ex 11 tannins

lagyan mo pa structures

tannins

Are complex substances usually occurs as mixtures of polyphenols that are difficult to separate because they do not crystallize

TANNINS & POLYPHENOLS

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

non-crystallization

tannins & polyphenols are ___ compounds that with water form colloidal solutions possessing an acid reaction and a sharp puckering taste

TANNINS & POLYPHENOLS

•they are non-crystallizable compounds that with water form colloidal solutions possessing an acid reaction and a sharp puckering taste

polyphenols

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

water-soluble

polyphenols (water or lipid-soluble?)

additives

•because of polyphenols’ similarity to tannins in terms of structure, they are used as __ in tanning agents

non-hydrolyzable

condensed tannins

hydrolyzable tannins

structure related to pyrogallol

non-hydrolyzable tannins

structure related to cathecol

hydrolyzable tannins

+HCL = phenolic acid + sugars

hydrolyzable tannins

+FeCl₃ = bluish black

hydrolyzable tannins

+BrH₂O = do not ppt

hydrolyzable tannins

Leather type: bloom

non-hydrolyzable tannins

+HCl = phlobaphenes (red dye)

non-hydrolyzable tannins

+FeCl₃ = brownish green

non-hydrolyzable tannins

+BrH₂O = forms ppt

non-hydrolyzable tannins

Leather Type: tanner’s red

1. Hydrolysable Tannins

2. Condensed Tannins

3. Pseudotannins

classification of tannins

hydrolysable tannins

Esters that are easily hydrolysable to yield:

◦Phenolic acid and sugar

◦Phenolic acids: Gallic acid OR Ellagic acid; Hexahydroxydiphenic

• phenolic acid and sugar

• phenolic acids: gallic acid or hexahydroxydiphenic

• +FeCl_{3 -} Bluish black

hydrolysable tannins yield

Cathecol, Phlobatannins or Proanthocyanidin

examples of condensed tannins

pseudotannins

false tannins

pseudotannins

•Does not precipitate proteins thus do not form leather yet it reacts with Fe salts

polyhydric phenols

tannins, when hydrolysed, yield relatively __

pyrogallol

Gallic acid → (hydrolysed)

cathecol

Protocatechuic acid → (hydrolysed)

•soluble in water, dilute alcohol, alkalis, and acetone; sparingly soluble in organic solvents

•causes precipitation of gelatin as well as alkaloids

•precipitated by salts of Cu, Pb, Sn, and aqueous solution of potassium dichromate

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

PROPERTIES OF TANNINS

•soluble in water, dilute alcohol, alkalis, and acetone; sparingly soluble in organic solvents

•causes precipitation of gelatin as well as alkaloids

•precipitated by salts of Cu, Pb, Sn, and aqueous solution of potassium dichromate

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

PROPERTIES OF TANNINS

•soluble in __; sparingly soluble in __

•causes precipitation of __ as well as alkaloids

•precipitated by salts of __, and aqueous solution of __

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

•Non-crystallizable

•With water forms colloidal solution

•Sharp puckering taste

•Causes precipitation of gelatin and alkaloids

•Their ability to precipitate proteins makes them an antiseptic and astringent

•Utilized in the process of vegetable tannins thus converting animal hides to leather

PROPERTIES OF TANNINS

•Non-crystallizable

•With _____ forms colloidal solution

•Sharp puckering taste

•Causes precipitation of ______ and alkaloids

•Their ability to __________ proteins makes them an ______ and ________

•Utilized in the process of vegetable tannins thus converting animal hides to _____

•produced by a plant as a feeding deterrent, as their binding to protein may reduce the dietary value of the plant as a food

•astringent in both GIT and skin abrasions

•used in tanning leather because of their ability to combine with proteins of animal hides

•used as an antidote for alkaloidal poisoning because of their ability to precipitate alkaloids from solutions of their salt forming an insoluble tannate

•used in the manufacture of inks/dyes because they form deeply colored compounds with iron salts

•solutions of tannins are used in the laboratory as reagents for the detection of gelatin, proteins and alkaloids

USES OF TANNINS

•Astringent

•Antiseptic

•Anti-diarrhea

•diuretics

•Anti-tumor (stomach and duodenal)

•Anti-inflammatory

•Anti-oxidant

•Hemostatic agent

medical used of tannins

•Maceration

Soaking

•Decoction

Soaking with the application of heat or with boiling

•Maceration – Soaking

•Decoction – Soaking with the application of heat or with boiling

•Solvent alcohol or water

EXTRACTION OF TANNINS

◦ Color: Brownish color

◦ Odor: Pungent odor

◦ Sharp, puckering taste

◦ State: Amorphous, non-crystalline

IDENTIFICATION TEST of tannin extract

color:

odor:

taste:

state:

-

Reagent	Theoretical Result	Interpretation
gelatin solution	Ppt	Presence of Tannins
	No ppt- negative	polyphenolic compound

10% GELATIN

Reagent	Theoretic Result	Interpretation

Reagent	Theoretical Result	Interpretation
Br2	do not precipitate	Hydrolysable tannin
	precipitate	Condensed Tannins

Br₂ Test

Reagent	Theoretical Result	Interpretation
Br2

brown or black

positive result of goldbeater’s skin test

gelatin salt solution

reagent of gelatin test

jelly-like precipitate

positive result of gelatin test

bluish black (hydrolysable tannins), brownish green and (+) in gelatin (condensed tannins), brownish green but (–) in gelatin (polyphenolic compounds)

positive result of ferric chloride test

formation of precipitate with condensed tannins only

Bromine Water Test result

formation of precipitate

Lime Water Test result

Brown solution and formation of precipitate

Iodine test result

matchstick test

test for catechin

Catechin in the presence of acid produces phloroglucinol which stains the lignified wood pink or red.

matchstick test result

A dilute solution of chlorogenic acid containing extract, slowly turns green indicating the presence of chlorogenic acid.

test for chlorogenic acid

Drug shows pink or red color, reaction produces phloroglucinol which along with vanillin gives pink or red color.

VANILLIN-HYDROCHLORIC ACID TEST result

Flavonoids

(What type of polyphenol?) Quercetin

Phenolic acids

(What type of polyphenol?) Caffeic acid

Stillbenes

(What type of polyphenol?) Resveratrol

Lignans

(What type of polyphenol?) Flaxseed