Quercetin

A substance belonging to the flavonoids, which are secondary plant substances and are responsible for the coloration of flowers, leaves and fruits. The large group of flavonoids also includes catechins (tannins) and anthocyanins (flower colorants).

Flavonoids have a uniform chemical structure with a phenylchroman backbone. This consists of three rings with attached hydroxyl groups. Numerous further substitutions result in a wide variety of flavonoids.

In plants, flavonoids mostly occur as glycosides. They have a sugar molecule on the middle ring C (rhamnose, glucose, galactose). Quercentin (quercitrin) is found as a glycoside linked to rhamnose in the bark of the American dyer's oak (Quercus tinctoria). It was used to dye wool, silk or cotton.

Quercetin has numerous biological effects: it has antioxidant, antiviral and anti-inflammatory properties and protects the cardiovascular system. Furthermore, tumor-protective (antiproliferative) and antiviral effects are described. The anti-inflammatory effect of quercetin is based on its antioxidant properties and the inhibition of inflammatory enzymes(cyclooxygenase, lipoxygenase): quercetin inhibits the release of inflammatory mediators such as leukotrienes and prostaglandins. Inhibition of histamine liberation from mast cells and basophilic granulocytes also has an anti-inflammatory effect.

Anti-allergic: Due to the stabilizing effect of quercetin on mast cells, the substance could have an anti-allergic effect analogous to the effect of the synthetic flavonoid analogue cromolyn sodium(cromoglycic acid).

Prevention of cardiovascular diseases: The most important cardiovascular effects of quercetin are its antioxidant and anti-inflammatory effects. Quercetin has also been shown experimentally to inhibit platelet aggregation.

Anti-inflammatory: Quercetin is indicated in all inflammatory diseases as it inhibits the formation of prostaglandins and leukotrienes and the release of histamine, as leukotriene B4 is a powerful bronchoconstrictor. The inhibitory effect of quercetin on xanthine oxidase reduces uric acid formation and can be used to treat gout.

400-500 mg three times/day p.o. The water-soluble quercetin preparation Quercetinchalkon is better absorbed. Dosage 250 mg three times/day p.o.

In pure form, the aglycone quercetin is poorly absorbed.

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