Flavonoids are a group of molecules widely distributed among various plant species.
Over 2000 individual chemicals have been isolated, investigated and tested.
The flavonoids as a group ,are potent antioxidants with specific ones capable of inhibiting the metabolism of carcinogens.
Flavonoids are grouped into the following types.
1. Flavones (tangeretin and nobiletin) are found in citrus fruits and are believed to modify cytochrome P450 enzymes and inhibit the invasiveness of certain tumors.
2. Flavonols (quercetin and kaempferol) are found in cereal grains and vegetables are potent inhibitors of P450 reactions.
3. Polyphenols (catechins) are found in green tea. They have been reported to inhibit the formation of nitrosamines. Nitrosamines are formed when nitrites, used in the curing of ham and bacon, combine with amino acids. Nitrosamines are known carcinogens.
4. Flavonones (naringin) are found in high concentration in grapefruit and are anti-carcinogenic.
5. Isoflavones, found in soybeans, are considered cancer protective foods. Isoflavones are hormone-like compounds with weak estrogenic and antioxidant activity. Genistein, isolated from soybeans, inhibits numerous enzyme systems and retards the blood supply to cancer cells.
6. Stilbenes are flavonoid-like compounds synthesized by grapes and berries and thought to repress cancer growth.