Scarlet paintbrush

Scarlet Paintbrush (Castilleja miniata and Related Castilleja Species): A Comprehensive Reference

1. Identity and Botanical Characterization

1.1 Nomenclature and Taxonomic Position

The name Castilleja miniata carries 19 synonyms at the species or varietal level. Its scientific epithet, miniata, means "cinnabar-red" in botanical Latin, a direct reference to the bright scarlet color of its bracts. It is likewise known by the common name Scarlet Paintbrush, though other species — including Castilleja indivisa and Castilleja coccinea — are also referred to by this name at times. Like Castilleja coccinea, it is occasionally called red paintbrush, and is more specifically known as the giant red paintbrush, great red paintbrush, common red paintbrush, and common paintbrush.

Castilleja miniata was formally described in 1838 by George Bentham, attributing the discovery to David Douglas. It is classified in the family Orobanchaceae. These plants are classified in the broomrape family Orobanchaceae following major rearrangements of the order Lamiales starting around 2001; sources which do not follow these reclassifications may place them in the Scrophulariaceae. The genus name Castilleja honors the 18th-century Spanish botanist Domingo Castillejo.

Because the common name "Scarlet Paintbrush" is shared across the Castilleja genus, the scientific and ethnopharmacological literature relevant to this reference article draws primarily on C. miniata for botanical and ethnobotanical details, and on the broader genus — particularly the well-studied C. tenuiflora, C. coccinea, and C. integra — for phytochemical and pharmacological data. This overlap is noted explicitly where applicable.

1.2 Morphology and Habitat

Giant red paintbrush is a perennial herb that grows 12 to 80 centimeters tall, though occasionally reaching 1 meter, with few to many branching stems. It can have a taproot or grow from rhizomes with branching roots. The lance-shaped leaves are 3 to 6 centimeters long, pointed, and coated in thin hairs. The inflorescence is made up of bright red to pale orange or orange-tipped bracts, between which emerge yellow-green, red-edged tubular flowers. Flowers bloom from May to September.

Native to western North America, it ranges from Alaska southward to Arizona and eastward to the Rocky Mountains and Ontario, thriving in diverse habitats such as mountain meadows, open forests, grasslands, coastal bluffs, and moist stream banks at elevations from sea level to subalpine zones.

1.3 Hemiparasitic Growth Strategy

As a root hemiparasite, C. miniata connects to the roots of nearby host plants — often grasses — to extract water and nutrients while still performing photosynthesis, which enhances its adaptability to both wet and dry conditions but makes it challenging to cultivate. This interaction necessitates physical attachment between host and parasite, either aboveground or belowground, through a unique organ known as the haustorium — a multifunctional organ that facilitates attachment, penetration, and connection with the host, creating a continuum for exchanging water, nutrients, hormones, proteins, and nucleotides.

Most Indian paintbrushes are partial parasites on other plants, their roots establishing connections with roots of other species. For this reason, they usually cannot be transplanted and are difficult to grow from seed.

1.4 Common Forms and Preparations in Herbal Use

In both traditional and modern contexts, the plant material used has consisted of aerial parts — specifically leaves, flowers, and bracts. Documented traditional preparations by Pacific Northwest tribes include decoctions of the entire plant. A decoction of seeds has also been recorded as a preparation taken as a cough medicine. In research settings, extracts have been prepared using ethanol, methanol, ethyl acetate, and aqueous (water) solvents, applied to aerial portions of the plant. No standardized or commercially regulated supplement forms (capsules, tablets, tinctures) for C. miniata specifically have been documented in the peer-reviewed or pharmacopoeial literature; this plant is not listed in any major pharmacopoeia or government dietary supplement monograph as of the available literature.

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2. Traditional and Historical Use

2.1 North American Indigenous Peoples

Several species of Castilleja have been used by Native Americans for medicinal, practical, and ceremonial purposes, as documented by ethnobotanist Daniel Moerman (1998). The breadth of traditional applications reflects the geographic spread and ecological diversity of the genus across North America.

For C. miniata specifically, the most thoroughly documented traditional medical uses come from Pacific Northwest tribes. The Gitksan, Nitinaht, and Nlaka'pamux Pacific Northwest tribes have taken a decoction of the entire plant to treat bleeding lungs, sore eyes, and backaches, and to serve as a diuretic and as a purgative. Historically, many Native American tribes, including the Gitksan Tribe of British Columbia, have used Castilleja flowers to treat various illnesses such as bleeding and coughing, and as a condiment on food.

Food uses were also documented. The flowers of Indian paintbrush were edible and sweet and were consumed in moderation by various Native American tribes as a condiment with other fresh greens. The nectar has also been eaten as candy.

Medicinal uses beyond the Northwest tribes have been recorded for related Castilleja species with shared common names. The Chippewa Indians used Indian Paintbrush as a medicine to treat rheumatism and as a bath rinse to make their hair glossy, with both applications attributed to the plant's selenium content. Nevada Indian tribes used the plant to treat sexually transmitted diseases and to enhance the immune system. These accounts, however, pertain to the genus broadly and are not species-verified for C. miniata specifically.

2.2 Mexican Traditional Medicine

Closely related species, especially Castilleja tenuiflora, have been part of documented Mexican traditional medicine with considerable historical depth. Castilleja tenuiflora (Orobanchaceae) is a perennial plant used since the 16th century in Mexican traditional medicine for the treatment of a number of health disorders including inflammation, stomach pain, and tumors. It is used in Mexican Traditional Medicine for the treatment of conditions associated with cancer symptomatology as well as for the treatment of coughs, dysentery, nausea, vomiting, and hepatic, gastrointestinal, and nervous disorders.

A decoction of the leaves and flowers of C. tenuiflora is used in Mexican traditional medicine for coughs and in the treatment of dysentery, nerves, nausea, and vomiting, as well as hepatic and gastrointestinal diseases.

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3. Key Constituents and Active Compounds

3.1 Iridoid Glycosides

Iridoids are among the most extensively characterized compound classes in the Castilleja genus. Chemical constituents from the Castilleja genus include iridoids such as aucubin, geniposide, geniposidic acid, bartsioside, 8-epiloganin, mussaenoside, carioptoside, catalpol, shanzhiside, adoxoside, macfadienoside, and 8-epiloganic acid.

The iridoid content of Castilleja species has been found to be qualitatively similar across species analyzed; major iridoids include aucubin, catalpol, penstemonoside, and shanzhiside methyl ester, with traces of 8-epiloganin and gardoside methyl ester.

More extensive studies have revealed that iridoids exhibit a wide range of bioactivity, including neuroprotective, anti-inflammatory, immunomodulatory, hepatoprotective, and cardioprotective effects. Anticancer, antioxidant, antimicrobial, hypoglycaemic, hypolipidemic, choleretic, antispasmodic, and purgative properties have also been reported for the iridoid class.

3.2 Phenylethanoid Glycosides (Phenylpropanoids)

Phenylethanoids documented in Castilleja include verbascoside, isoverbascoside, and myricoside. Verbascoside has been reported as a phenylethanoid glycoside with diverse activities, including strong anti-leukemic and cytotoxic activity against a murine cell line and anti-inflammatory activity. Verbascoside also has antioxidant activity and decreases NOS (nitric oxide synthase) activities and reduces NF-κB signaling.

Previous reports have described that apigenin, verbascoside, geniposide, and aucubin isolated from several medicinal plants show different neuroprotective effects. For instance, verbascoside is capable of inhibiting glutamate-induced intracellular Ca²⁺ influx with overproduction of nitric oxide and reduction of reactive oxygen species. Geniposide has shown a multifaceted neuroprotective effect in an Alzheimer mouse model.

3.3 Flavonoids

Flavonoids documented in the genus include apigenin, luteolin 5-methyl ether, and quercetin glycosides. In studies of C. tenuiflora, tenuifloroside and verbascoside were identified as major chemical constituents in the bioactive extract, while the flavonoids apigenin and luteolin-5-methyl ether were the minor compounds.

3.4 Lignans

Chemical analysis of the antidepressant methanol extract of C. tenuiflora allowed the isolation of (+)-piperitol-4-O-xylopyranosyl-(1→6)-O-glucopyranoside. This new furofuran lignan diglycoside was named tenuifloroside. This pharmacological and chemical study showed that the methanol extract displays sedative and hypnotic effects, and tenuifloroside was the first furofuran lignan of this chemical skeleton to be reported in the Castilleja genus.

Phytochemical profile alterations have been observed in C. tenuiflora during co-culture with its host plant; for C. tenuiflora, the lignans sesamin and eudesmin were proposed as differentially accumulated metabolites upon haustoria formation.

3.5 Alkaloids — Host-Derived and Endogenous

A number of Castilleja species contain alkaloids, including some assimilated from parasitized hosts via haustorial bridges. Alkaloids documented in the genus include (−)-ammodendrin, (−)-N′-methylammodendrin, (+)-13α-hydroxylupanin, and (+)-tetrahydrorhombifolin.

Castilleja species will also transfer certain alkaloids from host plants to their own tissues; for example, senecionine, a pyrrolizidine alkaloid, is transferred from Liatris punctata and Senecio species to the parasite. Pyrrolizidine alkaloids were found in C. rhexifolia and some C. sulphurea populations, while other populations of the same species contained quinolizidine alkaloids or none at all. The specific alkaloid profile of any given Castilleja individual may therefore be substantially determined by which host plant it parasitizes, creating significant chemical variability.

Importantly, neither Castilleja miniata nor Castilleja indivisa contained alkaloids in nectar when parasitizing alkaloid-containing hosts, as reported by Adler and Wink (2001).

3.6 Selenium

Some species of Castilleja are reported to absorb and concentrate selenium, producing potentially toxic effects in grazing animals, as documented by Rosenfeld and Beath (2013). Indian paintbrushes in general are considered selenium accumulators. Selenium is a necessary nutrient for animals, but only in small amounts; thus, selenium accumulators tend to be toxic to grazing animals and humans who eat them in quantity. The leaves and roots of common red paintbrush (C. miniata) contain selenium, which can be toxic if eaten.

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4. Scientific Evidence by Area of Use

Overarching note on evidence quality: The vast majority of published research on Castilleja species and their bioactive constituents is conducted in vitro (in cell cultures) or in vivo in rodent animal models. No controlled human clinical trials of Castilleja miniata or any closely related species have been identified in the peer-reviewed literature. All pharmacological findings described below must therefore be characterized as preliminary, preclinical evidence only, with the significant limitation that animal and cell-based results may not translate to human clinical outcomes.

4.1 Anti-Inflammatory Activity

Evidence level: Preclinical only (in vitro and murine animal models).

Castilleja tenuiflora has been used in Mexican traditional medicine as a treatment for cough, dysentery, anxiety, nausea, vomiting, and hepatic and gastrointestinal diseases. Researchers evaluated the ethanolic extract of the aerial parts of C. tenuiflora using the induced edema model with 12-O-tetradecanoylphorbol acetate (TPA) as an anti-inflammatory activity assay.

The following iridoids were isolated from the active fraction: geniposidic acid, aucubin, bartioside, 8-epi-loganin, mussaenoside, and the phenylpropanoid verbascoside. The most active iridoid was geniposidic acid, which was more active than the positive control indomethacin; the least active iridoid was mussaenoside. 8-epi-Loganin and mussaenoside had not previously been reported as anti-inflammatory compounds.

A separate study directly evaluated topical anti-inflammatory activity of C. tenuiflora extracts in a mouse model. The main compounds found in the extracts were isoverbascoside, verbascoside, and aucubin; none of the extracts showed cytotoxicity against the tested cell lines. In contrast, ethyl acetate and aqueous wild-grown extracts and ethyl acetate in-vitro-plant extract, each at 1.6 mg/ear, showed moderate anti-inflammatory activity similar to dexamethasone (1 mg/ear), with 38.2%, 39.3%, and 49.1% decreases of inflammation, respectively.

The authors concluded that the results confirm the potential of Mexican plants for the production of bioactive compounds and validate the ethnomedical use of Castilleja tenuiflora-like anti-inflammatory plants. These studies are animal-model and in-vitro experiments; no human trials exist.

4.2 Gastroprotective and Anti-Ulcerogenic Activity

Evidence level: Preclinical only (murine animal models).

Ethyl acetate extracts of both wild-grown and in-vitro-propagated C. tenuiflora (100 mg/kg) showed high anti-ulcerogenic activity with 88.3% and 83.1% inhibition, respectively, compared to famotidine (20 mg/kg, 32.8% inhibition) in the acute ulcer induction model. The authors concluded that C. tenuiflora extracts provided significant gastric protection and topical anti-inflammatory activity.

A further investigation focused on isolated compounds. Castilleja tenuiflora is used in Mexican traditional medicine for the treatment of gastrointestinal diseases and nervous disorders. Previous studies indicated that organic extracts from C. tenuiflora had gastroprotective effects and antidepressant activity; researchers aimed to evaluate the gastroprotective and antidepressant activity of fractions and isolated compounds from the methanolic extract in stressed mice. The cold restraint stress (CRS)-induced gastric ulcer model and behavioral tests (tail suspension test and forced swim test) were used.

These results are limited to rodent models; the doses (e.g., 100 mg/kg) are reported as animal doses and are not directly translatable to human clinical dosages without further pharmacokinetic study.

4.3 Central Nervous System Effects: Antidepressant, Anxiolytic, and Sedative Activity

Evidence level: Preclinical only (murine animal models).

Castilleja tenuiflora has been used for the treatment of several central nervous system (CNS) diseases. Researchers reported the antidepressant activity of the methanol extract from the leaves of this medicinal plant. The oral administration of the methanol extract at 500 mg/kg induced a statistically significant (p < 0.05) decrement of the immobility parameter on the Forced Swimming Test (FST) and an increment in the latency and duration of hypnosis induced by sodium pentobarbital (40 mg/kg, i.p.).

The extract of C. tenuiflora showed anxiolytic activity in the elevated plus maze model, which evaluates fear/anxiety based on time and number of entries into open arms.

Under forced swimming test conditions, oral administration of Ct extract at 500 mg/kg induced a significant (p < 0.05) decrement of the immobility parameter, while lower doses (50 and 100 mg/kg) did not produce any change compared to the vehicle group.

These are all animal-model experiments only. The effective dose in rodents (500 mg/kg, orally) cannot be extrapolated to human use without controlled clinical data, which does not yet exist.

4.4 Antioxidant Activity

Evidence level: Preclinical (in vitro).

Some researchers have documented antioxidant, cytotoxic, anti-inflammatory, antiulcerogenic, gastroprotective, and antidepressant activities from a few species of Castilleja. The antioxidant activity of Castilleja species has been attributed primarily to the phenylpropanoid verbascoside and to flavonoids such as apigenin and quercetin glycosides. These are identified through in-vitro assays; no human antioxidant trials involving Castilleja have been published.

4.5 Cytotoxic Activity

Evidence level: Preclinical (in vitro cell lines). Results mixed.

In vitro cytotoxic activity of C. tenuiflora extracts was evaluated against four carcinoma cell lines: colon (HF-6), breast (MCF-7), prostate (PC-3), and nasopharyngeal (KB), and the topical anti-inflammatory activity was evaluated in mouse ear edema induced by TPA. None of the extracts showed cytotoxicity against the tested cell lines. This result suggests that at the tested concentrations, the extracts did not exhibit anti-cancer activity in these particular cell lines, though the literature notes cytotoxic properties for the genus more broadly when different extraction solvents or cell lines are used.

4.6 Summary: No Human Clinical Evidence

Across all areas of investigated biological activity — anti-inflammatory, gastroprotective, antidepressant, anxiolytic, sedative, antioxidant, and cytotoxic — the scientific evidence for the Castilleja genus, and specifically for Castilleja miniata, is entirely preclinical. No randomized controlled trials, observational studies, or other forms of clinical evidence in human subjects have been identified in any peer-reviewed database for any of these activities.

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5. Body Systems and Health Areas Associated with Castilleja

Based on the verified traditional use and preclinical research, the following body systems and health areas have been associated with Castilleja species in the literature, with important caveats regarding the level of evidence in each case:

• Gastrointestinal system: Traditional use for stomach pain, dysentery, nausea, vomiting, hepatic disorders; preclinical evidence of gastroprotection and anti-ulcerogenic activity in rodent models. Evidence: traditional + preclinical.
• Respiratory system: Traditional use for cough treatment, bleeding lungs. Evidence: traditional only.
• Central nervous system: Traditional use for nervous disorders and anxiety; preclinical rodent data for antidepressant, anxiolytic, and sedative effects. Evidence: traditional + preclinical.
• Musculoskeletal system: Traditional use for backaches and rheumatism (genus-level, Chippewa). Evidence: traditional only.
• Urinary system: Traditional use as a diuretic. Evidence: traditional only.
• Immune and inflammatory system: Preclinical evidence of anti-inflammatory activity via iridoid glycosides and verbascoside. Evidence: preclinical only.
• Ocular system: Traditional use for sore eyes. Evidence: traditional only.
• Skin / topical: Traditional use for burns and injuries; preclinical topical anti-inflammatory testing. Evidence: traditional + preclinical.

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6. Dosage Forms and Dosages Reported in Research

No standardized human dosage has been established for any Castilleja species in any pharmacopoeia, government monograph, or human clinical trial. The following dosages are reported only as they appear in preclinical animal studies and are reproduced here strictly as a record of the scientific literature, not as recommended human doses:

• Methanol extract of C. tenuiflora leaves administered orally at 500 mg/kg to mice produced a statistically significant antidepressant effect in the Forced Swimming Test and a significant sedative/hypnotic effect with sodium pentobarbital co-administration.
• In a forced swimming test, oral administration at 500 mg/kg induced significant decrement of immobility, while doses of 50 and 100 mg/kg produced no significant effect.
• Ethyl acetate and aqueous wild-grown extracts and in-vitro plant extracts at 1.6 mg/ear showed moderate anti-inflammatory activity (38.2–49.1% reduction) in a mouse ear edema model.
• Ethyl acetate extracts at 100 mg/kg showed high anti-ulcerogenic activity (88.3% and 83.1% inhibition) in the acute ulcer induction model in mice, compared with famotidine at 20 mg/kg.

Traditional preparations consisted of whole-plant or seed decoctions consumed as a tea or topically applied wash, with no specific quantified doses recorded in the reviewed ethnobotanical literature.

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7. Safety Considerations and Interactions

7.1 Selenium Accumulation — Principal Safety Concern

The most extensively documented and source-verifiable safety concern for Castilleja miniata and related species is selenium accumulation. The leaves and roots of common red paintbrush (C. miniata) contain selenium, which can be toxic if eaten. Indian paintbrushes in general are considered selenium accumulators. Selenium is a necessary nutrient for animals, but only in small amounts; thus, selenium accumulators tend to be toxic to grazing animals and humans who consume them.

Some species of Castilleja are reported to absorb and concentrate selenium, producing potentially toxic effects in grazing animals, as documented by Rosenfeld and Beath (2013). The degree to which any individual plant accumulates selenium is variable and dependent on soil selenium levels in the area where the plant grows. It is unclear whether paintbrushes are selenium "indicator" plants limited to areas with high soil selenium, or "facultative" accumulators that can accumulate selenium but are not restricted to high-selenium soils.

Castilleja species are mostly edible and have been used as food by many people; however, some caution should be applied as many species can absorb a toxic level of selenium from the soil and from their host plants.

7.2 Differential Toxicity by Plant Part

The flowers of Indian Paintbrush were consumed in moderation by various Native American tribes as a condiment with other fresh greens. These plants can be potentially very toxic if the roots or green parts of the plant are consumed. This distinction between the relative safety of flowers (in moderate consumption) and the greater toxicity concern of roots and leaves aligns with the known distribution of selenium, which the National Park Service confirms is concentrated in leaves and roots.

7.3 Host-Derived Alkaloid Variability

A number of Castilleja species contain alkaloids, including some assimilated from parasitized hosts via haustorial bridges. This means the alkaloid profile — and therefore the safety profile — of any particular Castilleja plant may differ substantially depending on which host species it has parasitized. For example, senecionine, a pyrrolizidine alkaloid, is transferred from Liatris punctata and Senecio species to the parasite's tissues. Pyrrolizidine alkaloids are well-established hepatotoxins in humans. The potential for a Castilleja plant growing on a pyrrolizidine-alkaloid-producing host to contain these compounds is a documented concern in the botanical literature, though the degree of transfer and concentration in any given plant is not predictable without chemical analysis.

7.4 Absence of Cytotoxicity (In Vitro)

In one study, none of the tested C. tenuiflora extracts showed cytotoxicity against the tested cancer cell lines (colon, breast, prostate, nasopharyngeal). This finding, while limited to in-vitro methodology, suggests that the characterized phytochemical compounds at these extract concentrations did not display direct cellular toxicity in these models.

7.5 Lack of Interaction Data

No peer-reviewed human studies, pharmacokinetic studies, or drug-interaction studies for Castilleja miniata or closely related species have been identified in the literature. No government or pharmacopoeial body (NIH ODS, NCCIH, EMA, EFSA, WHO, ESCOP, Commission E, USP) has issued a monograph, safety assessment, or interaction profile for this species. In the absence of such data, no evidence-based statements about drug or supplement interactions can be made.

7.6 Regulatory and Pharmacopoeial Status

As of the date of the available literature, Castilleja miniata and the genus Castilleja broadly do not appear in any major international pharmacopoeia (European Pharmacopoeia, United States Pharmacopeia, WHO monographs) as recognized medicinal ingredients. The genus is not assessed by ESCOP, the German Commission E, EFSA, or listed on the NIH Office of Dietary Supplements fact sheet database. It is not assessed by NCCIH. Clinical evidence is entirely absent, and no regulatory-standard benefit-risk assessment exists for the genus in any jurisdiction reviewed.

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References

• Wikipedia — Castilleja miniata
• Washington Native Plant Society — Castilleja miniata
• U.S. National Park Service — Common Red Paintbrush (Castilleja miniata)
• Flora of North America — Castilleja (FNA)
• Wikipedia — Castilleja (genus)
• Wikipedia — Castilleja coccinea
• Wikipedia — Castilleja integra
• Herrera-Ruiz M et al. (2018). Anti-Inflammatory Activity of Iridoids and Verbascoside Isolated from Castilleja tenuiflora. PMC / Molecules.
• Herrera-Ruiz M et al. (2015). A New Furofuran Lignan Diglycoside and Other Secondary Metabolites from the Antidepressant Extract of Castilleja tenuiflora Benth. PMC / Molecules. doi:10.3390/molecules200713127
• In Vivo Gastroprotective and Antidepressant Effects of Iridoids, Verbascoside and Tenuifloroside from Castilleja tenuiflora Benth. PMC.
• Sanchez PM et al. (2013). In vivo anti-inflammatory and anti-ulcerogenic activities of extracts from wild growing and in vitro plants of Castilleja tenuiflora Benth. (Orobanchaceae). J Ethnopharmacol. doi:10.1016/j.jep.2013.10.002
• Stermitz FR et al. (1986). Iridoids and alkaloids from Castilleja host plants for Platyptilia pica. Biochemical Systematics and Ecology.
• ResearchGate — Anti-Inflammatory Activity of Iridoids and Verbascoside Isolated from Castilleja tenuiflora (full PDF access)
• Adler LS (2002). Host effects on herbivory and pollination in a hemiparasitic plant. Ecology 83(10).
• Calscape — Castilleja miniata (Scarlet Paintbrush)
• Lady Bird Johnson Wildflower Center — Castilleja miniata
• Haustorium Formation and Specialized Metabolites Biosynthesis Using Co-Culture of Castilleja tenuiflora Benth. and Baccharis conferta Kunth. Biology 2025; 14(8):990.