Quercetin

Quercetin is a plant flavonol belonging to the flavonoid group of polyphenols. It occurs in many fruits, vegetables, leaves, seeds and grains, with capers, red onions and kale named as common foods that contain appreciable amounts of it. It has a bitter flavor and is used as an ingredient in dietary supplements, beverages and foods. The source lead presents it as a food and supplement compound and does not describe it as an approved medicine, so this entry records it as a plant-derived substance used in the diet rather than as a prescription drug.