Quercetin (3,3',4',5,7-pentahydroxyflavone) is one of the most abundant and well-studied dietary flavonoids, found in onions, apples, berries, tea, and red wine. Commercial production primarily involves extraction from Sophora japonica flower buds or enzymatic hydrolysis of rutin.
Quercetin demonstrates broad-spectrum biological activities including antioxidant, anti-inflammatory, antihistamine, antiviral, and senolytic properties. It stabilizes mast cells, inhibits histamine release, and modulates NF-kB and NLRP3 inflammasome pathways. Commercially, quercetin is one of the top-selling flavonoid supplements, used in immune defense, allergy relief, cardiovascular health, and longevity formulations.
