IngredientsGlucosinolates constitute a natural class of organic compounds that contain sulfur and nitrogen and are derived from glucose and an amino acid. They are water-soluble anions and belong to the glucosides. More precisely, glucosinolates are natural, sulfur-rich anionic secondary metabolites, widely distributed in plants of the order Brassicales, mainly in the angiosperms families like Brassicaceae.
Glucosinolates share a common core structure consisting of a β-thioglucose linked by a sulfur atom to a (Z)-N-hydroximinosulfate ester, and a variable side chain derived from amino acids. Every glucosinolate contains a central carbon atom, which is bound to the sulfur atom of the thioglucose group, and via a nitrogen atom to a sulfate group (making a sulfated aldoxime). In addition, the central carbon is bound to a side group; different glucosinolates have different side groups, and it is variation in the side group that is responsible for the variation in the biological activities of these plant compounds.
Glucosinolates, of which nearly 200 types having different substituents have been identified, are classifiable into three classes based on the structure of different amino acid precursors: aliphatic glucosinolates, indole glucosinolates, and aromatic glucosinolates. Specifically, aliphatic glucosinolates derive from methionine, aromatic ones from phenylalanine, and indolic ones from tryptophan. The side-chain of the O-sulfate thiohydroximate moiety, which is derived from a different amino acid, contributes to the diversity of natural glucosinolates, with more than 130 structures identified and validated to date.
The essence of glucosinolate chemistry is their ability to convert into an isothiocyanate (a "mustard oil") upon hydrolysis of the thioglucoside bond by the enzyme myrosinase. Glucosinolates normally exist as intact compounds localized in vacuoles of different cell types. They are degraded to hydrolysis products by an endogenous glycosylated thioglucosidases enzyme known as myrosinase, which is physically separated in vacuoles of myrosin cells.
Glucosinolates occur as secondary metabolites of almost all plants of the order Brassicales. This includes the economically important family Brassicaceae as well as Capparaceae and Caricaceae. Outside of the Brassicales, the genera Drypetes and Putranjiva in the family Putranjivaceae are the only other known occurrences of glucosinolates.
Cruciferous vegetables include arugula (rocket), bok choy, broccoli, Brussels sprouts, cabbage, cauliflower, collard greens, daikon, horseradish, kale, kohlrabi, radish, turnips, wasabi, and watercress and are commonly consumed globally. The most commonly grown and utilized cruciferous vegetables include Brassica oleracea and Brassica rapa, which are almost entirely edible (leaves, inflorescence, root, stem, and seed). In addition, Brassica juncea, Brassica nigra, and Brassica carinata have been used as cruciferous vegetables for human consumption.
Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged.
Although chemical syntheses of glucosinolates have been devised to give access to these secondary metabolites, direct extraction from biomass remains the conventional method to isolate natural glucosinolates. As dietary supplements and in clinical research, glucosinolates are primarily delivered as:
Formulation strongly affects bioavailability, both in terms of inter- and intra-individual consistency with repeated doses, reflecting how broccoli sprout extracts are prepared (e.g., with or without exogenous myrosinase-catalyzed hydrolysis of glucoraphanin).
Armoracia rusticana (horseradish), a member of the Brassicaceae family, has been known since ancient times as a folk medicinal herb and as a plant of nutritional value and culinary interest. Horseradish has been cultivated and used as a medicine and condiment for at least 2,000 years. Early settlers brought the horseradish plant to America, and the plant was commonplace in gardens by the early 1800s.
Horseradish has long use medicinally, both externally and internally. Early Greeks used horseradish as an aphrodisiac and for lower back pain. It has been used historically in Europe as a cough expectorant and treatment for scurvy, food poisoning, tuberculosis, and colic. This plant was also widely used in traditional medicine as an expectorant, to soothe respiratory issues, and to help relieve rheumatism by stimulating blood flow in inflamed joints. The suggested traditional use for colds and respiratory infections was about 20 g of fresh root per day.
William Turner mentions horseradish as "Red Cole" in his Herbal (1551–1568), but not as a condiment. In The Herball, or Generall Historie of Plantes (1597), John Gerard describes it under the name raphanus rusticanus, stating that it occurs wild in several parts of England. After referring to its medicinal uses, he notes that "the Horse Radish stamped with a little vinegar put thereto, is commonly used among the Germans for sauce to eat fish with."
The traditional use of mustard-derived flavoring condiments, while contributing desirable flavor profiles to cooked food items, also provides food preservative properties which traditional societies have relied upon in the prevention of microbial spoilage of foods. This was particularly important in climatic conditions and ambient temperatures conducive to microbial growth leading to food spoilage, and the widespread use of mustard oil positively contributed to food storage properties and protection from microbial infection.
Fermentation as a preservation method for cruciferous vegetables has been used since ancient times, with fermented products such as sauerkraut representing centuries-old dietary traditions. This process results in fermented products that have a unique flavour and odour, high bioactivity, and a distinctly different phytochemical profile than raw vegetables.
In plants, glucosinolate and hydrolysis product compounds determine the distinct aroma, pungent flavors, and taste of foods, which were recognized across many agricultural cultures as identifying characteristics of the Brassica genus. The traditions to use horseradish plant for medicinal purposes are still applied in many countries. The pungent properties of mustard seeds — which contain glucosinolates, principally sinigrin — were valued in ancient Greek, Roman, and Ayurvedic traditions for topical and digestive applications, though these traditional attributions must be understood as predating any understanding of glucosinolate chemistry. These natural chemicals most likely contribute to plant defense against pests and diseases and impart a characteristic bitter flavor to cruciferous vegetables, properties which traditional practitioners exploited empirically across cultures.
When plant tissue containing glucosinolates is damaged, as is the case in the preparation (cutting, chopping, mixing) or chewing food, a β-thioglucosidase called myrosinase is released. The enzyme is normally stored separately from glucosinolates in different cells, or in different intracellular compartments, depending on the plant species. The hydrolysis of glucosinolate by myrosinase produces a molecule of β-d-glucose and an unstable aglycone; spontaneous reorganization of this intermediate results in the release of sulfate ion and in the formation of metabolites, the structures of which depend on the nature of the side chain of the glucosinolate and the physico-chemical conditions of the medium.
While intact glucosinolates are biologically inactive, various products, including isothiocyanates, nitriles, epithionitriles, and cyanides obtained through their hydrolysis, exhibit many different biological activities, among which several therapeutic benefits have been suggested.
Sulforaphane (SFN), an aliphatic isothiocyanate derived from cruciferous vegetables such as broccoli, has emerged as a chemopreventive dietary agent. SFN exerts multifaceted anticancer effects through the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)–antioxidant response element (ARE) pathways, inhibition of histone deacetylases (HDACs) and hypoxia-inducible factor-1α (HIF-1α), and regulation of apoptosis and autophagy.
Glucosinolate metabolites exert cancer-preventive activity through different mechanisms, including induction of the Nrf2 transcription factor, inhibition of expression of tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β), induction of apoptosis through inhibiting phase I enzymes and inducting phase II enzymes, interruption of caspase pathways and STAT1/STAT2, and inhibition of sulfotransferases.
Moreover, glucosinolates and their metabolites are effective in cancer treatment by inhibiting angiogenesis, upregulating natural killers, increasing expression of p53, p21, caspase 3 and 9, and modulating NF-κB.
Early studies have shown that SFN scavenges oxygen radicals by increasing cellular defenses against oxidative damage, mainly through the induction of phase II detoxification enzymes by nuclear factor erythroid 2-related factor 2 (Nrf2). More and more studies have shown that the anticancer mechanism of SFN also includes induction of apoptotic pathway in tumor cells, inhibition of cell cycle progression, and suppression of tumor stem cells.
Accumulating evidence supports that epigenetic modification is an important factor in carcinogenesis and cancer progression. Studies on the mechanisms underlying the anticancer effects of SFN have shown that SFN can reverse such epigenetic alterations in cancers by targeting DNA methyltransferases (DNMTs), histone deacetyltransferases (HDACs), and noncoding RNAs.
Accumulating evidence increasingly supports the beneficial effects of dietary glucosinolates on overall health, including as potential anticancer agents, because of their role in the prevention of the initiation of carcinogenesis via the induction of cellular defense detoxifying/antioxidant enzymes and their epigenetic mechanisms, including modification of the CpG methylation of cancer-related genes, histone modification regulation, and changes in the expression of microRNAs (miRNAs).
The anti-inflammatory effects of sulforaphane and other isothiocyanates may involve increased Nrf2 activity and inhibition of NF-κB.
The order of preference for antimicrobial activity among hydrolysis products is: indole-isothiocyanate byproducts (e.g., indole-3-carbinol) > aromatic-isothiocyanate > sulfur-isothiocyanate > aliphatic-isothiocyanate > nitrile- and/or amine-derivatives. The inclusion of dietary cruciferous vegetables rich in glucosinolates may counter antibiotic-resistant bacteria in the food chain arising from the overuse of antibiotics in animal rearing practices.
After ingestion, glucosinolates could be partially absorbed in their intact form through the gastrointestinal mucosa. However, the largest fraction is metabolized in the gut lumen. When cruciferous vegetables are consumed without processing, myrosinase enzyme present in these plants hydrolyzes the glucosinolates in the proximal part of the gastrointestinal tract to various metabolites, such as isothiocyanates, nitriles, oxazolidine-2-thiones, and indole-3-carbinols. When cruciferous vegetables are cooked before consumption, myrosinase is inactivated and glucosinolates transit to the colon where they are hydrolyzed by the intestinal microbiota.
Since most cruciferous vegetables are cooked prior to eating, bacterial myrosinase in the gut, rather than plant myrosinase, is responsible for the initial step in glucosinolate degradation. In a feeding study involving 45 healthy subjects, the mean conversion rate of glucosinolates (of which 85% was glucoraphanin) to dithiocarbamates over a 24-hour period was estimated to be around 12% with wide variations among participants (range, 1.1 to 40.7%).
The bioavailability of glucosinolates and their breakdown products can be affected by preparation and processing conditions. Storing Brassica plants at ambient temperature and in a domestic refrigerator led to the differential loss of total glucosinolate content by 11 and 27%, respectively.
The steam method provided the least affected sample in terms of glucosinolates content, compared to the conventional boiling water method, which led to the highest losses in the contents of glucosinolates (57 and 81% in Brassica oleracea and Brassica rapa cultivars, respectively).
Cooking has been shown to greatly decrease bioavailability as heat deactivates endogenous plant myrosinase, thus any conversion of glucosinolates to isothiocyanates would occur in the gut lumen by the gut microbiome. Many studies show high degradation of glucosinolates yet low yield of isothiocyanates and nitriles, and it is not clear if this is because of further metabolism of isothiocyanates and nitriles, or metabolism of glucosinolates to alternate endpoints. This is complicated by the unstable nature of isothiocyanates, which have been shown to spontaneously degrade and react with other compounds.
While preclinical evidence shows promising anti-inflammatory and antioxidant properties of glucosinolates, clinical trials in humans are still insufficient, due to methodological heterogeneity and factors affecting the production of the bioactive compounds. Their limited and variable bioavailability remains a key challenge.
Historically, a major research focus has been the anticancer effect of glucosinolates. Epidemiological studies have consistently associated cruciferous vegetable intake with reduced cancer risk, while mechanistic research has elucidated the capacity of sulforaphane to modulate redox balance, detoxification pathways, and epigenetic processes. Recent clinical trials have further demonstrated its potential to reduce carcinogenic biomarker levels and support metabolic detoxification.
Extensive studies have reported the potential chemopreventive activity of sulforaphane, an isothiocyanate derived from glucoraphanin, occurring in large amounts in Brassica genus plants. Sulforaphane was found to be active against several forms of cancer. A growing body of data shows that sulforaphane acts against cancer at different levels, from development to progression, through pleiotropic effects.
Because of its efficacy, safety, nontoxicity, lack of side effects, and low cost, bioactive sulforaphane is widely recognized as a promising chemopreventive agent with effects against many kinds of cancers, such as cervical, breast, and bladder cancer; renal cell carcinoma; non-small-cell lung cancer; and colon and prostate cancers.
Since first isolated from broccoli and demonstrated to have cancer chemoprotective properties in rats in the early 1990s, over 3,000 publications have described its efficacy in rodent disease models, underlying mechanisms of action, or, to date, over 50 clinical trials examining pharmacokinetics, pharmacodynamics, and disease mitigation.
Limitations of the clinical cancer evidence: Despite a near quarter century since the (re)discovery of sulforaphane, studies on the pharmacodynamic actions of sulforaphane in humans have been quite limited. This point stands in stark contrast to the many hundreds of publications probing mechanisms of action in cell culture and animal models. Dozens of targets and pathways have been identified as potential mediators of the chemoprotective actions of sulforaphane, but few have undergone serious validation.
Observational studies have been conducted to determine if consumption of cruciferous vegetables affects cancer risk in humans, but there is insufficient clinical evidence to indicate that consuming isothiocyanates in cruciferous vegetables is beneficial, according to a 2017 review.
Emerging evidence from experimental studies has shown that glucosinolate metabolites can reduce oxidative stress, inflammation, endothelial dysfunction, and cardiomyocyte death, indicating that these compounds may also have beneficial effects on the cardiovascular system.
Several clinical trials have tested glucosinolate-rich preparations for cardiovascular outcomes, with mixed results:
Despite the evidence from basic science research, human data regarding glucosinolate intake and coronary heart disease (CHD) risk are limited. Overall, the cardiovascular evidence from human trials is preliminary and mixed; effects in individual interventions have not been consistent across studies.
There is increasing interest in the impact of glucosinolates on glycemic control. Isothiocyanates, such as raphasatin and sulforaphane, may prevent or reduce glycemic-related complications in animal and human studies.
In a 4-week parallel, randomized, double-blind, placebo-controlled study including 81 human participants with type 2 diabetes, 10 g/day broccoli sprout powder (225 μmol sulforaphane daily) decreased fasting serum insulin and insulin resistance by 18.2% and 14.2%, respectively. Positive results were also seen in a randomized double-blind, placebo-controlled study including 97 Scandinavian patients with type 2 diabetes.
Studies indicate that cruciferous vegetables and their glucosinolates may have an impact on a number of cardiometabolic disorders. Improvements in glycemic control, blood pressure, and lipid profile have been identified, which may lead to a reduction or delay in disease progression. However, as with cardiovascular outcomes, the body of clinical evidence remains limited in scale and consistency.
Glucosinolate metabolites, particularly sulforaphane, may exert a beneficial effect on neurological and psychiatric conditions, such as depression, schizophrenia, autism, Alzheimer's disease, and multiple sclerosis.
Isothiocyanates have attracted considerable scientific interest for their protective effects against various diseases, thanks to their antioxidant, anti-inflammatory, and neuroprotective properties.
A notable area of clinical investigation is autism spectrum disorder (ASD). A randomized, double-blind, placebo-controlled trial evaluated the effects of broccoli sprout-derived sulforaphane on behavior in 40 young men (age, 13 to 27 years) with moderate to severe autism spectrum disorder (ASD). Additional trials across different formulations have been registered and completed, as documented in clinical trial registries.
Preclinical evidence suggests that glucosinolates and their metabolites, particularly sulforaphane, exhibit several biological properties that may be relevant to neurological and psychiatric conditions. A number of potential mechanisms include the modulation of the hypothalamic-pituitary-adrenal axis, oxidative stress, and inflammatory pathways.
Overall, the neurological evidence base for glucosinolates in humans is at an early stage; most supportive findings come from preclinical models, and clinical trials in neurological conditions are limited in number and scale.
One of the most clinically documented applications involves enhancement of the detoxification of airborne pollutants. A pivotal randomized controlled trial by Egner et al. (2014) conducted in Qidong, China, tested a broccoli sprout beverage containing glucoraphanin and sulforaphane against a placebo in a heavily polluted environment. This study, titled "Rapid and sustainable detoxication of airborne pollutants by broccoli sprout beverage," was published in Cancer Prevention Research in 2014 and demonstrated significantly increased urinary excretion of the carcinogens benzene and acrolein in the treatment group relative to placebo. This trial is widely cited as one of the more rigorous pieces of human clinical evidence in the glucosinolate literature.
Sulforaphane, an isothiocyanate derived from glucoraphanin, has antioxidant and anti-inflammatory effects that may be beneficial for improving liver function. However, few studies regarding the effects of glucoraphanin on the biological markers related to liver function — such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), and gamma-glutamyltransferase (γ-GTP) — in healthy individuals have been reported. A randomized, double-blind, placebo-controlled parallel-group trial compared the effects of broccoli sprout supplements enriched in glucoraphanin (n=35) with those of placebo supplements (n=35). This was the first study to report that the intake of high doses (137.1 μmol/d) of glucoraphanin in the form of supplements for a long period (24 weeks) may be useful for liver health without safety concerns.
Sulforaphane has been indicated as an important dietary component for musculoskeletal disorders, with studies reporting improvements in measures for both muscle and bone. Historically, the understanding of the effects of glucosinolates on skeletal muscle comes from trials of their application in animal production settings, with results indicating that although growth performance may be affected, muscle had an improved antioxidant status and fatty acid profile. Human clinical evidence for this area specifically is limited.
Epidemiological studies suggest a potential role of glucosinolates and isothiocyanates on human health. However, evidence from intervention studies, due to heterogeneity in features of study design, duration, participants, food or food components administered, and outcomes analyzed, is still insufficient.
This lack of recent studies is largely due to the difficulty of standardizing dosages, variability in preparation methods (e.g., raw or cooked), and the bioavailability of key compounds and their bioactive derivatives. A 2021 overview of registered clinical trials confirmed that the duration of studies was varying between one or a few days up to 12 weeks, and the markers associated with the bioavailability included the dosage of the native glucosinolate, derivatives (e.g., sulforaphane), or metabolic products analyzed mainly in plasma and urine, while those related to human health included markers directly and/or indirectly associated with prostate cancer, cognitive function, and cardiovascular health including inflammatory and antioxidant markers.
No universally established therapeutic dosage for glucosinolates exists as a recognized regulatory standard. The following dosages have been reported in peer-reviewed clinical research:
Following enzymatic breakdown, some glucosinolates in brassica vegetables produce sulforaphane, phenethyl, and indolylic isothiocyanates that possess anticarcinogenic activity. In contrast, progoitrin and indolylic glucosinolates degrade to goitrin and thiocyanate, respectively, and may decrease thyroid hormone production.
Oxazolidine-2-thiones inhibit thyroid function by blocking the incorporation of iodine into thyroxine precursors and by suppressing thyroxine secretion from the thyroid. Importantly, the magnitude of the effect depends on the specific vegetable and dose: radioiodine uptake to the thyroid is inhibited by 194 μmol of goitrin, but not by 77 μmol of goitrin. Collards, Brussels sprouts, and some Russian kale (Brassica napus) contain sufficient goitrin to potentially decrease iodine uptake by the thyroid. However, turnip tops, commercial broccoli, broccoli rabe, and kale belonging to Brassica oleracea contain less than 10 μmol of goitrin per 100-g serving and can be considered of minimal risk.
Glucosinolate derivatives can adversely affect the thyroid gland. Especially organisms with hypothyroidism are prone to negative effects of glucosinolate-rich products. Critically, without botanical myrosinase, anti-thyroidal thiocyanate ions and goitrin can still be generated in the animal body. Thus, the inactivation of myrosinase during cooking will have no effect on the anti-nutritional effect of glucosinolates in cruciferous vegetables. Additionally, the relatively fast conversion to thiocyanate ions, which block the uptake of iodine into the thyroid, can be protected against by simultaneous administration of iodine.
Unless new scientific data confirms a lack of negative effect of brassica sprouts on thyroid function in humans, they should not be excluded from the group of goitrogenic products.
A clinical trial reported no adverse effects on the thyroid gland after the daily consumption of a broccoli sprout extract beverage (600 μmol/d of glucoraphanin) for 12 weeks. This applies to the glucoraphanin/sulforaphane pathway specifically; the risk from progoitrin-containing species is a distinct consideration.
Minor gastrointestinal complaints were recorded in clinical studies with broccoli sprout preparations. In one cross-over trial, 2 of 50 participants randomized to receive a sulforaphane-rich beverage (150 μmol/day) complained of nausea or bitter taste and dropped out of the study. Ingestion of large amounts of glucosinolate-containing preparations such as horseradish can cause bloody vomiting and diarrhea.
Nitriles depress growth, cause liver and kidney lesions, and in severe cases lead to liver necrosis, bile duct hyperplasia, and megalocytosis of tubular epithelium in the kidney. These effects have been most extensively documented in animal models and at high dietary exposures (particularly in livestock fed large amounts of rapeseed meal); their relevance at typical human dietary or supplemental doses has not been established.
Horseradish is part of the cabbage and mustard family; therefore, it may suppress thyroid function. The isothiocyanates may irritate mucous membranes on contact or if inhaled.
Glucosinolate-derived isothiocyanates are known to induce and modulate phase II detoxification enzymes and also to inhibit certain phase I cytochrome P450 enzymes. Through induction of CYP enzymes (particularly via the Nrf2/ARE pathway), high-dose glucosinolate supplementation has theoretical potential to alter the metabolism of drugs metabolized by these enzymes. However, direct clinical pharmacokinetic drug–glucosinolate interaction studies in humans are limited in the published peer-reviewed literature.
Information regarding safety and efficacy in pregnancy and lactation is lacking for concentrated glucosinolate preparations such as DIM (3,3′-diindolylmethane).
In individuals with sufficient iodine intake, moderate consumption of goitrogenic foods is unlikely to cause significant thyroid dysfunction. However, in people with an iodine deficiency or those who already have an underactive thyroid, excessive consumption of goitrogens could exacerbate thyroid problems.
No clinical adverse events were reported in a phase I dose-escalation study using 75–300 μmol glucosinolates daily for 7 days. In a Johns Hopkins cross-over trial of broccoli sprout extract, there were only three grade 1 mild gastrointestinal adverse events reported and no significant changes in laboratory values (comprehensive metabolic panel, full blood count, coagulation panel, and thyroid tests) taken pre- and post-intervention. Broccoli sprouts are widely consumed in many parts of the world, and there have been no reported concerns with respect to their tolerance and safety in humans at typical dietary intake levels, though the evidence at high supplemental doses specifically requires continued monitoring.
Health conditions that Glucosinolates may help support.
Body systems that Glucosinolates may help support.
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