Flavones and Flavonols

Tabak, C. et al.. Chronic obstructive pulmonary disease and intake of catechins, flavonols, and flavones the MORGEN Study, Am. J. Respir. Crit. Care Med., 164, 61, 2001. 

Flavonols and flavones have a double bond between C2 and C3 in the flavonoid structure and an oxygen atom at the C4 position. Furthermore, flavonols also have a hydroxyl group at the C3 position. Dihydroflavonols have the same structure as flavonols without the double bond between C2 and C3. 

Hirvonen T, Pietinen P, Virtanen M, Ovaskainen ML, Hakkinen S, Albanes D and Virtamo J. 2001. Intake of flavonols and flavones and risk of coronary heart disease in male smokers. Epidemiology 12 62-67. 

Lin J, Rexrode KM, Hu F, Albert CM, Chae CU, Rimm EB, Stampfer MJ and Manson JE. 2007. Dietary intakes of flavonols and flavones and coronary heart disease in US women. Am J Epidemiol 165 1305-1313. 

Exarchou, V. et al., Do strong intramolecular hydrogen bonds persist in aqueous solution Variable temperature gradient IH, 1H-13C GE-HSQC and GE-HMBC NMR studies of flavonols and flavones in organic and aqueous mixtures. Tetrahedron, 58, 7423, 2002. 

A range of ST cDNAs has been identified from functional genomics studies of A. thaliana, including one (AtST3) that has been shown to encode a flavonoid 7-ST. Unlike BFST3, AtST3 recombinant protein accepts a number of flavonol and flavone aglycones, as well as their 3-O-monosulfated derivatives.However, strict specificity to the 7-hydroxyl was found. 

Approaches to inhibit anthocyanin production that target CHS can cause plant sterility, as flavonols play a role in fertility in some species. It is possible to inhibit anthocyanin production by targeting an enzyme such as DFR, which still allows the formation of flavonols and flavones. Sense or antisense DFR transgenes have been used to reduce or prevent anthocyanin production in several species (Table 3.4), with results similar to those for CHS... 

Jam, confectionery, and herb compositional data are presented in Table 4.12. Honey contains low levels of both flavonols and flavones, and the presence of the flavanone naringenin has also been documented. Fruit jams also contain low levels of flavonols and catechins, which generally reflect the flavonoid profile of the whole fruit. 

An initial estimate of flavonoid intake of 1000 mg/day was calculated in the United States during the 1970s using semiquantitative food composition data (Table 4.13). " This estimate was not questioned until the 1990s with the calculation of dietary flavonol and flavone... 

Several dietary flavonoid intake studies have now been completed using the Dutch composition data often with additional estimates of flavonoid content of local food preferences such as berries (Table 4.14). Comparison of these intake studies indicates that quercetin is consistently the main contributor to flavonol and flavone intake. In the Netherlands, for example, quercetin accounts for 70% of the 23 mg/day total flavonol and flavone intake followed by kaempferol (17%), myricetin (6%), luteolin (4%), and apigenin (3%). ... 

Herrmann, K., Flavonols and flavones in food plants a review, J. Food TechnoL, 11, 433, 1976. 

Hirvonen, T. et al., Flavonol and flavone intake and the risk of cancer in male smokers (Finland), Cancer Causes Control, 12, 789, 2001. 

Data based on analysis of particular diets avoid these limitations but are usually restricted to a few PPT because of the difficulties and cost associated with quantifying so many individual compounds of known structure, to say nothing of the serious difficulties associated with quantifying the uncharacterized derived polyphenols. " When such data are available, they are usually for PPT as aglycones released by hydrolysis (to simplify the analysis still further) and generally for the flavonols and flavones first studied by Hertog et al. since these... 

Certain flavonoids are used by plants to protect them from invasion by parasites. For example, poplar (Populus spp.) cultivars produce a chemical barrier to parasitization by mistletoe (Viscum album).Resistant poplar cultivars were significantly higher in flavonols and flavones compared to susceptible cultivars. Likewise, in Streblus asper the bark and wood of trees that are resistant to the parasite Cuscuta reflexa hold higher levels of flavonoids, as well as steroids and alkaloids. 

Several epidemiological studies have reported inverse relation between intakes of flavonols and flavones and cardiovascular heart diseases (CHD). 

The same authors [204] confirmed these results in the Seven Country Study. The contribution of flavonols and flavones in explaining the variance in coronary heart disease mortality rates across 16 cohorts from seven countries was studied. Flavonol and flavone intake was inversely correlated with mortality from coronary heart disease. These finding are in line with the results of a cohort study in Finnland [205], where a significant inverse gradient was observed between dietary intake of flavonoids and total and coronary mortality. 

A modest but not significant inverse correlation between the intake of flavonols and flavones and subsequent mortality rates was found in a prospective cohort study of US Health Professionals by Rimm et al [206]. The authors do not exclude that flavonoids have a protective effect in men with established coronary heart disease although strong evidence was missing. Also other studies failed to demonstrate a significant statistical association between the intake of polyphenols and CHD. In Great Britain for instance coronary and total mortality even rose with the intake of the major flavonol source, tea [207], The most likely explanation for the latter observation is that in this study tea consumption merely acted as a marker for a lifestyle that favours the development of cardiovascular disease. Indeed, men with the highest intake of tea and flavonols tended to be manual workers, and they smoked more and ate more fat [208],... 

Additionally, men in the highest quartile of flavonol and flavone intake showed a reduced incidence of stroke in a Dutch cohort [18], while a prospective study in postmenopausal women found no association between total flavonoid intake and stroke mortality [15],... 

D) The isoflavonoid genistein also inhibited the contractions induced by noradrenaline, KC1 or PMA with similar IC 0 values than that of flavonols and flavones, which suggests that position 2 or 3 of the phenyl ring is not essential for the vasodilator activity. 

Merken, H.M., Merken, C.D., and Beecher, G.R. 2001. Kinetics methods for the quantitation of anthocyanidins, flavonols, and flavones in foods. J. Agric. Food Chem. 49 2727-2732. 

---