Tannins and Simple Phenolics Lecture Flashcards

A set of 100 flashcards covering the definition, classification, properties, and sources of tannins and simple phenolics based on the PHARM 272 lecture.

Plant phenols

Aromatic compounds characterized by an aromatic ring bearing a hydroxyl group.

Shikimic acid pathway

One of the biosynthetic pathways for plant phenols, also known as the Phenylpropanoid pathway.

Amino acid precursors

Aromatic amino acids such as phenylalanine, tyrosine, and tryptophan from which plant phenols are derived.

Examples of phenolic compounds

Simple phenols, flavonoids, quinones, lignins, and tannins.

Tannin (Historical Origin)

Term first used by Seguin to denote substances that react with animal hide protein to prevent decomposition and create leather.

Definition of Tannins

High molecular weight poly-hydroxy phenolic compounds capable of forming strong complexes with proteins and other macromolecules.

Nitrogen status of Tannins

They are non-nitrogenous compounds.

Chemical precursors (Definition 2)

Condensation products of Gallic acid or Flavan-3-ol, as well as their glycosides.

Plant distribution

Widely found in angiosperms and gymnosperms, specifically in the leaf, seed, root, bud, wood, and stem.

Tissue locations

Often found in secondary phloem, xylem, and between the cortex and epidermis.

Physiological role in growth

Tannins help regulate the growth of plant tissues.

Enzymatic inhibitory effect

Tannins inhibit many enzymes due to protein precipitation, providing a protective function in barks and heartwoods.

Hydrogen transfer role

Tannins play a role in plant cell hydrogen transfer due to their high affinity for oxygen.

Defensive roles

Act as deterring agents against predators and a barrier to microorganisms.

Astringent property

The ability to react with mucous membrane proteins to cause precipitation.

Physical appearance

Non-crystalline, generally powdery or flaky.

Solubility

Soluble in water, alcohol, dilute alkalis, glycerols, and acetone; sparingly soluble in other organic solvents.

General coloration

Generally dark yellow to reddish brown in color.

Precipitation with heavy metals

Tannins form precipitates with heavy metals such as Lead.

Precipitation with Nitrogenous salts

Tannins precipitate alkaloidal salts.

Precipitation with Proteins

Tannins precipitate proteins such as gelatin.

Iron salts reaction

Forms a colored reaction when treated with $FeCl_3$.

Ammonia/Potassium ferricyanide reaction

Produces a deep red color.

Dietary sources of astringency

Tea, berries, and wine; causes a dry and puckery aftertaste.

Fruit sources

Strawberries and blueberries.

Nut sources

Almonds and walnuts.

Herb and spice sources

Clovie, vanilla, cinnamon, and cumin.

Styptics

A medicinal use of tannins for stopping bleeding.

Internal application

Used for the protection of inflamed surfaces of the mouth and throat.

Anti-diarrhoeal

A medicinal property of tannins used to treat diarrhea.

Antidote use

Employed as antidotes for poisoning by heavy metals, alkaloids, and glycosides.

Skin condition treatments

Used for bleeding abrasions, skin ulcers, and as a cicatrizant on gangrenous wounds.

Schistosomiasis

Tannins have molluscidal activity used to interrupt the transmission cycle of this disease.

Anti-viral effects

Reported medicinal property of tannins against viruses.

Treatment for stings/plants

Used to treat poisons from poison oak or bee stings for instant relief.

Manufacture uses

Used in the production of dyes, ink, wine processing, and leather.

True Tannins

High molecular weight poly-phenolic compounds ($1000$ to $5000\,Da$) that convert animal hide to leather.

Goldbeater’s skin test

A qualitative test used to detect true tannins.

Hide powder test

A quantitative test for tannins based on their adsorption on standard hide powder.

1% Gelatin solution

A solution used to precipitate true tannins.

Pseudotannins

Low molecular weight monomeric polyphenols that do not respond to the Goldbeater’s skin test.

Pseudotannin examples

Eugenol, gallic acid, catechins, chlorogenic acid, phloroglucinol, and salicylic acid.

Gallic acid sources

Rhubarb and materials containing gallitannins.

Catechin sources

Catechu, acacia cutch, Australian kinos, cocoa, and guarana.

Chlorogenic acid sources

Mate, unroasted coffee, and a small quantity in Nux vomica.

Ipecacuanhic acid

A pseudotannin found in Ipecacuanha.

Hydrolysable Tannins

Tannins that can be broken down by enzymes (e.g., tannase) or acids.

Hydrolysable Tannin precursors

Phenolic acid (gallic or ellagic acid) and a glucose residue.

Structure of Hydrolysable Tannins

Phenolic acids united by ester linkages to a central sugar molecule, usually D-glucose.

Gallotannins

Hydrolysable tannins composed of gallic acid units.

Ellagitannins

Hydrolysable tannins composed of hexahydroxydiphenic acid units.

Depside bond

An ester bond linking two or more monocyclic aromatic units in polyphenolic compounds like gallotannins.

Ellagitannin linkage

Galloyl groups are linked through C-C bonds.

Tannic acid

An example of a hydrolysable tannin structure involving gallic acid units.

Gallitannin Hydrolysis

Produces Gallic acid upon acid hydrolysis.

Ellagitannin Hydrolysis

Yields ellagic acid upon acid hydrolysis.

Lactonization

The process by which hexahydroxydiphenic acid becomes ellagic acid during chemical hydrolysis.

Gallitannin Solubility

Rapidly soluble in water.

Ellagitannin Solubility

Slowly soluble in water.

Gallic acid + Iron salts

Produces a blue fluorescence.

Ellagic acid + Iron salts

Produces a blue fluorescence.

Hydrolysable tannin dry distillation

Produces pyrogallols and other phenolic compounds.

Gallitannin Plant Sources

Rhubarb, cloves, red rose petals, bearberry leaves, Chinese galls, Turkish galls, hamamelis, chestnut, and maple.

Ellagitannin Plant Sources

Pomegranate rind and bark, myrobalans, eucalyptus leaves, kousso, and oak bark.

Corilagin

A specific example of a hydrolysable tannin.

Geraniin

A specific example of a hydrolysable tannin.

Condensed Tannins

Derivatives of flavonols (catechin and flavonol-3-4-diol) that are not hydrolysable.

Condensed Tannin Synonyms

Non-hydrolysable tannins, pro-anthocyanidins, or catechol type tannins.

Condensed Tannin Biosynthesis

Formed by the condensation of flavanol units via C-C bonds to form polymers.

Sugar content in Condensed Tannins

They do not contain sugar residues.

Condensed Tannin reaction with Iron salts

Solutions turn green.

Phlobaphenes

Red insoluble compounds formed when condensed tannins are treated with acids or enzymes.

Condensed Tannin dry distillation

Produces catechol.

Proanthocyanidins (PAs)

Term for condensed tannins derived from their acid-catalyzed oxidation into red anthocyanidins.

Anthocyanidin pigment

Pigment responsible for colors in flowers, leaves, fruits, juices, and wines.

Condensed Tannin Bark sources

Cinnamon, wild cherry, cinchona, willow, acacia, and hamamelis.

Condensed Tannin Root sources

Krameria (rhatany) and male fern.

Condensed Tannin Seed sources

Cocoa, kola, and areca.

Condensed Tannin Fruit sources

Cranberries and grapes (red wines).

Condensed Tannin Leaf sources

Hamamelis and tea.

Condensed Tannin Extract/Juice sources

Catechu, mangrove, and eucalyptus.

Propelargonidin

A type of proanthocyanidin where $R^{1} = H$ and $R^{2} = H$.

Procyanidin

A type of proanthocyanidin where $R^{1} = OH$ and $R^{2} = H$.

Prodelphinidin

A type of proanthocyanidin where $R^{1} = OH$ and $R^{2} = OH$.

Complex Tannins

Tannins biosynthesized from both a hydrolysable tannin (mostly C-glucoside ellagitannin) and a condensed tannin.

Anogeissusin A

An example of a complex tannin ($R = H$).

Anogeissusin B

An example of a complex tannin ($R = OH$).

Flavano-ellagitannin

A structural description for complex tannins like anogeissusin.

Gelatin test

A chemical test used to identify tannins by precipitation.

Catechin test

A specific chemical test for identify catechins.

Chlorogenic acid test

A chemical test used to identify chlorogenic acid.

Lead acetate test

A chemical test used to precipitate tannins using lead salts.

Precipitation of alkaloidal salts

A test used to detect tannins through the formation of precipitates with alkaloids.

Monomeric components

Low molecular weight units that make up pseudotannins.

Shikimic acid

The starting point of the pathway for tannin biosynthesis.

Poly-hydroxy phenolic

The chemical classification of tannins based on their multiple hydroxyl groups on aromatic rings.

Tannase

An enzyme capable of hydrolyzing hydrolysable tannins.

Hexahydroxydiphenic acid

The specific phenolic acid unit found in ellagitannins.

Catechol type tannins

Another name for condensed tannins based on their dry distillation product.

C-glucoside ellagitannin

A common hydrolysable component found within complex tannins.