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What is the term used to denote substances present in plant extract which react with protein of animal hide, prevent their putrefaction and convert hide and skin into leather?
What is the term used to denote substances present in plant extract which react with protein of animal hide, prevent their putrefaction and convert hide and skin into leather?
Tannins
What are tannins?
What are tannins?
Polyhydroxy phenolic compounds.
Which color are tannins typically?
Which color are tannins typically?
Dark brown or reddish brown
What is the taste of tannins?
What is the taste of tannins?
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In what states are tannins found?
In what states are tannins found?
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What are tannins soluble in?
What are tannins soluble in?
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What are the red colored complexes formed when flavonoid catechins are heated with acids?
What are the red colored complexes formed when flavonoid catechins are heated with acids?
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Which plant examples fall under the category of complex tannins?
Which plant examples fall under the category of complex tannins?
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What is the Gold beater’s skin test used to qualitatively detect?
What is the Gold beater’s skin test used to qualitatively detect?
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What are the two types of tannins based on their ability to convert animal hide to leather?
What are the two types of tannins based on their ability to convert animal hide to leather?
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What is the molecular weight range of true tannins?
What is the molecular weight range of true tannins?
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What color reaction do tannins exhibit with iron in identification tests?
What color reaction do tannins exhibit with iron in identification tests?
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What is the purpose of the Phenazone test in the identification of tannins?
What is the purpose of the Phenazone test in the identification of tannins?
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Explain the principle behind the Gold beater's skin test for tannins.
Explain the principle behind the Gold beater's skin test for tannins.
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What is the purpose of the Catechin test, and what is the principle behind it?
What is the purpose of the Catechin test, and what is the principle behind it?
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How is the test for chlorogenic acid performed, and what is the expected result?
How is the test for chlorogenic acid performed, and what is the expected result?
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What is the botanical origin and family of Hamamelis, and which part of the plant is used?
What is the botanical origin and family of Hamamelis, and which part of the plant is used?
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Describe the process of collecting and drying Hamamelis leaves.
Describe the process of collecting and drying Hamamelis leaves.
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Study Notes
Tannins
- The term "tannin" was first coined by Seguin in 1796 to describe substances in plant extracts that react with animal hide proteins, preventing putrefaction and converting hide and skin into leather.
Definition and Properties
- Tannins are complex substances that occur as mixtures of polyphenols, which are difficult to separate and don't crystallize.
- They can also be defined as polyhydroxy phenolic compounds.
- Physical properties: dark brown or reddish brown color, puckering taste, non-crystalline state, and solubility in water, alcohol, dilute alkalis, glycerols, and acetone.
- Chemical properties include precipitation, anti-oxidizing properties, astringency, carcinogenicity, and reaction with salts and potassium ferricyanide and ammonia.
Precipitation
- Tannins can precipitate solutions of gelatin, alkaloids, glycosides, heavy metals, and proteins.
Anti-Oxidizing Properties
- Tannins have anti-oxidant properties due to the accumulation of OH groups on a small nucleus.
Astringent Properties
- Tannins can react with protein of mucous membrane, causing precipitation.
Carcinogenicity
- Prolonged use of tannin-containing plant materials can cause cancer, such as oral and esophageal cancer from habitual use of Areca catechu.
Classification
- Tannins can be classified into two types: true tannins and pseudo tannins.
- True tannins are polyhydroxy phenolic compounds that convert animal hide to leather, precipitating proteins, and giving a positive Gold beater's skin test.
- Pseudo tannins are phenolic compounds of plant origin that don't convert animal hide to leather but give a positive Gold beater's skin test.
Identification Tests
- Color reaction: Tannins give a color reaction with iron.
- Matchstick test: A pink or red color appears on a matchstick dipped in plant extract, dried, moistened with hydrochloric acid, and warmed near a flame.
- Gelatin test: A 0.5-1% solution of tannin precipitates a 1% solution of gelatin containing 10% sodium chloride.
- Phenazone test: Tannins are precipitated by adding a 2% solution of phenazone to a filtrate solution.
- Gold beater's skin test: A black or brown color appears on Gold beater's skin when soaked in a 2% hydrochloric acid solution, washed, and transferred to a 1% solution of ferrous sulphate, indicating the presence of tannins.
Examples of Tannin-Containing Plants
- Hamamelis (Botanical origin: Hamamelis virginiana, Family: Hamamelidaceae, Part used: Dried leaves)
- Cinchona
- Cinnamon
- Tea
- Quercus
- Castanea
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Description
Test your knowledge on tannin classification based on properties, examples, and classification criteria such as self condensation, hydrolysable tannins, and tanning tests.
