Pennycress (Thlaspi arvense L.): A Comprehensive Reference
1. Identity and Botanical Profile
Nomenclature and Taxonomy
Thlaspi arvense L., known by the common name field pennycress, is a flowering plant in the cabbage family Brassicaceae. Other English common names include stinkweed, bastard cress, fanweed, frenchweed, and mithridate mustard. The common name "pennycress" is derived from the shape of the seed pods resembling an old English penny. Pennycress is a member of the tribe Thlaspideae within the Brassicaceae, and it resides in lineage II of that family, along with the Brassica genus — including the economically important oilseed crops Brassica rapa and Brassica napus. Pennycress is a diploid relative of Arabidopsis thaliana, a model species used to study many adaptive phenotypes.
Morphology and Growth
Thlaspi arvense is a foetid, hairless annual plant growing up to 60 cm tall, with upright branches. The stem leaves are arrow-shaped, narrow, and toothed; it blooms between May and July, with racemes or spikes of small white flowers that have 4 sepals and 4 longer petals. Later it produces round, flat, winged pods with a deep apical notch measuring approximately 1 cm across, which contain small brown-black seeds. Pennycress is planted and germinates in the fall and overwinters as a small rosette; the central stem and upper side stems terminate in erect racemes of small white flowers, and flowers are self-pollinated, producing a penny-sized, heart-shaped, flat seed pod with up to 14 seeds.
Geographic Distribution and Habitat
T. arvense is native to Eurasia and is a common weed throughout much of North America. It is a common agricultural weed that prefers cultivated areas and is commonly found along roadsides, in waste areas, cropland, weedy meadows or pastures, and gardens with full sun and moderate moisture, particularly on loam and clay soils.
Common Preparations and Forms
Pennycress enters traditional and investigational use in several physical forms:
- Preparations in traditional medicine often involved making teas (infusions/decoctions), tinctures, or poultices from the whole herb or seeds.
- The bitter, tender young leaves can be eaten raw or cooked as a potherb; they have a distinct garlicky mustard flavor, and the bitterness can be reduced by parboiling in one or two changes of water.
- The empty seed pods have a peppery flavor and can be used as a mustard powder substitute.
- The seed contains approximately 36% oil, making cold-pressed seed oil one of the principal commercial and investigational preparations.
- Defatted seedmeal — the residue after oil pressing — is the form investigated in agricultural biofumigant studies (see below).
2. Traditional and Historical Use
European Folk and Herbal Traditions
Pennycress has been mentioned in European herbals since the Middle Ages, often under the name Thlaspi or "Motherwort of the field." Herbalists such as Nicholas Culpeper described its use for inflammations of the kidneys, urine retention, and womb disorders. By the 16th century, German herbal compendiums — including Rembert Dodoens' Cruydeboeck — cited field pennycress for mild diuretic and anti-inflammatory uses.
Though not as storied as other herbs, field pennycress was valued for centuries in folk medicine, particularly for its diuretic and cleansing properties; in some traditions the plant was thought to "cleanse the blood" and protect against scurvy in times of scarcity. It was also applied externally to bruises, boils, and swellings. Less commonly, pennycress was included in herbal formulas for coughs or mild bronchial irritation.
Tibetan Medicine
The seeds are used in Tibetan medicine and are considered to have an acrid taste and a cooling potency; they are described as anti-inflammatory and febrifuge, and used in the treatment of pus in the lungs, renal inflammation, appendicitis, and seminal and vaginal discharges.
Chinese Materia Medica
In Chinese traditional medicine, the entire plant has been described as antidote, anti-inflammatory, blood tonic, depurative, diaphoretic, expectorant, febrifuge, and hepatic, and is antirheumatic and diuretic. It is described as used in the treatment of carbuncles, acute appendicitis, intestinal abscess, post-partum pain, dysmenorrhoea, and endometriosis.
Persian and Himalayan Traditions
Seventeenth- and eighteenth-century Persian physicians, influenced by Unani medicine, began prescribing pennycress water infusions for bloating and urinary issues. In Himalayan folk medicine, dried seed powder was combined with honey to relieve joint stiffness.
Nature of Traditional Evidence
It is important to note that all of the above represents historical and ethnobotanical accounts drawn from folk-herbal compendiums and ethnopharmacological literature. None of these traditional uses have been validated by controlled clinical trials in humans. They are recorded here solely to document the historical record and should not be construed as established therapeutic claims.
3. Key Constituents and Active Compounds
Glucosinolates and Their Hydrolysis Products
Glucosinolates (thioglucoside-N-hydroxysulphates) constitute a homogeneous class of naturally occurring thiosaccharidic compounds mainly found in the botanical order Brassicales; they can be hydrolyzed by the endogenous enzyme myrosinase to produce D-glucose and various degradation products including isothiocyanates, depending on the aglycone portion.
Sinalbin and sinigrin (2-propenylglucosinolate), plus several other aliphatic, benzylic, and indole glucosinolates, have been identified in Thlaspi arvense and related species. Pennycress press-cake meal contains the glucosinolate sinigrin — also the glucosinolate present in horseradish; when live tissues are crushed, sinigrin is degraded by myrosinase into the pungent and biologically active compounds isothiocyanate and allyl isothiocyanate, which function as pest deterrents, and this characteristic smell is the reason pennycress is sometimes called "stinkweed."
Research by Gmelin and Virtanen (1959) showed that seeds of Thlaspi arvense yield both a garlic oil and a mustard oil, and demonstrated that this was due to the formation of allyl thiocyanate (3-thiocyanatoprop-1-ene). Fractionation of seedmeal extracts identified two major phytotoxins by gas chromatography–mass spectrometry and NMR: 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), constituting 80.9% and 18.8%, respectively, of the active fraction.
The exact function of glucosinolates in the plant is not fully clarified, though their potent odor and taste suggest a role in herbivore and microbial defense; they are known for fungicidal, bactericidal, nematicidal, and allelopathic properties, and have attracted research interest because of potential cancer chemoprotective attributes. Isothiocyanates, one of the principal hydrolysis products, show the best anti-carcinogenic activity among glucosinolate breakdown products.
Stinkweed seeds contain high levels of glucosinolates (including sinigrin), and digestion releases the irritant oil allyl thiocyanate.
Flavonoids
Pennycress contains glucosinolates, flavonoids, saponins, and sulfur compounds, which are considered to contribute to its pharmacological properties. Key active compounds documented for T. arvense include glucosinolates such as sinigrin and flavonoids including kaempferol glycosides. Arabidopsis seed coats — and by extension related Brassicaceae — accumulate proanthocyanidins (PAs), a class of flavonoid chemicals (polymerized flavan-3-ols, or condensed tannins) that protect against a variety of biotic and abiotic stresses and help maintain seed dormancy and viability.
Seed Oil Fatty Acid Composition
The pennycress seed contains approximately 36% oil, with erucic acid as its largest fatty acid component (33%–38%), and with linoleic and linolenic acids as the other two major components. The primary fatty acids found in field pennycress oil are principally erucic acid (32.8 wt%) and linoleic acid (22.4 wt%). Across different provenances, seed oil content ranges from approximately 28.89% to 42.57%, with significant differences among populations.
Alpha-tocopherol (714 ppm) is the primary tocopherol found in field pennycress oil, and the overall tocopherol concentration of field pennycress oils is approximately 851 ppm.
Other Identified Compounds
Other identified constituents include amines such as choline, acetylcholine, bursine, histamine, flavonoids, polypeptides, and tyramine.
4. Mechanisms of Action
Glucosinolate–Myrosinase System
The principal mechanism through which pennycress exerts documented biological effects is the glucosinolate–myrosinase hydrolysis system. Glucosinolates are hydrolyzed by myrosinase to produce D-glucose and various degradation products including isothiocyanates. When live tissues are crushed, sinigrin is degraded by myrosinase into the pungent and biologically active compounds isothiocyanate and allyl isothiocyanate. This enzymatic cascade is responsible for the plant's characteristic pungent odor and many of its documented antimicrobial and biofumigant activities.
Antimicrobial Activity
Studies indicate that field pennycress possesses antibacterial properties, effective against certain bacteria such as Staphylococci and Streptococci; the presence of glucosinolates, which break down into compounds like isothiocyanates, contributes to these antimicrobial and anti-inflammatory effects. Allyl isothiocyanate (AITC) is a highly volatile organic compound identified as a potential antibacterial agent against food spoilage bacteria.
Biofumigant and Phytotoxic Activity
Defatted field pennycress seedmeal was found to completely inhibit seedling germination and emergence when added to a sandy loam soil at levels of 1.0% w/w or higher. When seeds of wheat, arugula, and sicklepod were exposed to volatilized AITC and ATC, germination of all three species was completely inhibited at concentrations of 5 ppm or less; in field studies where seedmeal was applied at 0.50, 1.25, and 2.50 kg/m², all treatments significantly reduced dry weight of bioassay plants compared to controls, with the highest seedmeal rate decreasing dry matter to less than 10% of the control after 30 days. Field pennycress seedmeal appears to offer excellent potential as a biofumigant for high-value horticultural crops for both conventional and organic growers.
Erucic Acid Metabolism
Erucic acid is a 22-carbon monounsaturated acid that is absorbed, distributed, and metabolized like other fatty acids, primarily via mitochondrial beta-oxidation and to a lesser extent peroxisomal beta-oxidation; like other longer-chain fatty acids, the rate of mitochondrial beta-oxidation is comparatively lower for erucic acid, and elevated erucic acid levels can induce liver peroxisomal oxidation pathways as a compensatory mechanism.
5. Scientific Evidence by Area
5.1 Antimicrobial Activity
Evidence characterization: Preliminary; primarily in-vitro and observational.
The plant has been reported to have broad antibacterial activity, effective against the growth of Staphylococci and Streptococci. The glucosinolate breakdown products including isothiocyanates are attributed to the antimicrobial and anti-inflammatory effects observed in laboratory settings; research also explores antioxidant activity and use as an antipyretic agent, supporting some traditional claims, but much of this research is still in early stages, with many studies conducted in laboratory settings and requiring further validation through human trials.
No controlled human clinical trials evaluating T. arvense specifically as an antimicrobial agent have been identified in the peer-reviewed literature at this time. Antibacterial data is derived principally from in-vitro assays and older ethnopharmacological literature. Evidence quality is therefore low.
5.2 Anti-inflammatory and Antipyretic Activity
Evidence characterization: Traditional/historical; no controlled human trials identified.
Traditional uses often centered on diuretic properties — believed to stimulate urine flow and aid in flushing out excess fluids — and the plant was also utilized as an anti-inflammatory agent and for its febrifuge (fever-reducing) qualities. In Tibetan medicine, the seeds are described as anti-inflammatory and febrifuge, being used in the treatment of pus in the lungs, renal inflammation, appendicitis, and seminal and vaginal discharges.
While in-vitro data on glucosinolate and isothiocyanate activity within the Brassicaceae family broadly supports anti-inflammatory mechanisms at the molecular level, no published controlled clinical trials specifically examining T. arvense preparations in humans for these indications have been identified. All claims in this area remain rooted in traditional use and extrapolation from related plant chemistry.
5.3 Biofumigant / Agricultural Antimicrobial
Evidence characterization: Strong at the experimental level; not a human-health use.
The best-supported scientific evidence for pennycress biological activity concerns its use as an agricultural biofumigant. Fractionation of field pennycress seedmeal extracts identified two major phytotoxins — allyl isothiocyanate (AITC) and allyl thiocyanate (ATC) — constituting 80.9% and 18.8%, respectively, of the biologically active fraction. When seeds of wheat, arugula, and sicklepod were exposed to volatilized AITC and ATC, germination of all three species was completely inhibited at concentrations of 5 ppm or less; in field studies, all application rates significantly reduced dry weight of bioassay plants, and field pennycress seedmeal was concluded to offer excellent potential as a biofumigant for high-value horticultural crops.
5.4 Digestive and Hepatic Applications
Evidence characterization: Traditional only; no clinical trials identified.
In some traditional practices, field pennycress was considered a "blood purifier" and used to address skin eruptions, rheumatism, and digestive sluggishness; historical accounts mention its application for conditions such as renal inflammation, appendicitis, dysmenorrhea, and post-partum pain. It was used to aid digestion and support liver function in European folk traditions.
No human clinical trials examining hepatic or digestive endpoints for T. arvense preparations have been identified. Evidence is exclusively traditional and ethnopharmacological.
5.5 Women's Health and Reproductive Applications
Evidence characterization: Traditional only; no clinical trials identified.
The seeds have traditionally been attributed with expectorant and emmenagogue (menstruation-stimulating) properties and were used in small doses to regulate menstrual cycles or relieve urinary tract discomfort. Traditional Chinese medicine sources describe use for post-partum pain, dysmenorrhoea, and endometriosis. Some traditional references note use for controlling internal bleeding and profuse menstruation.
No controlled human studies evaluating any of these applications have been identified. These accounts derive solely from historical herbal literature and ethnobotanical surveys.
5.6 Antioxidant Activity
Evidence characterization: Preliminary; limited to physicochemical analysis and indirect inference.
Studies of pennycress seeds from different provenances have compared oil content, fatty acid composition, and antioxidant properties. Alpha-tocopherol, a known lipid-soluble antioxidant, is the primary tocopherol found in pennycress seed oil at 714 ppm. This constitutes indirect compositional evidence for antioxidant potential, but it does not constitute clinical evidence of benefit in humans.
5.7 Animal Feed Safety — An Area of Active Research
Evidence characterization: Emerging; animal study data available.
Domesticated pennycress, a newly developed winter annual oilseed crop grown in the Upper Midwestern USA, has garnered significant interest because of its high seed oil content; compared to native field pennycress, domesticated varieties possess improved agronomic and compositional properties that allow grain and meal to be used as an animal feed ingredient. In a broiler study, CoverCress™ grain (a domesticated, gene-edited pennycress variety) was found to be safely fed to broilers when included at a target rate of 4% in diets and with total glucosinolate levels not exceeding 4.9 µmoles g⁻¹. In those experiments, no significant negative effects were observed in processing, liver, kidney, or thyroid weights, T3, T4, blood chemistries, macropathology, or histopathology between control and CoverCress grain-treated groups.
6. Body Systems and Health Areas Associated With Pennycress
- Renal/Urinary System: Traditional use centered on diuretic properties, believed to stimulate urine flow and aid in flushing out excess fluids.
- Reproductive System: Seeds attributed with emmenagogue properties in traditional use, described for regulating menstrual cycles.
- Respiratory System: Tibetan medicine describes the seeds as used in the treatment of pus in the lungs. European folk traditions also included the plant in formulas for coughs and mild bronchial irritation.
- Digestive System: Traditionally used to aid digestion and support liver function.
- Musculoskeletal System: Antirheumatic properties are attributed to the whole plant in traditional references.
- Integumentary System: External application to bruises, boils, and swellings has been described in traditional European use.
- Immune/Inflammatory System: The entire plant is described in traditional Chinese sources as anti-inflammatory, antidote, and depurative.
7. Dosage Forms and Reported Dosages
No standardized or pharmacopoeia-approved dosage for Thlaspi arvense as a human dietary supplement has been identified in peer-reviewed literature, official monographs, or government regulatory databases. The following dosage forms and figures are recorded solely from folk or non-clinical sources:
- Infusion (tea) for sore throat: One traditional recipe called for preparing an infusion of the Thlaspi arvense plant and drinking 30 ml once per day.
- Agricultural biofumigant: In field biofumigation studies, seedmeal was applied at rates of 0.50, 1.25, and 2.50 kg/m².
- Animal feed inclusion (domesticated variety): A 4% inclusion rate in diet (with total glucosinolate levels not exceeding 4.9 µmoles g⁻¹) was evaluated as a safe feeding target in broiler chickens.
No human clinical trial reporting specific dosage regimens for T. arvense preparations has been identified.
8. Safety Considerations
Erucic Acid Content and Human Consumption
High erucic acid content — exceeding 300 g per kg of total seed oil dry matter — makes the oil from pennycress landraces unsuitable for food purposes; pennycress landraces also contain glucosinolates, which make the usage as food undesirable. Due to the high erucic acid content, the seeds are unsuitable for human consumption.
Interest in the safety of erucic acid arose when studies in rats associated the dietary intake of high doses of erucic acid with myocardial lipidosis and heart lesions. Erucic acid is a 22-carbon monounsaturated acid metabolized primarily via mitochondrial beta-oxidation; like other longer-chain fatty acids, the rate of mitochondrial beta-oxidation is comparatively lower for erucic acid, and elevated levels can induce liver peroxisomal oxidation pathways as a compensatory mechanism.
Glucosinolate Toxicity
The plant contains glucosinolates, particularly in its seeds, which can be toxic, especially in large quantities. When eaten by animals or humans, glucosinolates can inhibit thyroid gland functioning, causing enlargement and atrophy of the thyroid (goiter).
High-Dose Toxicity in Traditional Accounts
Use with caution is advised in traditional literature, as large doses can cause a decrease in white blood cells, nausea, and dizziness.
Livestock and Milk Contamination
When present in hay or other fodder, pennycress seeds or leaves can be toxic to animals, as well as contaminate milk and meat with unpleasant flavors. The oil can cause profuse swelling of the fore stomachs, mucosal necrosis, and bleeding of the cecum and colon in animals; affected animals become colicky, develop bloody diarrhea, and may die if the seed source is not removed. The oil is stable in the rumen and can be transferred to milk. Dairy products and meat may be tainted if cattle graze on pennycress; excessive grazing by livestock may also result in poisoning.
Brassicaceae Allergy
Allergic reactions are rare but possible, especially for those sensitive to other members of the Brassicaceae family.
Dairy Milk Taint
The mustard-garlic flavor of the leaves is not a favorite of grazing animals, but the milk of dairy cows can be affected if they eat pennycress.
Drug Interactions
No published studies examining pharmacokinetic interactions between T. arvense preparations and pharmaceutical drugs in humans have been identified. The thyroid-disrupting potential of glucosinolates (goitrogenic activity) raises a theoretical concern for individuals taking thyroid medications, but no interaction data specific to this plant has been documented in the clinical literature.
Domestication Efforts to Reduce Toxicity
Using CRISPR genome editing, pennycress oil composition has been improved by eliminating erucic acid content and increasing oleic acid content through knocking out the Fatty Acid Elongase 1 (FAE1) gene, thereby making the oil equivalent in composition to canola and improving efficiency of its conversion to sustainable aviation fuel and other biofuels. Compared to native field pennycress, domesticated varieties possess improved agronomic and compositional properties that allow grain and meal to be used as an animal feed ingredient.
9. Overall Evidence Summary
Research on pennycress (Thlaspi arvense) as a dietary supplement or medicinal ingredient is in a very early and preliminary stage. Research explores antioxidant activity and use as an antipyretic agent, supporting some traditional claims, but much of this research is still in early stages, with many studies conducted in laboratory settings and requiring further validation through human trials. The body of evidence for human health applications is almost entirely composed of ethnobotanical documentation, in-vitro studies, and traditional accounts rather than controlled clinical trials.
The strongest scientific evidence for any biological activity of T. arvense relates to its glucosinolate-derived compounds — particularly AITC and ATC — in the context of agricultural biofumigation and antimicrobial activity in laboratory settings. Pennycress gene homologues revealed high sequence conservation in glucosinolate biosynthesis, metabolism, and transport pathways. Animal feed safety research using domesticated, low-erucic-acid varieties represents an active and emerging area of investigation.
Raw-seed preparations, unprocessed seed oil, and large doses of any part of the plant carry documented safety risks, particularly the high erucic acid content of seeds (rendering them unsuitable for direct human consumption) and the goitrogenic and irritant potential of glucosinolate hydrolysis products. The traditional uses described across Tibetan, Chinese, and European traditions require clinical validation before any therapeutic claims can be established.
References
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