Quercetin is an antioxidant flavonol found naturally in a variety of foods such as apples, plums, red grapes, green tea, elderflower and onions, to name just a few. Quercetin is a flavonol compound widely distributed in plant kingdom with various biological activities. Quercetin is a flavonol compound. Flavonoids mostly exist in the form of glycosides, which form a variety of flavonoid glycosides due to the different types and positions of sugars connected. The sugars that make up flavonoid glycosides are mostly monosaccharides. Flavonols are less water-soluble, while their glycosides are more soluble in water. The market for Quercetin is growing rapidly as its health benefits become more widely known. Quercetin has been found to fight inflammation and acts as a natural antihistamine. In fact, Quercetin's antiviral properties seem to be the focus of many studies, with numerous studies highlighting Quercetin's ability to prevent and treat the common cold and flu.
Among the latest papers on this powerful antioxidant is a review published in March 2019 in Phytotherapy Research that reviewed nine randomized controlled trials on the effects of Quercetin on metabolic syndrome.
Metabolic syndrome is a cluster of health problems that increase the risk of Ⅱ diabetes, heart disease and stroke, including high blood pressure, high blood sugar, high triglyceride levels and fat around the waist. While the comprehensive study found no effect on fasting glucose, insulin resistance, or hemoglobin A1c levels, further subgroup analysis showed that Quercetin supplementation "significantly reduced" fasting glucose in studies taking at least 500 mg daily for at least eight weeks.
Quercetin can also cause tumor regression by interacting with DNA to activate the mitochondrial pathways of apoptosis (programmed cell death in damaged cells), according to a study published in 2016. Quercetin was found to induce cytotoxicity of leukemia cells, and the effect was dose-dependent. Limited cytotoxic effects were also found in breast cancer cells. Overall, Quercetin allowed mice with cancer to live five times longer than untreated controls. The potential use of Quercetin as an adjunct to cancer therapy deserves further exploration.