TANNINS

1. Tannins
Chemically:mixture of polyphenols.
Difficulttoseparate because not crystallize able .
Chromatographicmethods.
Chemical classification:basedon
1) Identityof phenolicnuclei andonthe waytheyare joined i.e Gallicaid,polyhydriccompounds
esterifiedwithglucose.
These esterhydrolysistogive phenolicacidandsugar.So called Hydrolysable Tannins.
2) Non-Hydrolysable/CondensedTannins:polyphenoliclinkedtocarbohydratesandproteins,
resultfromcondensationof twoormore flavan-3-olsi.e (Catechin) orof flavan-3,4-diolsi.e
(Leucocyanidins) andwhentreatwith hydrolyticagent,thesetanninstendpolymerizedyield
insolublered-colorPHLOBAPHENES.
Tanninsare Non-crystallize compounds.
Whentreated withwaterto formcolloidal solutionspossesacidreactionandsharppuckeringtaste.
Tanninscausr ptecipitationof solutionof gelatinandalkaloids.
Tannonsformdark blue or greenish-blacksoluble compoundwithferricsalt.
It givesdeeptedcolourwithpotassiumferriccyanide andammonia.
Theyare precipitate bysaltof copper,leadandtinand strongaqueouspotassiumdichromate solution.
In alkaline solutionthere manyderivativesabsorboxygen.
Tanninsprecipitate proteinfromsolutionandcombine withproteinandrenderingthemresistantto
proteolyticenzymeswhenappliedtolivingtissues.Thisactionisknownas astringent.
Tanninsare usedin GIT disturbances.
As astringent.
On skinabrassionsandburns.
Tanninsprecipitatesoutthe proteinsof exposedtissuesandformmildlyantisepticprotective coat
underwhichregenerationof newtissuestakesplace .
Prolongeduse of Tanninscause hazardous;

2. 1) Habitual chewingof Betel nuts(Arecacatechu) alkaloidcontainingdrugrichincondensed
Catechin-tannincause highrate of oral and esophageal cancerinIndiaandSouthAfrica.
2) Drinkordinarytea leaves (Camelliasinensis).Britishaddmilktotea to reduce esophageal
obstruction.
3) Experimently subcutaneousINJof tanninrichArecacatechu andRhus capallinacause malignant
mesenchymal tumorinrats.
Tanninsabilitytoprecipitatesoutproteinusesinprocessof vegetable tanning,whichconverts
animal hidestoLeather,butalsoas preservative because of antisepticquality.
USES
1) Varietyof Leathers:Hydrolysable typesform“Bloom”.
2) Non-Hydrolysableproduce tanner’sred.
3) Deeplycolouredcompoundsobainfromironsaltusedoncommercial scale inmanufacture
of inks.
4) Tanninsbecause of precipitationqualityusedaslaboratoryreagentindetectionof gelatin,
proteinandalkaloids.
5) Antidotal treatmentof alkaloidalpoisoningandinactivate alkaloidbyforminginsoluble
tannate.
PLANTS CONTAININGTANNINS
1) NUT GALL
2) KINO
3) MYROBALAN
4) CATECHU
5) CASTANEA
6) KRAMERIA
NUTGALL
Excresence obtainfromyoungtwigsof Quercusinfectoria.
Excrescence cause byincisionof Hymenopterousinsect(Cynipstinctoria)
CONSTITUENTS
Tannicacid 50-70%
Gallicacid 2-4%
Ellagicacid

3. Starch
Resin
USES:
1) Tanning
2) Dyeingindustry
3) Inkmanufacturing
4) Astringent