QuercetinQuercetin, a water soluble plant pigment (or, flavonoid), is found in plants and foods and cannot be produced in the human body. It is one of the most bioactive flavonoids, helping to support cardiometabolic, cellular and immune health. It is also considered a phytoestrogen. This quercetin supplement also promotes cardiovascular health by protecting lipids from oxidation and supports the health of capillaries by enhancing their strength and integrity.