PlantTannins Flashcards
1
Q
Guest lecture by?
A
- Dr. Peter Constabel
- Plant Tannins: Healthy foods and phytochemical chameleons
2
Q
What are tannins?
A
- Large polymeric polyphenols with protein-binding and precipitating ability (functional defn)
- Have aromatic rings (hydrophobic interactions) and hydroxyls (can form h-bonds)
3
Q
Where are tannins found?
A
- Found in plants as variable and heterogeneous mixtures (dimers, oligomers, polymers)
4
Q
What are the 2 major types of tannins?
A
- Hydrolyzable tannins
- Condensed tanins
5
Q
Where are there high concentrations of condensed tannins?
A
- Trees (bark, roots, leaves)
- Forest systems (litter, soils)
6
Q
What is the most abundant natural product on the planet?
A
- Tannins
7
Q
What are some examples of the diverse biological effects of tannins?
A
- Anti-feedant
- Antimicrobial
- Antioxidant
8
Q
Why are people interested in tannins?
A
- Tanning leather
- Flavour and stability of beer and wine
- Found in natural foods, important for healthy diet
- Strong invitro antioxidants, in vivo not clear
- Impacts on gut microbiome
- Inhibit bacterial adhesion
- Improve nitrogen uptake in cattle
9
Q
Tanning leather
A
- Uses tannins to bind protein, prevent bacterial growth, soften leather
10
Q
How do tannins affect beer and wine?
A
- Important for flavour and stability
- Dry mouth-feel, puckering
- Tannins in wine come from grape skin and oak wood
- Tannins in beer from barley and hops
- Beer haze is a tannin-protein precipitate
11
Q
What natural foods can tannins be found in? Which food has high bacterial adhesion inhibition?
A
- Nuts, grains, lentils and beans (in seed coat)
- Berries and other fruit (skin and seeds)
- High concentrations in cocoa, cinnamon, persimmon, apple, blueberry, and salal
- Cranberry A-type condensed tannins inhibit bacterial adhesion
12
Q
Why are tannins important for a healthy diet?
A
- Linked to reduced risk of cardiovascular disease, metabolic syndrome, neurodegenerative disorders, others
13
Q
How do tannins affect cattle?
A
- Tannins in cattle feed can improve nitrogen uptake, prevent cattle bloat and reduce methane release (inhibit rumen protein breakdown)
14
Q
Why do plants make (so much) tannin?
A
- Anti-nutritive defences against herbivores (bind proteins at neutral or acidic pH)
- Defence against pathogens
- Protect seeds from stress by sealing the seed coat
- May act as in vivo antioxidants to protect against stressful oxygen radicals
- Influence N cycling in soils
- Protect against metal soil metal toxicity (Al), bind iron (Fe)
15
Q
Examples of tannins role as antifeedant and antimicrobial
A
- Beavers prefer low-tannin aspen bark, tree-feeding caterpillars not so much
- High tannin poplars are more resistant to poplar rust
