tannins.pptx

TANNINS
MOSTAFA MAHMOUD HEGAZY PH.D

Tannins
 Phenolic compounds
 Precipitate animal proteins in hides
and converting them into leather.
“Tanning Industry”
 Present in plants, ex. grapes, cranberry,
hamamelis and tea leaves.

Classification of tannins
1- True tannins: High molecular weight from about
1000 to 5000 amu.
2- Pseudotannins: (low molecular weight )
 Give negative goldbeater's skin test
 Concentrated solutions, give precipitates with gelatin
 Gallic acid: Galls, rhubarb and most drugs that contain
gallitannins
 Catechins: Catechu, cocoa and most drugs containing
condensed tannins.
 Chlorogenic acid: Coffee particularly when unroasted.
 Ipecacuanhic acid: Ipecacuanha.

Classification of true tannins:
 1- Hydrolysable tannins (pyrogallol tannins)
 A- Gallitannin: On hydrolysis , it gives gallic acid
and glucose ex. clove.
 B- Ellagitannin: On hydrolysis it gives ellagic acid
and glucose ex. pomegranate.
 2- Condensed tannins (catechol tannins):
polymeric flavan-3-ol
 3- Complex tannins
Ellagic acid

Hydrolysable tannins (pyrogallol tannins)
 Hydrolyzed by acids or enzymes such as
tannase (rumen bacteria).
 Formed from several molecules of gallic and
hexahydroxydiphenic acids united by ester
linkages to a central sugar (mainly glucose).
 Their solutions turn blue with iron salts like
gallic acid.
Tannic acid

Hydrolysable tannins (pyrogallol tannins)
 On dry distillation gallic acid and similar
components are converted into pyrogallol.
 Gallitannins: Rhubarb rhizome, clove buds, red
rose petals, galls, hamamelis leaves and chestnut
bark.
 Ellagitannins: Pomegranate rind and bark,
eucalyptus leaves, myrobolan and oak bark.
Ellagic acid
gallic acid
Hexahydroxydiphenic acid

Tannic acid
Grandinin
1,2,3,4,6-Pentagalloyl glucose

Condensed tannins (Catechol) (proanthocyanidins)
 not readily hydrolyzed and no sugar moiety.
 polymeric flavan-3-ol structures (usually di- and trimers).
 On dry distillation they yield catechol.
 their solutions turn to green with ferric chloride like
catechol .

On treatment with acids or enzymes converted into phlobaphenes
(phlobatannins).
 Phlobaphenes give the characteristic red color to many drugs such as
red cinchona bark
Barks: e.g. cinnamon, hamamelis and cinchona.
Roots and rhizomes: e.g. krameria and male fern.
Flowers: e.g. lime and hawthorn.
Seeds: e.g. cocoa, kola and areca.
Leaves: e.g. hamamelis, hawthorn and tea, especially green tea.
Extracts and dried juices: catechu and Indian kino.

COMPLEX TANNINS
 These represent a group of tannins that are
biosynthesized from both hydrolysable
tannin and condensed tannin. (mostlya C-
glucoside ellagitannin) (flavono-ellagitannin)
 Members of Fam. Combretaceae, Myrtaceae
and Fagaceae


IDENTIFICATION OF TANNINS:
1-tannin + ferric chloride (FeCl3) :
Bluish black colour with hydrolysable tannin.
Brownish black colour with catechol.
2-Gelatin test: Solution of tannins (about 5-1%) precipitate 1% Solution of
gelatin containing l0 % sodium chloride Gallic acid and other
pseudotannins also precipitate. gelatin if the solutions are sufficiently
concentrated.
3- Bromine water: only condensed tannin gives ppt. with bromine water.

4-Gold beater's skin test:
a soak a small piece of Gold beater's skin membrane in 2%
hydrochloric acid ( HCL).
b- rinse with distilled water.
c- place the piece for 5 minutes in the tannin solution to be
tested.
d- wash with distilled water
e- transfer to 1% ferrous sulfate (FeSO4) solution.
f- a brown or black colour in the skin denote the presence of
tannins.

Quantitative determination of tannin:
1- Hide powder method:The difference in the dry weight of the
extract before and after treatment with hide powder is taken as a
measure for tannin content.
2- Copper acetate method: Gravimetric method using copper
as precipitant.

Uses of Tannins:
Medicinally: Astringent, haemostatic, antidiarrheal, potent
antioxidant, an antidote in alkaloid and heavy metals toxicity.
 Skin toner: (as general but Hamamelis is common cosmetics ingredient)
1- Anti-inflammatory properties minimize redness and inflammation.
2- Reduce cell damage as antiaging agent, tannins act as an antioxidant
against free radicals.
3- As a natural astringent, they help remove excess oil from and
constricting pores without drying out the skin.

 uses
 coffee chlorogenic acid slimming and protect from diseases related
oxidative stress (diabetes and cardiovascular diseases)
 treatment of burns.
 They act as anti-diarrheals, although not recommended ?? in this
respect as they usually delay elimination of bacterial toxins from the
body. ex. albumin tannate
 Tannins have been employed as antidote in poisoning by heavy metals,
alkaloids and certain glycosides due to their precipitation as tannates.

Uses of hamamelis tannins
1- inflammatory skin conditions e.g. Acne
2- Hemorrhoids and varicose veins
3- Inflammation of prostate
4- skin preparations as antiaging and anti-
wrinkle
5- Internally acute, non-specific diarrhea

Cranberry
Constituents:
- Proanthocyanidins,
Action and uses:
- Treatment and prophylaxis of cystitis and urinary tract
infections.
- Prophylaxis of formation of kidney stones.
Mechanism of action:
Anti-adherence action Uropathogenic E. coli adhere to the mucosal
cells of the urinary bladder by adhesins on the pili that protrude
from their surfaces.
Cranberry proanthocyanidins reduces the ability of bacteria to
adhere to the cells lining the wall of the bladder and urethera
thus flushing it out of the body before they can do damage.
Dosage: 400 mg of a concentrated cranberry juice extract 2 to 4
times per day.

Pine Bark
‫الصنوبر‬ ‫لحاء‬
Origin: dried stem bark of pinus pinaster, family
Pinaceae
Active constituents :
Tannins: proanthocyanidins (condensed tannin)
Flavonoids like catechin, epicatechin
the extract called "Pycnogenol®“
Uses:
Antioxidant, Anti-inflammatory, Antimicrobial and
Capillary Fragility treatment
antiaging of skin

 Major sources of commercial tannins ,
rehtael ni esu rof
,yrtsudni
era
deniatbo
morf chestnut bark trees.
 Pharmaceutical tannin is prepared from oak galls.
Chestnut bark Castalagin
Oak galls Tannic acid

Uses of Tannins:
Industrially:In leather tanning, ink manufacture.
In labs: Reagent for detection of proteins, alkaloids and heavy metals
because of their precipitating properties.
• grapeseed extract tannins medicinal uses and Egyptian products (if any)
• tea extract tannins medicinal uses and Egyptian products (if any)
• Hawthorn tannins

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