quercetin gummies

Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it.^[2][3] It has a bitter flavor and is used as an ingredient in dietary supplements, beverages, and foods.

Quercetin is a flavonoid widely distributed in nature.^[2] The name has been used since 1857, and is derived from quercetum (oak forest), after the oak genus Quercus.^[4][5] It is a naturally occurring polar auxin transport inhibitor.^[6]

Quercetin is one of the most abundant dietary flavonoids,^[2][3] with an average daily consumption of 25–50 milligrams.^[7]

In red onions, higher concentrations of quercetin occur in the outermost rings and in the part closest to the root, the latter being the part of the plant with the highest concentration.^[8] One study found that organically grown tomatoes had 79% more quercetin than non-organically grown fruit.^[9] Quercetin is present in various kinds of honey from different plant sources.^[10]

In plants, phenylalanine is converted to 4-coumaroyl-CoA in a series of steps known as the general phenylpropanoid pathway using phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumaroyl-CoA-ligase.^[11] One molecule of 4-coumaroyl-CoA is added to three molecules of malonyl-CoA to form tetrahydroxychalcone using 7,2′-dihydroxy-4′-methoxyisoflavanol synthase. Tetrahydroxychalcone is then converted into naringenin using chalcone isomerase.

Naringenin is converted into eriodictyol using flavanoid 3′-hydroxylase. Eriodictyol is then converted into dihydroquercetin with flavanone 3-hydroxylase, which is then converted into quercetin using flavonol synthase.^[11]

Quercetin is the aglycone form of a number of other flavonoid glycosides, such as rutin (also known as quercetin-3-O-rutinoside) and quercitrin, found in citrus fruit, buckwheat and onions.^[2] Quercetin forms the glycosides quercitrin and rutin together with rhamnose and rutinose, respectively. Likewise guaijaverin is the 3-O-arabinoside, hyperoside is the 3-O-galactoside, isoquercitin is the 3-O-glucoside and spiraeoside is the 4′-O-glucoside. CTN-986 is a quercetin derivative found in cottonseeds and cottonseed oil. Miquelianin is the quercetin 3-O-β-D-glucuronopyranoside.^[12]

A number of taxifolin (also known as dihydroquercetin) glycosides also exists.

Isoquercetin is the 3-O-glucoside of quercetin.

Pharmacokinetics[edit]

The bioavailability of quercetin in humans after oral intake is very low, with one study concluding it must be less than 1%.^[15] Intravenous injection of quercetin shows a rapid decay in concentration described by a two-compartment model (initial half-life of 8.8 minutes, terminal half-life of 2.4 hours).^[15] Because it undergoes rapid and extensive metabolism, the biological effects presumed from in vitro studies are unlikely to apply in vivo.^{[2][16][17][18]} Quercetin supplements in the aglycone form are less bioavailable than the quercetin glycoside often found in foods, especially red onions.^[2][19] Ingestion with high-fat foods may increase bioavailability compared to ingestion with low-fat foods,^[19] and carbohydrate-rich foods may increase absorption of quercetin by stimulating gastrointestinal motility and colonic fermentation.^[2]