A bioflavonoid ingredient from plants. Quercetin occurs naturally in red wine, tea, onions, kale, tomatoes, berries, and many other fruits and vegetables, with the highest concentrations found in plant leaves and skins. Among its chief benefits, quercetin functions as an antioxidant, anti-inflammatory agent, and skin-healing ingredient, likely owing to the stimulating effect it has on the immune system, of which skin is our body's first line of defense.
Quercetin is present in some herbal ingredients, too, including St. John's wort and ginkgo biloba.
In terms of skin care, research has shown that a lipid-based delivery system is optimal for quercetin to exert antioxidant benefits (Source: International Journal of Pharmaceutics, January 2013, pages 56-66). Even more exciting, this type of formula provides an intial burst of quercetin followed by sustained release over a 24-hour period. When quercetin is mixed with silicone and lipids, the intake is greater, as confirmed by testing on human skin (Source: Skin Pharmacology and Physiology, November 2012, pages 57-67.
More good news on the skin care front: quercetin can help defend skin from UVB-related damage, reduce the production of an elastin-degrading enzyme, and help heal and improve the appearance of scars (Sources: European Journal of Pharmaceutical Sciences, December 2012, pages 857-864; Journal of Photochemistry and Photobiology, September 2012, pages 126-131;
Journal of Ethnopharmacology, May 2010, pages 106-114; International Journal of Molecular Medicine, March 2010, pages 347-352; Chinese Medical Sciences Journal, September 2006, pages 179-183; The Journal of Trauma, November 2004, pages 1,032-1,037; and www.naturaldatabase.com).
Ginkgo biloba leaf extract
St. John's wort