(MIDTERM) Extraction of Tannins Flashcards
The term _______________________ to denote substances present in plant extracts which were able to combine with protein of animal
hides, prevent their putrefaction and convert them into leather
‘tannin’ was first applied by Seguin in 1796
Comprise a large group of complex substances that are widely distributed in the plant kingdom
Tannins
When tannins occur in appreciable quantities, they are usually localized in
specific plant parts, such as ______________________
leaves, fruits, barks or stems
Usually occur as ___________________ that are difficult to separate because
they do not crystallize
MIXTURES OF POLYPHENOLS
Contribute a protective function in ________________
barks and heartwoods
The characteristic properties of tannins derive from the accumulation within a
moderately sized molecule of a substantial number of phenolic groups many of which are associated with o-dihydroxy and o-trihydroxy orientation within a phenyl ring.
Tannins
Non-crystallizable compounds that form colloidal solutions with water
Tannins
Possess an acid reaction
Tannins
Has a sharp “_______________” taste.
puckering
Soluble in alcohol, glycerin, dilute alkalis
Tannins
Insoluble in organic solvents except alcohol
Tannins
4 Classification of Tannins
- Hydrolyzable Tannins
- Condensed Tannins
- Complex Tannins
- Phlorotannins
“PYROGALLOL TANNINS”
Hydrolyzable Tannins
May be hydrolyzed by acids or enzymes such as tannase.
Hydrolyzable Tannins
They are formed from several molecules of phenolic acids such as gallic and hexahydroxydiphenic acids which are united by ester linkages to a central glucose molecule
Hydrolyzable Tannins
composed of gallic acid units
GALLITANNINS
Hydrolyzable Tannins
Two principal types:
- GALLITANNINS
- ELLAGITANNINS
composed of hexahydroxydiphenic acid units
ELLAGITANNINS
“CONDENSED TANNINS; PROANTHOCYANIDINS”
Nonhydrolyzable Tannins
Not readily hydrolysed to simpler molecules and they do not contain a sugar moiety
Nonhydrolyzable Tannins
Contain only phenolic nuclei but frequently are linked to carbohydrates or proteins.
Nonhydrolyzable Tannins
Tend to polymerize when treated with hydrolytic agents, yielding insoluble,
usually red-colored products, known as phlobaphenes
Nonhydrolyzable Tannins
Tend to polymerize when treated with hydrolytic agents, yielding insoluble,
usually red-colored products, known as ___________________
phlobaphenes
On dry distillation: yield catechol; these tannins are therefore sometimes called
_________________
CATECHOL TANNINS
On dry distillation: yield catechol; these tannins are therefore sometimes called
CATECHOL TANNINS
Nonhydrolyzable Tannins
Both hydrolysable and condensed tannins are highly soluble in _________________ but insoluble in organic solvents such as solvent ether, chloroform, and
benzene
water and alcohol
The general method for the extraction of tannic acid is either with ______________________, or with mixture of water, alcohol, and ether
water- saturated ether
If the drug consists of __________________, it may be removed by ether
chlorophyll or pigment
In such cases, free acids such as __________________ go along with ether,
whereas true tannin gets extracted in water
Gallic and ellagic acid
STEPS OF Extraction of Tannins
- Solid-liquid extraction
- Vacuum filtration
- Extract recovery
- Rotary evaporation
- Pulverizing
Precipitates ____________________
GELATIN AND ALKALOIDS
Precipitates ___________________ (and can combine with proteins)
proteins from solutions
Precipitated by salts of _______, ___ and _____.
COPPER,
TIN, &
LEAD
Precipitated by strong ________________________
solutions.
potassium dichromate solution or 1% chromic acid
Form dark blue or greenish black soluble compounds with _________ salts.
FERRIC
Chemical Tests:
- Goldbeater’s Skin Test
- Gelatin Test
- Phenazone Test
- Match Stick Test
- Test for Chlorogenic Acid
Produce a deep red color with ____________________________
POTASSIUM FERRICYANIDE AND AMMONIA
Exposure to tannin solution to Goldbeater’s skin (membrane from an Ox intestine)
Goldbeater’s Skin Test
Goldbeater’s Skin Test
Positive result:
BROWN OR BLACK COLOR ON THE SKIN
Gallic acid and other pseudotannins are able to precipitate ________________
Gelatin Test
Solutions are sufficiently concentrated to produce precipitation
Gelatin Test
All tannins are precipitated
Phenazone Test
Phenazone Test
Positive Result:
BULKY AND OFTEN COLORED PPT.
General test for condensed tannins (cathecins)
Match Stick Test
A _______________ is dipped in tannin extract followed by hydrochloric acid and warmed near a flame
match stick
Match Stick Test
Positive result:
PINK OR RED COLORATION OF WOOD
Attributed to __________________________ in the wood yieldin the color
Phlorogloucinol reacting with the lignin
A type of pseudotannin
Test for Chlorogenic Acid
Extract is treated with aqueous ammonia and exposed to air
Test for Chlorogenic Acid
Test for Chlorogenic Acid
Positive result:
DEVELOPMENT OF A GREEN COLOR
Tannic acid with ferric salts are invariably used in the _____________________
manufacture of inks
- Tannic acid with ferric salts are invariably used in the manufacture of inks.
- Used for tanning – treating animal hides to produce leather
- Employed as a pharmaceutical aid
- Used as a mordant.
- Invariably employed as clarifying agent
- Employed as a coagulant
- Used in the large-scale production of gallic acid and pyrogallol.
- Employed as a reagent
- Precipitating agen
Uses of Tannins
Used for tanning – treating animal hides to produce _____________
leather
Employed as a _______________
pharmaceutical aid
Used as a ____________
mordant
Invariably employed as ________________
clarifying agent
Employed as a ________________
coagulant
Used in the large-scale production of __________________
gallic acid and pyrogallol
Employed as a _______________
reagent
Precipitating agent
Uses of Tannins
