Fish Mint

This is the most reproducible activity in animals. The steam-distilled volatile oil reduced xylene-, formaldehyde- and carrageenan-induced edema in mice and rats, and lowered prostaglandin E2 (via COX-2), nitric oxide and TNF-α in LPS-stimulated macrophages ^{8Reference 8Li et al. · 2013In vitroHouttuynia cordata volatile oil exhibited anti-inflammatory effects in vivo and inhibited nitric oxide and TNF-α in vitro — animal modelView study →}. Separate work shows the four major leaf flavonoids — rutin, hyperoside, isoquercitrin and quercitrin, plus their aglycone quercetin — and several purified polysaccharides dampen inflammation and lung injury in influenza and hepatic ischemia-reperfusion models, largely through TLR4/NF-κB suppression ^{9,10,20Reference 9Tang et al. · 2023AnimalTherapeutic effects on H1N1-induced pneumonia in mice and intestinal biotransformation of four main flavonoids from Houttuynia cordata — animal modelView study →Reference 10Li et al. · 2025AnimalAn anti-complement homogeneous polysaccharide from Houttuynia cordata ameliorates acute pneumonia from viral–bacterial co-infection — animal modelView study →Reference 20Yu et al. · 2026AnimalHouttuynia cordata polysaccharide alleviates hepatic ischemia-reperfusion injury by regulating macrophage polarization via TLR4/NF-κB — animal modelView study →}. Effects are dose-dependent and consistent across labs, but every study is preclinical and the active preparation varies (oil vs flavonoid vs polysaccharide).

Gap: No human anti-inflammatory trial, and the three active fractions behave differently — a result for the volatile oil says nothing about a water infusion.

Houttuynia’s most chemically interesting antiviral story. A steam distillate of the fresh plant directly inactivated HSV-1 in vitro without cytotoxicity, an effect traced to volatile carbonyls including 2-undecanone (methyl n-nonyl ketone) and lauraldehyde ^{1Reference 1Hayashi et al. · 1995In vitroVirucidal effects of the steam distillate from Houttuynia cordata and its components on HSV-1, influenza virus, and HIV — in vitroView study →}. Water extracts block HSV-1, HSV-2 and even acyclovir-resistant HSV-1 by inhibiting viral binding/penetration and NF-κB activation ^{3,4Reference 3Chen et al. · 2011In vitroHouttuynia cordata blocks HSV infection through inhibition of NF-κB activation — in vitroView study →Reference 4Hung et al. · 2015In vitroHouttuynia cordata targets the beginning stage of herpes simplex virus infection — in vitroView study →}. The standout is a class of flavonoids found only in this genus — the houttuynoids, in which a houttuynin chain is tethered to a hyperoside core; houttuynoids A–E and M show potent anti-HSV activity (IC50 values in the low-micromolar range) in plaque assays ^{2,5,6Reference 2Chen et al. · 2012In vitroHouttuynoids A–E, anti-herpes simplex virus active flavonoids with novel skeletons from Houttuynia cordata — in vitroView study →Reference 5Li et al. · 2017In vitroAnti-herpes simplex virus type 1 activity of Houttuynoid A, a flavonoid from Houttuynia cordata — in vitroView study →Reference 6Li et al. · 2017In vitroHouttuynoid M, an anti-HSV active houttuynoid from Houttuynia cordata — in vitroView study →}. All data are in vitro; no animal or human herpes study exists.

Gap: Purely in vitro. The houttuynoids are scarce, structurally complex, and there is no evidence a tea, tincture or topical delivers an antiviral concentration in vivo.

This is the herb’s headline traditional use and the source of its COVID-era attention. Against SARS-CoV, an extract inhibited the viral 3C-like protease (3CLpro) and RNA-dependent RNA polymerase in enzyme assays while raising CD4+/CD8+ T-cells and IL-2/IL-10 in mice — an immune-plus-antiviral mechanism, but not a clinical result ^{7Reference 7Lau et al. · 2008In vitroImmunomodulatory and anti-SARS activities of Houttuynia cordata — in vitro / animal modelView study →}. The stronger animal evidence is for influenza: crude and purified polysaccharides and total flavonoids repeatedly reduce H1N1-induced acute lung injury in mice, partly by remodelling the gut–lung axis, and an anti-complement polysaccharide protects against viral–bacterial co-infection pneumonia ^{9,10Reference 9Tang et al. · 2023AnimalTherapeutic effects on H1N1-induced pneumonia in mice and intestinal biotransformation of four main flavonoids from Houttuynia cordata — animal modelView study →Reference 10Li et al. · 2025AnimalAn anti-complement homogeneous polysaccharide from Houttuynia cordata ameliorates acute pneumonia from viral–bacterial co-infection — animal modelView study →}. Older in vitro work reports virucidal action against influenza and HIV-1 as well ^{1Reference 1Hayashi et al. · 1995In vitroVirucidal effects of the steam distillate from Houttuynia cordata and its components on HSV-1, influenza virus, and HIV — in vitroView study →}. The SARS-CoV-2 literature is dominated by molecular docking and is not evidence of efficacy ^{14Reference 14Kumar et al. · 2014AnimalAntihyperglycemic activity of Houttuynia cordata Thunb. in streptozotocin-induced diabetic rats — animal modelView study →}.

Gap: No human antiviral trial of houttuynia alone; the coronavirus case is enzyme/docking-level, and influenza data are mouse lung-injury models, not infection-prevention in people.

A long traditional use as a “herbal antibiotic” with moderate in vitro support. An ethanol extract of a houttuynia poultice was bactericidal against methicillin-resistant Staphylococcus aureus (MRSA), inhibiting biofilm formation and inducing IL-8 ^{11Reference 11Sekita et al. · 2016In vitroAnti-bacterial and anti-inflammatory effects of ethanol extract from Houttuynia cordata poultice — in vitroView study →}. The essential oil shows antibacterial and antifungal activity in India-sourced material, though potency tracks the highly variable oil composition ^{12Reference 12Verma et al. · 2017In vitroChemical composition and allelopathic, antibacterial, antifungal, and antiacetylcholinesterase activity of fish-mint (Houttuynia cordata) from India — in vitroView study →}. More recently, extracts inhibited S. aureus and Pseudomonas aeruginosa clinical isolates from diabetic-foot ulcers in vitro ^{13Reference 13Geng et al. · 2025In vitroIn vitro activity of Houttuynia cordata against bacteria isolated from diabetic foot — in vitroView study →}. Effects are real but preparation-dependent and unconfirmed in any controlled human infection.

Gap: All activity is in vitro; minimum inhibitory concentrations are modest versus conventional antibiotics, and no clinical antibacterial outcome has been shown.

Several independent streptozotocin-induced diabetic-rat studies converge. A standardised extract (200–400 mg/kg for 21 days) significantly lowered fasting glucose and raised insulin, attributed to pancreatic β-cell protection and up-regulation of the insulin-dependent glucose transporter GLUT-4 alongside antioxidant activity ^{14Reference 14Kumar et al. · 2014AnimalAntihyperglycemic activity of Houttuynia cordata Thunb. in streptozotocin-induced diabetic rats — animal modelView study →}. Ethanolic and fermented preparations reproduce glucose-lowering and lipid-improving effects in the same model ^{15,16Reference 15Rahman et al. · 2024AnimalImpacts of Plu kaow (Houttuynia cordata) ethanolic extract on diabetes and dyslipidemia in STZ-induced diabetic rats — animal modelView study →Reference 16Sakuludomkan et al. · 2021AnimalEffects of fermented Houttuynia cordata on diabetic rats and on insulin resistance in 3T3-L1 adipocytes — animal modelView study →}. The signal is consistent across labs but confined to rodents; the herb is eaten as a “medicinal salad” for blood sugar in north-east India, which motivates the work.

Gap: Animal-only, all in chemically-induced diabetes; no human glucose or HbA1c data, and doses were high relative to culinary intake.

Water extracts inhibited systemic anaphylaxis and local allergic reactions in mice by stabilising mast cells — reducing degranulation, histamine release and calcium influx ^{17Reference 17Li et al. · 2005AnimalInhibitory effects of Houttuynia cordata water extracts on anaphylactic reaction and mast cell activation — animal modelView study →} — and suppressed IgE-mediated responses by blocking multiple steps of FcεRI signalling ^{18Reference 18Han et al. · 2009AnimalHouttuynia cordata water extract suppresses anaphylactic reaction and IgE-mediated allergic response by inhibiting FcεRI signaling in mast cells — animal modelView study →}. A related Th2-suppressing effect (lower IL-4, IL-5) supports use in allergic inflammation. This coexists with an important paradox: the injectable houttuynia preparation is itself a documented cause of anaphylactoid reactions, apparently via the MRGPRB2/X2 receptor ^{26Reference 26Sun et al. · 2022Mrgprb2 gene plays a role in the anaphylactoid reactions induced by Houttuynia cordata injection — animal / mechanisticView study →} — the oral extract calms mast cells while the parenteral product can trigger them.

Gap: Efficacy data are murine; the mast-cell-stabilising oral effect must not be conflated with the parenteral product’s anaphylaxis risk (see Safety).

Largely a constituent-level story. The leaf is rich in quercetin, quercitrin, hyperoside and rutin, flavonoids with well-characterised radical-scavenging chemistry, and in vivo diabetic-rat studies report lower oxidative-stress markers and activation of the Nrf2/HO-1 antioxidant axis after dosing ^{14,15,16Reference 14Kumar et al. · 2014AnimalAntihyperglycemic activity of Houttuynia cordata Thunb. in streptozotocin-induced diabetic rats — animal modelView study →Reference 15Rahman et al. · 2024AnimalImpacts of Plu kaow (Houttuynia cordata) ethanolic extract on diabetes and dyslipidemia in STZ-induced diabetic rats — animal modelView study →Reference 16Sakuludomkan et al. · 2021AnimalEffects of fermented Houttuynia cordata on diabetic rats and on insulin resistance in 3T3-L1 adipocytes — animal modelView study →}. The activity is plausible and mechanism-mapped rather than demonstrated as a standalone clinical benefit.

Gap: Rests on known flavonoid chemistry plus secondary in vivo markers; no dedicated human antioxidant-status trial.

Two threads. In HepG2 hepatocytes, an extract curbed high-glucose-induced lipid accumulation by activating AMP-activated protein kinase (AMPK) ^{19Reference 19Kang et al. · 2014In vitroHouttuynia cordata attenuates lipid accumulation via AMP-activated protein kinase signaling in HepG2 cells — in vitroView study →}. In vivo, a purified polysaccharide reduced liver injury (lower ALT/AST, less oxidative stress) in a mouse hepatic ischemia-reperfusion model by steering macrophages away from a pro-inflammatory state via TLR4/NF-κB ^{20Reference 20Yu et al. · 2026AnimalHouttuynia cordata polysaccharide alleviates hepatic ischemia-reperfusion injury by regulating macrophage polarization via TLR4/NF-κB — animal modelView study →}. Supportive but sparse.

Gap: One cell-line study and one animal model; no repeated replication and no human liver data.

Preliminary. Five bioactive alkaloids isolated from houttuynia were cytotoxic to a panel of human cancer cell lines (lung A549, ovarian SK-OV-3, melanoma SK-MEL-2, CNS XF-498, colon HCT-15) in vitro ^{21Reference 21Kim et al. · 2001In vitroCytotoxic alkaloids from Houttuynia cordata — in vitroView study →}. More recent work reports the essential oil inhibits diffuse large B-cell lymphoma cells and slows tumour growth in mice ^{22Reference 22Peng et al. · 2026In vitroHouttuynia cordata Thunb. essential oil inhibits diffuse large B-cell lymphoma growth — in vitro / animal modelView study →}. These are early-stage cytotoxicity findings, not evidence of anticancer use.

Gap: Cell-line and single-model data only; cytotoxicity to cancer lines does not establish selectivity, safety or clinical benefit.

Diuresis is a core traditional and pharmacopoeial indication — in Chinese medicine houttuynia is used to promote urination and drain damp-heat, and “diuretic” is among its listed herbal actions ^{27Reference 27Wu et al. · 2021ReviewHouttuynia cordata Thunb: an ethnopharmacological review — reviewView study →}. Modern experimental confirmation is almost absent; the property is asserted in reviews but not backed by controlled measurement of urine output or electrolyte handling.

Gap: Essentially traditional. No modern pharmacological study quantifies a diuretic effect, so the score reflects documented use rather than tested activity.

Houttuynia is eaten as a leaf vegetable across East and Southeast Asia and is generally well tolerated as a food, but three cautions deserve mention. First, it can provoke genuine allergic reactions in sensitive individuals. Second — and largely absent from most monographs — the plant contains aristolactams, structural analogues of the nephrotoxic and carcinogenic aristolochic acid I; a 2025 mouse study found the predominant aristolactams (AL I, AL BII) caused only modest kidney changes at dietary levels, attributed to low oral bioavailability and metabolism to less toxic forms, and concluded typical dietary consumption is likely safe while urging monitoring of aristolactam content ^{24Reference 24Xue et al. · 2025AnimalSafety evaluation of aristolactams from the edible herb Houttuynia cordata: implications for dietary exposure and food safety — animal modelView study →}. Third, the injectable houttuynia preparation used in Chinese hospitals (not the oral herb) has a well-documented record of serious anaphylactoid reactions: a systematic review of 1,232 adverse-drug-reaction cases found anaphylactic shock accounted for roughly 59% of the most severe events and was responsible for the reported deaths, with risk raised by intravenous administration and by combining the injection with macrolide, cephalosporin or penicillin antibiotics ^{25,26Reference 25Wang et al. · 2010Systematic reviewAdverse events to Houttuynia injection — systematic reviewView study →Reference 26Sun et al. · 2022Mrgprb2 gene plays a role in the anaphylactoid reactions induced by Houttuynia cordata injection — animal / mechanisticView study →}. These injection risks do not transfer to culinary or oral use, but they underscore that the herb is immunologically active.

Interactions and CYP450 — not assessed for the oral herb. The only documented interactions concern the injectable product co-administered with macrolide, cephalosporin or penicillin antibiotics (higher adverse-reaction risk) ^{25Reference 25Wang et al. · 2010Systematic reviewAdverse events to Houttuynia injection — systematic reviewView study →}. No oral-herb–drug pharmacokinetic interaction (including CYP450) has been studied; assume unknown rather than absent.