lec 9 Flashcards
What is the origin of the term ‘tannin’?
‘Tannin’ is derived from the French ‘tanin’ (tanning substance)
What are the key characteristics of tannins?
They can combine with animal hides to convert them into leather and bind strongly to proteins, precipitating them from solution.
Name the two main classifications of tannins.
- Hydrolysable tannins
- Condensed tannins
What are hydrolysable tannins primarily composed of?
A central glucose molecule linked to molecules of gallic acid or hexahydroxydiphenic acid
What are condensed tannins also known as?
Procyanidins or catechol tannins
What structural feature characterizes condensed tannins?
Polymeric flavans consisting of molecules of catechin and epicatechin joined by C-C bonds
What are pseudo-tannins?
Simple phenolic substances with a relatively low molecular weight, often present with tannins
What is the pharmacodynamic effect of tannins?
They are large polar molecules that are poorly absorbed through the skin or gastrointestinal tract.
What is astringency in relation to tannins?
The ability of tannins to react with and crosslink proteins in mucus and epithelial cells, rendering the mucosa less permeable.
How do tannins exert their anti-diarrheal effect?
By producing a protective layer of coagulated protein on the mucosa and inhibiting the viability of infecting microorganisms.
What is the antiulcer activity of tannins attributed to?
Their ability to suppress gastric acid secretion and prevent experimentally induced gastric ulcers.
What is the mechanism of haemostatic activity of tannins?
Localized vasoconstriction and formation of an ‘artificial clot’ due to tannin-protein interaction.
What impact do tannins have on bowel flora composition?
They can significantly change the levels of particular microflora, potentially reducing uraemic toxins in renal failure.
What is the antioxidant activity of tannins?
Tannins, such as gallic acid, can scavenge reactive oxygen species (ROS) and demonstrate greater activity than ascorbic acid.
True or False: High doses of tannins can lead to adverse reactions.
True
What are glucosinolates?
Amino acid-derived glycosides containing sulfur and nitrogen.
What happens to glucosinolates upon hydrolysis?
They are transformed into isothiocyanates.
What are the potential effects of isothiocyanates on the thyroid gland?
They can interfere with thyroid function and may act as goitrogens.
What anticancer potential do glucosinolates have?
They may inhibit chemical carcinogenesis and alter cancer-promoting hormone levels.
What type of vegetables are associated with a reduced cancer risk according to epidemiological studies?
Vegetables from the Brassica genus, such as broccoli and cabbage.
What is the role of sulforaphane in cancer prevention?
It involves the induction of phase II detoxification enzymes and has antioxidant and anti-inflammatory properties.
Fill in the blank: Glucosinolates are found in the families _______.
[Brassicaceae/Cruciferae, Capparidaceae & Rosaceae]
