Polygonum cuspidatum or Giant Knotweed or Japanese Knotweed owes its antioxidant benefits to its resveratrol content. It is a traditional Chinese Medicine used for circulation and heart health. Resveratrol has been shown to exert an antiinflammatory and antiaging effects in vitro and in animal models. However, these studies had subjects take resveratrol supplements, not use a skin cream containing resveratrol.
Resveratrol is a member of a group of plant compounds called polyphenols. Resveratrol is found in the skin of red grapes, but other sources include peanuts and berries. Most resveratrol capsules sold in the U.S. contain extracts from the Japanese and Chinese knotweed plant Polygonum cuspidatum. Other resveratrol supplements are made from red wine or red grape extracts.
This ingredient is not to be confused with Polygonum Multiforum (different composition from a related plant) and Pueraria lobata (which is also called Kudzu).
High-speed counter-current chromatography separation and purification of resveratrol and piceid from Polygonum cuspidatum
An Antiinflammatory and Reactive Oxygen Species Suppressive Effects of an Extract of Polygonum Cuspidatum Containing Resveratrol
Biological & Pharmaceutical Bulletin, January 1995, pages 162–166