Monkey Flower (Erythranthe guttata / Mimulus guttatus)
1. Identity and Botanical Classification
Accepted Name and Synonymy
Monkey flower's currently accepted scientific name is Erythranthe guttata (DC.) G.L.Nesom, a rhizomatous perennial herb in the family Phrymaceae, characterized by erect to ascending stems 15–65 cm tall, opposite ovate-elliptic leaves, and showy yellow bilabiate flowers with red spots that bloom from April to September. The species was given its first scientific name, Mimulus guttatus, in 1813 by Augustin Pyramus de Candolle; in 2012 it was moved to the genus Erythranthe by Guy L. Nesom. In research contexts, particularly in genetics and ecology, the species is still widely referred to as Mimulus guttatus.
The common name "monkeyflower" stems from the flower's two-lipped corolla, which resembles a monkey's face or a mime's grimace — a feature that inspired the original genus name Mimulus from the Latin mimus (actor or mimic). The species epithet guttata originates from the Latin guttatus, meaning spotted or drop-like, in reference to the distinctive red spots adorning the yellow petals. Common names include seep monkeyflower, common yellow monkeyflower, yellow monkeyflower, and common monkeyflower, with regional variants such as golden monkeyflower.
According to GBIF taxonomy, Erythranthe guttata is classified within kingdom Plantae, phylum Tracheophyta, class Magnoliopsida, order Lamiales, family Phrymaceae, genus Erythranthe. The genus Mimulus as a strict botanical name now has a narrower definition: plants are known horticulturally as "Mimulus" and were formerly placed in the genus Mimulus when it was defined broadly to include about 150 species. Mimulus, as a botanical name, now represents a genus of only seven species, with most former species transferred to Diplacus or Erythranthe.
The genus historically also includes other medically referenced species: Mimulus ringens (Allegheny monkeyflower, found in the eastern United States), Mimulus pilosus (hairy monkeyflower, a Californian annual), Mimulus aurantiacus (sticky or bush monkeyflower, recently reclassified as Diplacus aurantiacus), and Mimulus luteus (yellow monkeyflower of South American origin). The present article focuses primarily on E. guttata (M. guttatus), the species most extensively documented in ethnobotanical, phytochemical, and clinical literature, with relevant references to closely related taxa.
Morphology and Habitat
A herbaceous wildflower, Erythranthe guttata grows along the banks of streams and seeps throughout much of western North America from sea level to 12,000 feet (3,700 m). Both annual and perennial forms occur throughout the species' range. It is found in a wide range of habitats including the splash zone of the Pacific Ocean, the chaparral of California, Western U.S. deserts, the geysers of Yellowstone National Park, alpine meadows, serpentine barrens, and even on the toxic tailings of copper mines. Its distribution spans from Alaska and Yukon through much of the western United States.
Common Commercial and Supplemental Forms
Monkey flower is encountered in the following forms in commerce and herbal practice:
- Bach Flower Remedy (Mimulus): The active ingredient listed is Mimulus (Mimulus guttatus) at 5X HPUS potency, in an inactive base of 27% grape alcohol solution; 'HPUS' indicates the ingredient is in the official Homeopathic Pharmacopoeia of the United States. Each Bach flower remedy is created by dipping a particular type of flower in water and then preserving the fragrant liquid with brandy.
- Herbal tea / decoction: Aerial parts (leaves and stems) prepared as a water infusion or decoction, a traditional preparation documented in multiple Native American traditions.
- Poultice: Fresh or dried leaves crushed and applied directly to the skin.
- Tincture: Alcoholic extract of the whole plant, as referenced in 19th-century eclectic medical literature.
- Food use: Leaves consumed raw or cooked; they have a slightly bitter flavor and are added to salads or used as a lettuce substitute.
2. Traditional and Historical Use
Native American Traditions
Monkey flower (Mimulus guttatus) has been used for food and medicine by a variety of North American indigenous peoples. Documented tribal uses include:
- Kawaiisu: A decoction of stems and leaves was used as a steam bath for chest and back soreness (analgesic use).
- Shoshoni: A poultice of crushed leaves was applied to wounds or rope burns (dermatological aid).
- Yavapai: A decoction was taken as a tea for stomachache (gastrointestinal aid).
- Mendocino Indians: Plants were used as a substitute for lettuce; Miwok: Boiled leaves were consumed as food.
- Salt substitute: Because the plant easily absorbs sodium chloride from the soil, the ashes of dried and burned leaves were used as a salt substitute.
- Anticonvulsant and antidote: A root concoction was used for treating epilepsy; a plant concoction was used as a wash to counteract poisons.
The Kumeyaay tribe used monkey flower (in the case of the sticky monkeyflower, Mimulus aurantiacus) primarily for medicinal purposes, from poultices for burns and wounds to treatments for colds, coughs, flu, stomach disorders, and heart ailments.
For Mimulus ringens (Allegheny monkeyflower), a decoction of ground leaves and stems was used to treat feelings of nausea, and tea from the plant was also used for colds, fevers, sore throats, gas, colic, and indigestion.
Eclectic Medicine (19th-Century North America)
King's American Dispensatory is a 19th-century medical and botanical textbook, first published in 1854, covering the uses of herbs in American medical practice, especially by practitioners of Eclectic medicine, the botanical school of medicine in the 19th and early 20th centuries. The landmark 18th edition was published in 1898, co-authored by eclectic physician Harvey Wickes Felter and pharmacist John Uri Lloyd.
Mimulus pilosus (hairy monkey-flower), a small annual native to California, was documented in King's American Dispensatory. According to this reference, a tincture of the plant, in the dose of from 3 to 10 minims, repeated 3 or 4 times a day, was recommended as beneficial in rheumatism, neuralgia, and other painful disorders; in cardiac affections following rheumatic attacks, it was described as having proven serviceable in several cases. In obstinate bronchial and laryngeal affections, the tincture, made with diluted alcohol and used in the form of a spray, was reported as beneficial. It was noted that other species of Mimulus were believed to possess similar properties.
Bach Flower Remedy System (20th-Century Britain)
Bach Flower Remedies, a system of 38 flower-based essences, were created by Dr. Edward Bach in the 1930s as part of his holistic approach to emotional and physical healing. Monkey flower (Mimulus guttatus) was incorporated into this system; the keywords for prescribing it are "fear or anxiety of a known origin." Mimulus is prescribed for fears with identifiable causes — such as fear of heights, public speaking, or specific situations — and is distinguished from Aspen, which treats vague, nameless anxieties without clear triggers. Flower remedies are marketed as food supplements, which under relevant regulatory frameworks means they are not subject to legal efficacy requirements.
3. Key Constituents and Active Compounds
Phenylpropanoid Glycosides (PPGs)
The foliage of yellow monkeyflower contains a diverse suite of phenylpropanoid glycosides (PPGs), a class of compounds with many known biological activities. Using 1H and 13C NMR and UV and MS chromatography techniques, researchers positively identified five PPGs from the leaves of yellow monkeyflower; four of these compounds occur in other species and one was previously undescribed. UV and high-resolution tandem MS data putatively identified 11 additional foliar compounds as PPGs.
The five confirmed PPGs identified in M. guttatus leaf tissue include: mimuloside (a novel, previously undescribed compound unique to this species), conandroside, verbascoside (also known as acteoside), and calceolarioside A and related calceolarioside variants. These compounds were identified under the study keywords: Mimulus guttatus, phenylpropanoid glycosides, mimuloside, conandroside, verbascoside, and calceolarioside.
Researchers have also investigated patterns of genetic variation in these phytochemical defenses (PPGs) across Mimulus guttatus populations. Substantial variation was found in the constitutive multivariate PPG phenotype and in constitutive levels of individual phytochemicals within plants (among leaves of different ages), within populations (among full-sibling families), and among populations. Populations consisting of annual plants generally, but not always, had lower concentrations of phytochemicals than did populations of perennial plants.
General Phenolic and Flavonoid Profile
Some phytochemical studies have identified the presence of flavonoids, phenolic compounds, and other antioxidants in monkey flower, which are generally recognized for their potential to combat oxidative stress and support overall cellular health. While no comprehensive phytochemical monograph of E. guttata has been produced, the plant's family (Phrymaceae, formerly a branch of Scrophulariaceae sensu lato) is known for a characteristic secondary chemistry: many plant species within the Scrophulariaceae sensu lato contain PPGs.
Trichomes and Surface Chemistry
Many trichomes produced by M. guttatus are glandular with sticky secretions; the species also produces a suite of foliar secondary compounds — phenylpropanoid glycosides. These glandular trichomes contribute to the plant's physical defense and are associated with the "stickiness" described in some related species such as M. aurantiacus.
Astringent / Tannin-Type Constituents
The plant is classified as astringent, poultice, and vulnerary in traditional botanical references. The astringency characteristic is consistent with the presence of polyphenolic compounds with protein-precipitating properties, though a full characterization of tannin content specific to E. guttata is not available in the peer-reviewed literature reviewed here.
Biological Activities of Key Compounds
The most thoroughly studied PPG found in monkey flower, verbascoside (also called acteoside), has been characterized primarily through studies on other plant species. Several biological properties have been described for verbascoside, including anti-inflammatory, antimicrobial, antitumor, and antioxidant activities. Among these activities, free radical scavenging is the most representative. Biological activities such as antioxidant, anxiolytic, neuroprotective, anticancer, anesthetic, antimicrobial, and sedative effects have been demonstrated in cell cultures and animal studies for this class of compound.
Calceolarioside A, another PPG identified in monkey flower, has been assessed in animal pain models. In an inflammatory-based persistent pain model (the formalin test), calceolarioside A at the high dose tested (100 μg/paw) reduced licking activity by 35% in the first phase and 75% in the second phase; in carrageenan-induced thermal hyperalgesia, calceolarioside A (50 and 100 μg/paw) significantly reversed thermal hyperalgesia. These studies were conducted in rodent models for calceolarioside A isolated from Calceolaria species, not directly from M. guttatus.
Phenylpropanoid glycosides have been shown to deter feeding by generalist herbivores. This ecological role further supports the inference that PPGs in monkey flower may have biologically active properties, though direct pharmacological studies in humans are lacking.
4. Scientific Evidence by Area of Use
4a. Anxiety, Fear, and Psychological Conditions (Bach Flower Remedy Context)
Monkey flower's most prominent modern use is as Bach Flower Remedy "Mimulus," prescribed for anxiety and known fears. The following summarizes the human clinical evidence for this application.
Systematic Reviews: Bach flower remedies continue to be popular and proponents make a range of medicinal claims. A systematic review, published in the Swiss Medical Weekly (2010), searched five electronic databases without restrictions on time or language. All randomised clinical trials of flower remedies were included — seven such studies were located. All but one were placebo-controlled, and all placebo-controlled trials failed to demonstrate efficacy. It was concluded that the most reliable clinical trials do not show any differences between flower remedies and placebos.
A separate systematic review (Thaler et al., 2009, published in BMC Complementary and Alternative Medicine) assessed whether Bach Flower Remedies are safe and efficacious for psychological problems and pain by performing a systematic review of the literature. Four randomised controlled trials and two additional retrospective, observational studies were identified. Three RCTs of BFRs for students with examination anxiety, and one RCT of BFRs for children with attention-deficit hyperactivity disorder (ADHD) showed no overall benefit compared to placebo. Due to the number and quality of the studies, the strength of the evidence was rated as low or very low.
Individual RCTs Involving Mimulus: One German RCT randomized 61 students to a pre-determined combination of 10 Bach flower remedies — including mimulus — or placebo in a four-week cross-over design. A UK RCT randomized 100 students to at least one week of Five Flower Rescue Remedy or placebo, with measurements taken at baseline, the night before the examination, and after the examination using validated anxiety scales. Both trials did not detect any differences in efficacy between Bach flower remedies and placebo for the treatment of examination anxiety.
NCCIH Assessment: According to the National Center for Complementary and Integrative Health (NCCIH), there is no convincing scientific evidence that Bach flower remedies are effective for treating psychological conditions or physical illnesses. Studies evaluating flower remedies for anxiety have not demonstrated effectiveness beyond placebo.
Evidence strength: Consistently negative across all placebo-controlled RCTs and two systematic reviews. The overall body of evidence is rated low to very low quality. No clinically meaningful effect has been demonstrated for monkey flower/Mimulus Bach remedy for anxiety, fear, or related psychological indications in humans.
4b. Wound Healing and Dermatological Applications
The use of monkey flower leaf poultices for wounds, burns, and skin irritations is well-documented in ethnobotanical records but has not been subjected to clinical trials. The Shoshoni applied a poultice of crushed leaves to wounds or rope burns. A decoction of the leaves and stems was used as a herbal steam bath for chest and back soreness, and a poultice of crushed leaves was applied to wounds and rope burns. The astringent and vulnerary classification of the plant is consistent with traditional wound-care use, as astringent compounds may help contract tissue and inhibit microbial colonization, but this mechanism has not been confirmed in clinical settings for E. guttata specifically.
The verbascoside and calceolarioside content of the foliage could plausibly account for some antimicrobial and anti-inflammatory activity when applied topically, given demonstrated activities of these compound classes in other botanical contexts, but no controlled trials using M. guttatus preparations on human skin wounds have been published.
Evidence strength: Preclinical only (ethnobotanical and phytochemical). No human clinical trial data exist for wound or dermatological applications.
4c. Gastrointestinal Conditions
Multiple Native American traditions recorded use of monkey flower preparations for gastrointestinal complaints. The Yavapai took a decoction of the plant as a tea for stomachache. Tea from Mimulus ringens was also used for colds, fevers, sore throats, gas, colic, and indigestion. No clinical or preclinical pharmacological studies examining gastrointestinal outcomes specifically attributable to monkey flower preparations have been identified in the peer-reviewed literature.
Evidence strength: Traditional use only. No clinical or preclinical experimental data available.
4d. Respiratory Conditions
In 19th-century eclectic medical practice, the tincture of Mimulus pilosus, made with diluted alcohol and used in the form of a spray, was reported as beneficial in obstinate bronchial and laryngeal affections. These reports are observational and anecdotal in nature, predating controlled clinical methodology.
Evidence strength: Historical anecdotal/case reports only. No controlled clinical studies available.
4e. Antioxidant and Anti-inflammatory Properties
The phytochemical profile of monkey flower — particularly the presence of verbascoside, calceolarioside, and other PPGs — provides a theoretical basis for antioxidant and anti-inflammatory properties. Verbascoside has been associated with antitumor, antimicrobial, anti-inflammatory, anti-thrombotic, and wound-healing properties in preclinical studies. However, these properties have been established for verbascoside as a compound class, primarily sourced from other plant species (e.g., lemon verbena, mullein, Calceolaria). Exceedingly little is known about the secondary chemistry of M. guttatus itself in terms of bioactivity.
Evidence strength: Indirect and theoretical. The biological activities attributed to PPG compounds found in monkey flower are based on studies of those compounds from other plant sources. No pharmacological or clinical studies of monkey flower extracts for antioxidant or anti-inflammatory purposes have been published.
5. Body Systems and Health Areas
- Nervous system / psychological: Primary association in modern use (Bach flower therapy for fear and anxiety). Evidence base is negative in clinical trials.
- Integumentary (skin): Traditional poultice use for wounds, burns, rope burns, and skin irritation. Consistent with astringent and vulnerary plant classification.
- Gastrointestinal: Traditional use in multiple Native American cultures for nausea, stomachache, colic, and indigestion.
- Respiratory: Traditional steam bath use for chest soreness; 19th-century eclectic use as a bronchial/laryngeal spray.
- Musculoskeletal / pain: A tincture of the plant was used by eclectic practitioners for rheumatism, neuralgia, and other painful disorders.
- Cardiovascular: In cardiac affections following the sequence of rheumatic attacks, the tincture was reported as serviceable in several clinical cases by eclectic physicians.
6. Dosage Forms and Dosages Reported in Sources
Eclectic Tincture (Historical — Mimulus pilosus)
A tincture of the plant, in the dose of from 3 to 10 minims, repeated 3 or 4 times a day, was stated in King's American Dispensatory (1898) as potentially beneficial in rheumatism, neuralgia, and other painful disorders. (A minim is approximately 0.06 mL; 3–10 minims = approximately 0.18–0.6 mL per dose.)
Bach Flower Remedy (Contemporary)
The commercial Bach Remedy product lists active ingredient as Mimulus guttatus at 5X HPUS potency in a 27% grape alcohol solution. Standard dosage guidelines for Bach Flower remedies as tested in clinical trials involved administration over two-to-four-week periods, as described in the published RCTs. One RCT used a combination of 10 Bach flower remedies including mimulus over a four-week cross-over design; another RCT administered Rescue Remedy or placebo for at least one week. Specific per-drop or per-dose concentrations for mimulus alone are not reported independently in the published trials.
Traditional Food Use
Young leaves and stems were eaten as salad greens or as potherbs; the older leaves are bitter and pungent. No quantified portion sizes are reported in ethnobotanical sources.
7. Safety Considerations
General Safety Profile
Most of the available evidence regarding the safety of Bach flower remedies has a high risk of bias. Only four of the six studies included in one systematic review for safety explicitly reported adverse events. No serious adverse events attributable specifically to monkey flower (Mimulus Bach remedy) have been reported in the reviewed clinical trials.
Clinical trials show that Bach flower remedies perform no better than placebo. Their safety profile and lack of known drug interactions make them a low-risk complement, though they should not replace evidence-based treatments for moderate to severe conditions.
Alcohol Content
Each Bach flower remedy is created by dipping a flower in water and preserving the liquid with brandy. Bach flower remedies differ from homeopathy in that they do not use extreme dilutions. Individuals who must avoid alcohol (e.g., those in recovery, certain religious practices, or with specific hepatic conditions) should note the alcohol preservation base of commercial Bach flower remedy preparations.
Heavy Metal Bioaccumulation Concern (Habitat-Dependent)
Monkey flower is found growing on the toxic tailings of copper mines. Some Californian populations of Mimulus guttatus grow on abandoned copper mines, and populations growing on soil with normally toxic levels of copper were found to be tolerant to this heavy metal. There was also indication of an increase in tolerance to zinc, lead, and nickel in the copper-tolerant populations. This means that plants harvested from contaminated mine-tailings environments may bioaccumulate heavy metals; wild-harvested plant material should be sourced from uncontaminated habitats to avoid inadvertent heavy metal exposure. This is a factual ecological consideration rather than a toxicological finding specific to medicinal preparations.
Sodium / Salt Substitute Context
Because the plant easily absorbs sodium chloride salt from the soil, the ashes of dried and burned leaves were historically used as a salt substitute. This property implies variable sodium content depending on growth substrate, which may be a consideration for individuals on sodium-restricted diets who consume the plant as a food.
Lack of Regulatory Approval for Medicinal Claims
Flower remedies are marketed as food supplements, avoiding legal efficacy requirements. The available systematic review evidence does not support claims of clinical effectiveness for these remedies. No regulatory body (including the U.S. FDA, EMA, or WHO) has issued a monograph approving Mimulus guttatus or any monkey flower species for medicinal use based on controlled clinical evidence.
Research Status and Evidence Gaps
Clinical trials specifically involving Mimulus guttatus in human populations are scarce, and its effects have not been conclusively demonstrated in rigorous scientific studies. The initial discovery and elucidation of yellow monkeyflower's secondary chemistry was described as important for continued study of the genetics and ecology of this model species, with the authors noting that exceedingly little was known about its secondary chemistry prior to the 2014 work. There may be as many as 1,000 scientific papers focused on this species, but the combined research interest has been primarily in evolution, genetics, and ecology — particularly plant-insect interactions — rather than in pharmacology or clinical medicine.
References
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