Houttuynia

Houttuynia (Houttuynia cordata Thunb.)

1. Identity and Botanical Description

Taxonomy and Nomenclature

Houttuynia cordata Thunb. (H. cordata), a perennial herb belonging to the family Saururaceae, is a well-known ingredient in traditional Chinese medicine with several therapeutic properties. It is also known by the common names fish wort, chameleon plant, heartleaf, or Chinese lizard tail, and is native to the mountainous regions of China, Japan, Korea, and Southeast Asia, occurring at altitudes of 300–2,600 m along the Himalayas. In Chinese traditional medicine, the plant is known as Yuxingcao (鱼腥草), which translates to "fishy-smelling herb," referencing its distinctive aroma when the plant is crushed. In Japan it is called Dokudami, meaning "poison-blocking plant."

Houttuynia cordata Thunb. is a rhizomatous, herbaceous, and perennial plant widely distributed in Asia. It grows in wet, shaded roadsides, hillsides, and field ridges, or is slightly submerged in water, as long as it is partially or fully exposed to the sun. The plant grows to an average height of 15–50 cm, has a slender stem and heart-shaped leaves, and bears greenish-yellow flowers. The stems are cylindrical and break easily, and they have distinct subsections and residual fibrous roots.

The genome of H. cordata diverged from that of Saururus chinensis around 33.4 million years ago; it consists of 2.24 Gb with 76 chromosomes (4n = 76) and has undergone three whole-genome duplication events. These whole-genome duplications played a crucial role in shaping the H. cordata genome and influencing the gene families associated with its medicinal properties.

Official Designations and Regulatory Status

It has been designated as a dual-purpose plant for pharmaceuticals and food by the Ministry of Health of the People's Republic of China. H. cordata is not only edible and medicinal but is also used in various aspects of daily life such as fermented beverages, nutraceuticals, feed, and cosmetics.

Parts Used and Common Preparations

It is derived from the fresh whole grass or dried aboveground part of H. cordata, a plant belonging to the family Houttuyniaceae. The whole plant may be used medicinally, and preparations span traditional and modern pharmaceutical forms:

• Decoction (aqueous extract): A traditionally prepared aqueous extract (i.e., decoction) of H. cordata is widely used in Traditional Chinese Medicine (TCM) to treat inflammatory disease.
• Tea: It is often used as a cold tea to promote health.
• Injectable pharmaceutical preparation: Injectable H. cordata has been used clinically for treating infectious disease, inflammation, and anaphylaxis.
• Tablets and solid-dose forms: Standardized tablet preparations such as "fufang yuxingcao" exist in the Chinese market, with quality assured based on the baicalin content.
• Fresh or dried culinary use: The leaves and rhizomes are consumed as vegetables, spices, and condiments in some regions.

The chemical constituents in H. cordata vary depending on harvest seasons, plant origins, drying processes, and other factors.

2. Traditional and Historical Use

Traditional Chinese Medicine (TCM)

Houttuynia cordata Thunb. has been used as a traditional Chinese medicine for more than 1,500 years. It is an important traditional Chinese medicine that exhibits heat-clearing and detoxification, and is also known as "Folding Ear Root." It was first documented in the "Famous Doctors' Record." The Compendium of Materia Medica regards H. cordata as an herb that can "dissipate heat and poisonous carbuncles and swellings."

In the TCM framework, it has a pungent, slightly cold taste and is associated with the lung meridian. It is spicy and cold, enters the lung meridian, and has the effects of clearing heat and detoxicating, deswelling and treating sores, promoting urination and removing dampness, clearing heat and relieving dysentery, and invigorating stomach and promoting digestion. It can be used to treat pulmonary abscess, toxic swelling of sores and ulcers, hemorrhoidal hemorrhage, and heat accumulation in the spleen and stomach.

It plays an important role in traditional health care and disease treatment, as its aboveground stems and leaves have a long medicinal history in China and are used in the treatment of pneumonia and lung abscess. In clinical treatment, it can usually be combined with other drugs to treat dysentery, cold, fever, and mumps.

Regional and Ethnic Traditions Across Asia

Its application has been described in China, Korea, Japan, India, and other Asian regions, and H. cordata has been eaten and used as medicine by local people for the past few thousand years. Currently, it is also harvested for daily food and medicine in the Yarlung Zangbo Valley in Assam, India.

The Hakka and Hokles communities of Guangdong province, China, as well as the Maonan community, rely on various parts of the H. cordata plant for the preparation of herbal soup, tea, baths, and decoctions, using it to treat ailments such as enteritis, sore throat, cough, flu, dysentery, and diarrhea; the local name for this species in their region is "Yuxingcao." The Lisu people in Nujiang, North-West Yunnan, China, refer to the plant as "Cabaie" and use it to treat tonsillitis, nephritis, enteritis, and snakebites. In Thailand, the plant is known as "Pak Kan Thong" and is consumed as a favored vegetable in the eastern northern regions.

H. cordata, also known as "yuxingcao," is a wild vegetable recognized for both its edibility and medicinal value, and is locally processed in various ways, including stir-frying and cold salads.

3. Phytochemistry: Key Constituents and Active Compounds

General Chemical Profile

A variety of chemical constituents are characteristic of the plant; those isolated from H. cordata include volatile oils, alkaloids, flavonoids, and phenolic acids. Flavonoids and volatile oils are the main active components. Many studies describe H. cordata as predominant in bioactive compounds such as volatile oils, flavonoids, alkaloids, terpenoids, polyphenols, steroids, and polysaccharides.

Volatile Oils and Principal Odiferous Compounds

Houttuynin is the main component of the volatile oil from H. cordata. Houttuynin originates from fatty acid metabolism, specifically palmitic acid. Palmitic acid is converted to palmitoyl-CoA by acetyl-CoA synthetase, followed by mitochondrial fatty acid β-oxidation; this cycle continues until decanoyl-CoA is formed, which is then converted to decanoic acid by thioesterase, which is further oxidized to decanoylacetaldehyde (houttuynin, C₁₂H₂₂O₂, MW 198.16). Houttuynin is prone to instability and can readily transform into 2-undecanone (methyl nonyl ketone, C₁₁H₂₂O) during production. The aldehyde group of houttuynin can be transformed into a hydroxyl group, reacting with sodium sulfate to form water-soluble sodium houttuyfonate (SH, C₁₂H₂₃NaO₅S, MW 302.36).

Steam distillation extract contains essential oils including monoterpenes, sesquiterpenes and their oxides, oxidized diterpenes, and phenylpropene derivatives; nonyl ketones (2.10–40.36%), bornyl acetate (0.4–8.61%), and β-myrcene (2.58–18.47%) are the main components in essential oils.

Flavonoids

The flavonoids in H. cordata include rutin, hyperoside, quercetin, and quercitrin, and most of them are combined with rhamnose in the form of glycosides. The full flavonoid profile includes quercetin, rutin, hyperin, afzelin, quercitrin, isoquercitrin, kaempferol, quercetin hexoside, avicularin, apigenin, isorhamnetin, and phlorin, among others. Key genes involved in the β-oxidation process for biosynthesis of houttuynin—one of the volatile oils responsible for the plant's distinctive fishy smell—and genes involved in flavonoid biosynthesis, particularly quercetin metabolism, have been identified in H. cordata.

In inhibitory effects on herpes simplex virus type 1 (HSV-1) assay, norcepharadione B showed good inhibitory activity against the replication of HSV-1. Among the isolated compounds, quercitrin and quercetin-3-O-beta-D-galactopyranoside showed excellent DPPH radical-scavenging properties, with IC₅₀ values of 31 and 63 μM, respectively.

Chen et al. isolated a new combination of houttuynin and hyperoside (houttuynoids A–E), four new flavonoid compounds, and Chou et al. isolated houttuynoside A and houttuynamide A.

Alkaloids

The alkaloids present include aristolactam A, 3,4-dimethoxy-N-methyl aristolactam, lysicamine, noraritolodione, norcepharadione B, 3,5-didecanoyl-pyridine, 7-chloro-6-demethyl-cepharadione B, cis- and trans-N-(4-hydroxystyryl)benzamide, 2-nonyl-5-decanoylpyridine, and several other phenanthrolactam and pyridine derivatives.

Phenolic Acids and Other Compounds

Phenolic acids are the most isolated components in H. cordata, including linolenic acid, linoleic acid, oleic acid, palmitic acid, stearic acid, quinic acid derivatives, caffeic acid derivatives, neochlorogenic acid, chlorogenic acid, and cryptochlorogenic acid, among others.

Polysaccharides

H. cordata polysaccharide (HP), with a molecular weight of approximately 43 kDa, has been purified from H. cordata water extract; it is composed predominantly of galacturonic acid, galactose, glucose, and xylose in a molar ratio of 1.56:1.49:1.26:1.11, and NMR analyses revealed it to be a pectin-like acidic polysaccharide. Modern pharmacological studies have confirmed that H. cordata polysaccharide (HCP) is one of its key active components responsible for anti-inflammatory, antioxidant, and immunomodulatory effects.

Sodium Houttuyfonate (Pharmaceutical Derivative)

Sodium houttuyfonate, an additional compound derived from sodium bisulfite and houttuynin, has shown various pharmacological effects, including antifungal, antibacterial, anti-inflammatory, and cardiovascular protective activities. For the first time, sodium houttuyfonate and 2-undecanone were detected simultaneously in mouse serum and gastrointestinal tissue after oral administration, and sodium houttuyfonate is detected within a short period of time in the systemic circulation and tissues without conversion to 2-undecanone.

4. Mechanisms of Action

Anti-Inflammatory Pathways

Experimental studies suggest that the therapeutic potential of H. cordata is mediated via modulation of key molecular pathways—including inhibition of NF-κB and COX-2 activities, as well as activation of Nrf2-dependent antioxidant defenses—thereby reducing inflammatory cytokine secretion and oxidative stress.

An ethyl acetate fraction derived from H. cordata extract suppressed nuclear translocation of the NF-κB p65 subunit, which correlated with an inhibitory effect on IκBα phosphorylation, and also attenuated the activation of MAPKs (p38 and JNK); results suggest that the anti-inflammatory properties may stem from suppression of NF-κB and MAPK signaling pathways.

In LPS-primed RAW 264.7 cells, the active biomolecules sodium houttuyfonate and 2-undecanone extracted from H. cordata essential oil were demonstrated to have a significant anti-inflammatory impact, and at the same concentration, sodium houttuyfonate showed a significant decrease in TNF-α (p < 0.001) and IL-1β levels compared to 2-undecanone.

A polysaccharide fraction (HBHP-3) isolated from H. cordata showed inhibitory effects on the production of NO, iNOS, IL-1β, and TNF-α, and inhibited the activation of the NF-κB pathway in macrophages.

Antiviral Mechanisms

Water extract of H. cordata has been reported to inhibit the infection of herpes simplex virus (HSV) through inhibition of NF-κB activation, as well as severe acute respiratory syndrome (SARS) through inhibition of SARS CoV 3C-like protease and RNA-dependent RNA polymerase.

Against influenza virus H1N1, the survival rate and life span of mice infected with H1N1 were significantly improved through the combined action of rutin, hyperoside, isoquercitrin, and quercitrin in the extract; 50–200 μg/mL extract effectively reduced the H1N1 virus titre in lung tissue, and neuraminidase activity was inhibited in both in vivo and in vitro experiments.

Results from decimal reduction time and transmission electron microscopy revealed that the H. cordata polysaccharide (HP) has anti-viral effects by deforming and inflating virus particles, thereby inhibiting the penetration of viruses in target cells.

Previous studies found that H. cordata water extract stimulates significant proliferation of mouse splenic lymphocytes, increases the proportion of CD4+ and CD8+ T cells, and exhibits significant antiviral properties by inhibiting SARS-CoV RNA-dependent RNA polymerase (RdRp) and 3C-like protease (3CLpro) enzymes.

Antibacterial Mechanisms

Sodium houttuyfonate (SH) was tested for its inhibitory effects on Pseudomonas aeruginosa; it exhibited inhibitory action against swimming and twitching movements in 24 hours and swarming in 48 hours in a dose-dependent manner, and 1× minimum inhibitory concentration (MIC) caused bacteria to lose nearly all of their motility; the expression levels of structural genes flgB and pilG were significantly down-regulated, implying that SH inhibition of P. aeruginosa motility is due to inhibition of flagella and pili bioformation.

Immunomodulatory Mechanisms

Production of pro-inflammatory cytokines and PGE2 in rat macrophages, proliferation of mouse splenic lymphocytes, and the proportion of CD4+ and CD8+ T cells in rats were all up-regulated by the water extract of H. cordata. H. cordata regulates immunity, enhances the immune barriers of the vagina, oral cavity, and intestinal tract, and combined with the antibacterial and antiviral activity of its extract, effectively reduces pathogen infection.

Antitumor Mechanisms

The active compounds isolated from H. cordata that contribute to antitumor activity include decanoylacetaldehyde, flavonoids such as quercetin, quercitrin, and rutin, and alkaloids such as aristolactam, isoquinoline, and pyridine. Houttuyninum, an active constituent, inhibits phosphorylation of HER2/Neu receptor tyrosine kinase and the tumor growth of HER2/Neu-overexpressing cancer cells.

5. Scientific Evidence by Area of Use

5.1 Respiratory Tract Infections and Lung Disease

H. cordata is a Chinese herbal medicine commonly used to treat upper respiratory tract infection and bronchitis. In pharmacological studies, H. cordata showed organ protective activity, such as reducing the release of inflammatory factors to alleviate lung injury.

In a model of chronic obstructive pulmonary disease (COPD) induced by LPS combined with cigarette smoke for 4 weeks, 24.3 mg/kg sodium houttuyfonate decreased the mRNA levels of TLR4, MyD88, and NF-κB p65, though the researchers noted that differences in the adaptability of humans and rats to cigarette smoke mean this research still needs more investigation.

A previous study proved that sodium houttuyfonate (an additional compound from sodium bisulfite and houttuynin) had beneficial effects in the prevention of pulmonary fibrosis (PF) induced by bleomycin in mice. Macromolecular polysaccharides contribute to alleviating lung injury by reducing pulmonary edema and protein exudation of bronchoalveolar lavage fluid.

Evidence strength: The evidence base for respiratory applications is predominantly from preclinical (animal and cell-based) studies. In the severe acute respiratory syndrome (SARS) virus infection outbreak in 2003, H. cordata was listed as one of the drugs for the treatment of SARS. It was chosen as one of eight TCM remedies for SARS owing to its anti-inflammatory effects. However, large-scale, randomized controlled clinical trials in humans remain lacking.

5.2 Antibacterial Activity

H. cordata exhibits promising antibacterial activity against both Staphylococcus aureus and Pseudomonas aeruginosa, including drug-resistant strains, without cytotoxic effects on eukaryotic cells. A study randomized 72 patients with diabetic foot ulcers into three groups receiving methicillin, meropenem, and HC, respectively, providing some clinical-level evidence, though the study population was limited and additional independent replication is needed.

H. cordata prepared from fresh leaves is commonly used to treat skin abscess diseases; in a study using a water solution of HCP ethanol extract, 1%, 5%, and 10% concentrations significantly inhibited the formation of methicillin-resistant Staphylococcus aureus (MRSA) and Fusarium nucleatum biofilms at 24 h in a concentration-dependent manner.

Evidence strength: Primarily in vitro and animal studies, with limited small-scale clinical data. Robust placebo-controlled RCTs in humans are absent.

5.3 Antiviral Activity

Several studies have reported inhibitory effects of H. cordata on different types of viral diseases. Houttuynia cordata extract has been shown to have anti-viral effects including inhibition of SARS-CoV 3C-like protease and RNA-dependent RNA polymerase.

Regarding COVID-19 specifically: In light of the COVID-19 pandemic, Das et al. reported inhibitory activity of phytocompounds isolated from H. cordata on the SARS-CoV-2 virus; 177 phytocompounds were characterized and docking experiments were performed against the three main replication proteins (Mpro, PLpro, and ADRP), and one compound, 6-hydroxyondansetron, exhibited a high binding affinity for Mpro and PLpro receptors. However, this data was obtained from docking experiments, which need to be confirmed with experimental evidence.

H. cordata polysaccharide (HP) was more effective than ethanol extract in reducing MNV-1 (murine norovirus) plaque formation; when MNV-1 was treated with 500 μg/mL HP, the infectivity of MNV-1 decreased to an undetectable level.

Evidence strength: Predominantly in vitro and animal studies, plus computational docking analyses. There are no published large-scale human clinical trials for antiviral efficacy against any specific viral pathogen.

5.4 Anti-Inflammatory Activity

Experiments in vivo and in vitro showed significant anti-inflammatory activity, and chemical derivatives of H. cordata exert potential therapeutic activity against rheumatoid arthritis.

A clinical trial involving mangosteen, Lithospermum officinale, Tribulus terrestris L., and H. cordata extracts in the treatment of mild to moderate acne showed that inflammation and noninflammatory skin lesion counts were significantly reduced. However, this study used a combination product, making it impossible to attribute effects solely to H. cordata.

Research on H. cordata eye drops combined with olopatadine hydrochloride in the treatment of vernal keratoconjunctivitis revealed a synergistic effect of this combination.

Evidence strength: The mechanistic evidence for anti-inflammatory action is strong at the molecular and cellular level. Clinical evidence in humans is limited and mostly confined to combination-product studies or small trials.

5.5 Antitumor Activity

Antitumor action is an important pharmacological activity of H. cordata, and studies have shown that it has a notable effect on lung tumor, liver tumor, colon tumor, and breast tumor. Modern pharmacological studies have indicated that the extracts of H. cordata have certain antitumor activities, and H. cordata has an inhibitory effect on the proliferation of a variety of tumor cells.

Evidence strength: Currently limited to preclinical (in vitro and animal) evidence. No clinical trials in human cancer patients are reported in the peer-reviewed literature reviewed here.

5.6 Immunomodulation

Polysaccharides from H. cordata have been confirmed to be a potential immune enhancer, which could significantly increase the expression of IL-1β, TNF-α, MIP-1α, MIP-1β, and RANTES in human peripheral monocytes, and also have certain anti-inflammatory effects.

Evidence strength: Most immunomodulatory evidence derives from in vitro studies using human cells and animal models. Clinical human evidence remains largely absent.

5.7 Hepatoprotective and Renoprotective Activity

Several in vitro and in vivo studies and clinical trials have found that H. cordata extracts have antioxidant, anti-inflammatory, anti-tumor, antibacterial, hepatoprotective, renoprotective, immunomodulatory, and potent antiviral effects. A study published in Biomedicine (Taipei) investigated protective effects of H. cordata aqueous extract against acetaminophen-induced liver injury.

In a murine model of 70% hepatic ischemia for 60 min followed by reperfusion, mice were administered low-dose (50 mg/kg) or high-dose (100 mg/kg) HCP or the positive control N-acetylcysteine (150 mg/kg); liver injury was assessed by serum ALT/AST levels, histopathology, oxidative stress markers, and inflammatory cytokines, and macrophage polarization and the TLR4/NF-κB pathway were analyzed.

Evidence strength: Evidence is preclinical; no human clinical trials specifically examining hepatoprotection or renoprotection by H. cordata have been identified in the peer-reviewed sources reviewed here.

5.8 Antioxidant Activity

The bioactive compounds of H. cordata have the potential to exhibit various activities including anti-oxidant, anti-mutagenic, anti-inflammatory, antibacterial, and antifungal properties. The quercitrin and quercetin glycoside fractions show the strongest radical-scavenging properties in DPPH assays, as described under the phytochemistry section.

Evidence strength: Antioxidant effects have been demonstrated primarily in vitro. No significant human clinical trials on oxidative stress endpoints are available.

5.9 Anti-Diabetic and Metabolic Activity

H. cordata possesses several important medicinal properties, such as anti-cancer, antiviral, and anti-diabetic activities. The synergistic use of H. cordata shows effective activity in alleviating diabetes insulin resistance.

Evidence strength: Preliminary and largely limited to in vitro and animal models. Clinical evidence for glycemic or metabolic endpoints in humans is not established.

6. Body Systems and Health Areas

Based on the pharmacological research literature, H. cordata has been studied in relation to the following body systems and health areas:

• Respiratory system: H. cordata is used against health issues such as cold, cough, fever, pneumonia, and mumps, due to its anti-inflammatory, antibacterial, antiviral, antioxidant, and antitumor effects.
• Immune system: It has antibacterial, anti-inflammatory, antiviral, antioxidant, antitumor, and immunity-enhancing pharmacological effects.
• Cardiovascular system: Sodium houttuyfonate has shown cardiovascular protective activities.
• Gastrointestinal system: Traditionally used for dysentery, diarrhea, and enteritis; mouse ulcerative colitis model experiments demonstrated effective anti-inflammatory activity at concentrations of 100 mg/kg and 300 mg/kg.
• Hepatic/renal systems: Studied for hepatoprotective and renoprotective activity in animal models.
• Skin: Prepared from fresh leaves, H. cordata is commonly used to treat skin abscess diseases, with significant effects reported.
• Oncology (preclinical): Active compounds studied for effects on lung, liver, colon, and breast tumor cell lines.

7. Dosage Forms and Reported Dosages

The following dosages and preparations are those reported directly in peer-reviewed studies and official sources; they are not recommendations:

• Animal studies — sodium houttuyfonate (oral/systemic): 24.3 mg/kg sodium houttuyfonate was used in a rat COPD model.
• Animal studies — H. cordata polysaccharide (HCP): Mice were administered low-dose (50 mg/kg) or high-dose (100 mg/kg) HCP in a hepatic ischemia-reperfusion injury model.
• Animal studies — ulcerative colitis: Effective anti-inflammatory activity was demonstrated at concentrations of 100 mg/kg and 300 mg/kg in mouse UC model experiments.
• In vitro — antiviral (polysaccharide): Viruses were mixed with 100, 250, and 500 μg/mL of HP, HWE, or HEE; when MNV-1 was treated with 500 μg/mL HP, its infectivity decreased to an undetectable level.
• Injectable pharmaceutical preparation: In China, the intramuscular injection was approved in 1978, and the intravenous formulation was approved in 1994.
• Quality control markers: The quality of Houttuynia cordata injection (HCI) is assured based on the content of methyl n-nonyl ketone, whose content is set at least 1.0 μg/mL injection.

8. Safety Considerations

Injectable Preparations: Serious Adverse Reactions

The most significant and well-documented safety concern involves parenteral (intravenous and intramuscular) preparations of H. cordata, which carry a profile of adverse reactions distinct from oral/traditional use.

Yuxingcao herbal injection (YHI), produced from a herbal extract of H. cordata, caused severe adverse drug reactions in four children, two of which were fatal, during the first half of 2006; in response, the SFDA halted YHI use in hospitals in June 2006.

The intramuscular injection was approved in China in 1978, and the intravenous formulation in 1994; as serious adverse reactions were reported, China's State Food and Drug Administration (SFDA) temporarily suspended the use and approval of seven kinds of Houttuynia injectable preparations since June 1, 2006. In September 2006, the SFDA allowed pharmaceutical companies to apply for re-use only with the intramuscular formulation after re-evaluation of safety, and required that drug warning information—"This product can cause serious allergic reactions"—be added to the drug instruction.

A systematic review including a total of 645 articles with 1,232 adverse drug reaction (ADR) cases reported that respiratory diseases accounted for 52.44% of all cases of Houttuynia injection ADRs, followed by reproductive system diseases (4.30%) and urinary system diseases (3.73%); multiple systems or organs were involved in ADRs, with the top five being the respiratory system (37.42%), skin (34.66%), digestive system (25.49%), and circulatory system.

The adverse event reports of HC injection are accumulating remarkably as HC injection clinical applications have increased; previous studies demonstrated that the major side effects of HC injection were anaphylactoid reactions.

Anaphylaxis Risk

Network pharmacology analysis identified houttuynia as an herb with a high risk of inducing anaphylactic shock, with beta-sitosterol, chlorogenic acid, and palmitic acid among its components being identified as potential allergens.

Oral and Traditional Use Safety

The safety profile of oral preparations (decoctions, teas, dietary consumption) is generally more favorable than that of injectables. H. cordata is not only edible and medicinal but also used in nutraceuticals and fermented beverages. The Chinese Ministry of Health included it on the list of medicines and foods in 1998. No significant adverse effects have been systematically reported for oral decoction use at traditional doses in the published literature reviewed here.

Variability in Composition

The chemical constituents in H. cordata vary depending on harvest seasons, plant origins, drying processes, and other factors, which has implications for the consistency and predictability of both efficacy and safety of preparations. The chemical composition of H. cordata aqueous decoction (HCD) varies with geographical sourcing; sixteen samples purchased from Sichuan, Hubei, and Anhui provinces showed variation.

Known Interactions

No well-documented drug–drug interactions for oral H. cordata preparations have been identified in the peer-reviewed literature. The 2009 review published in Regulatory Toxicology and Pharmacology focused on interactions associated specifically with the injectable formulation in the context of anaphylaxis. H. cordata shows potential in combination with other drugs; research on H. cordata eye drops combined with olopatadine hydrochloride in the treatment of vernal keratoconjunctivitis revealed the synergistic effect of this combination.

Pregnancy and Special Populations

No systematic clinical evidence on the safety of H. cordata preparations in pregnant or lactating women has been identified in the peer-reviewed sources reviewed here. Classical TCM sources describe it as a "cold" herb with contraindications in cold-deficiency patterns.

Overall Evidence Characterization

The scientific evidence base for H. cordata is substantial in terms of volume of in vitro and animal studies, with a wide range of documented pharmacological activities. However, the translation to human clinical efficacy remains preliminary for virtually all indications. H. cordata has a wide range of bioactive substances, but its therapeutic potential has not been fully exploited; it could provide a new non-toxic approach to the treatment of many diseases. The critical gap is the paucity of rigorously conducted, large-scale, randomized controlled clinical trials in human populations for any specific therapeutic indication. The safety data for injectable preparations is robust and negative, and has led to regulatory action in China; the oral dietary supplement form lacks an equivalent body of systematic human safety or efficacy data.

References

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• Pharmacological Effects of Houttuynia cordata Thunb (H. cordata): A Comprehensive Review — PMC (2022)
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• A near-complete assembly of the Houttuynia cordata genome provides insights into the regulatory mechanism of flavonoid biosynthesis — PMC (2024)
• The constituents and their bioactivities of Houttuynia cordata — PubMed (2009)
• Antiviral Effects of Houttuynia cordata Polysaccharide Extract on Murine Norovirus-1 (MNV-1) — PMC (2019)
• An ethyl acetate fraction derived from Houttuynia cordata extract inhibits the production of inflammatory markers by suppressing NF-κB and MAPK activation — PMC (2014)
• Structural characterization and immunomodulatory effect of a polysaccharide HCP-2 from Houttuynia cordata — PMC (2020)
• A Comparative Study of Sodium Houttuyfonate and 2-Undecanone for Their in Vitro and in Vivo Anti-Inflammatory Activities and Stabilities — PMC (2015)
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• Network Pharmacology and Molecular Docking Elucidate the Underlying Pharmacological Mechanisms of Houttuynia cordata in Treating Pneumonia Caused by SARS-CoV-2 — PMC (2022)
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• Structural characterization and anti-inflammatory activity of a pectin polysaccharide HBHP-3 from Houttuynia cordata — International Journal of Biological Macromolecules (2022)
• Houttuynia cordata Polysaccharide Alleviates Hepatic Ischemia-Reperfusion Injury by Regulating Macrophage Polarization via Inhibiting the TLR4/NF-κB Signaling Pathway — Biomedicines (2026)
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• Houttuynia Cordata Thunb: Anti-Inflammatory and Therapeutic Properties — Nature Research Intelligence
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