Japanese knotweed, or polygonum cuspidatum in scientific name and Hu Zhang in mandarin, is really mighty medicinally, just like its literal English translation of Hu Zhang – tiger cane. The underground part of this herb has already been used as medicine for thousands of years, mainly treating Lyme disease, cough, joint pain, chronic bronchitis, jaundice, amenorrhea, hypertension, and so on. In addition to its extensive medicinal uses, it is also cultivated as ornamental plant and cooked as food too. Its edible parts, including edible leaves and shoots, are eaten as vegetable. And its root is used for making refreshing cold drinks to replace tea in summer. Besides, its sap can dye rice noodles while giving it a distinctive sour flavor. However, in many countries it is considered as one of invasive plants and called as Japanese knot weed because of its fast growth and developed underground root system. What a shame people there just want to eradicate this herb instead of making full use of it. This is partly because the Japanese knotweed health benefits remain unknown to the public. For that reason, it is necessary to let more people redefine this medicinal herb by getting to know this herb’s history, characteristics, medicinal uses in Traditional Chinese medicine (TCM), and other more information.
What is Japanese knotweed?
Medicinally it mainly refers to the dried rhizomes and roots of Polygonum cuspidatum Sieb. et Zucc., a plant in the family Polygonaceae. This plant is native to China, Japan, and Korea. Therefore, it gets a variety of different names, such as Bushy Knotweed Root, Rhizoma Polygoni Cuspidati, Knotweed Rhizome, Fallopia japonica, giant knotweed, Japanese bamboo, Japanese Knotwood, Mexican Bamboo, Reynoutria japonica, Japanese Fleece flower and so on. In China it is mainly found in Jiangsu, Jiangxi, Shandong, Sichuan and other places. Best harvesting seasons are spring and autumn. After the digging, remove fibrous roots, wash clean, chop into segments or thick slices when it is fresh, dry in the sun, and used raw or fresh.
This is a shrub-like herbaceous perennial, 1 meter or more. Underground rhizomes is decumbent, woody, yellow, and with obvious knots. Stems are erect, cylindrical, hollow, and with glabrous surface scattered with many red or purplish spots. Leaves are alternate, broad ovate to nearly oblong, 7 to 12cm long, 5 to 9cm wide, and with short pointed apex and rounded or cuneate base. Petiole is 1 to 2.5cm long. Membranous sheath is brown and caducous. Small but dense flowers are unisexual, dioecious, and with axillary panicles. Pedicels are long and with wings in the upper part. Achene is ovate, reddish-brown, shiny, wrapped in the wing-shaped perianth, and with three edges. Its flowering period is from July to September and Fruiting period is from September to October.
Main chemical constituents of roots and rhizomes are free anthraquinone and its glycosides, stilbene compounds, protocatechuic acid, catechin, 2,5-dimethyl-7-hydroxychromone, 2-methoxy-6-acetyl-7-methyljuglone, torachrysone-8-OD-glucoside, β-sitosterol glucoside, glucose, rhamnose, polysaccharides, 12.99% amino acids, copper, iron, manganese, zinc, potassium, potassium and so on. And free anthraquinone and its glycosides mainly include emodin, physcion, Chrysophanol, anthraquinone glycosides or Physcion-8-O-β-D-glucoside, fallacinol, and so on. And stilbene compounds are resveratrol or 3,4,5-trihydroxystilbene and Polydatin or resveratrol-3-O-β-D-glucoside.
Japanese knotweed benefits
When it comes to Japanese knotweed uses, something has to be mentioned is the resveratrol, which actually is a natural antibiotics from 72 plants, covering 12 families and 31 genera. And it is mainly found in grape peel, peanuts, mulberry, pines (for example, Scotch Pine, Eastern white pine, etc.), and plants in the family Polygonaceae (giant knotweed or Hu Zhang). Resveratrol was first purified from a leguminous plant native to Peru in 1974. Resveratrol is actually a type of chemical produced to increase the plant’s resistance to the environmental stresses, such as bad weather, microbial infection, etc. This matter has significant pharmacological and biological effects, such as fighting cancer, protecting nerve, defying aging, reducing inflammation, prolonging life, and so on. The best example that can illustrate its health benefits is the phenomenon called French Paradox, namely the fact that Frenchman’s diet contains a lot of saturated fat but few people suffer from coronary heart disease. And later studies revealed that this should give the credit to resveratrol-rich table wine at the French dinner tables. So, today on the market you can buy a variety of related products, such as Japanese knotweed supplement, extract, capsules, tincture, tablets, tea, and more. And now let’s take a look at the description from its pharmacology.
Modern pharmacological actions of polygonum cuspidatum
1. Anthraquinone injection has significant antihypertensive effect on anesthetized rabbits;
2. Resveratrol has a therapeutic effect on peroxidized corn oil induced liver injury in rats;
3. Emodin and naphthoquinone are with antibacterial activity;
4. Experiments by electrical stimulation of the superior laryngeal nerve in cats showed that emodin, PD, and compound prescription of Polygonum cuspidatum had antitussive effect;
5. It has anti-cancer effect;
6. Its oxalic acid can cause hypoglycemic shock in rabbits by intravenous injection. In addition, this herb can reduce the incidence and mortality of diabetes in experimental animals;
7. Polydatin (200mg/kg) can significantly reduce serum cholesterol in normal rats by intragastric administration for 7 consecutive days. But polygonum cuspidatum decoction showed no obvious effect, which might be associated with less resveratrol contained in decoction;
8. Its decoction has obvious hemostasis on traumatic bleeding and certain hemostasis on upper gastrointestinal bleeding by taken orally;
Proven Japanese knotweed recipes
In accordance with Chinese Materia Medica, it is bitter and sour in flavor and slightly cold in properties and goes to two meridians of liver and gall bladder. Main functions include quickening blood circulation to dissipate stasis, dispelling wind and removing obstruction in the meridians, clearing heat and promoting diuresis, and detoxification. Essential uses and indications are amenorrhea, dysmenorrhea, endless lochia after delivery, concretions and gatherings, traumatic injury, wind-damp impediment pain, damp-heat jaundice, stranguria with turbid discharge and morbid leucorrhea, sores, snakebite, burn due to hot liquid or fire. Recommended Japanese knotweed dosage is from 10 to 15 grams in decoction, soaked wine, pills, or powder.
1. According to Yao Seng Yuan Ji Yan Fang (YAO Seng-yuan’s Collection of effective recipes), this herb is used alone for five strangury.
2. According to Zhou Hou Fang (Handbook of Prescriptions for Emergencies), Japanese knotweed root is made into decoction for swelling hands and feet by toxic attacks by soaking feet.
3. According to Qian Jin Fang (Thousand Pieces of Gold Formulae), it combines with Tu Gua Gen (Trichosanthes cucumeroides Root) and Niu Xi (Achyranthes Root) to treat amenorrhea.
4. According to Ben Cao Tu Jing (Illustrated Canon of Herbology), it is used alone to make pills for the treatment of hemorrhoid bleeding.
Japanese knotweed side effects and contraindications
Japanese knotweed herb contains emodin, tannins and a variety of phenolic compounds, which are considered with slight toxicity. Therefore, overdose may stimulate gastric react and cause gastrointestinal reactions, mainly include dry mouth, mouth pain, nausea, vomiting, abdominal pain, diarrhea, etc. It may lead to collapse and shock in the case of excessive water loss. No obvious irritation is found when used externally but excitement and chills and so on may occur. Besides, use it with care during pregnancy.