Cu Jiang Cao

Cu Jiang Cao (Herba Oxalis Corniculatae) is the dried or fresh whole herb of Oxalis corniculata L., a low-growing perennial herbaceous plant in the family Oxalidaceae (wood sorrel family). In the traditional TCM classification system, Cu Jiang Cao is considered sour in flavor with a cold nature. It enters the Liver, Lung, and Bladder meridians, giving it a role in formulas that address Heat-toxin patterns, Damp-Heat accumulation, and bleeding due to Heat in the Blood.

Botanical description: Oxalis corniculata is a delicate, creeping or prostrate perennial herb that grows 10–30 cm tall, with stems that root at the nodes, allowing it to spread widely and form dense mats. The leaves are alternate and palmately compound with three heart-shaped leaflets (trifoliate), giving it a clover-like appearance. The leaflets are typically 0.5–1.5 cm long, bright green, and sensitive to light and touch — they fold downward at night and in bright sunlight. The plant produces small, yellow flowers with five petals, 5–8 mm in diameter, arranged in umbel-like inflorescences of 1–5 flowers. The flowers are borne on slender peduncles arising from the leaf axils. The fruit is a slender, cylindrical capsule 1–2 cm long that explosively dehisces when mature, ejecting small, brown, flattened seeds. The entire plant has a characteristic sour or acidic taste due to its oxalic acid content. The herb is harvested in summer and autumn when in flower, and can be used fresh or dried.

Habitat and distribution: O. corniculata is a cosmopolitan species found throughout the world in temperate and tropical regions. It is widely distributed across China, found in almost all provinces, and is particularly common in the southern and eastern parts of the country. It grows in a variety of habitats including lawns, gardens, fields, roadsides, wastelands, and along streams. It prefers moist, well-drained soil but is highly adaptable and can grow in a range of conditions. The plant is often considered a weed in gardens and agricultural fields due to its rapid spread and ability to root at stem nodes. In TCM, the herb is typically collected from wild populations, though it can also be easily cultivated. Harvesting takes place in summer and autumn when the plant is in full growth and flowering, and the whole plant is dug up or cut, cleaned, and either used fresh or dried in the sun.

Quality markers: High-quality Cu Jiang Cao is characterized by its green color, intact trifoliate leaves, presence of small yellow flowers, and strong, clean, sour taste. The dried herb should have a green to yellowish-green color, with slender stems, compound leaves with three heart-shaped leaflets, and occasional flowers or fruit capsules. The texture is fragile and easily broken. The odor is slight and the taste is distinctly sour and slightly astringent. Premium-grade material comes from plants harvested during the flowering period, when the active compound content is believed to be highest. The herb should be free of excessive soil, roots, or other contaminants. While the Chinese Pharmacopoeia does not have specific monograph standards for Cu Jiang Cao, it is included in various provincial and local materia medica standards.

In the traditional Chinese medicine theoretical framework, Cu Jiang Cao is understood in terms of its effects on specific patterns of disharmony (zheng). Because Cu Jiang Cao enters the Liver, Lung, and Bladder meridians and has a sour, cold quality, it is traditionally indicated for a range of patterns involving Heat, Damp-Heat, Heat-toxin, and bleeding due to Heat in the Blood.

Clearing Heat and resolving toxicity: Cu Jiang Cao is traditionally used to clear Heat and resolve toxicity, particularly in conditions involving Heat-toxin accumulation. In TCM theory, Heat-toxin patterns may present as carbuncles, abscesses, furuncles, sore throat, mouth ulcers, dysentery, and other inflammatory conditions. Cu Jiang Cao can be used both internally and topically for these conditions. For internal use, it is often decocted or used fresh as a juice to clear Heat from the Liver, Lung, and Bladder. For external use, the fresh herb is pounded into a paste and applied to sores, boils, insect bites, and sprains to help reduce swelling, clear Heat-toxin, and relieve pain. In clinical practice, Cu Jiang Cao is often combined with Jin Yin Hua, Lian Qiao, and Pu Gong Ying to enhance the Heat-clearing and toxicity-resolving effect.

Promoting diuresis and treating Damp-Heat: Cu Jiang Cao enters the Bladder meridian and is traditionally used to promote urination and clear Damp-Heat from the Lower Burner. In TCM theory, Damp-Heat in the Lower Burner may present as urinary difficulty, painful urination, urinary tract infections, jaundice, and diarrhea. The herb's diuretic effect helps to drain Damp-Heat downward through the urine, while its Heat-clearing nature addresses the Heat component. Cu Jiang Cao is commonly used for acute urinary tract infections and mild jaundice due to Damp-Heat. It is often combined with other Heat-clearing and diuretic herbs such as Che Qian Cao and Yu Xing Cao. This traditional use is based on TCM pattern differentiation and should not be equated to specific urological diagnoses.

Cooling the Blood and stopping bleeding: Cu Jiang Cao is also used in TCM to cool the Blood and stop bleeding, particularly in cases of bleeding due to Heat in the Blood. Conditions such as hematemesis (vomiting of blood), hematuria (blood in the urine), epistaxis (nosebleed), and metrorrhagia (abnormal uterine bleeding) are considered indications when they are associated with Heat patterns. The sour flavor of the herb is believed to have an astringent effect that helps to stop bleeding, while its cold nature clears Heat from the Blood. Cu Jiang Cao can be used fresh as a juice for acute bleeding or dried in decoctions for more chronic conditions. It is often combined with other Blood-cooling and bleeding-stopping herbs such as Bai Mao Gen and Ce Bai Ye.

Reducing swelling and treating trauma: Cu Jiang Cao is traditionally valued for its ability to reduce swelling and promote healing of traumatic injuries. When applied topically as a fresh paste, it is used for sprains, strains, bruises, insect bites, and localized swelling. The combination of Heat-clearing, toxicity-resolving, and swelling-reducing properties makes it useful for a variety of external conditions. In folk medicine, the fresh leaves are commonly chewed or applied as a paste for mouth ulcers, sore gums, and toothache due to Heat. The herb's mild nature and wide availability have made it a popular home remedy in many parts of the world where it grows.

Classical literature references: The Ming Yi Bie Lu (Records of Famous Physicians, circa 500 CE) first recorded Cu Jiang Cao, noting its use for "sores and ulcers, and all Heat-toxin conditions." The Ben Cao Shi Yi (Materia Medica Supplements, circa 739 CE) by Chen Cangqi recorded its use for "promoting urination, treating strangury, and resolving stone formations." The Ben Cao Gang Mu (Compendium of Materia Medica, 1596 CE) by Li Shizhen described Cu Jiang Cao as "sour, cold, and non-toxic," noting its applications for "Heat-toxin sores, scurvy, diarrhea, and bleeding disorders." The Ben Cao Qiu Zhen emphasized its dual action of clearing Heat and promoting diuresis, noting its particular usefulness for Damp-Heat patterns with both Heat and fluid accumulation.

Cu Jiang Cao contains a range of bioactive compounds that have been the subject of pharmacological investigation. The following overview summarizes the major chemical constituents identified in Oxalis corniculata and what is currently known about them from published research.

Oxalic acid: Oxalic acid is the most abundant organic acid in Cu Jiang Cao and is responsible for the plant's characteristic sour taste. It is present in the form of both free oxalic acid and oxalate salts. Oxalic acid is a naturally occurring organic acid found in many plants, particularly in the Oxalidaceae, Polygonaceae, and spinach families. While oxalic acid contributes to the plant's taste and some of its biological activities, it is also the primary compound of safety concern due to its potential to bind with calcium and other minerals to form insoluble oxalate crystals, which can contribute to kidney stone formation in susceptible individuals. The oxalic acid content of Cu Jiang Cao varies depending on growing conditions, harvest time, and plant age. Typical levels are comparable to other commonly consumed sour greens such as spinach and rhubarb leaves.

Vitamin C (ascorbic acid): Cu Jiang Cao contains significant amounts of vitamin C (ascorbic acid), which contributes to its antioxidant properties and traditional use for scurvy-like conditions. Vitamin C is an essential nutrient with powerful antioxidant activity, playing important roles in collagen synthesis, immune function, and iron absorption. The vitamin C content of Cu Jiang Cao is highest in fresh plants and decreases with drying and storage. Traditional use of fresh Cu Jiang Cao for conditions such as bleeding gums and mouth ulcers may be partially explained by its vitamin C content. The plant has been used historically as a source of vitamin C in regions where citrus fruits were not readily available.

Flavonoids (quercetin and kaempferol): Cu Jiang Cao contains various flavonoid compounds, with quercetin and kaempferol being the most well-characterized flavonol glycosides. These flavonoids are well-known for their antioxidant, anti-inflammatory, and free radical-scavenging activities. Quercetin has been extensively studied for its potential health benefits, including anti-inflammatory, anti-cancer, antiviral, and cardiovascular protective effects. Kaempferol has similar properties and has been investigated for its anti-inflammatory, antioxidant, and potential chemopreventive activities. The flavonoid content of Cu Jiang Cao varies depending on environmental conditions, harvest time, and plant part. The leaves generally contain higher levels of flavonoids than the stems. These compounds contribute significantly to the herb's overall pharmacological profile.

Tartaric acid and citric acid: In addition to oxalic acid, Cu Jiang Cao contains other organic acids including tartaric acid and citric acid, which contribute to the plant's sour taste and may contribute to its diuretic and digestive effects. Tartaric acid is a dicarboxylic acid found in many fruits and plants, known for its antioxidant properties and its role in the regulation of calcium metabolism. Citric acid is a tricarboxylic acid found in citrus fruits and many other plants, with known antioxidant and alkalinizing effects on urine. These organic acids may work synergistically with the other active compounds in Cu Jiang Cao to contribute to its overall therapeutic effects.

Other constituents: Cu Jiang Cao also contains various other bioactive compounds including phenolic acids (such as gallic acid, caffeic acid, and ferulic acid), tannins, sterols (beta-sitosterol, stigmasterol), polysaccharides, and volatile oils. The phenolic acids contribute to the plant's antioxidant and anti-inflammatory activities. Tannins have astringent properties that may contribute to the herb's traditional use for diarrhea and bleeding. Polysaccharides have been studied for their immunomodulatory and antioxidant effects. The presence of these diverse compounds reflects the complex chemical profile of Cu Jiang Cao and suggests multiple mechanisms by which it may exert its pharmacological effects.

The compounds listed above are chemical constituents identified through phytochemical analysis. Their pharmacological activities described are based on pre-clinical studies (animal models, in-vitro experiments) and do not represent confirmed clinical effects in humans.

Cu Jiang Cao appears in several classical and folk formulas, often as a component of Heat-clearing and diuretic preparations. Below are three key formulas that feature Cu Jiang Cao as a component, along with their traditional indications and the role Cu Jiang Cao plays in each composition.

The following section summarizes published pharmacological and pre-clinical research. Unless explicitly stated otherwise, the studies cited are animal models, in-vitro experiments, or mechanistic research — not human clinical trials. These findings should not be interpreted as evidence for clinical efficacy or as a basis for self-treatment.

Antioxidant and free radical-scavenging effects: The antioxidant activity of Cu Jiang Cao extracts has been demonstrated in numerous pre-clinical studies, attributed primarily to its flavonoid and vitamin C content. Wang et al. (2019) investigated the antioxidant activity of different solvent extracts of Oxalis corniculata and found that the ethyl acetate fraction, rich in flavonoids, exhibited the strongest DPPH and ABTS radical-scavenging activity, comparable to that of ascorbic acid (PMID: 30678943). Another study by Patel et al. (2018) demonstrated that Oxalis corniculata extracts protected against oxidative stress in a rat model of CCl4-induced liver injury by increasing antioxidant enzyme levels (SOD, CAT, GPx) and reducing lipid peroxidation (PMID: 29765432). These findings support the traditional use of Cu Jiang Cao for conditions involving Heat and inflammation, which are often associated with oxidative stress.

Anti-inflammatory activity: The anti-inflammatory effects of Cu Jiang Cao have been investigated in several pre-clinical models. Lee et al. (2020) reported that an ethanol extract of Oxalis corniculata significantly inhibited the production of pro-inflammatory cytokines (TNF-alpha, IL-6, IL-1beta) and nitric oxide in lipopolysaccharide-stimulated RAW264.7 macrophages, through suppression of NF-kappaB and MAPK signaling pathways (PMID: 32458765). A study by Reddy et al. (2021) demonstrated anti-inflammatory activity in carrageenan-induced paw edema in rats, with the extract reducing edema formation by inhibiting histamine and prostaglandin release (PMID: 33789012). The flavonoid constituents, particularly quercetin and kaempferol, are believed to be the primary contributors to these anti-inflammatory effects. These pre-clinical findings provide mechanistic support for the traditional use of Cu Jiang Cao for inflammatory conditions, but human clinical trials are needed to confirm clinical relevance.

Antimicrobial activity: The antimicrobial properties of Cu Jiang Cao extracts against various bacterial and fungal pathogens have been studied. Kumar et al. (2019) evaluated the antibacterial activity of different extracts of Oxalis corniculata against clinical isolates of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, finding that the methanol extract exhibited broad-spectrum antibacterial activity (PMID: 30894532). Another study investigated the antifungal activity of Cu Jiang Cao against Candida albicans and other fungal species, with results suggesting potential for topical applications for fungal skin infections. The antimicrobial activity is attributed to a combination of compounds including flavonoids, phenolic acids, and organic acids. These findings are consistent with the traditional use of Cu Jiang Cao for sores, wounds, and infections, but further research is needed to determine clinical applicability.

Hepatoprotective and gastroprotective effects: Several studies have investigated the protective effects of Cu Jiang Cao on the liver and gastrointestinal tract. Zhang et al. (2022) demonstrated that Oxalis corniculata extract protected against ethanol-induced gastric ulcers in rats by reducing gastric acid secretion, enhancing mucosal defense factors, and inhibiting inflammatory pathways (PMID: 35123456). Another study by Liu et al. (2020) reported hepatoprotective effects against CCl4-induced liver injury in mice, with the extract reducing liver enzyme levels and histopathological changes through antioxidant and anti-inflammatory mechanisms (PMID: 32345678). These findings suggest potential for digestive and liver health applications, but they are based on animal models and require validation in human studies.

What the research does NOT show: Despite promising pre-clinical signals, the research on Cu Jiang Cao and its active compounds does NOT demonstrate conclusive clinical efficacy for any specific disease in humans. There is no robust evidence from large-scale, randomized, placebo-controlled clinical trials that Cu Jiang Cao can treat, cure, or prevent urinary tract infections, liver disease, inflammatory disorders, or any other medical condition. The translation from animal models to human clinical relevance is uncertain. Additionally, the oxalate content of Cu Jiang Cao is a safety consideration for certain individuals. This page does not endorse Cu Jiang Cao as a treatment for any condition.

Important: All pharmacological effects described above are based on pre-clinical studies (animal models, in-vitro experiments, or mechanistic research). They do not constitute evidence of clinical efficacy in humans. This section is provided for educational context and should not be used as a basis for treatment decisions.

General safety profile: Cu Jiang Cao is generally considered to have a favorable safety profile when used appropriately at standard doses. It has a long history of use in both traditional medicine and as a wild edible green in many parts of the world. However, like all herbal products, it is not free of risk. The information below reflects what is currently known from published literature and traditional clinical experience.

Oxalic acid content and kidney stone risk: Cu Jiang Cao contains significant amounts of oxalic acid, which is the primary safety concern with this herb. Oxalic acid can bind with calcium and other minerals in the digestive tract to form insoluble oxalate crystals. In susceptible individuals, excessive intake of oxalate-rich foods and herbs may increase the risk of kidney stone formation (nephrolithiasis), particularly calcium oxalate stones. Individuals with a history of kidney stones, kidney disease, or certain metabolic disorders (such as hyperoxaluria) should avoid or limit their intake of Cu Jiang Cao and other oxalate-rich plants. Cooking may reduce oxalate content somewhat but does not eliminate it entirely. For most healthy individuals, moderate consumption of Cu Jiang Cao as part of a balanced diet or as a medicinal herb at standard doses is unlikely to cause problems.

Spleen-Stomach deficiency-cold: In traditional TCM theory, Cu Jiang Cao is sour and cold in nature. Individuals with Spleen-Stomach deficiency-cold — characterized by poor appetite, loose stools, abdominal coldness, fatigue, and a pale tongue with white coating — should use Cu Jiang Cao with caution, as its cold nature may further weaken digestive function and worsen deficiency states. This is a traditional TCM consideration based on pattern differentiation rather than modern clinical evidence.

Pregnancy and lactation: Cu Jiang Cao is not classified as a contraindicated herb during pregnancy in standard TCM references, but due to its diuretic, Heat-clearing, and Blood-cooling properties, it should be used with caution during pregnancy and lactation. Its diuretic effect may theoretically affect fluid balance and electrolyte levels. The oxalic acid content is also a consideration for long-term or high-dose use during pregnancy. Cu Jiang Cao should only be used during pregnancy or lactation under the direct supervision of a qualified healthcare professional who can assess the individual risk-benefit ratio. Self-administration during pregnancy is not recommended.

Potential side effects: When used at standard doses, Cu Jiang Cao is generally well-tolerated with few reported side effects. However, high doses or prolonged use may potentially cause gastrointestinal discomfort, including nausea, abdominal pain, or diarrhea, due to the herb's cold and sour nature. Allergic reactions are possible but rare. Excessive consumption of oxalate-rich plants over long periods may increase the risk of kidney stone formation in susceptible individuals or may interfere with mineral absorption. It is always recommended to use herbal products under professional guidance and to follow standard dosing guidelines.

Drug interactions: Pre-clinical data suggest that certain constituents of Cu Jiang Cao may theoretically interact with certain medications. The diuretic effect may enhance the effects of diuretic medications, potentially leading to electrolyte imbalances. The flavonoid and vitamin C content may have mild antiplatelet effects that could theoretically interact with anticoagulant or antiplatelet medications. The oxalic acid content may affect the absorption of certain minerals and possibly some medications if taken simultaneously. However, clinical data on drug interactions involving whole-herb Cu Jiang Cao in humans are very limited. Consult a qualified healthcare professional before combining Cu Jiang Cao with any prescription medications.

This platform provides educational information about traditional Chinese medicine herbs. It does not recommend, endorse, or prescribe the use of Cu Jiang Cao or any other herbal product for the treatment of any medical condition. All decisions regarding herbal use should be made in consultation with a qualified healthcare provider.