PCOG LAB Exercise 11 - Tannins (Theoretical)

Tannins

These are complex substances usually occurs as mixtures of polyphenols that are difficult to separate because they cannot crystallize

TANNINS & POLYPHENOLS

first applied to plant constituents capable of transforming raw animal skin into leather

TANNINS & POLYPHENOLS

they have arisen from simple polyphenols that have undergone polymerization

Colloidal

Tannins are non-crystallizable compounds that, with water, form __________ solutions possessing an acid reaction and a sharp puckering taste

Polyphenols

These include a wide range of plant substances that possess in common, an aromatic ring bearing two or more hydroxyl groups

True

True or False: Polyphenols tend to be water-soluble

Polyphenols

because of their similarity to tannins in terms of structure, they are used as additives in tanning agents

Non-hydrolyzable

[Hydrolyzable or Non-hydrolyzable] aka Condensed Tannins

Non-hydrolyzable

[Hydrolyzable or Non-hydrolyzable] Structure: related to cathecol

Non-hydrolyzable

[Hydrolyzable or Non-hydrolyzable] + HCl: phlobaphenes (red dye)

Non-hydrolyzable

[Hydrolyzable or Non-hydrolyzable] + FeCl3: brownish green

Non-hydrolyzable

[Hydrolyzable or Non-hydrolyzable] + Br H2O: forms ppt

Non-hydrolyzable

[Hydrolyzable or Non-hydrolyzable] Leather Type: tanner's red

Hydrolyzable

[Hydrolyzable or Non-hydrolyzable] Structure: related to pyrogallol

Hydrolyzable

[Hydrolyzable or Non-hydrolyzable] + HCl: phenolic acid + sugars

Hydrolyzable

[Hydrolyzable or Non-hydrolyzable] + FeCl3: bluish black

Hydrolyzable

[Hydrolyzable or Non-hydrolyzable] + Br H2O: do not ppt

Hydrolyzable

[Hydrolyzable or Non-hydrolyzable] Leather Type: bloom

Phenolic acid and sugar

Hydrolysable tannins are esters that are easily hydrolysable to yield _______ and ________

Gallic acid or Hexahydroxydiphenic

Examples of phenolic acids

Phlobatannins or Proanthocyanidin

Other terms for condensed tannins (2)

PSEUDOTANNINS

False Tannins; Does not precipitate proteins thus do not form leather yet it reacts with Fe salts

Pyrogallol

Hydrolysis of gallic acid would yield ________

Cathecol

Hydrolysis of protocatechuic acid would yield _________

Precipitate

Tannins can _______ proteins from solution and can combine with it which renders the protein resistant to proteolytic enzymes

Cu, Pb, Sn, and aqueous solution of potassium dichromate

Tannins are precipitated by salts of ___, ___, ___, and aqueous solution of potassium dichromate

True

True or False: Tannins cause precipitation of gelatin as well as alkaloids

Soluble in polar compounds, sparingly soluble in organic solvents

Tannins are (soluble/sparingly soluble) in water, dilute alcohol, alkalis, and acetone; (soluble/sparingly soluble) in organic solvents

Sharp puckering taste

Tannins have a __________ taste

Astringent and Antiseptic

Their ability to precipitate proteins makes them an _________ and __________

Leather

Tannins are utilized in the process of vegetable tannins thus converting animal hides to _____

feeding deterrent

[Uses] Tannins are produced by a plant as a _________, as their binding to protein may reduce the dietary value of the plant as a food

astringent

[Uses] Tannins act as ________ in both GIT and skin abrasions

proteins

[Uses] Tannins are used in tanning leather because of their ability to combine with __________ of animal hide

Alkaloidal poisoning

[Uses] Tannins are used as an antidote for _________ because of their ability to precipitate alkaloids from solutions of their salt forming an insoluble tannate

Activated Charcoal, Magnesium Oxide, Tannic Acid

Components of universal antidote

iron salts

[Uses] Tannins are used in the manufacture of inks/dyes because they form deeply colored compounds with _______ salts

gelatin, proteins and alkaloids

[Uses] solutions of tannins are used in the laboratory as reagents for the detection of ___________________ (3)

Astringent; Antiseptic; Anti-diarrhea; diuretics; Anti-tumor (stomach and duodenal); Anti-inflammatory; Anti-oxidant; Hemostatic agent

Medical uses of tannins (8)

alcohol or water

Solvents that can be used to extract tannins (2)

Maceration

This process extracts tannins by soaking

Decoction

This process extracts tannins by soaking with the application of heat or with boiling

Brownish color

Color of Tannin extract

Pungent Odor

Odor of tannin extract

Sharp, puckering taste

Taste of tanning extract

Amorphous, non-crystalline

State/appearance of tannins

Ether

Which among the following reagents will tannins be insoluble? Alcohol, water, acetone, ether

Gelatin Precipitate

Positive result of 10% gelatin test

Tannins

Positive Gelatin test confirms presence of ______

Polyphenolic Compound

Negative gelatin test confirms presence of _______

Precipitate

Positive result in Bromine Test

Condensed Tannins

Precipitation in bromine test confirms presence of ___________ tannins

Hydrolysable tannins

Negative bromine test confirms presence of __________ tannins

brown or black

Positive result of Goldbeater's skin test

2% HCl; 1% solution of ferrous sulfate

Goldbeater's Skin Test, soak a small piece of goldbeater's skin in _________ with distilled water and place in the solution to be tested for five minutes. After such, wash with distilled water and transfer to __________

bluish black

Result of Hydrolysable tannins in Ferric Chloride Test

brownish green

Result of non-hydrolysable tannins in ferric chloride test

formation of precipitate

Lime Water test positive result

Brown solution and formation of precipitate

Iodine test positive result

Pink or red color on the matchstick

Test for catechin positive result

Phloroglucinol

The pink or red color on the matchstick in catechin test is due to formation of _________

Green color

Positive result of test for chlorogenic acid

shows pink or red color (due to phloroglucinol)

Positive result of Vanillin-Hydrochloric acid test

1:10:10

In vanillin-hydrochloric acid test, the mixture of vanillin, alcohol, dilute HCl to be used is ________

Hamamelis

Witch hazel leaves are also known as _________