Potent polyphenolic antioxidant that is abundant in red grapes and, therefore, in red wine (unfortunately for some of us, not in white wine). Resveratrol has been reported in numerous studies to be one of the most potent natural chemopreventive agents inhibiting the cellular processes associated with tumor development, including initiation, promotion, and progression. It also has significant anti-inflammatory properties.
Conversely, there is research showing it to be associated with cell death when applied in pure doses directly to skin cells and exposed to UV radiation. Of course, this has nothing to do with how resveratrol is used in skin-care products, but it is an interesting example of how more is not necessarily better when it comes to skin-care ingredients!
Other research has shown that resveratrol applied to skin seems to have a stimulating and protecive effect on glutathione, the body's master antioxidant. (Sources: Free Radical Biology and Medicine, October 2014, pages 213-223; Anticancer Research, September–October 2004, pages 2783–2840; Medicinal Chemistry, November 2005, pages 629–633; Molecular Nutrition and Food Research, May 2005, pages 405–430; Antioxidant Redox Signal, December 2001, pages 1041–1064; and Mutation Research, Genetic Toxicology and Environmental Mutagenesis, September 2001, pages 171–180).