Polyphenols - Flavonoids Part 1

Question 1

What is Resveratrol?

Answer 1

Resveratrol
* A polyphenol and stilbenoid - two aromatic rings joined by two carbons that are double bonded to one another
* Formed in response to a fungal attack
* Find a lot in grape seed and skin, Vitis vinifera and Japanese knotweed, Polygonum cuspidatum.
* Its thought that the resveratrol in red wine is core to the healthy Mediterranean diet, and French ‘paradox’ that French people have low heart disease levels while eating a lot of cheese etc!

Many in vivo and in vitro studies show a huge range of actions; it is rapidly metabolised in the body, and a high fat breakfast or meal reduces bioavailablity.

Question 2

What are Flavanoids?

Answer 2

Flavonoids
* Flavonoid is a collective term for polyphenolic compounds.
* They consist of **two phenolic rings (A and B) joined in the middle by a central pyran ring (C) **- look at image in notes
* Flavonoids give colour to plants..
* Many flavonoids are yellow and protect plants against sunlight/ free radical damage, which explains why almost all are anti-oxidants.

Discovery of Rutin
* “Vitamin P” isolated from oranges in 1930s, a new vitamin
* Later identified as a flavonoid, rutin.

Most research has been done in vitro and in vivo; but anti oxidant, anti inflammatory, relaxing to smooth muscle, anti-carcinogenic, inhibits some enzymes, and more eg anti viral and anxiolytic

Question 3

What are the pharmacokinetics of flavonoids?

Answer 3

They have poor bioavailability: converted into the aglycone by bowel flora, then undergo further breakdown.

Levels of a flavonoid aglycone in the bloodstream vary:
* Whether administered as an aglycone or glycoside.
* The nature of the bowel flora.
* Enteric and enterohepatic recycling (eliminated to the gut and then reabsorbed) allow flavonoids to be accumulated in vivo over time.

Question 4

What clinical studies have been run on flavonoids?

Answer 4

Clinical studies are usually done on foods

• Protective effect of various flavonoid-rich foods against neurodegeneration, cancer and cardiovascular diseases.
• Decreased risk of CVD.
• Improves venous tone, enhances microcirculation in patients with venous insufficiency, assists healing of venous ulcers and relieves symptoms of acute haemorrhoids.

Diet can really matter!

Question 5

What are the subclasses of flavonoids?

Answer 5

Subclasses of flavonoids are all interrlated in the way they are formed in the plant
* Anthocyanidins
* Chalcones
* Flavanols
* Flavanones: flavanone, hesperetin, and
naringenin.
* Flavones: apigenin, and luteolin.
* Flavonols: quercetin, kaempferol and
myricetin

Flava – prefix: no double bond in the C ring
itself.
Flavo – prefix: double bond between C2 and
C3”

Question 6

What are Anthocyanidins: glycosides and anthocyanins?

Answer 6

Blue, red, purple in berries, flower and vegetables. Pelargonidin, delphinidin, cyanidin and their glycosides.

Health effects of anthocyanins
* Antioxidant, anti-inflammatory
and anticarcinogenic properties.
* Protection against both heart
disease and certain types of
cancer
* Reduction in the risk of diabetes
* Helpful in cognitive function
disorders
* Venotonic
* Helps to improve night vision.

Clinical studies with anthocyanin-rich foods
* Ocular fatigue: prevented myopic refractory
shift (blackcurrant anthocyanins).
* Important for generation of visual purple.
* Halted progression of cataracts.
* Improved oxidative status in healthy adults,
overweight adults, and adult smokers.
* Reduced oxidative DNA damage and a
significant increase in glutathione.
* Reduced the concentration of LDLcholesterol and increase plasma
antioxidants, inhibited platelet aggregation.

Other clinical studies
* Beneficial in dialysis patients.
* Prevented atherosclerosis.
* Improved memory performance.
* Anti-inflammatory.
* Reduced proliferation and
increased apoptosis in colon
tumours.”