Ingredients3-Butenyl isothiocyanate (also known as but-3-en-1-yl isothiocyanate or 3-butenylmustard oil, abbreviated as 3-BITC or BNCS) is a naturally occurring organosulfur compound belonging to the isothiocyanate family. With the CAS registry number 3386-97-8, it is an organic compound characterized by its isothiocyanate functional group (–N=C=S) attached to a four-carbon butenyl chain. Its molecular formula is C5H7NS, and it is registered in the PubChem compound database under CID 76922.
As an isothiocyanate, its core functional structure conforms to the general formula R–N=C=S, where R is an alkyl or aryl group — in this case, an alkenyl (butenyl) carbon chain carrying a terminal double bond. A structurally related compound, 4-methylthio-3-butenyl isothiocyanate (4-MTBI, CAS 13028-50-7), is a distinct molecule found principally in radish (Raphanus sativus) and should not be confused with 3-butenyl isothiocyanate.
3-Butenyl isothiocyanate is typically a colorless to pale yellow liquid with a pungent odor reminiscent of mustard or horseradish, which is common among isothiocyanates. It is soluble in organic solvents and exhibits moderate stability under standard conditions. Due to its reactive nature, it can participate in various chemical reactions, including nucleophilic substitutions and additions. Like other isothiocyanates, these substances are usually insoluble in water, show little stability in water and at extreme pH conditions, and are thermally degraded.
3-Butenyl isothiocyanate is the enzymatic hydrolysis product of gluconapin (also written as gluconapin or 3-butenyl glucosinolate). The glucosinolate gluconapin (3-butenyl glucosinolate) is a major aliphatic glucosinolate found in rapeseed (Brassica napus and related species). In formal nomenclature, gluconapin carries the side chain designation "3-Butenyl" within the broader classification of aliphatic glucosinolates found in Brassica oilseed crops.
Glucosinolates all contain a β-D-thioglucose group, a sulfonated oxime moiety, and a variable side chain R. They are hydrolyzed by the enzyme myrosinase (thioglucoside glycohydrolase, EC 3.2.3.1), releasing glucose to give an unstable aglycone, which then eliminates sulfate (SO42−) and forms the isothiocyanate R–N=C=S.
Isothiocyanates are stress-response chemicals formed from glucosinolates in plants often belonging to the Cruciferae family, and more broadly the Brassica genus, which includes broccoli, watercress, kale, cabbage, collard greens, Brussels sprouts, bok choy, mustard greens, and cauliflower.
3-Butenyl isothiocyanate is obtained specifically from cruciferous species in which gluconapin is a prominent glucosinolate. Natural sources from which 3-butenyl isothiocyanate may be obtained include cabbage, horseradish, mustard, cole crops, turnip, and rutabaga. Among individual species:
The glucosinolates sinigrin and gluconapin (prominent in Brussels sprouts, cabbage, cauliflower, turnip, rutabaga, and kale) are associated with strong bitterness in these vegetables. The presence of significant quantities of gluconapin in Brassica rapa cultivars is mainly responsible for their bitter taste.
3-Butenyl isothiocyanate is not historically documented as an isolated compound in traditional medicine; its traditional relevance derives from the long-established use of the plants that contain its glucosinolate precursor, gluconapin. The agricultural use of cruciferous vegetables dates back many centuries. Cruciferous vegetables originated from the Irano-Turanian region approximately 20 million years ago and have been cultivated as human food crops across Europe, Asia, and the Americas for a very long time.
Brassica nigra (black mustard) is widely used in traditional herbal therapies across various cultures due to its rich nutritional and pharmacological properties. Beyond their culinary roles, Brassica plants have held an important place in traditional medicine as stimulants to improve circulation and absorption, as antiseptics to treat wounds and infections, as pain relievers, and as remedies for respiratory ailments.
Traditionally, mustard leaves are used for the treatment of various diseases, and due to the unique, sharp, hot, pungent flavour, mustard is used as a spice. Mustard-based preparations containing pungent glucosinolate hydrolysis products have been used in food cultures across South Asia, East Asia, and Europe for millennia. The Moutarde de Dijon tradition of Burgundy, France, for instance, centers on the hydrolysis of glucosinolates in Brassica juncea seeds: In the production of "Moutarde de Dijon," gluconapin (GNA, 3-butenyl glucosinolate) must be present at a low level, while high sinigrin (SIN, 2-propenyl glucosinolate) content is required for the condiment's characteristic hot taste.
The natural role of glucosinolates in plants is as plant defense compounds. The enzyme myrosinase removes the glucose group in sinigrin (and related glucosinolates) to produce allyl isothiocyanate, the compound responsible for the pungent taste of Dijon mustard. This reactive material is toxic to many insect predators and its production is triggered when the plant is damaged — an effect that has been called the "mustard oil bomb."
Glucosinolates are stored in plant cells, and only after tissue damage do the compounds come in contact with thioglucosidases (myrosinases). Hydrolysis of glucosinolates yields glucose and an aglycone, which is a precursor for mainly volatile isothiocyanates with strong biocidal activity.
Specifically for gluconapin: The seeds of rapeseed contain the glucosinolates gluconapin, glucobrassiconapin, and progoitrin, and the enzyme myrosinase which can hydrolyze these glucosinolates respectively to 3-butenyl, 4-pentenyl, and 2-hydroxy-3-butenyl isothiocyanates.
Tissue disruption — for example, by chewing — starts the breakdown of glucosinolates into isothiocyanates, which provides protection to plants against insects, as isothiocyanates are pungent metabolites. Critical to the formation of isothiocyanates is the plant enzyme myrosinase, as well as β-thioglucosidases occurring in the human gastrointestinal microbiome, which convert precursor glucosinolates into bioactive isothiocyanates.
Sinigrin and related glucosinolates are hydrolyzed to their respective isothiocyanates by plant myrosinase and by a number of Gram-positive intestinal flora, including Lactobacillus agilis and species of Streptomyces, Bacillus, and Staphylococcus. This means that the conversion of ingested gluconapin to 3-butenyl isothiocyanate can occur in the human gut even when the plant enzyme has been inactivated by cooking.
Dietary isothiocyanates are efficiently absorbed in vivo, and oral bioavailability of these compounds may reach ≥80%. One of the main challenges in harnessing the health benefits of isothiocyanates is improving their bioavailability. Bioavailability depends on several factors, mostly due to the chemical structure of a molecule and its interaction with the environment. Research on ITCs as beneficial agents has been slowed by their relatively poor solubility in water, poor stability at extreme pH conditions, and susceptibility to thermal degradation.
The precursor glucosinolates are metabolized into isothiocyanates by the action of plant myrosinase, and the isothiocyanates then undergo further metabolism initially through conjugation with glutathione (GSH) by glutathione S-transferases (GSTs). This conjugation is followed by the formation of an isothiocyanate-Cys-Gly intermediate by gamma glutamyltranspeptidase (GTP), and ultimately the mercapturic acid — isothiocyanate-N-acetyl cysteine (isothiocyanate-NAC) — is formed. All of these metabolites have been detected in urine and plasma after ingestion of cruciferous vegetable preparations or isothiocyanates themselves in humans, with the mercapturic acids being the most predominant species.
Absorbed isothiocyanates are rapidly conjugated to glutathione in the liver and then sequentially metabolized in the mercapturic acid pathway before being excreted in the urine. ITCs are principally metabolized through the mercapturic acid pathway in vivo, giving rise to N-acetylcysteine conjugates which are excreted in the urine; analytical methods have been developed to allow detection of ITCs and their metabolites, and total urinary ITC equivalent is considered an excellent biomarker of human exposure to ITCs.
The electrophilic –N=C=S group is the core reactive moiety of all isothiocyanates, including 3-butenyl isothiocyanate. An initial reaction between the –N=C=S group of isothiocyanates and the cysteine sulfhydryl group of glutathione (γ-glutamylcysteinylglycine) takes place spontaneously but is enhanced by glutathione S-transferase (GST), giving rise to the corresponding conjugates. This electrophilic reactivity underpins the ability of isothiocyanates to modify cellular protein targets, including those involved in detoxification signaling.
Epidemiological studies suggest that chronic consumption of cruciferous vegetables can lower the overall risk of cancer. Natural ITCs are key chemopreventive ingredients of cruciferous vegetables, and one of the prime chemopreventive mechanisms of natural isothiocyanates is the induction of Nrf2/ARE-dependent gene expression that plays a critical role in cellular defense against electrophiles and reactive oxygen species.
Nrf2 is a transcription factor bound to the protein Keap1 in the cytosol. Keap1 responds to oxidative stress signals or chemical inducers by freeing Nrf2. Isothiocyanates can react with sulfhydryl residues of Keap1, causing the release of Nrf2. Nrf2 can then translocate to the nucleus and bind to the antioxidant response element (ARE) located in promoters of genes coding for antioxidant and detoxifying enzymes, including glutathione S-transferases (GSTs), thioredoxin, NAD(P)H quinone oxidoreductase 1 (NQO-1), and heme oxygenase 1 (HO-1).
Many isothiocyanates are potent inducers of phase II detoxifying enzymes, including GSTs, UDP-glucuronosyl transferases (UGTs), NQO1, and glutamate cysteine ligase (GCL), that protect cells from DNA damage by carcinogens and reactive oxygen species.
Cruciferous vegetables are rich sources of glucosinolates, which are degraded into isothiocyanates by enzymatic action of plant-specific myrosinase or intestinal flora. A significant portion of the chemopreventive effects of isothiocyanates appears to be associated with the inhibition of the metabolic activation of carcinogens by cytochrome P450s (Phase I enzymes), coupled with strong induction of Phase II detoxifying and cellular defensive enzymes.
Inductions of Phase II cellular enzymes are largely mediated by the antioxidant responsive element (ARE), which is regulated by the transcriptional factor Nrf2. Additional potent regulatory mechanisms of Nrf2 include the different signaling kinase pathways (MAPK, PI3K, PKC, and PERK) as well as other non-kinase dependent mechanisms.
In cell-based research specifically on 3-butenyl isothiocyanate, the compound was studied for mechanisms of cell death using reactive oxygen species (ROS) assay, mitochondrial membrane potential (MMP) assay, microscopic analysis, and cell cycle analysis. The mechanistic analysis indicated that it induced the death of prostate cancer cells via apoptosis.
Cruciferous vegetables contain a complex mix of phytochemicals including glucosinolates, which can convert to bioactive isothiocyanates. These bioactive compounds have broad antibiotic, anticancer, antioxidant, antiadipogenic, anti-inflammatory, antiapoptotic, and neuroprotective properties.
The most substantive study specifically on 3-butenyl isothiocyanate comes from a 2016 investigation published in the Journal of Food Science and Technology. The study assessed the cytotoxic potential of 3-butenyl isothiocyanate isolated from Brassica juncea L. Czern var. Pusa Jaikisan against human cancer cell lines including prostate, bone osteosarcoma, cervical, liver, neuroblastoma, and breast cancer. The compound was observed to be most effective against the prostate cancer cell line, and was further studied for mechanism of cell death using neutral red assay, reactive oxygen species assay, mitochondrial membrane potential assay, microscopic analysis, and cell cycle analysis. The mechanistic analysis indicated that it induced cell death of prostate cancer cells via apoptosis.
Evidence characterization: This evidence is limited to in vitro (cell culture) experimentation only. No animal model studies or human clinical trials specifically evaluating 3-butenyl isothiocyanate as an anticancer agent are available in the peer-reviewed literature. Cell-line results cannot be directly extrapolated to predict human efficacy or dosing.
Broader context from isothiocyanate class research: Natural isothiocyanates are abundantly found in cruciferous vegetables such as broccoli, watercress, Brussels sprouts, cabbage, and cauliflower. Epidemiological studies have shown that consumption of cruciferous vegetables is inversely associated with the risk of many types of cancer. However, these epidemiological associations pertain to total isothiocyanate intake from whole foods and are not specific to 3-butenyl isothiocyanate as an isolated compound.
Isothiocyanates are bioactive products resulting from enzymatic hydrolysis of glucosinolates. Although the antimicrobial activity of ITCs against foodborne and plant pathogens has been well documented, little is known about their antimicrobial properties against human pathogens specifically.
3-Butenyl isothiocyanate has been documented as a minor component in horseradish extract preparations tested for antimicrobial activity. A horseradish root extract containing 59.9% allyl isothiocyanate (AITC), 35.8% phenylethyl isothiocyanate (PEITC), and 1.5% 3-butenyl ITC was assessed for antimicrobial activity against resistant strains of Clostridia. The contribution of 3-butenyl isothiocyanate specifically to the antimicrobial effect of this mixed extract was not isolated from the contributions of the other isothiocyanates present.
Several studies suggest glucosinolates have a potential role in treating metabolic disorders, including cancer, diabetes, and inflammation. Some glucosinolates have shown broad-spectrum antimicrobial activity against gram-positive and gram-negative bacteria and antifungal activity against fungal strains.
Evidence characterization: Antimicrobial evidence for 3-butenyl isothiocyanate specifically is preliminary and largely inferential from its structural class. No dedicated clinical studies on the antimicrobial utility of this specific compound against human pathogens have been identified.
Isothiocyanates may modulate the expression and activity of biotransformation enzymes involved in the metabolism and elimination of xenobiotics (e.g., carcinogens) from the body. In cultured cells and animal models, isothiocyanates also exhibited antioxidant and anti-inflammatory activities and interfered with numerous cancer-related targets and pathways.
Limited data from clinical trials suggest that glucosinolate-rich foods can increase phase II enzyme activity in humans. However, these clinical data are drawn from studies of cruciferous vegetables generally, or from well-characterized isothiocyanates such as sulforaphane and phenethyl isothiocyanate, and are not specific to 3-butenyl isothiocyanate.
Evidence characterization: Mechanistic plausibility for antioxidant and Phase II enzyme-inducing activity is well-established for isothiocyanates as a chemical class. Human clinical evidence for these effects from 3-BITC specifically is absent.
In vitro and animal studies have found that isothiocyanates induce beneficial biological effects in carcinogenesis, cardiovascular and neurological diseases for more than 50 years. Glucosinolates and their breakdown products, isothiocyanates, are bioactive compounds with anti-inflammatory, antioxidant, and anticancer properties mediated through key pathways such as Nrf2, NF-κB, and epigenetic regulation. However, their limited and variable bioavailability remains a key challenge.
Isothiocyanates from cruciferous vegetables have been studied extensively in cells and in animals for their disease preventive and therapeutic effects. However, translating their utility to human populations has been both limited and challenging. Although promising effects on blood pressure, lipid profiles, and glycaemic control have been observed from cruciferous vegetable interventions, clinical studies are often limited by small sample sizes, study heterogeneity, and high inter-individual variability, particularly related to gut microbiota and host metabolic phenotype.
Cruciferous vegetables such as bok choi, broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, kale, kohlrabi, mustard, radish, rutabaga, turnip, and watercress are rich sources of glucosinolate precursors of isothiocyanates. Unlike some other phytochemicals, glucosinolates are present in relatively high concentrations in commonly consumed portions of cruciferous vegetables. For example, one-half cup of raw broccoli might provide more than 25 mg of total glucosinolates.
For 3-butenyl isothiocyanate specifically, quantified dietary exposure data are largely available from rapeseed and turnip research. In horseradish root, 3-butenyl isothiocyanate is present at approximately 0.85 mg/100 g, making it a trace constituent compared to allyl isothiocyanate at 96 mg/100 g in the same plant.
No established commercial dietary supplement form providing 3-butenyl isothiocyanate as a defined isolated constituent has been identified in authoritative sources. The compound is used primarily as a research chemical and flavoring agent. 3-Butenyl isothiocyanate has functional uses registered as a flavoring agent. The Flavor and Extract Manufacturers Association (FEMA) has listed it, and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) has evaluated safety aspects of this compound as a food additive.
3-Butenyl isothiocyanate can be synthesized from the corresponding precursor compounds, often derived from cruciferous vegetables, which are known to contain glucosinolates that can yield isothiocyanates upon enzymatic hydrolysis. Research preparations typically involve enzymatic extraction from Brassica plant material using myrosinase or autolysis protocols.
Published human dosage data specific to 3-butenyl isothiocyanate are not available, reflecting the absence of human clinical trials on this compound in isolation. In the 2016 in vitro cytotoxicity study, cells were treated at IC50 and IC70 concentration levels to assess apoptotic mechanisms; assays including cell viability (neutral red assay), mitochondrial membrane potential (MMP), reactive oxygen species (ROS), and cell cycle analysis were applied at these concentrations to characterize the mechanism of action. Specific numerical IC50 values were not available from the abstract.
In humans, chewing of Brussels sprouts releases approximately 39% of the glucosinolates as isothiocyanates, measured in the urine, whereas no chewing results in the excretion of 26% of isothiocyanates — illustrating the importance of mechanical disruption in liberating isothiocyanates from plant precursors. These data pertain to total isothiocyanates, not 3-BITC specifically.
Sulfur compounds in rapeseed known to have a potential toxic effect on the thyroid include, among others, 5-vinyl-2-thiooxazolidone (VTO = goitrin), 3-butenyl isothiocyanate, gluconapin, and glucobrassicin. This recognition of 3-butenyl isothiocyanate as a potentially thyroid-disrupting compound is explicit in the published literature on Brassica oilseed safety.
Animal studies have documented the antithyroid effects of gluconapin and its hydrolysis product. Studies in rats fed compounds including 3-butenyl isothiocyanate (BNCS) for 21 days, combined with glucosinolate and 3-butenyl cyanide (BCN), examined thyroid effects. The major antinutritional effect of glucosinolates reported is their interference with thyroid function, especially in livestock and poultry which are routinely fed on rapeseed–mustard meal.
It is important to distinguish 3-butenyl isothiocyanate from its close relative, the cyclized product goitrin: Cyclized 2-hydroxy-3-butenyl isothiocyanate (goitrin), derived from progoitrin — a different glucosinolate found alongside gluconapin — is a stable, water-soluble isothiocyanate derivative that represents a health risk because of its goitrogenic properties, specifically the inhibition of iodine uptake into the thyroid gland, which can result in goiter formation. The 2-hydroxy-3-butenyl ITC produced from progoitrin is unstable and undergoes cyclization to produce 5-vinyl-2-oxazolidinethione (goitrin). Previous investigations showed that these compounds are responsible for depression of growth and thyroid enlargement in non-ruminant animals. 3-Butenyl isothiocyanate itself, derived from gluconapin rather than progoitrin, is a distinct compound but is likewise flagged in rapeseed toxicology literature.
Brassica vegetables are a rich source of sulfur compounds such as glucosinolates and isothiocyanates, which provide health benefits but are also suspected of having a goitrogenic effect. A systematic review adhering to PRISMA guidelines analyzed results from 123 articles of in vitro, animal, and human studies describing the impact of Brassica plants and extracts on thyroid mass and histology, blood levels of TSH, T3, T4, iodine uptake, and the effect on thyroid cancer cells. The broader evidence base for goitrogenic effects in humans at normal dietary levels remains mixed.
Rapeseed flours, concentrates, and isolates cannot be used in food products without detoxification to remove glucosinolates or toxic products resulting from the hydrolysis of glucosinolates, such as nitriles, isothiocyanates including 3-butenyl isothiocyanate, and 5-vinyl oxazolidine-2-thione (VTO), under the influence of the endogenous enzyme myrosinase. Detoxification of rapeseed involves continuous two-hour extraction of rapeseed meal using water to remove isothiocyanates, which can remove up to 97% of VTO.
To use the name "canola," an oilseed plant must meet internationally regulated standards specifying that the solid component shall contain less than 30 micromoles of any one or any mixture of 3-butenyl glucosinolate, 4-pentenyl glucosinolate, 2-hydroxy-3-butenyl glucosinolate, and 2-hydroxy-4-pentenyl glucosinolate per gram of air-dry, oil-free solid. This regulatory threshold directly reflects the recognized need to limit the dietary intake of gluconapin (precursor to 3-butenyl isothiocyanate) in oilseed products.
At concentrations typically found in foods, glucosinolates are not toxic to humans and can be useful flavor components. The principal safety concerns around 3-butenyl isothiocyanate relate to chronic high-level exposure through rapeseed-based animal feed rather than normal human dietary consumption of Brassica vegetables.
The electrophilic –N=C=S group of all isothiocyanates, including 3-BITC, can react non-selectively with protein cysteine residues, which is the basis for both their biological activity and their potential for cellular toxicity at high concentrations. Natural isothiocyanates affect intracellular signaling kinase cascades to regulate Keap1/Nrf2 activities and induce phase II cytoprotective and detoxifying enzymes. They are also directly conjugated to cellular protein targets, and these events aid in the chemopreventive effects.
The scientific evidence base for 3-butenyl isothiocyanate as a stand-alone bioactive compound is substantially less developed than that for other isothiocyanates such as sulforaphane, allyl isothiocyanate, phenethyl isothiocyanate, or benzyl isothiocyanate. Key research gaps include:
The two isothiocyanates best studied in human clinical trials are sulforaphane (SFN) and phenethyl isothiocyanate (PEITC), which have been used in small human clinical trials against a variety of diseases. Results suggest an opportunity to incorporate such compounds — or more likely preparations derived from their source plants — into larger human disease mitigation efforts. 3-Butenyl isothiocyanate lacks even this level of clinical investigation to date.
Health conditions that Butenyl isothiocyanate may help support.
Body systems that Butenyl isothiocyanate may help support.
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