TANNINS TANNINS -- IIIIII

M. Ahsan Khalid, M. Ahsan Khalid, B.PharmB.Pharm, Pharm. D, Pharm. DM.PhilM.Phil Scholar (RIPS/RIU)Scholar (RIPS/RIU)

HIPSHIPS--HUKICHUKIC

PHARM. DChemical Pharmacognosy- I

Lecture 32 May 19th, 2011

Condensed TanninsCondensed Tannins

Are Are polymerspolymers of 2 to 50 (or more) of 2 to 50 (or more) flavonoidflavonoid unitsunits that are joined by carbonthat are joined by carbon--carbon bonds, which are not susceptible to carbon bonds, which are not susceptible to being cleaved by hydrolysis.being cleaved by hydrolysis.

All hydrolyzable tannins and most All hydrolyzable tannins and most condensed tannins are water soluble condensed tannins are water soluble --some some very largevery large condensed tannins are condensed tannins are insolubleinsoluble..

Condensed TanninsCondensed Tannins Condensed tannins are oligomeric and polymeric proanthocyanidins

consisting of coupled flavan-3-ol (catechin) units.

(oligomeric or polymeric proanthocyanidins =condensed proanthocyanidins = condensed tannins).

Biosynthetically the condensed tannins are formed by the successive condensation of the single building blocks (up to more than 50 may be included in a single condensed tannin).

The coupling pattern of the catechin units in condensed tannins can vary considerably.

NOTE:Oligomeric: a polymer that consists of 2, 3, or 4 monomeres.

Polymer: Any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule.

Condensed Condensed Tannins/ProanthrocyanidinsTannins/Proanthrocyanidins

They are not readily hydrolysed to simpler They are not readily hydrolysed to simpler molecules and they do not contain a sugar molecules and they do not contain a sugar moiety (unlike hydrolysable tannins).moiety (unlike hydrolysable tannins).

On treatment with On treatment with acidsacids or or enzymesenzymes, , condensed tannins are converted into condensed tannins are converted into redredinsoluble compounds known as insoluble compounds known as phlobaphenesphlobaphenes. .

Condensed Condensed Tannins/ProanthrocyanidinsTannins/Proanthrocyanidins

PhlobaphenesPhlobaphenes give the give the characteristic red colourcharacteristic red colourto many drugs such as red to many drugs such as red cinchona barkcinchona bark, which , which contains these phlobatannins and their contains these phlobatannins and their decomposition products. decomposition products.

These tannins are therefore sometimes called These tannins are therefore sometimes called catechol tannins (as they yield catechol)catechol tannins (as they yield catechol). .

Like catechol itself, their (condensed tannin) Like catechol itself, their (condensed tannin) solutions turnsolutions turn greengreen withwith ferric chloride.ferric chloride.

Plants rich in Condensed TanninsPlants rich in Condensed Tannins BarksBarks: cinnamon, wild cherry, cinchona, willow, : cinnamon, wild cherry, cinchona, willow,

acacia (wattle, mimosa), oak bark, acacia (wattle, mimosa), oak bark, HamamelisHamamelis..

FlowersFlowers: Lime and Hawthorn: Lime and Hawthorn

SeedsSeeds: cocoa, : cocoa, guaranaguarana, kola , kola

FruitsFruits: cranberries, grapes, hawthorn: cranberries, grapes, hawthorn

LeavesLeaves –– HamamelisHamamelis, hawthorn, tea leaves , hawthorn, tea leaves (especially green tea)(especially green tea)

Extracts and dried juices:Extracts and dried juices: catechu, acacia, East catechu, acacia, East Indian Indian kinokino and eucalyptus and eucalyptus kinokino

Complex TanninsComplex Tannins The structures of the

complex tannins are built up from a gallotannin unit or an ellagitannin unit, and a catechin unit.

Fig: Acutissimin A, the usual representative of the complextannins.

Hamamelis leaf & barkHamamelis leaf & barkSome drugs (e.g. tea, Some drugs (e.g. tea,

Hamamelis leaves Hamamelis leaves and Hamamelis bark) and Hamamelis bark) contain both contain both hydrolysable and hydrolysable and condensed tannins.condensed tannins.

HamamelisHamamelis LeafLeaf

Definition:Definition: Witch Witch hazel leaves consists hazel leaves consists of the dried leaves of of the dried leaves of Hamamelis virginiana,Hamamelis virginiana,Hamamelidaceae). Hamamelidaceae).

It should contain no It should contain no less than less than 30% 30% tannins.tannins.

HamamelisHamamelis FlowersFlowers

Witch hazel leaves Witch hazel leaves ––HamamelisHamamelis ConstituentsConstituents

GallitanninsGallitannins EllagitanninsEllagitannins Free gallic acidFree gallic acid ProanthrocyanidinsProanthrocyanidins Bitter principlesBitter principles Volatile oilVolatile oil

HamamelisHamamelis -- UsesUses

AstringentAstringent HaemostaticHaemostatic

(Both due to tannins)(Both due to tannins)

CatechuCatechu Definition:Definition: Gambir or Gambir or

pale catechu is a dried pale catechu is a dried aqueous extract prepared aqueous extract prepared from the leaves and from the leaves and young twigs of a climbing young twigs of a climbing shrub, shrub, Uncaria gambirUncaria gambir(Rubiaceae). (Rubiaceae).

It should be carefully It should be carefully distinguished from black distinguished from black catechu or cutch. The catechu or cutch. The plant is Native to plant is Native to Malaysia and Indonesia.Malaysia and Indonesia.

Catechu: UsesCatechu: Uses

Uses in medicine as Uses in medicine as an astringent.an astringent.

Catechu: ConstituentsCatechu: Constituents

CatechinsCatechins Catechutannic acidCatechutannic acid Catechu redCatechu red QuercetinQuercetin GambirGambir--florescinflorescin

Catechu: Allied DrugsCatechu: Allied Drugs

Cutch or black Cutch or black catechucatechu

BLACK CATECHU PALE CATECHU BIOLOGICAL SOURCE -. Heart wood of Acacia catechu /Aacacia chundraFamily- leguminosaePreparation:Pieces of heartwood are boiled with water till the drug is exhausted & the resulting solution is stored in clay pits wherein the semi solid mass known as cutch gets absorbed & the liquid remaining behind is dried & cut into small pieces. Chemical Constituents: Contains acacia catechin & quercetinChemical Test: 1. it gives a pink colour with vanillin & HCl2. aqueous extract of drug when treated with lime water gives a brown colour. Uses: Astringents, treatment of ulcers, diarrhoea, & in tanning industry.

BIOLOGICAL SOURCE -. leaves of Uncaria gambierFamily: rubiaceaePreparation: The leaves are boiled with water & resulting solution is concentrated to obtain pale yellow viscous solution which is further dried to obtain cylindrical pieces. Chemical Constituents:Pale catechu contains chlorophyll, catechu red & gambier fluorescein. Chemical Test: Alcoholic extract of drug when treated with NaOH & light pet ether shows green fluorescence. Uses: Same as black catechu General test for condensed tannins is the MATCH

STICK TEST: When a match stick is dipped in tannin extract followed by HCl & warmed near a flame it turns

pink in colour. The wood of the matchstick has lignin. Upon hydrolysis of the tannins due to HCl, phloroglucinol is formed which reacts with the lignin of the wood to produce the pink colour.

Kino’sKino’s

Kino:Kino: applies to a applies to a number of dried number of dried juices, rich in juices, rich in phlobatanninsphlobatannins. Were . Were formally used for their formally used for their astringent properties: astringent properties: diarrhoea (e.g. diarrhoea (e.g. lozenges)lozenges)

Include eucalyptus Include eucalyptus kino or red gum from kino or red gum from Eucalyptus rostrata.Eucalyptus rostrata.

Tannins Tannins -- PropertiesProperties

WaterWater--solublesoluble

Also soluble in dilute alkali, alcohol, Also soluble in dilute alkali, alcohol, glycerol and acetoneglycerol and acetone

Slightly soluble in other organic solvents.Slightly soluble in other organic solvents.

Solutions precipitate heavy metals, Solutions precipitate heavy metals, alkaloids, glycosides and gelatin.alkaloids, glycosides and gelatin.

Tannins Tannins Properties: Properties:

If a If a dilute ferric chloridedilute ferric chloride solution is added to an solution is added to an aqueous extract of aqueous extract of hamamelishamamelis leaves leaves (containing both types of tannins), a (containing both types of tannins), a blueblue colour colour is produced which then changes to is produced which then changes to orangeorange--greengreen as more ferric chloride is added.as more ferric chloride is added.

Free gallic acidFree gallic acid gives an gives an orangeorange colour with colour with potassium iodate.potassium iodate.

Tannin Properties: Hydrolysable or Tannin Properties: Hydrolysable or Condensed?Condensed?

With With ferric saltsferric salts, , gallogallo--tanninstannins and and ellagiellagi--tanninstannins give give blueblue--blackblackprecipitates.precipitates.

CondensedCondensed tannins give tannins give brownbrown--greengreen precipitates. precipitates.

Condensed tanninsCondensed tannins turn turn redred with with vanillinvanillin and and HCLHCL..

GalloGallo--tanninstannins give a give a pinkpink colour with colour with potassium iodate.potassium iodate.

EllagitanninsEllagitannins react (are coloured) with react (are coloured) with nitrousnitrous acidacid in the presence of in the presence of acetic acidacetic acid. Colour reaction: . Colour reaction: pinkpink purplepurple blueblue..

TLCTLC is used to analyze extracts (visualized under UV light and with is used to analyze extracts (visualized under UV light and with the reagents mentioned above)the reagents mentioned above)

HPLCHPLC can also be used.can also be used.

PseudoPseudo--TanninsTannins

PseudoPseudo--tannins are compounds of tannins are compounds of lower lower molecular weight than true tanninsmolecular weight than true tannins and they and they do do not respond to the goldbeater’s skin test.not respond to the goldbeater’s skin test.

Gallic acid:Gallic acid: rhubarb rhubarb Catechins:Catechins: catechu, acacia cutch, many catechu, acacia cutch, many

Australian kinos, cocoa, guarana and many Australian kinos, cocoa, guarana and many other drugs containing condensed tanninsother drugs containing condensed tannins

Chlorogenic acid:Chlorogenic acid: coffee (particularly unroasted) coffee (particularly unroasted) and nux Vormica (a small quantity only).and nux Vormica (a small quantity only).

Ipecacuanhic acidIpecacuanhic acid: ipecacuanha: ipecacuanha

COFFEECOFFEEBiological Source Biological Source --.: seeds of Coffee .: seeds of Coffee arabicaarabicaFamily: Family: RRubiaceaeubiaceaeGeographical Source Geographical Source --.: South India, Indonesia .: South India, Indonesia Collection: Collection: The unripe fruit is dark green & is collected when it turns red. The unripe fruit is dark green & is collected when it turns red.

Each fruit has 2 Each fruit has 2 loculeslocules containing one seed each. containing one seed each. Chemical Constituents: Chemical Constituents: Contains caffeine which is a salt of Contains caffeine which is a salt of chlorogenicchlorogenic acid, volatile oil acid, volatile oil

known as known as caffeolcaffeol, enzymes &other , enzymes &other phenolicphenolic principles. principles. Use:Use: Stimulant, diuretic & source of caffeine Stimulant, diuretic & source of caffeine Chem. Test:Chem. Test:1.Murexide test1.Murexide test-- caffeine when heated with caffeine when heated with HClHCl & potassium & potassium

chlorate gives a residue which on exposure to ammonia chlorate gives a residue which on exposure to ammonia vapoursvapours gives purple gives purple colourcolour. .

2.Caffeine forms a white precipitate with tannin solution2.Caffeine forms a white precipitate with tannin solution

TEATEA BIOLOGICAL SOURCE BIOLOGICAL SOURCE --.: prepared leaves .: prepared leaves

of of TheaThea sinensissinensis Family: Family: TheaceaeTheaceae GEOGRAPHICAL SOURCE GEOGRAPHICAL SOURCE --. India, . India, SrilankaSrilanka Chemical Constituents: Chemical Constituents: Caffeine, Caffeine, theobrominetheobromine, , theophyllinetheophylline, , oxidaseoxidase

enzyme & tannins enzyme & tannins Uses: & chem. Tests: Same as coffeeUses: & chem. Tests: Same as coffee

Camellia sinensis/Thea sinensisCamellia sinensis/Thea sinensis Polyphenols Polyphenols strong strong

antianti--oxidant effect.oxidant effect. Leaves: cancer Leaves: cancer

preventative (Japan).preventative (Japan). Clinical trials indicate that Clinical trials indicate that

green tea helps to green tea helps to promote weight loss and promote weight loss and treat hepatitis.treat hepatitis.

May prevent tooth decay.May prevent tooth decay. Trials show a hypotensive Trials show a hypotensive

effect.effect.

NB: GreenNB: Green--tea: caffeine tea: caffeine needed for effects.needed for effects.