A flavonoid substance derived from apples and the bark of apple trees. As for topical application to skin, in-vitro and animal research has shown that it has antioxidant ability, can interrupt melanin synthesis to potentially reduce skin discolorations, inhibits the formation of MMP-1 (which helps protect collagen-generating fibroblasts in skin’s support structure from breaking down), and also serves as a penetration enhancer, which means it can, when properly formulated, help other beneficial ingredients go beyond the superficial layers of skin (Sources: The FEBS Journal, August 2008, pages 3,804-3,814;   Phytochemistry, April 2007, pages 1,189-1,199; Biological and Pharmaceutical Bulletin, April 2006, pages 740-745; European Journal of Pharmaceutics and Biopharmaceutics, March 2004, pages 307-312; International Journal of Pharmaceutics, April 2003, pages 109-116).