Japanese Knotweed

Jul 26, 2022

Scientific Name(s): Polygonum cuspidatum Siebold & Zucc.
Common Name(s): Fleeceflower, Huzhang, Japanese bamboo, Japanese knotweed, Mexican bamboo


Huzhang (Japanese Knotweed) has been used in traditional Chinese medicine as well as in Japan and Korea for many years. Although used for various applications, few clinical studies validate claims and guidance regarding dosing or safety is limited.

For information specific to the activity of resveratrol, see Resveratrol.


Clinical evidence on which to base dosing guidelines is limited. One clinical study used an oral extract of P. cuspidatum 200 mg containing resveratrol 40 mg over 6 weeks for anti-inflammatory effect.




Do not use. Avoid use during lactation because information is lacking.


None well documented.

Adverse Reactions

Clinical evidence is limited.


Information is limited.

Scientific Family

  • Polygonaceae (Buckwheat)


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. Chen 2013 ,  Peng 2013 ,  USDA 2013


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. Hao 2012 ,  Li 2013 ,  Peng 2013


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. Chen 2012 ,  Du 2013 ,  Hao 2012 ,  Kirino 2012 ,  Li 2013 ,  Peng 2013 ,  Piotrowska 2012 ,  Shen 2011 ,  Zhang 2012

Emodin and phsycion demonstrate anti-inflammatory effects. Shen 2011  The stilbene content, including resveratrol, resveratroloside, polydatin, and piceatannol, are responsible for observed antioxidant activity. Kirino 2012 ,  Piotrowska 2012

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. Babu 2005 ,  Chen 2013 ,  Hao 2012 ,  Peng 2013

Uses and Pharmacology

Research reveals no clinical data regarding the use of Japanese knotweed for antioxidant effect.

Anti-inflammatory effects

Animal data

Reductions in inflammation and improvements in wound-healing rates were demonstrated with topical application of P. cuspidatum extract in studies in mice. Bralley 2008 ,  Peng 2013 ,  Wu 2012  With oral extract reductions in tumor necrosis factor alpha (TNF-alpha), interleukin (IL-6) and C-reactive protein were found in animals with experimentally induced arthritis. Han 2012  An analgesic effect was also demonstrated in rodents. Han 2012

Clinical data

Limited clinical studies have been conducted. A study among healthy volunteers found a decreased expression of modulators of inflammation in mononuclear cells following 6 weeks of P. cuspidatum extract daily containing resveratrol 40 mg. Ghanim 2010  A small study (N = 20) found decreased plasma TNF-alpha and IL-6 versus placebo. Zahedi 2013

Antimicrobial activity

Animal data

In vitro studies have shown broad antibacterial and antifungal activity of P. cuspidatum extracts. Peng 2013 ,  Piotrowska 2012 ,  Song 2006  Activity against Streptococcus mutans has been investigated in oral health. Ban 2010 ,  Pandit 2012  An ethanol extract showed inhibitory activity against HIV-1 in vitro. Lin 2010 ,  Peng 2013

Clinical data

There are no clinical data regarding the use of P. cuspidatum as an antimicrobial agent.

Antioxidant effects

Animal data

Studies in rats and mice have shown antioxidant properties of P. cuspidatum that are generally attributed to the chemical constituents of resveratrol, polydatin, piceatannol, and anthraquinones and stilbenes. Kim 2010 ,  Peng 2013 ,  Piotrowska 2012 ,  Zhang 2012  Carbon tetrachloride–induced liver injury and induced acute cerebral ischemia were reduced by oral extracts of P. cuspidatum. Kim 2010 ,  Zhang 2012  In models of vascular dementia and Parkinson disease in rats, P. cuspidatum extract and polydatin administered orally resulted in improved cognitive and behavioral measures and increased antioxidant capacity in the relevant tissues. Li 2012 ,  Wang 2011

Clinical data

There are no clinical data regarding the use of P. cuspidatum for antioxidant effect.


Animal data

In vitro studies using oral, lung, and prostate cancer cells, and in hepatocarcinoma, glioma, and leukemia have been conducted. Ethanol, methanol and aqueous P. cuspidatum extracts show pro-apoptotic activity and inhibition of angiogenesis, as well as direct cytotoxicity. Hu 2012 ,  Jeong 2010 ,  Lin 2010 ,  Shin 2011  Mice with Ehrlich carcinoma had an increased lifespan when given P. cuspidatum extract. Peng 2013

Clinical data

Research reveals no clinical data for the use of P. cuspidatum regarding cancer.


Animal data

Studies conducted in the 1980s and 1990s in rodent models of hyperlipidemia showed decreased total cholesterol, as well as decreased triglycerides and low-density lipoprotein. Peng 2013  Oral polydatin from P. cuspidatum showed similar results in rabbits and hamsters. Du 2009 ,  Xing 2009

Clinical data

There are no clinical data regarding the use of P. cuspidatum in hyperlipidemia.


Clinical evidence on which to base dosing guidelines is lacking. One study used an oral extract of P. cuspidatum 200 mg over 6 weeks. The preparation was standardized to contain resveratrol 40 mg. Zahedi 2013

Topical application of P. cuspidatum extract has been studied in mice for anti-inflammatory effects. Bralley 2008 ,  Wu 2012

Pregnancy / Lactation

Do not use in pregnancy. Huzhang is listed as an abortifacient in traditional Chinese medicine texts. Peng 2013

Avoid use during lactation; information regarding use during lactation is lacking.


The area under the curve of carbamazepine and its active metabolite were increased in rats fed P. cuspidatum, suggesting an increased risk of carbamazepine toxicity. Chi 2012

Adverse Reactions

Clinical evidence on which to base guidance is limited. A study conducted in basketball players over 6 weeks did not report adverse events. Zahedi 2013


Information is limited. Du 2013 ,  Peng 2013  The oral median lethal dose (LD50) of anthraquinones in mice is approximately 9 g/kg body weight. The LD50 of emodin and polydatin is 250 and 1,000 mg/kg, respectively. Parenteral polydatin caused peritonitis in a subacute toxicity test in animals. No hemolysis, agglutination reaction, or systemic anaphylaxis/skin allergy was found in tests conducted in rabbits. Peng 2013

source :: https://www.drugs.com/npp/japanese-knotweed.html