Quercetin is a flavonoid and, to be more specific, a flavonol. It is the aglycone form of a number of other flavonoid glycosides, such as rutin and quercitrin, found in citrus fruit, buckwheat and onions. Quercetin forms the glycosides quercitrin and rutin together with rhamnose and rutinose, respectively. Quercetin is found to be the most active of the flavonoids in studies, and many medicinal plants owe much of their activity to their high quercetin content. Quercetin has demonstrated significant anti-inflammatory activity because of direct inhibition of several initial processes of inflammation. For example, it inhibits both the manufacture and release of histamine and other allergic/inflammatory mediators. In addition, it exerts potent antioxidant activity and vitamin C-sparing action. Quercetin is sometimes promoted to help prevent or treat different types of cancer. It has also been promoted to help with the symptoms of chronic prostatitis (swelling of the prostate gland) and to relieve some of the neurologic complications of diabetes.
Quercetin also shows anti-tumour properties. A study in the British Journal of Cancer showed that, when treated with a combination of quercetin and ultrasound at 20 kHz for 1 minute duration, skin and prostate cancers show a 90% mortality within 48 hours with no visible mortality of normal cells. Recent studies have supported that quercetin can help men with chronic prostatitis, and both men and women with interstitial cystitis, possibly because of its action as a mast cell inhibitor. Quercetin may have positive effects in combating or helping to prevent cancer, prostatitis, heart disease, cataracts, allergies/inflammations, and respiratory diseases such as bronchitis and asthma. It also has been claimed to have antidepressant properties, however any claim of quercetin action against neurological diseases should be treated with skepticism due to the fact that quercitin is a neurotoxin in vitro. Quercetin is a common chemical pigment in the rinds and barks of a wide variety of plants.
Quercetin's anti-histamine action may help to relieve allergic symptoms and asthma symptoms. The anti-inflammatory properties may help to reduce pain from disorders such as arthritis. Men who are concerned about prostate problems would also benefit from quercetin. Quercetin may also help reduce symptoms like fatigue, depression and anxiety. Quercetin appears to have anti-inflammatory and antioxidant properties. It has been promoted as being effective against a wide variety of diseases, including cancer. While some early lab results appear promising, as of yet there is no reliable clinical evidence that quercetin can prevent or treat cancer in humans. Quercetin is said to have a number of uses, but most of these are based on early findings from lab studies. Some early studies have suggested quercetin has antihistamine properties, and it is often promoted to help control allergies and asthma.