IngredientsThe scientific name for the plant commonly called "Barneby's star-thistle" or "Barnaby's thistle" is Centaurea solstitialis L., placed in the family Asteraceae. It is also known as golden starthistle, yellow cockspur, and St. Barnaby's thistle (or Barnaby thistle). The name "Barneby" or "Barnaby" used in common parlance derives from the feast day of St. Barnabas (June 11, Old Style calendar), around which the plant historically came into flower in its native range. The specific epithet solstitialis pertains to the longest day of the year, in reference to the ability of yellow star thistle to flower very late into the summer.
The genus name Centaurea came from the popular name of various plants in the late 14th century, from Medieval Latin centaurea, from Latin centaureum, from Greek kentaureion, meaning "centaur," so called because the plant's medicinal properties were said to have been discovered by Chiron the centaur. A synonym for the species is Leucantha solstitialis.
Centaurea solstitialis, the yellow star-thistle, is a species of thorny plant in the genus Centaurea. A winter annual, it is native to the Mediterranean Basin region and invasive in many other places. During the vegetative stage it forms a rosette of non-spiny leaves, between 5–20 centimetres in diameter. As the summer approaches, it produces a flowering stem up to 1 metre in height.
The lower leaves form a rosette up to six inches wide, deeply lobed, and covered in fine, woolly hairs that give the foliage a gray-green color. A distinguishing characteristic is the bracts of the yellow flower heads, which contain stout, needle-like, straw-colored spines one to two inches long that radiate from the flower head in the shape of a star.
The plant's native range spans temperate Asia — including Cyprus, Iran, Iraq, Jordan, Lebanon, Syria, Turkey, Armenia, Azerbaijan, Georgia, Tajikistan, and Turkmenistan — and Europe — including Hungary, Ukraine, Albania, Bulgaria, Bosnia and Herzegovina, Greece (including Crete), Croatia, Italy (including Sardinia and Sicily), North Macedonia, Montenegro, Romania, Serbia, Slovenia, Spain, and France (including Corsica) — as well as parts of North Africa, including Algeria, Morocco, and Tunisia. It has been introduced in several parts of the world, including Australia, Argentina, Chile, and the USA, where it can become an invasive species and noxious weed.
Six subspecies of yellow starthistle have been described; four occur in Europe and three in Turkey. The yellow starthistle found in North America is thought to be a mixture of these subspecies, although no published studies through 2020 have distinguished different subspecies in North America.
The plant's aerial parts — principally the flowering heads, leaves, and stems — are the primary portions used in herbal and ethnobotanical traditions. Various species within the genus Centaurea have been documented in ethnobotanical records for treating a range of ailments, primarily through infusions, decoctions, or topical applications of flowers, aerial parts, or roots. In the scientific literature, preparations of C. solstitialis documented in pharmacological studies include aqueous extracts from fresh or dried flowers, ethanol (80%) extracts of aerial parts, chloroform fractions, and methanolic extracts of roots, stems, and flowering parts, each used to isolate and assess different chemical constituents and biological activities.
The plant is also eaten as a vegetable. Centaurea solstitialis is regarded as an important honey source plant in California and other western states.
A 2023 peer-reviewed review in PeerJ assessed the biogeography of cultural uses of yellow starthistle (Centaurea solstitialis L.) and found that the species was rich in pharmaceutically active compounds and that the species had been traditionally used for medicinal purposes, as raw material, and as food. Ethnobotanical uses were reported almost exclusively in its native range.
Centaurea solstitialis is known in Turkish as "gelin dikeni" and it has been used to treat hemorrhoids, peptic ulcers, common colds, malaria, and herpes infections around the lips of children. The fresh spiny flowers of Centaurea solstitialis ssp. solstitialis are used for the treatment of peptic ulcers in Turkey.
Field surveys on traditional medicine in Turkey revealed that several plants, including Centaurea solstitialis ssp. solstitialis, are used for the treatment of ulcers. Various extracts prepared from these plants were tested using a water immersion-stress ulcer model in rats to confirm the claimed activities. Pharmacological experiments clearly demonstrated that the aqueous extracts of all the plants given orally showed significant antiulcerogenic activity.
It is used in Turkish folk medicine for the treatment of ulcers. Several Centaurea species are used to alleviate pain and inflammatory symptoms in rheumatoid arthritis, high fever, and headache in Turkish folk medicine.
One important mechanism of plant invasion is the use of "allelochemicals" or "novel weapons" — chemical defenses that confer competitive advantages. However, these chemicals are precisely what confers them ethnobotanical and medicinal properties. In their native range, natural communities have been exposed to these chemicals for extended periods, allowing native communities to develop a tolerance to these chemicals. These plant chemical compounds are precisely the ones responsible for the numerous ethnobotanical and medicinal uses that can frequently be found in the native ranges of these weeds.
A systematic review of the ethnobotanical literature compared the native range of C. solstitialis — native from Eurasia and invasive across the Americas and Australia — with any reference or reports of cultural and ethnobotanical use across the world regions in which it is considered invasive. The authors found that traditional medicinal use had not transferred with the plant into its introduced ranges to any significant extent, meaning the body of documented ethnomedicinal use is concentrated in Turkey, the Mediterranean basin, and neighboring Near Eastern and Central Asian cultures.
The most pharmacologically significant and extensively studied chemical class in C. solstitialis are the sesquiterpene lactones (STLs), specifically those of the guaianolide structural type. The guaianolide type sesquiterpene lactones chlorojanerin, 13-acetyl solstitialin A, and solstitialin A were identified as the anti-ulcerogenic components of the chloroform extract of the aerial parts of Centaurea solstitialis ssp. solstitialis (Asteraceae).
Three sesquiterpene lactones — centaurepensin (= chlorohyssopifolin A), chlorojanerin, and 13-acetyl solstitialin A — isolated from the aerial parts of Centaurea solstitialis L. ssp. solstitialis were investigated for antimicrobial and antiviral activities.
Through bioassay-guided fractionation and isolation procedures, two sesquiterpene lactones, solstitialin A and acetyl solstitialin, were isolated and defined as the active components of C. solstitialis.
Phytochemical study of ethyl acetate and n-butanol extracts led to the isolation of an undescribed guaianolide named 3-(4-hydroxybenzoyl)-cynaratriol and a known sesquiterpene lactone, along with three known flavonoid glycosides.
Some researchers isolated different sesquiterpene lactones — repin, solstitialin, and cynaropicrin — from C. solstitialis and C. repens, demonstrating their toxicity toward cell culture systems.
The major constituents of Centaurea species were reported to be sesquiterpene lactones, flavonoids, and fatty acids. Flavonoid glycosides have been identified from the flowers and leaves of C. solstitialis. The highest phenolic and flavonoid contents were found in the n-butanol extract of the aerial parts of Centaurea solstitialis growing in Algeria. Algerian taxa of Centaurea and related genera have been the object of many phytochemical investigations highlighting their richness in bioactive secondary metabolites, mainly flavonoids and sesquiterpene lactones.
Chemical composition of C. solstitialis volatile oil from Croatia, studied with gas chromatography–mass spectrometry, showed dominant components as hexadecanoic acid, α-linolenic acid, germacrene D, and heptacosane. Thirty-one compounds representing 91.5% of the essential oil were identified, with hexadecanoic acid (50.2%) and tetradecanoic acid (10.1%) found to be the major compounds in one study.
Saturated fatty acids (SFAs) were totalled at 25.05%, monounsaturated fatty acids (MUFAs) at 19.60%, and polyunsaturated fatty acids at 19.86%. The major fatty acid compounds were oleic acid (18.54%), linoleic acid (10.07%), palmitic acid (8.28%), stearic acid (6.82%), and γ-linolenic acid (6.75%).
Tyramine was found to be the most important biologically active amine present in C. solstitialis, with a mean concentration of 2.0 mg/100 g of dry weight. Roy et al. (1995) isolated and characterized two potent neuroexcitotoxic compounds, aspartic and glutamic acids, from alcoholic extract of C. solstitialis, demonstrating their toxicity towards mouse cortical explants. They also stated that other nitrogenous neurotoxic compounds were present in their extracts.
Studies of Algerian Centaurea and related genera have led to the isolation and identification of more than 155 secondary metabolites, including 14 phenolic acids, 65 flavonoids, 59 sesquiterpene lactones, 6 triterpenoids, 14 other compounds, and essential oils. Various crude extracts and isolated compounds from Algerian Centaurea species have shown important biological activities, such as cytotoxic, antimicrobial, antioxidant, and antiplasmodial activities.
The most robustly studied pharmacological application of C. solstitialis is its traditional use for peptic ulcers. This use is documented in Turkish ethnomedicine and has been the subject of targeted laboratory and preclinical investigation.
Preclinical (animal) evidence: The fresh spiny flowers of Centaurea solstitialis ssp. solstitialis are used for the treatment of peptic ulcers in Turkey. An ethanol (80%) extract of the plant exhibited significant anti-ulcerogenic effect on the ethanol-induced ulcerogenesis model in rats. The ethanol extract was further fractionated by successive solvent extractions with n-hexane, chloroform, ethyl acetate, and n-butanol. All fractions showed significant anti-ulcerogenic activity; however, the effect of the chloroform fraction was found to be more prominent with 99.5% ulcer inhibition. Bioassay-guided fractionation yielded sesquiterpene lactones as the active components. The main components responsible for the activity of the chloroform fraction were determined as chlorojanerin and 13-acetyl solstitialin A.
A follow-up study further characterized the active compounds: The guaianolide-type sesquiterpene lactones chlorojanerin, 13-acetyl solstitialin A, and solstitialin A were identified as the anti-ulcerogenic components of the chloroform extract of the aerial parts of Centaurea solstitialis ssp. solstitialis (Asteraceae). These compounds were investigated by using various in vivo ulcer models in rats and mice.
In a laboratory study, aqueous extracts of fresh or dried flowers of C. solstitialis given orally showed significant (p<0.01) antiulcerogenic activity in rats.
Evidence strength: Preclinical only (rodent models, in vitro). The bioassay-guided identification of active sesquiterpene lactones provides mechanistic plausibility, but no human clinical trials have been conducted. The evidence is preliminary.
Preclinical (animal) evidence: The antinociceptive and antipyretic effects of Centaurea solstitialis L. subsp. solstitialis were investigated using a p-benzoquinone-induced writhing reflex for antinociceptive activity and a Freund's Complete Adjuvant-induced pyrexia model for antipyretic activity in mice. The ethanolic extract from the aerial parts of the plant was shown to possess significant antinociceptive (p < 0.01) and antipyretic (p < 0.01) activities. The extract was submitted to subsequent solvent extractions and chromatographic processes. Through bioassay-guided fractionation and isolation procedures, two sesquiterpene lactones, solstitialin A and acetyl solstitialin, were isolated and defined as the active components.
Both C. solstitialis ssp. solstitialis and C. depressa were shown to possess significant anti-nociceptive and anti-pyretic effects. EtOH extracts obtained from aerial parts of both plants exerted significant anti-nociceptive activity more prominent and close to that of the reference compound acetyl salicylic acid at the same dose level without inducing any apparent gastric lesion. The EtOH extracts from aerial parts of both Centaurea plants exhibited potent anti-pyretic activity, although less potent than acetyl salicylic acid.
Evidence strength: Preclinical only (mouse models). No human clinical trials have been conducted. The evidence is preliminary but provides mechanistic grounding in identified sesquiterpene lactones.
In vitro evidence: Three sesquiterpene lactones — centaurepensin (= chlorohyssopifolin A), chlorojanerin, and 13-acetyl solstitialin A — isolated from the aerial parts of C. solstitialis ssp. solstitialis were investigated for antimicrobial and antiviral activities. For antimicrobial activity, both standard and isolated strains of Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Staphylococcus aureus, Candida albicans, and C. parapsilosis were employed by the microdilution method. Herpes simplex type-1, a DNA virus, and Parainfluenza, an RNA virus, were employed for the determination of antiviral activity using Vero cell lines. Ampicillin, ofloxacin, ketoconazole, fluconazole, acyclovir, and oseltamivir were used as reference drugs.
13-Acetyl solstitialin A displayed remarkable antibacterial activity against isolated strains of E. faecalis at 1 μg/mL concentration, which was close to the effective concentrations of ampicillin. The same compound also showed significant activity against further organisms tested.
For comparison, three sesquiterpene lactones (13-acetylsolstitialin A, centaurepensin, and chlorojanerin) isolated from the aerial parts of Centaurea solstitialis L. ssp. solstitialis showed inhibitory activity against standard S. aureus with MIC values of 16 μg/mL.
Evidence strength: In vitro only. Findings are promising but cannot be extrapolated to clinical efficacy without further pharmacokinetic, pharmacodynamic, and clinical research.
In vitro evidence: Centaurea solstitialis subsp. solstitialis is used in Turkish folk medicine. One study was the first to determine in vitro biological effects of ethanolic extract from the flowering parts of C. solstitialis L. ssp. solstitialis collected from the Mugla province of Turkey. Cytotoxic effect was evaluated against Daudi, A549, and HeLa cancer cells and one normal BEAS-2B cell line using the MTT assay. Flow cytometric analysis and caspase-3 activity assay were performed to detect apoptotic cell death. Angiogenic factor (VEGF) secretion and the release of IL-1α, IL-6, and TNF-α by cells treated with the extract were measured using ELISA assay. The extract exhibited cytotoxic activities against all cancer cell lines used.
Erenler et al. investigated the antiproliferative activities of methanol extract of the root, stem, and flowering parts of C. solstitialis L. subsp. solstitialis on C6 cells (rat glioma) and HeLa cells in vitro and found that the methanol extract of the stem exhibited the most antiproliferative activity.
Studies indicate that the cytotoxicity level changes depending on the different Centaurea species and solvents used for extract preparation and the type of cell lines used.
Evidence strength: In vitro only. All published anticancer data for C. solstitialis is at the cell-line level. No animal tumor models or human clinical data exist in the peer-reviewed literature. This evidence is highly preliminary and cannot support clinical claims.
The antioxidant activity and total phenolic and flavonoid contents of derived extracts (chloroform, ethyl acetate, and n-butanol) of the 70% hydroalcoholic extract of the aerial parts of Centaurea solstitialis growing in Algeria were assessed. The antioxidant capabilities were assessed using DPPH radical scavenging and Cupric Ion Reducing Antioxidant Capacity (CUPRAC) assays. The extracts of aerial parts of C. solstitialis showed significant antioxidant activities.
Evidence strength: In vitro assays only. Standard DPPH/CUPRAC methods are screening tools; clinical relevance of these findings has not been established.
No standardized human dosage has been established for any preparation of Centaurea solstitialis. The following dosage forms and concentrations appear specifically in the cited pharmacological studies:
There are no published human clinical trials reporting dosage, frequency, or duration of use for any form of C. solstitialis as a dietary supplement or herbal medicine.
The most rigorously documented toxicological hazard associated with C. solstitialis concerns horses and equids, not humans. Prolonged ingestion of Yellow Starthistle (Centaurea solstitialis) and Russian Knapweed (Centaurea repens) by horses has been shown to result in a fatal neurodegenerative disorder called equine nigropallidal encephalomalacia (ENE). Chronic ingestion causes nigropallidal encephalomalacia in horses with an abrupt onset of neurologic signs characterized by dystonia of lips and tongue, inability to prehend food, depression, and locomotor deficits.
The primary cause of nigropallidal encephalomalacia is prolonged consumption of yellow star thistle (Centaurea solstitialis) or Russian knapweed (Acroptilon repens), both members of the Asteraceae family containing toxic sesquiterpene lactone compounds. The specific toxins responsible, including repin and related compounds, demonstrate selective neurotoxicity to the substantia nigra and globus pallidus in horses.
As described by Cordy, C. solstitialis is able to induce nigropallidal encephalomalacia (NPE) in horses grazing on it for prolonged periods. The histopathology of the horse brain tissue with NPE was the same as for human Parkinson's disease (PD).
Prolonged ingestion of Centaurea solstitialis or C. repens produces a nervous disease in horses called equine nigropallidal encephalomalacia with rather stereotyped lesions and signs. Only horses are affected by feeding.
Considering the instability of these highly reactive epoxides, some researchers are skeptical that these components can be the final neurotoxins. The exact neurotoxic mechanism in horses remains under investigation.
Bioassay-guided fractionation of extracts from Centaurea species using the PC12 cell line has led to the identification of one of several putative agents that may contribute to ENE, namely the sesquiterpene lactone (SQL) repin, previously linked to ENE due to its abundance in C. repens. To characterize the molecular basis of repin-induced neurotoxicity, researchers designed a study to identify reactive functional groups contributing overall to its toxicity. The reaction of repin with glutathione (GSH) led to the exclusive addition of GSH to the α-methylenebutyrolactone, affording a GSH conjugate that lacked toxicity in the PC12 cell assay, while selective reduction of the α-methylenebutyrolactone double bond also resulted in loss of activity.
There are only limited studies that have determined the toxicity profile of Centaurea plants in order to evaluate their safety for human use. Substantially more detailed studies are required to rigorously investigate the therapeutic properties and phytochemistry, which may ultimately lead to the development of new plant-based therapeutic medicines. No human clinical trials assessing the safety or tolerability of C. solstitialis extracts in any preparation or dose have been published in the peer-reviewed literature. The reactive α-methylene lactone moiety present in the sesquiterpene lactone constituents is a structural class known for potential allergenicity and sensitization in some individuals exposed to plants in the Asteraceae family.
In North America, Centaurea solstitialis can be weedy or invasive and is listed as a state noxious weed in 46 states and on the California Invasive Plant Inventory. This invasive status means that collection, cultivation, or propagation may be subject to regulatory restrictions in many jurisdictions.
Centaurea solstitialis (Barneby star thistle) has a documented history of ethnomedicinal use, primarily in Turkey and the Mediterranean basin, for conditions including peptic ulcer, fever, pain, and infectious disease. Phytochemical research has identified specific bioactive constituents — chiefly guaianolide sesquiterpene lactones (solstitialin A, chlorojanerin, 13-acetyl solstitialin A, centaurepensin) and flavonoids — with measurable activity in preclinical models. However, all evidence for pharmacological efficacy is derived from in vitro cell-culture assays or rodent models. No human or clinical trials of any phase have been published. The compound class responsible for pharmacological activity (sesquiterpene lactones) overlaps with compounds implicated in equine neurotoxicity. The plant has not been assessed by major regulatory or pharmacopeial bodies (NIH, EMA, WHO, Commission E, ESCOP) as a recognized therapeutic agent, and no monograph exists for it in any major pharmacopeia. Its status as a dietary supplement ingredient is not established by regulatory recognition.
Health conditions that Barneby star thistle may help support.
Body systems that Barneby star thistle may help support.
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