Horopito

What Is Horopito?

Horopito is an evergreen New Zealand shrub whose leaves have a hot, peppery taste. It is a traditional Māori medicine, used for skin complaints, wounds and toothache, and its leaves are also used today as a peppery flavouring ^{27,28Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →Reference 28Ham et al. · 2026Effect of thermal and freeze-drying on the volatile composition of mountain horopito (Pseudowintera colorata) and kawakawa (Piper excelsum) — phytochemistryView study →}.

Horopito grows only in New Zealand, in forest margins and shrubland from the coast to the mountains ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}. Its leathery leaves are blotched with red where the plant grows in the open ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}.

The leaf’s pungency comes from polygodial, a compound first isolated from horopito in 1982 as an agent active against Candida ^{1Reference 1McCallion et al. · 1982In vitroAntibiotic substances from New Zealand plantsView study →}. Two trials of a horopito extract in recurrent vaginal thrush have been published, and most other research has been done in the laboratory ^{6,7Reference 6Kumari et al. · 2011RCTProtective effect of an oral natural phytonutrient in recurrent vulvovaginal candidiasis: a 12-month randomised study — randomised controlled trialView study →Reference 7Chopra et al. · 2013RCTProphylactic strategies in recurrent vulvovaginal candidiasis: a 2-year randomised study testing a phytonutrient vs itraconazole — randomised controlled trialView study →}.

The Māori name horopito is also used for a close relative, Pseudowintera axillaris, which has shiny green leaves and is not peppery ^{26,27Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

How Is Horopito Used?

Horopito leaf is taken mainly for fungal infections, especially Candida. A 2026 survey of Australian practitioners found it among the herbal medicines most often recommended for recurrent vaginal thrush ^{8Reference 8Everingham-Gordon et al. · 2026ObservationalTreatment recommendations for recurrent vulvovaginal candidiasis across complementary and conventional disciplines: a national survey — observational surveyView study →}.

• Liquid extract — the usual form in Western herbal practice.
• Tablets — a standardised leaf extract combined with other ingredients was the form tested in the thrush trials ^{6,7Reference 6Kumari et al. · 2011RCTProtective effect of an oral natural phytonutrient in recurrent vulvovaginal candidiasis: a 12-month randomised study — randomised controlled trialView study →Reference 7Chopra et al. · 2013RCTProphylactic strategies in recurrent vulvovaginal candidiasis: a 2-year randomised study testing a phytonutrient vs itraconazole — randomised controlled trialView study →}.
• Topical preparations — creams and other preparations applied to the skin ^{21Reference 21Corazza et al. · 2007Case reportContact vulvitis due to Pseudowintera colorata in a topical herbal medicament — case reportView study →}.
• Fresh leaf — chewed, or bruised and applied, in Māori practice ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

Traditional Uses

Māori Medicine

Horopito is the Māori name for the plant, which is also called ramarama ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}. The leaves were bruised and steeped in water, and the decoction was used for a skin complaint called paipai ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

The leaf was chewed for toothache ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}. Chewed leaf was also applied to wounds, which were said to heal quickly ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

The leaf was rubbed on the breast when weaning an infant, to give the milk a bitter taste ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

The name horopito covers both P. colorata and P. axillaris, and the recorded medicinal uses probably refer to both species ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

New Zealand Settler Use

European settlers and bushmen took up the plant. A leaf decoction was known as “bushman’s painkiller”, and the sap was taken for stomach ache ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

The bark was used as a substitute for quinine, and the plant was occasionally taken for diarrhoea ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}. It was also described as astringent, stimulating and anti-scorbutic, and a leaf infusion was taken for chest complaints ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

Indications

• Recurrent vaginal thrush [standardised oleoresin]
• Skin complaints [leaf decoction; Māori medicine]
• Wounds [chewed leaf; Māori medicine]
• Toothache [chewed leaf; Māori medicine]
• Stomach ache [sap; New Zealand settler use]
• Diarrhoea [leaf and bark; New Zealand settler use]
• Chest complaints [leaf infusion; New Zealand settler use]

Botany

Horopito (Pseudowintera colorata) is an evergreen shrub in the winter’s-bark family (Winteraceae). It grows up to 3.5 m tall, with upright trunks and dark bark, and the whole plant is hairless ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}.

Its leaves are alternate, elliptic and leathery, 2–6 cm long, with wavy edges. The upper surface is matt green to yellowish-green and blotched with red where the plant grows in exposed places. The underside is pale, often white, and sometimes flushed pink ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}. The leaves taste pungent and peppery ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}.

Leaves with wider red margins contain more polygodial and more anthocyanin pigment. Leaf-eating caterpillars avoid them, so the red works as a warning signal ^{25Reference 25Cooney et al. · 2012Red leaf margins indicate increased polygodial content and function as visual signals to reduce herbivory in Pseudowintera colorata — field/ecology studyView study →}.

The flowers are small, about 1 cm across, with narrow greenish-yellow petals. They grow singly or in clusters of up to three in the leaf axils, from November to March ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}. The fruit is a small fleshy berry, 5–6 mm across and dark red or black ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}.

Horopito is most easily confused with P. axillaris, which has shiny green leaves that are not white beneath and do not taste particularly peppery ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}.

Distribution

Horopito is endemic to New Zealand. It grows on the North, South and Stewart Islands, in coastal, lowland and mountain forest margins and in shrubland ^{26Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →}.

It is classed as Not Threatened nationally. It is often one of the few shrubs left in forests heavily browsed by deer, which do not eat it ^{26,27Reference 26de Lange · 2026Pseudowintera colorata fact sheet — species description, habitat, distribution and conservation status — floraView study →Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

Growing Conditions

Cultivation snapshot for Horopito

LifeperennialZoneUSDA 8–10

• Evergreen shrub of cool, moist temperate forests — think New Zealand bush understory, roughly hardiness zones 8–10.
• Tolerates part shade but develops its signature red-and-purple leaf blotching most strongly in brighter, more exposed positions.
• Prefers moist, free-draining, humus-rich soil and steady moisture; not a plant for hot, dry sites.
• Naturally very slow-growing, so expect patience — it forms a dense shrub to around 3.5 m over time.

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Pharmacology & Research

Most horopito research concerns one compound, polygodial, the pungent sesquiterpene dialdehyde in the leaf. Much of that work used polygodial isolated from other plants, such as Drimys winteri, Drimys brasiliensis and Warburgia ugandensis, rather than from horopito.

The human evidence is two randomized trials of a standardised horopito oleoresin (30% polygodial) in recurrent vaginal thrush, both from the same research group ^{6,7Reference 6Kumari et al. · 2011RCTProtective effect of an oral natural phytonutrient in recurrent vulvovaginal candidiasis: a 12-month randomised study — randomised controlled trialView study →Reference 7Chopra et al. · 2013RCTProphylactic strategies in recurrent vulvovaginal candidiasis: a 2-year randomised study testing a phytonutrient vs itraconazole — randomised controlled trialView study →}.

The anti-inflammatory, analgesic, antibacterial and anthelmintic findings come from animal and laboratory studies. Polygodial content varies about two-fold between plants ^{24,25Reference 24Wayman et al. · 2010Chemotaxonomy of Pseudowintera: sesquiterpene dialdehyde variants are species markers — phytochemistryView study →Reference 25Cooney et al. · 2012Red leaf margins indicate increased polygodial content and function as visual signals to reduce herbivory in Pseudowintera colorata — field/ecology studyView study →}.

1. Antifungal

Polygodial was first isolated from P. colorata as an anti-Candida agent in 1982 ^{1Reference 1McCallion et al. · 1982In vitroAntibiotic substances from New Zealand plantsView study →}. Later in-vitro work showed it is rapidly fungicidal against Candida albicans, C. krusei, Cryptococcus neoformans and dermatophytes, at potency comparable to amphotericin B. Unlike amphotericin B, it caused no hemolysis and kept its activity in the presence of ergosterol ^{2Reference 2Lee et al. · 1999In vitroIn vitro antifungal susceptibilities of Candida albicans and other fungal pathogens to polygodial, a sesquiterpene dialdehyde — in vitroView study →}.

It acts as a non-ionic surfactant that disrupts the fungal membrane, and it inhibits the plasma-membrane H⁺-ATPase ^{3Reference 3Kubo et al. · 2001In vitroAntifungal mechanism of polygodial — in vitroView study →}. Genome-wide screens in yeast add vacuolar alkalinization and disrupted Ca²⁺ signaling ^{4Reference 4Kipanga et al. · 2021In vitroInvestigating the antifungal mechanism of action of polygodial by phenotypic screening in Saccharomyces cerevisiae — in vitroView study →}.

Activity rises under acidic conditions ^{2Reference 2Lee et al. · 1999In vitroIn vitro antifungal susceptibilities of Candida albicans and other fungal pathogens to polygodial, a sesquiterpene dialdehyde — in vitroView study →}.

In yeast, polygodial damaged the cell membrane within minutes, and it markedly increased the activity of actinomycin D, an antibiotic that enters cells poorly ^{5Reference 5Kubo et al. · 1988In vitroPolygodial, an antifungal potentiator — in vitroView study →}.

In humans, two randomized trials by one group tested a standardized product (K-712: each 100 mg tablet containing 10 mg of P. colorata oleoresin at 30% polygodial, with a trace of olive) against itraconazole for recurrent vulvovaginal candidiasis. In an 82-woman, 12-month study, mycological cure at 6 months was comparable (78% vs 83%). Over the following 6 months without treatment, relapses were significantly fewer with K-712 (34.2 vs 65.7) ^{6Reference 6Kumari et al. · 2011RCTProtective effect of an oral natural phytonutrient in recurrent vulvovaginal candidiasis: a 12-month randomised study — randomised controlled trialView study →}.

A 122-woman, 2-year study found fewer relapses on K-712 (22 vs 39) and less growth of azole-resistant and non-albicans species. Overall mycological cure at 2 years was comparable between the groups ^{7Reference 7Chopra et al. · 2013RCTProphylactic strategies in recurrent vulvovaginal candidiasis: a 2-year randomised study testing a phytonutrient vs itraconazole — randomised controlled trialView study →}.

Gap: human evidence is one indication, one product and one research group, with no independent replication, no registered trial, and nothing on the tincture or capsule forms.

2. Anti-Inflammatory

Polygodial suppresses inflammation across several animal and cell models, almost always as the isolated molecule from Drimys species. In mice it inhibited paw edema caused by prostaglandin E₂, bradykinin, substance P, PAF and carrageenan, and protected against ovalbumin-induced anaphylaxis ^{13Reference 13da Cunha et al. · 2001AnimalAdditional evidence for the anti-inflammatory and anti-allergic properties of the sesquiterpene polygodial — animal (rat/mouse) in vivoView study →}.

In a sponge-implant model in mice it reduced macrophage infiltration, the pro-inflammatory chemokines CXCL1 and CCL2, mast-cell numbers and collagen deposition ^{14Reference 14Ferreira et al. · 2020AnimalSesquiterpene polygodial from Drimys brasiliensis down-regulates implant-induced inflammation and fibrogenesis in mice — animal in vivoView study →}.

Two mechanisms have been proposed. In pancreatic β-cells, polygodial reproduced dexamethasone-like MKP1/ERK signaling and caused the glucocorticoid receptor to move into the nucleus ^{15Reference 15Barrosa et al. · 2016In vitroPolygodial from Drimys brasiliensis triggers glucocorticoid-like effects on pancreatic β-cells — in vitro / in silicoView study →}. In THP-1 cells, polygodial and isotadeonal, an epimer made from it, blocked IκB-α phosphorylation and NF-κB reporter activity; isotadeonal was the more potent ^{16Reference 16Marín et al. · 2025In vitroInhibitory potential of the drimane sesquiterpenoids isotadeonal and polygodial in the NF-κB pathway — in vitro / in silicoView study →}.

No human anti-inflammatory data exist, and no study has tested a horopito preparation for an inflammatory outcome.

3. Analgesic

In rodents, a hydroalcoholic bark extract of Drimys winteri reduced pain in writhing, formalin and capsaicin models. Naloxone reversed the extract’s effect, pointing to opioid involvement. Polygodial isolated from the bark was 14- to 27-fold more potent than the extract in writhing models ^{12Reference 12Mendes et al. · 1998AnimalAnti-hyperalgesic properties of the extract and of the main sesquiterpene polygodial isolated from the barks of Drimys winteri — animal (mouse/rat) in vivoView study →}.

Polygodial activates the capsaicin receptor TRPV1 and the related TRPA1 ^{18,20Reference 18Paz et al. · 2022In vitroPolygodial, a drimane sesquiterpenoid dialdehyde purified from Drimys winteri, inhibits voltage-gated sodium channels — in vitroView study →Reference 20Dasari et al. · 2015In vitroSynthetic and biological studies of sesquiterpene polygodial: activity of 9-epipolygodial against drug-resistant cancer cells — in vitroView study →}. Rats treated with it as newborns, like rats given capsaicin, showed lasting reduced pain responses and fewer spinal resiniferatoxin binding sites ^{17Reference 17André et al. · 2004AnimalEvidence for the involvement of vanilloid receptor in the antinociception produced by the sesquiterpenes polygodial and drimanial in rats — animal in vivoView study →}.

In patch-clamp studies it also blocks the pain-signalling sodium channels NaV1.7 and NaV1.8 ^{18Reference 18Paz et al. · 2022In vitroPolygodial, a drimane sesquiterpenoid dialdehyde purified from Drimys winteri, inhibits voltage-gated sodium channels — in vitroView study →}.

All the efficacy data come from animals or isolated cells, using purified compound given by injection. There is no human analgesia data.

4. Antibacterial

Purified polygodial shows moderate activity against Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Escherichia coli, Salmonella) bacteria, with minimum bactericidal concentrations of 50–100 µg/mL ^{9Reference 9Kubo et al. · 2005In vitroAntibacterial activity of polygodial — in vitroView study →}.

A 2024 panel of drimane sesquiterpenes from D. winteri found polygodial the most active member, with MICs of 16–64 µg/mL against Enterococcus avium, Klebsiella pneumoniae, Salmonella typhi and E. coli ^{10Reference 10Montenegro et al. · 2024In vitroAntimicrobial activity of drimanic sesquiterpene compounds from Drimys winteri against multiresistant microorganisms — in vitroView study →}.

These are in-vitro findings on the isolated molecule from other species, with no whole-herb, topical or clinical data.

5. Anthelmintic

Bioassay-guided fractionation of Warburgia ugandensis, a Canellaceae plant that also makes polygodial, was tested against the nematode Caenorhabditis elegans. It identified polygodial (IC₅₀ 13.1 µM), warburganal and α-linolenic acid as the active compounds, with polygodial acting synergistically with α-linolenic acid ^{11Reference 11Liu et al. · 2018In vitroBioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis, and the mechanism of action of polygodial — in vitro (C. elegans model)View study →}.

The reactive α,β-unsaturated dialdehyde group was essential for activity. Polygodial inhibited mitochondrial ATP synthesis in the worms, and nematode strains resistant to the main drug classes were not resistant to it ^{11Reference 11Liu et al. · 2018In vitroBioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis, and the mechanism of action of polygodial — in vitro (C. elegans model)View study →}.

Gap: a single in-vitro study in a model nematode, using polygodial from Warburgia; no Pseudowintera-specific or in-vivo antiparasitic data.

6. Anti-Allergic

In sensitized mice, polygodial dose-dependently inhibited ovalbumin-induced paw edema and protected against anaphylactic shock. It also inhibited pleurisy caused by substance P and histamine ^{13Reference 13da Cunha et al. · 2001AnimalAdditional evidence for the anti-inflammatory and anti-allergic properties of the sesquiterpene polygodial — animal (rat/mouse) in vivoView study →}.

The implant study’s reduction in mast-cell numbers points the same way ^{14Reference 14Ferreira et al. · 2020AnimalSesquiterpene polygodial from Drimys brasiliensis down-regulates implant-induced inflammation and fibrogenesis in mice — animal in vivoView study →}.

Horopito preparations can also cause allergy. A case of allergic contact vulvitis from a topical P. colorata medicament has been reported ^{21Reference 21Corazza et al. · 2007Case reportContact vulvitis due to Pseudowintera colorata in a topical herbal medicament — case reportView study →}.

Gap: anti-allergic activity is animal-only and on isolated polygodial, while the herb carries an uncommon contact-allergy risk.

7. Anticancer

The anticancer activity belongs mainly to semisynthetic polygodial derivatives. A synthetic analogue, DRP-27, induced apoptosis in LNCaP prostate-cancer cells ^{19Reference 19Dasari et al. · 2018In vitroPolygodial analog induces apoptosis in LNCaP prostate cancer cells — in vitroView study →}. 9-Epipolygodial was more potent than polygodial against cancer cells and kept its activity against apoptosis-resistant and multidrug-resistant lines ^{20Reference 20Dasari et al. · 2015In vitroSynthetic and biological studies of sesquiterpene polygodial: activity of 9-epipolygodial against drug-resistant cancer cells — in vitroView study →}.

These are laboratory-made compounds tested in cell lines. No whole-herb or in-vivo tumor data exist, and horopito has no traditional use for cancer.

Mechanisms

Polygodial is a sesquiterpene dialdehyde. In fungi it acts as a non-ionic surfactant, disrupting the cell membrane and inhibiting the plasma-membrane H⁺-ATPase; in nematodes it inhibits mitochondrial ATP synthesis ^{3,11Reference 3Kubo et al. · 2001In vitroAntifungal mechanism of polygodial — in vitroView study →Reference 11Liu et al. · 2018In vitroBioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis, and the mechanism of action of polygodial — in vitro (C. elegans model)View study →}.

It activates the TRPV1 and TRPA1 receptors, which produce the burning, peppery sensation, and blocks pain-related sodium channels ^{18,20Reference 18Paz et al. · 2022In vitroPolygodial, a drimane sesquiterpenoid dialdehyde purified from Drimys winteri, inhibits voltage-gated sodium channels — in vitroView study →Reference 20Dasari et al. · 2015In vitroSynthetic and biological studies of sesquiterpene polygodial: activity of 9-epipolygodial against drug-resistant cancer cells — in vitroView study →}. Its anti-inflammatory effects have been studied at the NF-κB pathway and the glucocorticoid receptor ^{15,16Reference 15Barrosa et al. · 2016In vitroPolygodial from Drimys brasiliensis triggers glucocorticoid-like effects on pancreatic β-cells — in vitro / in silicoView study →Reference 16Marín et al. · 2025In vitroInhibitory potential of the drimane sesquiterpenoids isotadeonal and polygodial in the NF-κB pathway — in vitro / in silicoView study →}.

Clinical Trials

No registered clinical trials of horopito or polygodial were identified. The human evidence is two unregistered randomized trials of the standardized P. colorata oleoresin K-712 in recurrent vulvovaginal candidiasis ^{6,7Reference 6Kumari et al. · 2011RCTProtective effect of an oral natural phytonutrient in recurrent vulvovaginal candidiasis: a 12-month randomised study — randomised controlled trialView study →Reference 7Chopra et al. · 2013RCTProphylactic strategies in recurrent vulvovaginal candidiasis: a 2-year randomised study testing a phytonutrient vs itraconazole — randomised controlled trialView study →}.

Last checked: July 2026.

Phytochemistry

Horopito’s pungency comes from polygodial, a sesquiterpene dialdehyde. Leaves of plants from different parts of New Zealand contained 1.4–2.9% polygodial by dry weight ^{24Reference 24Wayman et al. · 2010Chemotaxonomy of Pseudowintera: sesquiterpene dialdehyde variants are species markers — phytochemistryView study →}.

A second sesquiterpene dialdehyde, 9-deoxymuzigadial, occurs at 0–2.9% of leaf dry weight. These dialdehydes differ between the Pseudowintera species and serve as species markers ^{24Reference 24Wayman et al. · 2010Chemotaxonomy of Pseudowintera: sesquiterpene dialdehyde variants are species markers — phytochemistryView study →}. Their levels also vary between individual horopito plants ^{23Reference 23Perry et al. · 1996Infraspecific variation of insecticidal sesquiterpene dialdehydes in Pseudowintera colorata — phytochemistryView study →}.

The red leaf colour comes from anthocyanins. Leaves with wider red margins contain more polygodial ^{25Reference 25Cooney et al. · 2012Red leaf margins indicate increased polygodial content and function as visual signals to reduce herbivory in Pseudowintera colorata — field/ecology studyView study →}.

The leaf essential oil contains about 29 compounds ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}. A headspace analysis found 105 volatile compounds in the leaf, with limonene the most abundant in fresh leaves; drying reduced limonene, α-cubebene and terpinen-4-ol ^{28Reference 28Ham et al. · 2026Effect of thermal and freeze-drying on the volatile composition of mountain horopito (Pseudowintera colorata) and kawakawa (Piper excelsum) — phytochemistryView study →}.

Constituent Summary

Figures are percent of leaf dry weight. Polygodial and the related sesquiterpene dialdehydes vary with leaf colour and between plants ^{24,25Reference 24Wayman et al. · 2010Chemotaxonomy of Pseudowintera: sesquiterpene dialdehyde variants are species markers — phytochemistryView study →Reference 25Cooney et al. · 2012Red leaf margins indicate increased polygodial content and function as visual signals to reduce herbivory in Pseudowintera colorata — field/ecology studyView study →}.

Dosage

The trialled product was a standardised oleoresin tablet. In Western herbal practice horopito is taken as a liquid extract.

Research Doses

Traditional Dosage

The leaf is intensely pungent. An infusion leaves a burning sensation in the throat and chest ^{27Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}.

Safety & Pregnancy

Horopito was well tolerated in the thrush trials ^{6,7Reference 6Kumari et al. · 2011RCTProtective effect of an oral natural phytonutrient in recurrent vulvovaginal candidiasis: a 12-month randomised study — randomised controlled trialView study →Reference 7Chopra et al. · 2013RCTProphylactic strategies in recurrent vulvovaginal candidiasis: a 2-year randomised study testing a phytonutrient vs itraconazole — randomised controlled trialView study →}. Its documented risks are contact allergy, irritation from concentrated preparations, and a laboratory finding that underlies a caution in epilepsy.

Full Safety & Interactions Detail

Contact allergy. A case of allergic contact vulvitis was reported from a topical P. colorata medicament ^{21Reference 21Corazza et al. · 2007Case reportContact vulvitis due to Pseudowintera colorata in a topical herbal medicament — case reportView study →}. Patch-testing is sensible before topical or intimate use.

Epilepsy and seizure disorders. In rat brain tissue, polygodial and drimanial from Drimys winteri inhibited glutamate uptake by astrocytes and increased glutamate release. The authors suggested this could be excitotoxic and called for caution in using these compounds ^{22Reference 22Martini et al. · 2006In vitroThe sesquiterpenes polygodial and drimanial in vitro affect glutamatergic transport in rat brain — in vitroView study →}. This is the basis for avoiding horopito in seizure disorders.

Irritation. Polygodial is a pungent TRPV1/TRPA1 activator, and a leaf infusion burns the throat and chest ^{18,27Reference 18Paz et al. · 2022In vitroPolygodial, a drimane sesquiterpenoid dialdehyde purified from Drimys winteri, inhibits voltage-gated sodium channels — in vitroView study →Reference 27Manaaki Whenua – Landcare Research · 2023Pseudowintera colorataView study →}. Concentrated extracts are best avoided in acute gastritis or peptic ulcer.

Interactions. Herb–drug interactions have not been studied for horopito or polygodial.

References

1. McCallion, R. F., Cole, A. L. J., Walker, J. R. L., Blunt, J. W., & Munro, M. H. G. (1982). Antibiotic substances from New Zealand plants. II. Polygodial, an anti-Candida agent from Pseudowintera colorata — in vitro. Planta Medica. https://pubmed.ncbi.nlm.nih.gov/7089094/
2. Lee, S. H., Lee, J. R., Lunde, C. S., & Kubo, I. (1999). In vitro antifungal susceptibilities of Candida albicans and other fungal pathogens to polygodial, a sesquiterpene dialdehyde — in vitro. Planta Medica. https://pubmed.ncbi.nlm.nih.gov/10232062/
3. Kubo, I., Fujita, K., & Lee, S. H. (2001). Antifungal mechanism of polygodial — in vitro. Journal of Agricultural and Food Chemistry. https://pubmed.ncbi.nlm.nih.gov/11312903/
4. Kipanga, P. N., Demuyser, L., Vrijdag, J., et al. (2021). Investigating the antifungal mechanism of action of polygodial by phenotypic screening in Saccharomyces cerevisiae — in vitro. International Journal of Molecular Sciences. https://pubmed.ncbi.nlm.nih.gov/34071169/
5. Kubo, I., & Taniguchi, M. (1988). Polygodial, an antifungal potentiator — in vitro. Journal of Natural Products. https://pubmed.ncbi.nlm.nih.gov/3286823/
6. Kumari, A., Bishier, M. P., Naito, Y., et al. (2011). Protective effect of an oral natural phytonutrient in recurrent vulvovaginal candidiasis: a 12-month randomised study — randomised controlled trial. Journal of Biological Regulators and Homeostatic Agents. https://pubmed.ncbi.nlm.nih.gov/22217987/
7. Chopra, V., Marotta, F., Kumari, A., et al. (2013). Prophylactic strategies in recurrent vulvovaginal candidiasis: a 2-year randomised study testing a phytonutrient vs itraconazole — randomised controlled trial. Journal of Biological Regulators and Homeostatic Agents. https://pubmed.ncbi.nlm.nih.gov/24152852/
8. Everingham-Gordon, R., Steels, E., Watson, C. J., & Steadman, K. J. (2026). Treatment recommendations for recurrent vulvovaginal candidiasis across complementary and conventional disciplines: a national survey — observational survey. International Journal of Clinical Pharmacy. https://pubmed.ncbi.nlm.nih.gov/42189444/
9. Kubo, I., Fujita, K., Lee, S. H., & Ha, T. J. (2005). Antibacterial activity of polygodial — in vitro. Phytotherapy Research. https://pubmed.ncbi.nlm.nih.gov/16372365/
10. Montenegro, I., Pazmiño, R., Araque, I., et al. (2024). Antimicrobial activity of drimanic sesquiterpene compounds from Drimys winteri against multiresistant microorganisms — in vitro. Molecules. https://pubmed.ncbi.nlm.nih.gov/38930909/
11. Liu, M., Kipanga, P., Mai, A. H., et al. (2018). Bioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis, and the mechanism of action of polygodial — in vitro (C. elegans model). International Journal for Parasitology. https://pubmed.ncbi.nlm.nih.gov/30031002/
12. Mendes, G. L., Santos, A. R., Campos, M. M., et al. (1998). Anti-hyperalgesic properties of the extract and of the main sesquiterpene polygodial isolated from the barks of Drimys winteri — animal (mouse/rat) in vivo. Life Sciences. https://pubmed.ncbi.nlm.nih.gov/9714424/
13. da Cunha, F. M., Fröde, T. S., Mendes, G. L., et al. (2001). Additional evidence for the anti-inflammatory and anti-allergic properties of the sesquiterpene polygodial — animal (rat/mouse) in vivo. Life Sciences. https://pubmed.ncbi.nlm.nih.gov/11787941/
14. Ferreira, B. A., Norton Filho, A. F., Deconte, S. R., et al. (2020). Sesquiterpene polygodial from Drimys brasiliensis down-regulates implant-induced inflammation and fibrogenesis in mice — animal in vivo. Journal of Natural Products. https://pubmed.ncbi.nlm.nih.gov/33232149/
15. Barrosa, K. H., Mecchi, M. C., Rando, D. G., et al. (2016). Polygodial from Drimys brasiliensis triggers glucocorticoid-like effects on pancreatic β-cells — in vitro / in silico. Chemico-Biological Interactions. https://pubmed.ncbi.nlm.nih.gov/27645309/
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