is hazardous
because it causes cancer. Habitual use of Areca catechu can
cause oral and esophageal cancer.

11. (v) Reaction with salts
(vi) Reaction with potassium ferricyanide and
ammonia

12. Importance of tannins
Medicinal Uses:
Antidote
Antiseptic
Algicidals
Astringents
Anti-carcinogenic
Industrial Uses:
Ink manufacture
Vegetable tanning
Preservatives
Biological Activities:
Inhibition of lipid per oxidation
Decrease in blood urea nitrogen
content
Inhibition of plasmin
Lipolysis in fat cells

13. Tannins
Hydrolysable tanninsCondensed tannins Complex tannins
1. Chemical Classification
Basedonidentityofphenolicnucleiinvolvedandonthe
waytheyarejoined.

14. (i) Hydrolysable tannins
•Thesetanninsarehydrolyzedbyenzymesoracidsand
theproductsofhydrolysisaregallicacidorellagic
acids.
•Theexamplesofhydrolysabletanninsaregallotannin
innutgall,rhubarb,cloveandchestnut;ellagitannin
fromoak,myrobalansandpomegranatebark
Precursors:
Phenolicacid(Gallicacid,Ellagicacid)
Glucoseresidue
Betweenphenolicacidsandglucosesugar,thereisester
linkage

15. Hydrolysable tannins
Gallitannins Ellagitannins
Properties:
Types:

16. EllagitanninsGallitannins
Pomegranate
Eucalyptus
Rhubarb
Clove
Hamamelis
Occurrence
Upon acid hydrolysis
of Ellagitannins,
Ellagicacid is
produces.
Upon acid hydrolysis
of Gallitannins, Gallic
acid is produces.
Hydrolysis
* Slowly soluble in
water.
* Present in plants in
open and ring forms
as Hexa hydroxy
diphenic acid.
* Rapidly soluble in
water.
* Free Gallic acid, in
plant, is converted to
gluco Gallitannins.
Properties

17. (ii) Condensed tannins
•Theyarealsocalledasnon-hydrolysabletannins,
phlobatanninsorproanthocyanidins.
•Theyarerelatedtoflavonoidpigments,becausetheyare
formedviaderivativesofflavones,likecatechinorflavan-3-ol
orflavan-3,4-diols.
•Theyaremuchresistanttohydrolysis.
•Unlikethehydrolysabletannins,ontreatmentwithenzymesor
mineralacids,theyarepolymerizedordecomposedintored
colouredsubstancescalledphlobaphenes,whichareinsoluble
inwater.
Precursors:
Flavonoid
Catechin
Flavonol-3-4-diol

18. Properties:
Examples:
Hamamelis
Cinchona
Cinnamon
When heated with acids, these are self condensated, polymerized
and converted to insoluble red colored complexes, called
Phlobaphenes.

19. (iii) Complex tannins
•Thesetanninsaremixturesofboth,hydrolysableand
condensedtannins
Examples:
Tea-Camellia sinensis
Quercus-Quercusrobus
Castanea-Castaneasativa

21. Tannins
True tannins Pseudo tannins
2nd Classification
Tanninisasubstancewhichisdetectedqualitativelybytanning
test(TheGoldbeater’sskintest)andquantitativelybyits
adsorptiononstandardhidepowder.
Depending upon this, tannins are of two types;
i) True tannins
ii) Pseudo tannins

22. Pseudo tanninsTrue tannins
Phenoliccompounds of plant
origin that don't convert animal
hide to leather but do give
positive Gold beater’s skin test,
are called pseudo tannins.
Polyhydroxyphenolic
compounds which convert
animal hide to leather by
precipitating proteins and give
positive Gold beater’s skin test,
are called true tannins.
Molecular weight is less than
true tannins.
Molecular weight is 1000-5000

23. Identification tests
Color reaction:
Tannins give color reaction with iron.

24. Identification tests
Matchstick test:
Dip matchstick in plant extract.
Dry it.
Moisten it with hydrochloric acid. And warm near flame.
Wood will turn pink or red in color due to phloroglucinol.
Gelatin test:
Solution of tannin (0.5%-1%) precipitates 1% solution of
gelatin containing 10% sodium chloride.

25. Identification tests
Phenazone test:
Take 5ml of aqueous extract of drug.
Add 0.5grams of sodium acid phosphate.
Warm it and cool.
Filter solution.
To the filtrate, add 2% solution of Phenazone.
Tannins will be precipitated.
Precipitates will be bulky and colored.

26. Identification tests
Gold beater’s skin test:
Gold beater’s skin is a membrane prepared from intestine of
Ox and behaves similarly to un tanned skin.
-Soak a small piece of Gold beater’s skin in 2% hydrochloric
acid.
-Rinse it with distilled water.
-Place it in solution to be tested for 5 minutes.
-Wash it with water and transfer to 1% solution of ferrous
sulphate.
-Black or brown color of skin indicates presence of tannins.
It is a quantitative test and +ive only for true tannins

27. Identification tests
Catechin test:
Catechin when heated with acid produce phloroglucinol.
Phloroglucinol can be detected with matchstick test.
Test for chlorogenic acid:
Treat extract containing chlorogenic acid with aqueous
ammonia and expose it to air. Green color will appear
gradually.

28. Tannins containing crude drugs
Hydrolysable tannins
-Myrobalan
-Bahera
-Arjuna
-Tannic acid
-Amla
•Condensed tannins
-Ashoka
-Black catechu
-Pale catechu
-Pterocarpus

29. Myrobalan
Synonym-Chebulic myrobalan, Harde,
Haritaki
B. Source-It consists of dried, ripe & full
matured fruits of Terminalia chebula, family-
Combretaceae
G. Source-Sub-himalayn track from Ravi to
West bengal, Assam, Bihar, Maharashtra, Madhya
Pradesh.
Cultivation-It is found growing at an altitute
of 1800m.
-It is not cultivated & fruits are collected from wild
growing forest plants.
-It is a tree, 15m in height, & 1.5 to 2.5m in diameter
-The tree is rounded crowned with spreading
branches & ovale leaves.
-It has yellowish-white flowers in the terminal spike.

30. Macroscopic characters
Colour-fruits are yellowish-brown
Odour-Odourless
Taste-astringent, slightly bitter & sweetish the end
Size-20-25mm long & 15-25 mm wide
Shape-Ovate & wrinkles longitudinally

31. Chemical constituents
Myrobalanfruitsareanimportantsourceoftannins.
Tanninsofmyrobalanareofpyrogallol
type(hydrosabletannins),yieldchebulicacid&d-
galloyl.
Chebulic,chebulinic,ellagic&gallicacidsarethe
othercontentsofmyrobalan
Uses-Astringent, laxative, stomachic & tonic. The
laxative property of myrobalan is due to anthracene
derivative present in the pericarp. Ingredient in the
formulation of Triphala.

32. Amla
Synonym-Emblica, Indian goose
berry, Amla
B. Source-It consists of dried, as well
as fresh fruits of the plants Emblica
officinalis. Family-Euphorbiaceae.
G. Source-Found in all deciduous
forest of India, Sri lanka, & Myanmar.

33. Cultivation & collection
It is grown by seed germination or propagated by
budding/cutting
It doesn't tolerate the frost or drought
It is normally found up to an altitude of 1500m
Seeds or seedlings are placed at a distance of 4.5 x 4.5m in red
loamy or coarse gravelly soil
Proper irrigation is required, drip irrigation is most suitable
Fertilizer in the dose-range of 750-900gms of Urea, 1kg-
superphosphate or 1-1.5kg potash per annum are sufficient
Pruning is done regularly & 4-6 branches about 0.75-1m
above the ground are retained
Cultivated plants bear comparatively large fruits. The tree
flowers in hot season & the fruits ripen during the winter.

34. Chemical constituents
Amla is a rich natural source of Vitamin-C.
Apart from that, fruits also contain about 0.5% fat,
phyllemblin & 5% tannin.
Amla fruits are also rich in mineral matters like
phosphorous, iron & calcium.
The fresh fruits contain about 75% mosture,
The fruits are dehydrated and stored. It is found that
vitamin content of dried fruit is not lost considerably
due to the presence of tannins, which retads oxidation
of Vit-C.

35. Identification tests
Alcoholic or aqueous extract of the crude drugs gives
blue colour with ferric chloride solution.
To aqueous extract add gelatin & sodium chloride,
milky white colour is produced.
Uses-diuretic, refrigerant & laxative.
--Dried fruits are given in diarrhoea & dysentery,
asthma & bronchitis
--Also useful in jaundice, dyspepsia & anaemia
-Prepn. Of Triphala & Chyawanprash , inks, hair
oils & shampoo.
-Possesses antioxidant property

36. Arjuna
Synonym-Arjuna bark,
Arjuna
B. Source-Arjuna consists of
dried stem bark of the plant
known as Terminaliaarjuna,
Family-Combretaceae
G. Source-Indian peninsula,
chotta-Nagpur region, North
east regions.

37. Cultivation & collection
Arjuna is found as naturally growing plant in the dense
forests
Arjuna can be successfully raised by sowing seeds
The seeds take about 21 days for germination
It needs moist fertile alluvial soil & rainfall in the range
of 75-190cm
It required the temperature of upto 45 degree
centigrades
The bark is also collected from wild growing plants & it
is reported that yield per tree varies from 9-55kg

38. Macroscopic characters
Colour-Colour of outer side as well as inner side of
bark is identical & is greyish-brown.
Odour-None
Taste-Astringent
Size-the pieces of various sizes, about 15 x 10cm
Shape-Flats

39. Chemical constituents
Arjuna contains about 15% of tannns(hydrosable)
Other Triterpenoid saponin, Arjunolic acid, β-
Sitosterol, Ellagic acid, Arjunic acid,
Crystallisable compounds-Arjunine & Arjunetine

40. Uses
Usedasacardio-tonic,cardioprotective,
antdysenteric.
Possessesdiuretic&tonicproperty
Thedrugsexhibitshypotensiveactionwith
vasodilation&decreasedheartrate.
ThediureticactivityofArjunabarkisduetoArjunolic
acid
Adulterant-Terminalia tomentosa

41. BLACK CATECHU PALE CATECHU
1.It is a tree 1. It is a climber-shrub
2. Itis obtained from the heart wood of the
plant-Acacia catechu, family-Leguminosae
2. It is obtained from the dried aqueous
extract prepared from leaves & young twigs
of shrub-Uncariagambier, family-
Rubiaceae
3. colour-light brown to black 3. Colour-Cinnamon brownin colour
4. Its synonym is Kattha 4. Itssynonym is Gambier
5. Active constituents-10% acacatechin, 30%
catechutannicacid
5. Active constituents-22-50% caechutannic
acid, 7-33% catechin,catechu red, quercetin
& gambirfluorescin
6. Do not contain any crystal or fluorescin
pigment(chlorophyll)
6. Contain crystal(phobaphene, chlorophyll)
7. Geographicalsource-India & Burma 7. Geographicalsource-Malayasia&
Indonesia
8. Gives -veresult for gambierfluorescintest8. Gives +veresult for gambierfluorescin
test