Flavonoids is the umbrella term given to some 4,000 compounds that impart the colorful pigment to fruits, vegetables and herbs. Also found in legumes, grains and nuts, flavonoids can act as effective antivirals, anti-inflammatories, antihistamines and antioxidants. They're useful for reducing cancer risk and serve to prevent or treat a wide variety of conditions.
While research generally supports the healing potential of flavonoids, only a few have been widely studied. Some standouts include genistein, found in soybeans and some other legumes; quercetin, found in apples and onions; PCOs (procyanidolic oligomers, also known as proanthocyanidins), found in abundance in pine bark and grape seed extract, as well as in red wine; citrus flavonoids, including rutin and hesperidin, found in oranges, grapefruits, tangerines and other citrus fruits; and polyphenols, particularly EGCG (epigallocatechin-gallate), found in green tea. Researchers feel the latter may be the most effective cancer-battling compound discovered to date.
Structure of Flavonoids
Various subgroups of flavonoids are classified according to the substitution patterns of ring C. Both the oxidation state of the heterocyclic ring and the position of ring B are important in the classification.
Examples of the 6 major subgroups are:
(generally in herbaceous families, e.g. Labiatae, Umbelliferae, Compositae).
3. Flavonol (generally in woody angiosperms) Quercitol (Ruta graveolens, Fagopyrum esculentum, Sambucus nigra) Kaempferol (Sambucus nigra, Cassia senna, Equisetum arvense, Lamium album, Polygonum bistorta). Myricetin.
Most of these (flavanones, flavones, flavonols, and anthocyanins) bear ring B in position 2 of the heterocyclic ring. In isoflavonoids, ring B occupies position 3.
A group of chromane derivatives with ring B in position 4 (4-phenyl-coumarins = neoflavonoıds) is shown below.
The Isoflavonoids and the Neoflavonoids can be regarded as abnormal flavonoıds.
As antioxidants, flavonoids (or "bioflavonoids") help prevent the cell damage caused by unstable oxygen molecules known as free radicals. Among the many benefits attributed to flavonoids are reduced risk of cancer, heart disease, asthma, and stroke. They may play a special role in protecting the brain. Flavonoids, like other antioxidants, do their work in the body by corralling cell-damaging free radicals and metallic ions. But flavonoids go beyond the yeoman work of your average antioxidant; scientists have found that certain flavonoids have antihistamine, antimicrobial, memory- and even mood-enhancing properties. Flavonoids are present in myriad fruits and vegetables.
Apples - Quercetin is the flavonoid that enables apples to keep the doctor away. Quercetin has been shown to: Reduce cancer risk, prevent heart attacks, stave off cataracts, control asthma, prevent recurrent gout attacks, and speed healing from acid reflux.
Green Tea - Green tea contains, among others, the cancer-fighting flavonoid epigallocatechin gallate (ECGC). ECGC is unique in that it seems to battle cancer at all stages, from thwarting chemical carcinogens, to suppressing the spread of tumors. ECGC is as much as 100 times more powerful an antioxidant as vitamin C, and 25 times more powerful than vitamin E. ECGC also may account for the antibacterial properties of green tea.
Chocolate - Chocolate contains many of the same flavonoids found in tea. The darker the chocolate, the more flavonoids present. Cocoa powder is the richest source by weight, and to maximize your benefits, make your hot chocolate from scratch. Homemade hot chocolate will provide you with more flavonoids than a store-bought mix.
Red Wine - Flavonoids are the source of the well-known "French Paradox" (the ability of the French to consume lots of fat-laden cheese without dropping like flies from heart attacks). The red wine they enjoy so well is flavonoid-rich, which lowers their risk of heart disease. And if a man is not a drinker, he can get almost all the same benefits from purple grape juice.
Pomegranates - Pomegranate juice may have almost three times the antioxidant potency of an equal volume of green tea or red wine.
Chamomile Tea - Relaxing chamomile tea is home to the flavonoid called apigenin, one of a handful of flavonoids recently found to have mood-enhancing properties. Currently the focus of intense study, they are thought to act on the same parts of the brain as common anti-anxiety drugs. In fact, certain synthetic flavonoids have been shown to have anxiolytic properties superior to diazepam.