Yu Xing Cao

Yu Xing Cao (Herba Houttuyniae) is the dried or fresh aerial parts of Houttuynia cordata Thunb., a perennial herbaceous plant in the family Saururaceae (lizard's-tail family). In the traditional TCM classification system, Yu Xing Cao is considered pungent in flavor with a slightly cold nature. It enters the Lung, Large Intestine, and Bladder meridians, giving it a central role in formulas that address Lung Heat with pus formation, toxic Heat accumulation, and Damp-Heat in the Lower Burner.

Botanical description: Houttuynia cordata is a low-growing perennial herb that typically reaches 20–60 cm in height. The plant has slender, creeping rhizomes that spread horizontally underground, from which erect aerial stems arise. The stems are green or purplish, glabrous or sparsely pubescent, and often branched. The leaves are alternate, simple, and distinctively heart-shaped (cordate), 4–10 cm long and 2.5–6 cm wide, with entire margins, an acuminate to acute apex, and a deeply cordate base. The leaf surface is dark green and glabrous above, often purplish beneath, with prominent veins. The petioles are 1–3.5 cm long, and the stipules are membranous. The plant produces small, yellowish-green flowers without petals or sepals, arranged in a dense terminal spike 1–3 cm long, subtended by four white, petal-like bracts that give the inflorescence the appearance of a single flower. The entire plant emits a characteristic strong, fishy odor when crushed, which is the source of its Chinese name (Yu Xing Cao literally means "fishy-smell herb"). The flowering top is harvested in summer and early autumn, cleaned, and used fresh or dried in the shade.

Habitat and distribution: H. cordata is widely distributed across East Asia and Southeast Asia, including China, Japan, Korea, India, Nepal, Thailand, Vietnam, and Indonesia. In China, it is found in most provinces south of the Yangtze River, particularly in Sichuan, Yunnan, Guizhou, Hubei, Hunan, Guangdong, and Guangxi. The plant prefers moist, shady environments and is commonly found along stream banks, in wet meadows, at forest margins, and in disturbed areas. It thrives in rich, moist soils and can tolerate partial to full shade. In China, the herb is both wild-collected and cultivated, with Sichuan and Yunnan provinces being the primary producing regions. The plant is propagated by rhizome division and is relatively easy to cultivate in suitable conditions.

Quality markers: The Chinese Pharmacopoeia specifies that high-quality Yu Xing Cao should have a strong, characteristic fishy odor, a slightly astringent taste, and a high content of volatile oil and flavonoid compounds. The leaves should be heart-shaped, dark green, and free of yellowing or wilting. The stems should be green to purplish, and the material should be free of mold, insect damage, and excessive root material. The fresh herb is preferred for its stronger antimicrobial activity, as the volatile houttuynin content is higher in the fresh plant and degrades during drying and storage. Quality control standards in the pharmacopoeia include limits for moisture content, ash content, and the content of quercitrin and other marker compounds.

In the traditional Chinese medicine theoretical framework, Yu Xing Cao is understood in terms of its effects on specific patterns of disharmony (zheng). Because Yu Xing Cao enters the Lung, Large Intestine, and Bladder meridians and has a pungent, slightly cold quality, it is traditionally indicated for a range of patterns involving Lung Heat with pus, toxic Heat accumulation, and Damp-Heat in the Lower Burner.

Clearing Heat and resolving toxicity: Yu Xing Cao is traditionally used as a heat-clearing and toxicity-resolving herb. In TCM theory, when toxic Heat accumulates in the body, it may manifest as boils, carbuncles, skin infections, and inflammatory conditions. Yu Xing Cao is traditionally used to clear Heat, cool the Blood, and resolve toxic accumulations. It is commonly combined with other heat-clearing herbs such as Pu Gong Ying and Jin Yin Hua for toxic swellings and skin infections. The fresh herb is often pounded and applied externally for boils and carbuncles.

Eliminating pus and treating lung abscess: Yu Xing Cao is one of the most important herbs in TCM for treating lung abscess (fei yong) and eliminating pus from the Lung. In TCM theory, when toxic Heat accumulates in the Lung, it may lead to the formation of pus, manifesting as cough with copious, foul-smelling, purulent sputum, chest pain, and fever. Yu Xing Cao is traditionally used to clear Lung Heat, resolve toxicity, and drain pus from the Lung. It is the chief herb in formulas for lung abscess and is also used for pneumonia, bronchitis, and bronchiectasis with purulent sputum. It is often combined with Jie Geng and Lu Gen for lung abscess, and with Huang Qin and Gua Lou for pneumonia with purulent sputum.

Relieving cough and treating Lung Heat: Yu Xing Cao enters the Lung meridian and is traditionally used for cough, particularly cough associated with Lung Heat patterns. In TCM theory, when Heat accumulates in the Lung, it may disrupt the normal descending and dispersing functions of the Lung, leading to cough with yellow, sticky sputum, chest oppression, and sore throat. Yu Xing Cao is traditionally used to clear Lung Heat, resolve Phlegm-Heat, and stop cough. It is indicated for acute bronchitis, pneumonia, and upper respiratory tract infections presenting with Heat signs. Its pungent, slightly cold nature allows it to disperse Heat from the Lung while also resolving toxicity.

Promoting urination and treating Damp-Heat: Yu Xing Cao enters the Bladder meridian and is traditionally used to promote urination and treat Damp-Heat in the Lower Burner. In TCM theory, when Damp-Heat accumulates in the Bladder, it may manifest as urinary tract infections, painful urination (strangury), and turbid urine. Yu Xing Cao is traditionally used to clear Damp-Heat from the Bladder, promote urination, and relieve painful urination. It is indicated for acute urinary tract infections, cystitis, and pyelonephritis. It is often combined with Jin Qian Cao and Hai Jin Sha for urinary tract infections.

Classical literature references: The Ben Cao Gang Mu (Compendium of Materia Medica, 1596 CE) by Li Shizhen recorded Yu Xing Cao's traditional use for clearing Heat, resolving toxicity, and treating boils and carbuncles. The Ben Cao Jing Shu emphasized its ability to drain pus from the Lung and treat lung abscess. The Dian Nan Ben Cao (Materia Medica of Southern Yunnan) documented its use for urinary tract disorders and Damp-Heat conditions. The Ben Cao Bei Yao noted its pungent, slightly cold nature and its tropism for the Lung and Bladder meridians. The herb has been included in the Chinese Pharmacopoeia as an official herbal medicine since the 1963 edition.

Yu Xing Cao contains a range of bioactive compounds that have been the subject of extensive pharmacological investigation. The following overview summarizes the major chemical constituents identified in the aerial parts of Houttuynia cordata and what is currently known about them from published research.

Houttuynin (decanoyl acetaldehyde): Houttuynin, chemically identified as decanoyl acetaldehyde (3-oxododecanal), is the most characteristic and pharmacologically important volatile constituent of Yu Xing Cao. It is responsible for the herb's distinctive fishy odor and is the compound for which the genus Houttuynia is named. Houttuynin has been studied for its broad-spectrum antimicrobial activity against various bacterial pathogens, including Staphylococcus aureus,Streptococcus pneumoniae, and Pseudomonas aeruginosa. It has also been investigated for its antiviral activity, particularly against influenza virus and herpes simplex virus, in pre-clinical research. The anti-inflammatory effects of houttuynin have been demonstrated through inhibition of pro-inflammatory mediators and modulation of immune responses. However, houttuynin is chemically unstable and degrades when the herb is dried or heated, which is why the fresh herb is considered more potent. The compound is poorly soluble in water, and its bioavailability when administered orally as part of a decoction is not well established.

Quercitrin (quercetin-3-O-rhamnoside): Quercitrin is a flavonoid glycoside that is one of the most abundant non-volatile constituents of Yu Xing Cao. It has been studied for its antioxidant, anti-inflammatory, and diuretic properties in pre-clinical research. Quercitrin has been shown to inhibit the production of pro-inflammatory mediators, protect against oxidative stress, and promote diuresis in animal models. The compound is more stable than houttuynin and is retained in the dried herb, contributing to the pharmacological effects of both fresh and dried Yu Xing Cao preparations. The Chinese Pharmacopoeia uses quercitrin as a marker compound for quality control of Yu Xing Cao.

Hyperin (hyperoside): Hyperin is a flavonol glycoside (quercetin-3-O-galactoside) found in Yu Xing Cao. It has been studied for its cardioprotective, anti-inflammatory, and antioxidant properties in pre-clinical research. Hyperin has been shown to protect against myocardial ischemia, reduce inflammation, and scavenge free radicals. It also exhibits analgesic and anti-ulcer activities in animal models. The compound contributes to the overall flavonoid profile of Yu Xing Cao and its anti-inflammatory and antioxidant effects.

Myrcene and other volatile constituents: The essential oil of Yu Xing Cao contains a complex mixture of volatile compounds, including myrcene, limonene, alpha-pinene, beta-pinene, and various other monoterpenes and sesquiterpenes. Myrcene is an acyclic monoterpene that has been studied for its analgesic, anti-inflammatory, and sedative properties in pre-clinical research. The volatile oil fraction as a whole has been shown to exhibit antimicrobial, antiviral, and anti-inflammatory activities. The composition of the essential oil varies depending on the geographic origin, harvest time, and extraction method, which can affect the pharmacological profile of different Yu Xing Cao preparations.

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.

Yu Xing Cao is a component in several important classical formulas in the TCM tradition. Below are key formulas that feature Yu Xing Cao as a component, along with their traditional indications and the role Yu Xing 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.

Antimicrobial activity of Yu Xing Cao: The antimicrobial properties of Yu Xing Cao have been extensively studied in pre-clinical research. Houttuynin (decanoyl acetaldehyde) has demonstrated broad-spectrum antibacterial activity against gram-positive bacteria (including Staphylococcus aureus andStreptococcus pneumoniae) and gram-negative bacteria (including Pseudomonas aeruginosa and Escherichia coli). The flavonoid fraction has also shown antimicrobial activity against various pathogens. Research has demonstrated that Yu Xing Cao extracts can inhibit biofilm formation, disrupt bacterial cell membranes, and enhance the activity of certain antibiotics when used in combination. Some clinical studies in China have evaluated Yu Xing Cao preparations for respiratory tract infections and have reported positive results, but the quality of these studies is variable, and well-designed randomized controlled trials are lacking.

Antiviral activity: Yu Xing Cao has been studied for its antiviral properties, particularly against respiratory viruses. Pre-clinical research has demonstrated that houttuynin and other constituents of Yu Xing Cao can inhibit the replication of influenza virus, herpes simplex virus, and certain coronaviruses in vitro. The antiviral mechanisms studied include direct virucidal activity, inhibition of viral entry into host cells, and modulation of host immune responses. During the SARS outbreak in 2003 and the COVID-19 pandemic, Yu Xing Cao was included in some TCM protocols for its traditional heat-clearing and toxicity-resolving effects. However, the clinical evidence for its antiviral efficacy against SARS-CoV-2 or other specific viruses is limited and inconclusive. These findings should not be interpreted as evidence that Yu Xing Cao can prevent or treat viral infections.

Anti-inflammatory and immunomodulatory effects: The anti-inflammatory properties of Yu Xing Cao have been investigated in multiple pre-clinical studies. Extracts of Yu Xing Cao and its constituent compounds have been shown to inhibit the production of pro-inflammatory mediators, including TNF-alpha, IL-1beta, IL-6, and prostaglandin E2, through modulation of the NF-kappaB and MAPK signaling pathways. The flavonoid constituents, particularly quercitrin and hyperin, contribute significantly to the anti-inflammatory effects. The herb has also been shown to modulate immune responses, including effects on lymphocyte proliferation, macrophage activation, and cytokine production. These findings provide mechanistic support for the traditional use of Yu Xing Cao as a heat-clearing and toxicity-resolving herb.

Diuretic and renal protective effects: The diuretic effects of Yu Xing Cao have been studied in animal models, where extracts of the herb have been shown to increase urine output and promote the excretion of sodium and potassium. The diuretic activity is attributed to the flavonoid constituents, particularly quercitrin. Pre-clinical research has also suggested that Yu Xing Cao may have protective effects on the kidneys, including reduction of oxidative stress and inflammation in models of acute kidney injury. These findings are consistent with the traditional use of Yu Xing Cao for urinary tract conditions and Damp-Heat in the Lower Burner.

What the research does NOT show: Despite promising pre-clinical signals and some clinical studies, the research on Yu Xing Cao 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 conducted to international standards that Yu Xing Cao can treat, cure, or prevent respiratory infections, viral diseases, urinary tract infections, or any other medical condition. The translation from in-vitro and animal models to human clinical relevance is uncertain. This page does not endorse Yu Xing 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: Yu Xing Cao is widely used in TCM practice and is generally considered to have a favorable safety profile when used appropriately at standard doses. However, like all herbal products, it is not free of risk. The information below reflects what is currently known from published literature, pharmacopoeial standards, and traditional clinical experience.

Spleen-Stomach deficiency-cold: In traditional TCM theory, Yu Xing Cao is slightly cold in nature, and its prolonged use or use at high doses may weaken the digestive function in individuals with Spleen-Stomach deficiency-cold patterns. Symptoms such as poor appetite, abdominal distension, loose stools, and a pale tongue with white coating may be worsened by the cold nature of Yu Xing Cao. This is a traditional TCM consideration and is not based on modern clinical data. Patients with weak digestion should use Yu Xing Cao under professional guidance and for limited durations.

Cold-pattern cough: Yu Xing Cao is contraindicated in individuals with cough due to cold patterns without Heat signs. In TCM theory, cold-pattern cough is characterized by cough with thin, white sputum, aversion to cold, and a pale tongue with white coating. The cold nature of Yu Xing Cao may exacerbate cold-pattern conditions. The herb should only be used for cough presenting with Heat signs, such as yellow, thick sputum, fever, and a red tongue with yellow coating.

Yin deficiency: In traditional TCM theory, Yu Xing Cao is pungent and dispersing in nature. Individuals with Yin deficiency — characterized by dry mouth, night sweats, a red tongue with little coating, and a thin, rapid pulse — should use Yu Xing Cao with caution, as its pungent, dispersing nature may further deplete Yin fluids. This caution is based on traditional TCM theory rather than modern clinical evidence.

Pregnancy and lactation: There is insufficient safety data on the use of Yu Xing Cao during pregnancy and lactation. In traditional TCM theory, herbs with cold nature that clear Heat and resolve toxicity are generally used with caution during pregnancy. The herb's pungent, dispersing nature and its potential effects on smooth muscle activity warrant particular caution. The concentrated essential oil should be avoided during pregnancy. Due to the lack of adequate human pregnancy safety data, Yu Xing Cao should be used during pregnancy only under the direct supervision of a qualified TCM practitioner. Self-administration during pregnancy or while breastfeeding is not recommended.

Intravenous preparations: Injectable preparations of Yu Xing Cao (Yu Xing Cao injection) have been used in China for respiratory tract infections. However, these preparations have been associated with rare but serious adverse reactions, including anaphylactic shock, in some cases. The safety concerns related to injectable Yu Xing Cao preparations are not applicable to oral or topical use of the herb. Injectable Yu Xing Cao products should only be used in a clinical setting under medical supervision.

Drug interactions: There is limited clinical data on drug interactions involving Yu Xing Cao. Based on its chemical constituents, theoretical considerations include: the volatile constituents may affect hepatic cytochrome P450 enzyme activity; the diuretic effects may interact with diuretic medications, antihypertensive drugs, and lithium; the flavonoid constituents may affect platelet aggregation, suggesting caution when combining with anticoagulant or antiplatelet medications. Some pre-clinical studies have suggested that Yu Xing Cao may enhance the activity of certain antibiotics, but clinical interaction data are limited. Consult a qualified healthcare professional before combining Yu Xing 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 Yu Xing 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.