Main Functions: Quercetin is a potent antioxidant and has anti-inflammatory activity, protecting cellular structures and blood vessels from the damaging effects of free radicals. It improves blood vessel strength. Quercetin inhibits the activity of catechol-O-methyltransferase that breaks down the neurotransmitter norepinephrine. this effect may lead to elevated levels of norepinephrine and an increase in energy expenditure and fat oxidation. It also means quercetin acts as an antihistamine leading to relief of allergies and asthma. As an antioxidant, it reduces LDL cholesterol and offers protection from heart disease. Quercetin blocks an enzyme that leads to accumulation of sorbitol, which has been linked to nerve, eye, and kidney damage in diabetics.