|What are Flavonols and flavones?
Flavonols and flavones are plant-derived polyphenolic
compounds that are commonly consumed in the diet.
Flavonoids, present in fruits, vegetables, tea, red wine, or
herbs such as ginkgo biloba, soys, and milk thistle, have
demonstrated potential health benefits of lowering risks on
various chronic conditions. Most of the flavonoids are
considered to be safe and associated with limited side effects
What are the health benefits of flavonols and flavones?
Most flavonoids are believed to be chemo-protective, i.e.
lowering risks of cancers. The preventive effects of flavonoids
on cancer include different mechanisms, dependent on the
properties of that particular flavonoid. Some popular
flavonoids affect cytochrome P450 (CYP) enzymes involving a
detoxification process while some alter cytochrome enzymes
through binding to the aryl hydrocarbon receptor (AhR). 
Flavones (chrysin, baicalein, and galangin), flavanones
(naringenin) and isoflavones (genistein, biochanin A) inhibit the
activity of aromatase (CYP19), thus decreasing estrogen
biosynthesis, i.e. antiestrogenic effects. This may benefit
people at risk of breast and prostate cancers. Activation of
detoxifying enzymes results in the detoxification of
carcinogens, i.e. anticarcinogenic effects. 
Flavonoids such as fisetin, galangin, quercetin, kaempferol, and
genistein are potent non-competitive inhibitors of
sulfotransferase 1A1 (or P-PST); this could interfere
sulfation-induced cancer growth. 
Epidemiological studies have shown beneficial effects of
flavonoids on arteriosclerosis-related pathology in general and
neurodegeneration in particular. Flavonoids can protect the
brain by their ability to modulate intracellular signals promoting
cellular survival. Quercetin and structurally related flavonoids
(myricetin, fisetin, luteolin) showed a marked cytoprotective
capacity in in vitro experiments. But, researchers found that
quercetin did not protect substantia nigra neurons in vivo from
an oxidative insult (6-hydroxydopamine), probably due to
difficulties in crossing the blood-brain barrier. On the other
hand, treatment of permanent focal ischemia with a
lecithin/quercetin preparation decreased lesion volume. 
Epidemiological studies also indicating that high dietary intake
of flavonols reduces the risk of coronary heart disease.
Researchers showed that naturally occurring compounds
chrysin, apigenin, luteolin, quercetin and fisetin were
Unfortunately, most of the flavonoids have a low oral
bioavailability and some of them may interact with drugs
causing ineffectiveness of the therapies or amplifying the toxic
effects of the medicine. Nevertheless, the intake of substantial
amounts of plant-food in a normal diet is important to prevent
cancer or other chronic diseases.
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 Moon YJ, et al, Dietary flavonoids: effects on xenobiotic and carcinogen metabolism. Toxicol In Vitro.
2006 Mar;20(2):187-210. Epub 2005 Nov 11.  Woodman OL, Chan ECh. Vascular and anti-oxidant actions
of flavonols and flavones. Clin Exp Pharmacol Physiol. 2004 Nov;31(11):786-90.  Dajas F, et al,
Neuroprotection by flavonoids. Braz J Med Biol Res. 2003 Dec;36(12):1613-20. Epub 2003 Nov 17.W