It is known by the common name Japanese knotweed, is a tall, stout herbaceous perennial (Seiger, 2005) and is a member of the Polygonaceae (Seiger, 2005).
Protykin is an all-natural, high potency standardized extract of trans-resveratrol (20%) and emodin (10%) derived from the dried rhizome of Polygonum cuspidatum. Previous studies have demonstrated free radical scavenging and anti-inflammatory activities of resveratrol. AIM: To establish an optimal HPLC method for the determination of the (E)- and (Z)-diastereomers of resveratrol and resveratrol glucoside from the roots of Polygonum cuspidatum. METHODS: The determination was conducted by using reversed-phase high liquid chromatography. Red wine, in moderation, has long been thought of as heart healthy. However, the most popular source of resveratrol is from Japanese knotweed extract (Latin name:Polygonum cuspidatum). Resveratrol (3,5,4'-trihydroxystilbene) is a polyphenolic phytoalexin. When talk about resveratrol, we have to mention red wine since resveratrol is first popularly known in red wine. In fact, resveratrol was actually first isolated in 1940 from white hellebore roots by the Japanese scientist Michio Takaoka. Fallopia japonica, commonly known as Japanese knotweed, is a large, herbaceous perennial plant of the family Polygonaceae, native to East Asia in Japan, China and Korea. In North America and Europe the species is very successful and has been classified as an invasive species in several countries. There is a real lack of information and understanding of what Japanese knotweed is and the actual damage it can cause. Without actual advice and guidance, surveyors have been unsure of how to assess the risk of Japanese knotweed, which can result in inconsistent reporting of the plant in mortgage valuations. When talk about resveratrol, we have to mention red wine since resveratrol is first popularly known in red wine. In fact, resveratrol was actually first isolated in 1940 from white hellebore roots by the Japanese scientist Michio Takaoka. Red wine, in moderation, has long been thought of as heart healthy. However, the most popular source of resveratrol is from Japanese knotweed extract (Latin name:Polygonum cuspidatum) Jd8Shanghai Natural Bio-engineering Co., Ltd. Resveratrol (3,5,4'-trihydroxystilbene) is a polyphenolic phytoalexin.  The plant is generally referred to as Polygonum cuspidatum by American authors and as Reynoutria japonica in the United Kingdom and Europe. Recent evidence suggests that this plant should be reclassified as Fallopia japonica (Bailey, 1990).  Contents comparison of resveratrol and polydatin in the wild Polygonum cuspidatum plant and its tissue cultures.: Zhongguo Zhong Yao Za Zhi. 2006; 31(8):637-41 (ISSN: 1001-5302).Yu SH; Zha JP; Zhan WH; Zhang DQ.College of Pharmacy, Hebei Medical University, Shijiazhuang, China. AIM: To establish an optimal HPLC method for the determination of the (E)- and (Z)-diastereomers of resveratrol and resveratrol glucoside from the roots of Polygonum cuspidatum. METHODS: The determination was conducted by using reversed-phase high liquid chromatography. Polygonum cuspidatum, known by the common name Japanese knotweed, is a tall, stout herbaceous perennial (Seiger, 2005) and is a member of the Polygonaceae (Seiger, 2005). In China it is referred to as Hu Zhanz. Japanese knotweed is also known under the scientific names Fallopia japonica and Reynoutria japonica. Polygonum cuspidatum has many different positive medicinal uses, mainly from the stilbene compound, resveratrol, and its derivatives. Severe side effects directly from the derivatives of the plant, which are unknown, make it a useful herbal remedy. Polydatin is extracted from a traditional Chinese herbal medicine, Polygonum cuspidatum, and has a special effect in shock treatment. The aim of this study is to explain the cellular and molecular basis of Polydatin in shock treatment. AIM: To establish an optimal HPLC method for the determination of the (E)- and (Z)-diastereomers of resveratrol and resveratrol glucoside from the roots of Polygonum cuspidatum. METHODS: The determination was conducted by using reversed-phase high liquid chromatography. Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a stilbenoid, a type of natural phenol, and a phytoalexin produced naturally by several plants in response to injury or when the plant is under attack by pathogens such as bacteria or fungi. Food sources of resveratrol include the skin of grapes, blueberries, raspberries, and mulberries. As of 2014, there is limited evidence of health effects in humans. JAPANESE KNOTWEEDRoot(Fallopia japonica / syn. Polygonum cuspidatum) extracted by tincture in food grade alcohol Antiviral / Antimicrobial / Antiviral / Diuretic / Anti-inflammatory / Antitussive / Emmenagogue / Febrifuge. Plant Description/History: Knotweed is native of China, North and South Korea as well as Japan (Seiger, 2005). 
http://www.mdidea.com/products/herbextract/resveratrol/research.html https://www.linkedin.com/pulse/20140805055958-283555965-japanese-knotweed-extract-polygonum-cuspidatum-resveratrol-98 https://en.wikipedia.org/wiki/Japanese_knotweed http://www.hnkeyuan.com/antioxidants/resveratrol.html http://mdidea.com/products/herbextract/resveratrol/data02.html http://www.mdidea.com/products/herbextract/resveratrol/research.html http://klemow.wilkes.edu/Polygonum09.html http://www.mdidea.com/products/herbextract/resveratrol/research.html https://en.wikipedia.org/wiki/Resveratrol https://www.beneficialbotanicals.com/tincture-information/japanese-knotweed.html
what is Polygonum cuspidatum extract