Quercetin one of the most widely distributed flavonoids in plants. Its main natural sources in foods are lettuce, asparagus, onions, broccoli, fruits (apples, berry crops, and grapes), tea and wine. Quercetin is known for its antioxidant activity in radical scavenging and anti-allergic properties characterized by stimulation of immune system, antiviral activity, inhibition of histamine release and decrease in pro-inflammatory cytokines. All mentioned mechanisms of action contribute to the anti-inflammatory and immunomodulating properties of quercetin that can be effectively utilized in treatment of bronchial asthma and allergic rhinitis. Plant extract of quercetin is the main ingredient of many potential anti-allergic drugs and supplements. ("Molecules". 2016 May)

Quercetin and its derivatives are naturally occurring phytochemicals with promising bioactive effects. The antidiabetic, anti-inflammatory, antioxidant, antimicrobial, anti-Alzheimer’s, antiarthritic, cardiovascular, and wound-healing effects of Quercetin have been extensively investigated, as well as its anticancer activity against different cancer cell lines has been recently reported. Many studies had shown that Quercetin is a promising drug target for treating diabetes. A number of mechanisms have been proposed for the antihyperglycemic action of Quercetin, among which insulin sensitivity enhancement, glycogen synthesis promotion, and insulin resistance improvement are common. Quercetin was reported to reduce pain and inflammation associated with arthritis. Additionally, Quercetin has been reported as a potential drug for the treatment of rheumatoid arthritis to reduce joint inflammation. ("ACS Omega" May, 2020)

Quercetin has been studied for many years because of its ability to inhibit various viral infections. It has been reported to inhibit HIV and other retroviruses, such as herpes simplex virus type 1, poliovirus type 1, respiratory  virus, and to significantly decrease the production of infectious particles by hepatitis C virus. Quercetin has also been reported to exhibit antiviral activity against HBV, and influenza A virus.   Quercetin may act in more than one way to deter viral infection, exhibiting some preventive and powerful therapeutic effects.  ("Virology Journal" 2018, July).

Quercetin has unique biological properties that may improve mental/physical performance and reduce infection risk. ("Nutrients". 2016 Mar)

The average western diet supplies 15–40 mg of quercetin a day and higher dietary levels (> 33 mg/day) have been associated with decreased risk of CVD (Cardio Vascular Disease). Quercetin is also available over the counter in the form of supplements that can contain up to 250–1,500 mg quercetin. These large doses are used to “treat” a variety of ailments such as allergies, asthma, bacterial infections, arthritis, gout, eye disorders, hypertension, and neurodegenerative disorders. Supplementation of the diet with quercetin has been shown to reduce BP(Blood Pressure) in hypertensive individuals. We conducted a randomized, double-blind, placebo-controlled crossover trial finding significant reductions in BP. Reductions of this magnitude are clinically relevant and associated with a 14% and 9% decrease in mortality from stroke and coronary heart disease. Our studies to date with humans have not found any adverse side effects ("Pharmaceuticals" (Basel). 2010 Jan)

Quercetin has a skin protective effect against damage caused by UV radiation, histamine, or contact with toxic chemical compounds. Indeed, quercetin is able to reduce redness, itching, and inflammation of damage skin. ("Clin Cosmet Investig Dermatol." 2016)



DESIGN – The info below needs to be put into a chart

     Food                            Quercetin Content


Red leaf lettuce

                     30.6mg/100 g



                      23.6mg/100 g

Onions                                      22.0 mg/100 g

Cocoa powder                          20.0 mg/100 g

Cranberries                              14.0 mg/100 g

Apples                                      4.57 mg/100 g

Green tea                                 2.69 mg/100g

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