Japanese knotweed (Polygonum cuspidatum var. Japonicus or Hu Zhang) is an herb used in
traditional Chinese medicine. The root of the herb has been used clinically for increased lipid levels, endotoxic shock, infection, inflammation, cancer and other conditions.1
Over 67 compounds have been identified in Polygonum cuspidatum, including quinones, stilbenes, flavonoids, coumarins and lignans.1 One of the most remarkable compounds identified to date is the stilbenoid resveratrol, which studies have found to be of benefit in numerous conditions. The compound has even shown life-extending effects in yeast, worms and flies.2
Many may associate resveratrol with wine, however, trans-resveratrol is commonly derived from Japanese knotweed for use in dietary supplements.
Polygonum cuspidatum contains a compound known as polydatin, or piceid. Benefits associated with polydatin include cardiovascular, neuroprotective, anti-inflammatory, immunoregulatory, antioxidative and antitumor effects, as well as liver and lung protection.3 While polydatin and resveratrol act as precursors to each other in the body, research indicates that polydatin predominates in the serum following the administration of either compound.4
Polygonum cuspidatum is ranked among the top five herbs used most frequently in traditional Chinese medicine formulations for the treatment of chronic hepatitis B (HBV), a viral disease of the liver.5 In addition to resveratrol, polydatin is believed to be one the herb’s components that acts against the virus.
In mice exposed to carbon tetrachloride, treatment with polydatin reduced liver fibrosis and inflammation via inhibition of oxidative stress and inflammation.6 In another study involving carbon tetrachloride-exposed mice, pretreatment with polydatin for 5 days protected against increases in markers of liver injury and inflammation, in addition to protecting against a decline in antioxidant enzyme activities.7
In diabetic rats, supplementation with polydatin decreased fasting blood glucose, glycosylated hemoglobin, glycosylated serum protein, total cholesterol, triglyceride, and low-density lipoprotein cholesterol.8 In insulin-resistant human liver cells, the compound increased glucose uptake and usage and lowered lipid accumulation. Another study involving rats found that oral supplementation with polydatin prevented insulin resistance and fatty liver in animals given a high fat diet.9
In human colorectal cancer cells, polydatin revealed an antioxidant activity similar to that of resveratrol and demonstrated an inhibitory effect on cell growth.10
In rats with induced cerebral ischemia, administration of polydatin decreased the volume of the injured area and improved neurologic deficits, while lowering levels of cellular adhesion molecules in comparison with a control group that did not receive the compound.11 In rats with memory impairment induced by chronic insufficient blood flow, 30 days of oral polydatin supplementation reduced cognitive deficits in comparison with untreated animals, while lowering the production of malondialdehyde (a marker of oxidative stress) and increasing the activities of the antioxidant enzymes SOD and catalase.12 Polydatin also alleviated injury in cultured neurons deprived of oxygen and glucose. The findings suggest a potential use for polydatin against vascular dementia.
In rats subjected to hemorrhage and sepsis, polydatin improved organ function, prolonged survival and lowered multi-organ dysfunction syndrome incidence.13 It also suppressed oxidative stress and inflammation, while helping to protect against mitochondrial dysfunction.
Antimicrobial Effects and Beyond
Emodin is another P. cuspidatum compound identified as having health benefits. The compound is used to treat constipation and cancer in traditional Chinese medicine. According to a recent review, “Emerging evidence indicates that emodin possesses a wide spectrum of pharmacological properties, including anticancer, hepatoprotective, anti-inflammatory, antioxidant and antimicrobial activities.”14
Emodin has shown an ability to combat Epstein-Barr viral infection.15 In cultured rat cortical neurons, pretreatment with emodin derived from P. cuspidatum protected against amyloid beta-induced toxicity, leading the researchers to conclude that emodin is a viable candidate for treating Alzheimer’s disease.16
Extracts of Polygonum cuspidatum have shown effectiveness against a variety of conditions, including itstraditional use for menopausal complaints.17
An evaluation of P. cuspidatum’s antibacterial action found inhibitory effects against Streptococcus mutans, a bacterium that is involved in dental plaque and caries formation, in association with an alcohol extract of the root.18 An evaluation of the effects of a fraction of P. cuspidatum root against biofilm formation resulted in inhibited viability of Streptococcus mutans and Streptococcus sobrinus, leading the researchers to conclude that it was likely to be useful in the control of oral biofilms and dental caries.19
In addition to an antibacterial effect, research in mice has revealed an anti-inflammatory effect in association with P. cuspidatum extract that was comparable to that of trans-resveratrol and greater than that of nonsteroidal anti-inflammatory drug (NSAID) indomethacin.20 Another rodent study revealed anti-inflammatory and analgesic effects in association with P. cuspidatum extract, as well as an inhibitory effect against elevations in C-reactive protein (CRP, a marker of inflammation).21
Like Polygonum multiflorum, Polygonum cuspidatum has a laxative effect, which may be related to its anthraquinone content.22
In rats, an extract of P. cuspidatum accelerated wound healing, confirming one of its traditional uses.23
Like most plants, P. cuspidatum has significant antioxidant properties.24 In one study, extracts of the root scavenged two types of free radicals and protected against hydroxyl radical-induced DNA damage.25 The researchers also discovered that the extracts also inhibited cell growth and induced apoptosis in two human lung cancer cell lines.
“Hu Zhang has been prescribed in China for medical purposes for thousands of years,” Huan Zhang and colleagues observe in a 2013 review. “Reports in the literature have demonstrated Hu Zhang’s potential beneficial effects such as antimicrobial, antiviral, anti-inflammatory, estrogenic, neuroprotective, and cardioprotective activities.
They conclude that “Hu Zhang might be a valuable alternative medicine that could be integrated into conventional treatments,” adding that more research is needed.26
- Peng W et al. J Ethnopharmacol. 2013 Jul 30;148(3):729-45.
- Bhullar KS et al. Biochim Biophys Acta. 2015 Jun;1852(6):1209-18.
- Du QH et al. Pharm Biol. 2013 Nov;51(11):1347-54.
- Wang HL et al. Phytomedicine. 2015 May 15;22(5):553-9.
- Zhang L et al. Hepatology. 2010 Feb;51(2):690-8.
- Zhao X et al. Arch Biochem Biophys. 2017 Sep 1;629:1-7.
- Zhang H et al. PLoS One. 2012;7(9):e46574.
- Hao J et al. Eur J Pharmacol. 2014 Dec 15;745:152-65.
- Zhang Q et al. Mol Med Rep. 2015 Jan;11(1):603-10.
- Storniolo CE et al. Food Funct. 2014 Sep;5(9):2137-44.
- Cheng Y et al. Brain Res. 2006 Sep 19;1110(1):193-200.
- Li RP et al. Phytomedicine. 2012 Jun 15;19(8-9):677-81.
- Zeng Z et al. J Surg Res. 2015 Sep;198(1):192-9.
- Dong X et al. Phytother Res. 2016 Aug;30(8):1207-18.
- Yiu CY et al. Molecules. 2014 Jan 20;19(1):1258-72.
- Liu T et al. Brain Res. 2010 Aug 6;1347:149-60.
- Zhang CZ et al. J Ethnopharmacol. 2005 Apr 26;98(3):295-300.
- Song JH et al. Arch Oral Biol. 2006 Dec;51(12):1131-40.
- Song JH et al. J Ethnopharmacol. 2007 Jul 25;112(3):419-25.
- Bralley EE et al. J Inflamm (Lond). 2008 Feb 8;5:1.
- Han JH et al. Immunopharmacol Immunotoxicol. 2012 Apr;34(2):191-5.
- Qu Y et al. Zhongguo Zhong Yao Za Zhi. 2008 Apr;33(7):806-8.
- Wu XB et al. J Ethnopharmacol. 2012 Jun 14;141(3):934-7.
- Hsu CT et al. Biol Res. 2007;40(1):13-21.
- Lin YW et al. J Nat Med. 2010 Apr;64(2):146-52.
- Zhang H et al. Evid Based Complement Alternat Med. 2013;2013:208349.