PCOG TANNINS AND LIPIDS Flashcards
What are tannins primarily composed of?
A mixture of polyphenols that do not crystallize.
What are the usual sources of tannins?
Barks and stems.
What are some uses of tannins?
Astringent, antidote to alkaloidal poisoning, precipitants, and in the tanning and dyeing industry.
What is a caution associated with tannins?
They can be carcinogenic, such as in the chewing of betel nut.
What are pseudotannins?
Simpler phenolic substances with a molecular weight of around <1,000.
How do pseudotannins differ from true tannins?
Pseudotannins do not precipitate leather but can precipitate gelatin.
What is the molecular weight range of true tannins?
Around 1,000 to 5,000.
What is the significance of molecular size in true tannins?
They must be moderate-sized to effectively crosslink protein molecules.
What are the two classifications of true tannins?
Hydrolyzable tannins and non-hydrolyzable tannins.
What happens to hydrolyzable tannins when treated with 3N HCl?
They are easily hydrolyzed to sugar and phenolic acids.
What color indicates a positive test for tannins with FeCl3?
Blue-black color.
What is the result of the matchstick test for tannins?
A positive result shows a pink or red color.
What are hydrolyzable tannins primarily composed of?
They contain glucose, thus forming glycosides.
How are hydrolyzable tannins classified?
Based on the phenolic aglycones, such as gallotannin and ellagitannin.
What is the aglycone of gallotannin?
Gallic acid.
What distinguishes non-hydrolyzable (condensed) tannins from hydrolyzable tannins?
Non-hydrolyzable tannins contain flavonoids and do not readily hydrolyze to simpler molecules.
What are common sources of non-hydrolyzable tannins?
Cinnamon bark, hamamelis bark, Krameria, male fern roots, cocoa, kola, and areca seed.
What is a characteristic of complex tannins?
They are a hybrid mix of both hydrolyzable and non-hydrolyzable tannins.
What is the scientific name of witch hazel?
Hamamelis virginiana.
What are the uses of witch hazel?
It has astringent and hemostatic properties and is anti-inflammatory.
What is the scientific name of nutgall?
Quercus infectoria.
What causes the formation of nutgall?
The puncture of the insect Cynips tinctoria.
What is the primary use of nutgall?
In the tanning and dyeing industry, as well as an astringent.
What is the scientific name of Pomegranate?
Punica granatum.