Flavonoids

December 28, 2011 by  
Filed under Superfoods

Also see Bilberry

Also known as bioflavonoids, flavonoids are colourful antioxidants found in plants. They are responsible for the colours of fruits (e.g. the red or blue of grape and berry skins) and vegetables. Twelve basic classes (chemical types) of flavonoids have been recognized: flavones, isoflavones, flavans, flavanones, flavanols, flavanolols, anthocyanidins, catechins (including proanthocyanidins), leukoanthocyanidins, chalcones, dihydrochalcones, and aurones. Anthocyanidins and closely related flavonoids such as proanthocyanidins may collectively be referred to as anthocyanosides.

Apart from their antioxidant activity, flavonoids are known for their ability to strengthen capillary walls, thus assisting circulation and helping to prevent and treat bruising, varicose veins, bleeding gums and nosebleeds. They may also be useful in the treatment of heavy menstrual bleeding, where no apparent cause for this is found on medical investigation. A third beneficial effect of some flavonoids such as quercetin, rutin, curcumin, silymarin and green tea polyphenols is their reputed anti-inflammatory effect, which may be related to their ability to inhibit the enzymes cyclo-oxygenase and lipoxygenase, which can act on arachidonic acid in cell membranes to form potent inflammatory substances known as prostaglandins, some of which promote swellings and possibly symptoms such as headaches, rashes and joint pains.

Lemons (outer skin and white pith), and the central white core of citrus fruit generally, are a particularly rich source of flavonoids. The white pith of green peppers is also rich in flavonoids, as is the skin of colourful berries and grapes. Some herbs (such as Ginkgo biloba) are taken partly for the action of their flavonoids.

The names of some of the flavonoids

Anthocyanidins Blue pigments (which may appear red under some conditions) found in the skins of some berries, especially bilberries. Beneficial effects on eyesight and circulation, and some antibacterial action.
Hesperidin Found in citrus peel. Improves abnormal capillary fragility.
Myricetin One of the beneficial antioxidants found in Ginkgo biloba. Helps to prevent free radical damage to nerve cells.
Nobiletin Found in citrus fruits. Has anti-inflammatory action and assists detoxification.
Proanthocyanidins (also
known as pycnogenols)
Related to tannins, these are polyphenolic flavonoids found in pine bark, tea, peanut skins, cranberries and grape seeds and skins. Their antioxidant potency (particularly the varieties found in grape seeds) is reputedly 20 times greater than that of vitamin E.
Quercetin Found in apple peel, onions, tea, Ginkgo biloba and cabbage. Helps to prevent cataract formation. May help allergy-related problems such as hay fever, asthma and eczema. Promotes the more efficient cross-linking of collagen. Quercetin is structurally related to the anti-allergic drug disodium chromoglycate.
Rutin Found in buckwheat. Helps in the treatment of high blood pressure, bruising and haemorrhages under the skin, including redness due to radiation.

Linda Lazarides is Course Director of the School of Modern Naturopathy and author of eight books on health, nutrition and naturopathy.

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