Quercetin is a plant pigment belonging to a group of plant compounds called flavonoids, which are present in grains, fruits and vegetables. As an antioxidant, it may bind to and neutralize free radicals which are known to cause cellular damage. As an anti inflammatory agent, it may help reduce swelling and inflammation in the body. Individuals who take Quercetin supplement are looking for an immunity booster, inflammation reducer and improved general health.