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Japanese Knotweed
Scientific Name(s): Polygonum cuspidatum Siebold & Zucc.
Common Name(s): Fleeceflower, Huzhang, Japanese bamboo, Japanese knotweed, Mexican bamboo
Botany
P. cuspidatum is a perennial plant growing to approximately 2 m tall. It has mucous hollow stems with reddish purple spots and ovate/elliptical deciduous leaves (5 to 12 cm by 4 to 9 cm). The male and female flowers occur on separate plants, and the fruits are black/brown, shiny, and ovoid. The plant is native to eastern Asia, including Japan, China, and Korea. It is cultivated in those countries and in the US, and is propagated by seeds or the root. Synonyms include Pleuropterus cuspidatus (Siebold & Zucc.) Moldenke, Fallopia japonica (Houtt.) Ronse Decr., Pleuropterus zuccarinii (Small) Small, Polygonum cuspidatum Siebold & Zucc. var. compactum (Hook. f.) L.H. Bailey, and Reynoutria japonica Houtt.
Because of the plant's spreading rhizomes, P. cuspidatum is grown commercially as a major source for resveratrol production (see Resveratrol monograph), while also being considered a noxious, invasive class B or C weed in certain US states.
History
At least 100 prescriptions using the root exist in the Pharmacopoeia of the People's Republic of China to treat bronchitis and cough, gonorrhea, inflammation, infection, jaundice, hyperlipidemia and hypertension, menopausal symptoms and amenorrhea, and skin burns. The root is used extensively in traditional medicine in China, Japan, and Korea, and the young plant parts are eaten as a vegetable. P. cuspidatum is a primary source of resveratrol, which is widely available in the United States as a botanical dietary supplement.
Chemistry
Volatile essential oils are described for the leaves, but the roots are the main plant part used traditionally. Major constituent chemicals include quinines (eg, anthraquinone, naphthoquinone, phylloquinone) and emodin-type anthroquinones, stilbenes (eg, resveratrol, piceatannol polydatin), flavonoids (eg, quercetin, catechin, rutin), coumarins, lignans, and other compounds.
Emodin and phsycion demonstrate anti-inflammatory effects. The stilbene content, including resveratrol, resveratroloside, polydatin, and piceatannol, are responsible for observed antioxidant activity.
Methods of identification have been published, including high-performance liquid chromatography and thin-layer chromatography, which are based on the content of emodin and polydatin (minimum concentrations of 0.6% and 0.15%, respectively, per the Chinese pharmacopoeia). Chemical composition varies seasonally and with harvest time.
