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Quercetin - origins and benefits


Quercetin is one of the secondary plant substances (phytamines). Secondary plant substances come in a wide variety of chemical structures, each with specific properties. The best-known groups of secondary plant substances include: Polyphenols, isoflavones and carotenoids. Quercetin belongs to the group of polyphenols and their subgroup, the (bio-)flavonoids. There are over 5 of the organic flavonoids.000 different species that occur naturally in plants. They are responsible for the flower and leaf color of the plant as well as for protection against UV radiation, predators, viruses, fungi and bacteria. Quercetin is the most common flavonoid and can be used to build other flavonoids.

Quercetin is absorbed into the body via the (v.a small intestine into the blood. According to current studies, a little less than half of the amount consumed is absorbed by the body and it takes up to nine hours after consumption until the quercetin is available to the body. The body does not store quercetin permanently, but rather excretes it after approx. 35 hours off again. Therefore, quercetin should be administered regularly as part of therapy.


A high quercetin content can be found, for example, in capers (around 1600 mg quercetin per kg), onions (around 284-486 mg quercetin per kg), chives (245 mg), cranberries (156 mg), black currants (69 mg) and in kale (60 mg).

Quercetin is particularly important.a in the outer shells or Layers of plants (e.g. in tree bark) and fruits (e.g. contained in grapes, apples, onions) to protect them from free radicals. Of course, this also means that almost no quercetin is absorbed if the outer shells are removed before consumption. For example, Quince peels contain up to 180 mg of quercetin per kg. However, hardly any relevant amounts of quercetin can be found in the fruit body itself. However, only minimal amounts can be found inside. Onions also contain approx. 20% of the quercetin is directly under the shell and is therefore usually removed during skinning.

The cultivation method is also relevant for the quercetin content. For example, Tomatoes grown organically contain ~80% more quercetin than those grown conventionally. In addition, heat during cooking can cause further quercetin losses (according to studies up to 25%).

V. stands out under the tree bark.a that of the oak in terms of quercetin content, which also gives rise to the name “Quercetin” - because “quercus” is the Latin name for “oak”; more precisely: for the dyer oak (Quercus velutina). But over time, a very high quercetin content has also been found in the bark of other tree species. The QIDOSHA quercetin is obtained from the Japanese string tree (Sophora japonica), as its flower extract contains a particularly high amount of natural quercetin.

Benefits and mode of action

Since there have been hardly any scientific studies on quercetin in humans to date, so-called “health claims”, i.e.H Health promises associated with taking it are not permitted. The study situation therefore relates primarily toa on laboratory and animal experiments. However, since there are numerous promising starting points here, clinical studies on humans can be expected in the near future.

It is undisputed that quercetin appears to be a particularly strong antioxidant that is roughly comparable to OPC or epigallocatechin gallate (EGCG) from green tea leaves. The reason for this can be found in the chemical structure of quercetin - because it is a polyphenol that has an additional hydroxyl group instead of a sugar molecule. And the more OH groups a polyphenol has, the higher its antioxidant effect.

Another special feature of flavonoids such as quercetin is their ability to convert already oxidized substances (e.g. to regenerate vitamins C and E), i.e.H to give them back their antioxidant power.

In a meta-study from 2019 on the effect of quercetin in diabetes, researchers were able to find out based on animal studies that with doses of 10, 25 and 50 mg of quercetin each kg body weight there was a significant difference between the mean values ​​of serum glucose levels.

A Japanese study suggests that quercetin could have an anti-allergic effect by inhibiting the so-called histamine H1 receptor (H1R). The severity of allergy symptoms also increases in proportion to the activity of this receptor.

A study from the University of Naples postulates an anti-inflammatory effect of quercetin in that it is in principle able to reduce concentrations of the tissue hormone prostaglandin E2 and the fatty acid derivative leukotriene B4. Both substances are relevant for the initiation of inflammatory processes and are significantly involved in the release of inflammatory mediators such as histamine.

A study from 2007 could have a blood pressure lowering effect. The test subjects were administered 730 mg of quercetin daily for almost a month and a reduction in systolic (−7 ± 2 mm Hg) and diastolic (−5 ± 2 mm Hg) blood pressure was determined in patients with high blood pressure. Further clinical studies are therefore recommended.

How do I recognize a high-quality product?

When purchasing, you should make sure that the product is 100% natural. The premium flower extract should come from the Japanese string tree Sophora japonica and ideally have an extract ratio of 15:1. The water-alcohol extract used for production should be highly pure and contain no chemical solvents. Capsules can be perfectly integrated into your everyday life as a nutritional supplement.

Legal consumer information

German and European case law wants to protect consumers from supposedly misleading claims about effectiveness. The statements made here refer to the original Ayurvedic and TCM texts. This ancient knowledge, which is thousands of years old, is based on experiences that are passed on from generation to generation. It is not intended to claim that the products described here have an effect in the sense of western medicine. All products are nutritional supplements; they are not medications and have no medical effect. If you are sick and need medical care, please contact your doctor or pharmacist


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