1. FLAVONOIDS
Introduction
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2. What are flavonoids?
Flavonoids are a group of plant metabolites thought to provide health benefits through cell signalling pathways and antioxidant effects.
These molecules are found in a variety of fruits and vegetables.
Flavonoids are polyphenolic molecules containing 15 carbon atoms and are soluble in water.
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3. Different types of flavonoids?
The flavonoid family
Flavones: These include luteolin and apigenin.
Anthocyanidins: These include malvidin, pelargondin, peoidin and cyanidin. ...
Flavonones: These include hesperetin, eriodictyol and naringenin. ...
Isoflavones: This subgroup includes genistein, glycitein and daidzein.
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4. What are the benefits of flavonoids?
Flavonoids provide a number of benefits to the human body.
They:
Act as antioxidants.
Have a direct antitumor effect.
Enhance immunity (citrus fruits).
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5. Flavonoids, polyphenolic compounds found in plants, have antioxidant powers that may provide important health benefits.
Diets rich in flavonoids have been associated with reduced risk of a variety of diseases.
However, further research is needed to determine whether flavonoids alone are responsible for these benefits rather than the whole foods that contain flavonoids.
Flavonoid-rich foods include cocoa, apples, onions, cranberries, tea and red wine.
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6. Consist of Benzene ring (A) Pyran ring (C)
Phenyl ring at position 2 of pyran ring (B)
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7. Chem-465
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8. What’s a phenolic compound?
A secondary product that contains a phenol group
- a hydroxyl functional group on an aromatic ring. OH
Phenolics are a chemically diverse group: many
different properties and functions.
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9. MEP mevalonate pathway
The shikimate pathway(shikimic acid pathway) is a seven step metabolic route used by bacteria, fungi, algae, some protozoan parasites and plants for the biosynthesis of folates and aromatic amino acids (phenylalanine, tyrosine, and tryptophan).
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10. Biosynthesis of phenolics
Shikimic acid pathway is most common in plants. Converts simple carbohydrates into aromatic amino acids. Not present in animals.
PP13090.jpg
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11. Most plant phenolics are derived from cinnamic acid
formed from phenylalanine by phenylalanine ammonia lyase (PAL) enzyme.
PAL activity is inducible: fungal infection, low nutrient levels, high light
PAL
PP13090.jpg
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12. 2. Lignin - 2nd most abundant compound in plants
Major types of phenolics
1. Simple phenolics - e.g. coumarins
2. Lignin - 2nd most abundant compound in plants
3. Flavonoids - two aromatic rings, 2 pathways
anthocyanins, flavones/flavonols
4. Condensed tannins
polymerized flavonoids
5. Hydrolyzable tannins
made of phenolic acids and sugars
smaller molecules than condensed tannins
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13. 1. simple phenolics Fig. 13.10 Involved in defense against
insect herbivores
and fungi, some may
have allelopathic
function.
PP13101.jpg
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14. Simple phenolics Caffeic acid & ferulic acid implicated in
allelopathy.
Psoralen is one
of several
phototoxic
furanocoumarins,
(UV activated)
Fig
PP13111.jpg
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15. Furoanocoumarins can certain light wavelengths
Furoanocoumarins can certain light wavelengths. (common in Umbelliferae family – celery, parsnip)
Leaf rolling insects
Insects usually roll leaves for protection from predation and to create a habitat
Sometimes insects roll leaves to prevent furanocourmarins from being activated
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16. Furanocoumarins can bind to DNA or react with lipids and proteins
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17. Simple phenolics
Fig
PP13112.jpg
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18. Second most abundant compound in plants.
2. Lignin
Second most abundant compound in plants.
Highly branched polymer of phenylpropanoid groups (benzene-C3)
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19. often found in vessel elements, tracheids, and stems; confers structural support. Primary structural
role!
- Secondary role as a herbivore deterrent by reducing digestibility of plant matter
also difficult for microbes to degrade; its presence slows litter decomposition.
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20. 3. Flavonoids - basic structure is two aromatic
rings joined by a 3C bridge.
anthocyanins
flavones
flavonols
isoflavonoids
Fig
PP13102.jpg
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22. anthocyanins are pigments that give plant tissues
Fig
Flavonoids
a) Anthocyanidins and
anthocyanins are pigments
that give plant tissues
red, blue, and purple
color.
Pollinator attraction
Disperser attraction
PP13130.jpg
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24. b & c) flavones and flavonols UV absorbing
Flavonoids continued
b & c) flavones and flavonols
UV absorbing
protection against UV ( nm)
insect pollinator attraction
How we see the golden eyes…
How honeybees see golden eyes…
UV absorbing flavonols are present in the inner part of petals
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25. antimicrobial properties also involved in signalling
d) Isoflavonoids
common in legumes
antimicrobial properties
also involved in signalling
e.g. attracting rhizobia
Rhizobium is attracted to legumes through signaling by isoflavanoids released from roots.
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26. -formed by polymerization of flavonoid units -common in woody plants
Tannins
Condensed
-formed by polymerization of flavonoid units
-common in woody plants
Hydrolyzable
- contain phenolic acids: gallic acid, & simple sugars
- smaller molecules than condensed tannins
- more easily hydrolyzed and degraded
Tannins reduce growth and survival of many different kinds of herbivores
Also act as antioxidants - eat your isoflavonoids Johnny!
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27. Tannins also make protein less digestible.
Many foods contains tannins (e.g. tea, red wine) and have some healthy side effects for humans (e.g. disallowing constriction of blood vessels)
Tannins also make protein less digestible.
Animals can sense high levels of tannins in their food and opt for another food resource (e.g. mule deer, beavers).
High levels of tannins in diet can actually kill some animals.
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28. Condensed tannins are polymerized flavonoids.
PP13151.jpg
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29. Hydrolyzable tannins are made of phenolics and sugars.
Fig
PP13152.jpg
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30. tannins can bind digestion enzymes in the gut of herbivores.
The term “tannin” is derived from the tanning process in which raw animal hides are preserved by rubbing tannins on them. The tannins help to complex the proteins and keep them from degrading.
This protein-binding property of tannins lends them their toxicity to herbivores.
tannins can bind digestion enzymes in the gut of herbivores.
tannins also form complex polymers when bound to proteins which are difficult to digest, thus decreasing the nutritional value of the plant material.
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31. Care for a spot of milk in your tea?
Tannins can reduce nutritional value of tissues by binding to proteins, making them less digestible.
PP13161.jpg
Fig
Care for a spot of milk in your tea?
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33. Creosote bush, Larrea tridentata Leaves are 10-25% phenolic resin.
40% of resin is NDGA (nordihydroguaiaretic acid),
remainder is o-methylated flavones and flavonols.
Deters insect herbivory. Mammalian herbivores
select older leaves (less resin).
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34. Active compounds in creosote leaves.
· NDGA and similar compounds.
· Amino acids.
· Flavonoids.
· Volatile oils.
· Triterpenes.
· Saponins.
USDA formerly used NDGA as an antioxidant to prevent rancidity in food.
Now known to cause liver and kidney disease in lab animals.
Creosote has long been used in traditional Native American and Mexican
herbal medicine
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35. Creosote applications in herbal therapy
· To dissolve urinary kidney stones.
· Anti inflammatory for respiratory ailments (asthma) and arthritis
· To eliminate gallstones
· Against urinary infections
· For the treatment of venereal disease
· As an abortifacient
· Against diabetes
· Bronchitis and colds
· Rheumatism
· Against some types of cancer
· As a mouthwash against tooth decay and halitosis
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36. Lignin/Nitrogen ratio
After life effects of phenolic compounds.
Plant litter decomposition, and release of nutrients
from decomposing litter, are strongly influenced by
the chemical composition of the litter.
Litter higher in tannins and lignin decomposes more slowly.
Decomposition
rate
Lignin/Nitrogen ratio
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37. Bill Shakespeare, secondary chemist
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