Flavonols are a class of

flavonoid Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...

s that have the 3-hydroxyflavone backbone (IUPAC name : 3-hydroxy-2-phenylchromen-4-one). Their diversity stems from the different positions of the phenolic

-OH In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...

groups. They are distinct from flavanols (with "a") such as

catechin Catechin is a flavan-3-ol, a type of secondary metabolite providing antioxidant roles in plants. It belongs to the subgroup of polyphenols called flavonoids. The name of the catechin chemical family derives from '' catechu'', which is the ta ...

, another class of flavonoids. Flavonols are present in a wide variety of fruits and vegetables. In Western populations, estimated daily intake is in the range of 20–50 mg per day for flavonols. Individual intake varies depending on the type of diet consumed. The phenomenon of dual

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, ...

(due to

excited state intramolecular proton transfer Excited state intramolecular proton transfer (ESIPT) is a process in which photoexcited molecules relax their energy through tautomerization by transfer of protons. Some kinds of molecules could have different minimum-energy tautomers in different ...

or ESIPT) is induced by tautomerism of flavonols (and glucosides) and could contribute to plant

UV protection Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

and flower colour. Besides being a subclass of

flavonoids Flavonoids (or bioflavonoids; from the Latin word ''flavus'', meaning yellow, their color in nature) are a class of polyphenolic secondary metabolites found in plants, and thus commonly consumed in the diets of humans. Chemically, flavonoids ...

, flavonols are suggested by a study of cranberry juice to play a role along with

proanthocyanidin Proanthocyanidins are a class of polyphenols found in many plants, such as cranberry, blueberry, and grape seeds. Chemically, they are oligomeric flavonoids. Many are oligomers of catechin and epicatechin and their gallic acid esters. More compl ...

s, in the juice's ability to block bacterial adhesion, demonstrated by the compressing the fimbria of ''E. coli'' bacteria in the urinary tract so as to greatly reduce the ability of those bacteria to stay put and initiate an infection. Flavonol aglycones in plants are potent antioxidants that serve to protect the plant from

reactive oxygen species In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen ...

(ROS).

Flavonols

Flavonol glycosides

Drug interactions

Flavonoids have effects on CYP (

P450 Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compo ...

) activity. Flavonols are inhibitor of

CYP2C9 Cytochrome P450 family 2 subfamily C member 9 (abbreviated CYP2C9) is an enzyme protein. The enzyme is involved in metabolism, by oxidation, of both xenobiotics, including drugs, and endogenous compounds, including fatty acids. In humans, the prote ...

and

CYP3A4 Cytochrome P450 3A4 (abbreviated CYP3A4) () is an important enzyme in the body, mainly found in the liver and in the intestine. It oxidizes small foreign organic molecules ( xenobiotics), such as toxins or drugs, so that they can be removed from t ...

, which are

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...

s that metabolize most drugs in the body.

Technological uses

A 2013 study showed that it is possible by optical methods to quantify the flavonol accumulation in some fruit and thus to sort fruit according to fruit quality and storage durability.

Effects on health

A 2022 study indicated an association between consumption of flavonols (found in food) and a lower rate of decline of cognitive ability, including memory.

References

External links

* {{flavonol