Glucosinolate Products Research Articles

Survey of glucosinolate variation in leaves of Brassica rapa crops

The breakdown products of glucosinolates (gsl) are biologically active secondary metabolites involved in plant defense and human nutrition. We identified and quantified 14 different gsl present in the young leaves of 82 different varieties of Brassica rapa, including the following crops: Chinese cabbage, broccoleto, Pak choi and other leafy vegetables, turnip, sarson and rapeseed. We did not find crop specific gsl, but their quantity varied extensively among varieties and crops, except that the Chinese cabbage accessions tended to have similar gsl profile and amount. Gluconapin, glucobrassicanapin (aliphatic), neoglucobrassicin, glucobrassicin (indolic), and gluconaturtiin (aromatic) are the predominant gsl in most of the varieties surveyed. We also found two gsl not commonly found in B. rapa, 2-methyl-2-propenyl and n-butyl. Their identities were confirmed by HPLC-MS. Most of the Chinese cabbages contain lower amount of aliphatic than indolic gsl, whereas broccoleto, turnip and rapeseed all have much higher aliphatic gsl content than indolic gsl content. The predominant aliphatic gsl in most of the varieties contain 4-carbon side-chains. The lack of significant correlation observed between the conversion of 3- to 4-carbon side-chain gsl and the conversion of 4- to 5-carbon side-chain gsl suggests that these two elongation cycles are probably under the control of two independent genes in B. rapa. The absence of glucoraphanin in all accessions indicates that only functional Brgsl-Alk alleles are present in B. rapa.

Responses of Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) to olfactory cues associated with novel genotypes developed by Sinapis alba L. × Brassica napus L.

Many herbivorous insects use olfactory cues for host location. Extracts from Brassica napus L. have been shown to elicit electrophysiological and behavioural responses in the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (syn. C. assimilis (Paykull)) (Coleoptera: Curculionidae). These include volatile products of the hydrolysis of glucosinolates. Here we present results of a laboratory olfactometer study examining the attractiveness of odours from flowering racemes and foliage of Sinapis alba L. (an inappropriate host for larval development), B. napus (an excellent host for larval development) and lines derived from S. alba × B. napus selected from colonization studies to demonstrate resistance or susceptibility. Results of this study indicate differential attraction of C. obstrictus to the odours of resistant and susceptible lines and suggest the role of hydrolysis products of glucosinolates, particularly the attractive effects of 2-phenylethyl isothiocyanate.

The toxic effects of benzyl glucosinolate and its hydrolysis product, the biofumigant benzyl isothiocyanate, to Folsomia fimetaria

Natural isothiocyanates (ITCs) are toxic to a range of pathogenic soil-living species, including nematodes and fungi, and can thus be used as natural fumigants called biofumigants. Natural isothiocyanates are hydrolysis products of glucosinolates (GSLs) released from plants after cell rupture. The study investigated the toxic effects of benzyl-GSL and its hydrolysis product benzyl-ITC on the springtail Folsomia fimetaria, a beneficial nontarget soil-dwelling micro-arthropod. The soil used was a sandy agricultural soil. Half-lives for benzyl-ITC in the soil depended on the initial soil concentration, ranging from 0.2 h for 67 nmol/g to 13.2 h for 3,351 nmol/g. For benzyl-ITC, the concentration resulting in 50% lethality (LC50) value for F. fimetaria adult mortality was 110 nmol/g (16.4 mg/kg) and the concentration resulting in 50% effect (EC50) value for juvenile production was 65 nmol/g (9.7 mg/kg). Benzyl-GSL proved to be less toxic and consequently an LC50 value for mortality could not be estimated for springtails exposed to benzyl-GSL. For reproduction, an EC50 value was estimated to approximately 690 nmol/g. The study indicates that natural soil concentrations of ITCs may be toxic to beneficial nontarget soil-dwelling arthropods such as springtails.

Antioxidant and pro‐oxidant capacities of ITCs

Isothiocyanates (ITCs) are breakdown products of glucosinolates contained in cruciciferous vegetables. This heterogeneous family of molecules has the -N=C=S group as its common structural feature and possesses important cytoprotective properties. Their biological interactions are strongly related to modulation of cellular redox status, and a number of studies have documented their indirect antioxidant properties, particularly related to induction of phase-2 enzymes. On the other hand, some direct antioxidant behavior has also been observed for a limited number of ITCs. Paradoxically relevant pro-oxidant properties have also been documented, possibly related to the simultaneous induction of phase-1 enzymes. In this review, we will summarize and discuss the prevailing mechanisms for the antioxidant and pro-oxidant activity of ITCs, both in vivo and in vitro.

Glucosinolates and biofumigation: fate of glucosinolates and their hydrolysis products in soil

The bioactive hydrolysis products of glucosinolates, particularly the isothiocyanates, can be used to control soil pests and weeds by incorporating glucosinolate-containing plant material in soil—a practice known as biofumigation. The fate of glucosinolates and their hydrolysis products in soil determines both the efficacy and environmental impact of biofumigation. Knowledge of the processes by which these compounds are sorbed, degraded or otherwise lost from the soil is fundamental to developing effective, but environmentally benign biofumigation strategies. Effective biofumigation relies on maximum hydrolysis of the glucosinolate in the plant tissue to generate high isothiocyanate concentrations in the soil after incorporation. This is favoured by maximum cell disruption, by addition of water, and a high soil temperature. Residual glucosinolates are very weakly sorbed, readily leached and are microbially degraded and mineralised in soil. In contrast, isothiocyanates are strongly sorbed by the organic matter in soil, react strongly with nucleophilic groups present in soil, and are prone to volatilization losses in addition to microbial degradation and mineralisation. These loss processes are influenced by soil type, water content and temperature. Using appropriate incorporation strategies, sufficiently high isothiocyanate concentrations (>100 nmol g−1) can be achieved in soil using biofumigation for effective suppression of susceptible pests. The relatively rapid sorption and degradation of the isothiocyanates in the period of days after incorporation minimizes the risks of persistence in the environment or leaching. Biofumigation is therefore a promising technique which can be further developed to form part of IPM (Integrated Pest Management) strategies to reduce reliance on synthetic pesticides with minimal unintended impacts on the environment.

Identification, Synthesis, and Enzymology of Non‐natural Glucosinolate Chemopreventive Candidates

Isothiocyanates (ITCs) are one of the many classes of breakdown products of glucosinolates found in crucifers such as broccoli and are thought to be partially responsible for the reduced risk of degenerative diseases associated with the consumption of vegetables. The production of ITCs such as L-sulforaphane is dependent on the hydrolytic bioactivities of myrosinase, localized both within vegetable tissues and within flora of the human GI tract, and is associated with important cancer chemopreventive activities. We hypothesized that novel isothiocyanates with enhanced chemopreventive properties relative to L-sulforaphane could be identified and that their glucosinolate precursors could be synthesized. From a library of 30 synthetic ITCs, we identified several with bioactivities equal or superior to those of L-sulforaphane. The corresponding non-natural glucosinolate precursors to these novel ITCs were constructed and found to be substrates for myrosinase. By utilizing a novel RP-HPLC assay to monitor myrosinase-dependent hydrolysis reactions, 2,2-diphenylethyl glucosinolate and (biphenyl-2-yl)methyl glucosinolate were shown to exhibit 26.5 and 2.8 %, respectively, of the relative activity of sinigrin and produced their corresponding ITCs in varying yields. These data support the notion that non-natural glucosinolates can act as prodrugs for novel ITCs, with a mechanism of action reliant on their hydrolytic cleavage by myrosinase. Such non-natural glucosinolates may serve as very economical chemopreventive agents for individuals at risk for cancers of and around the GI tract.

Influence of cabbage processing methods and prebiotic manipulationof colonic microflora on glucosinolate breakdown in man

Glucosinolate consumption from brassica vegetables has been implicated in reduction of cancer risk. The isothiocyanate breakdown products of glucosinolates appear to be particularly important as chemoprotective agents. Before consumption, brassica vegetables are generally cooked, causing the plant enzyme, myrosinase, to be denatured, influencing the profile of glucosinolate breakdown products produced. Some human intestinal microflora species show myrosinase-like activity (e.g. bifidobacteria). We aimed to increase bifidobacteria by offering a prebiotic (inulin) in a randomised crossover study. Six volunteers consumed inulin (10 g/d) for 21 d followed by a 21 d control period (no inulin). Treatment periods were reversed for the remaining six volunteers. During the last 5 d of each period two cabbage-containing meals were consumed. Total urine output was collected for 24 h following each meal. Cabbage was microwaved for 2 min (lightly cooked) or 5.5 min (fully cooked). Faecal samples were collected at the start and after the inulin and control treatments. Bifidobacteria were enumerated by real-time PCR. Allyl isothiocyanate production was quantified by measuring urinary excretion of allyl mercapturic acid (AMA). Bifidobacteria increased following prebiotic supplementation (P < 0.001) but there was no impact of this increase on AMA excretion. AMA excretion was greater following consumption of lightly cooked cabbage irrespective of prebiotic treatment (P < 0.001). In conclusion, the most effective way to increase isothiocyanate production may be to limit the length of time that brassica vegetables are cooked prior to consumption.

Distribution of glucosinolates in some raw and processedBrassicavegetables grown in Croatia

The interest in food with chemoprotective properties has been steadily increasing due to many epidemiological studies indicating the lower probability of acquiring some kinds of cancer (e.g. colon, prostate, breast, cervical) in populations, whose diet includes large quantities of Brassica vegetables. The biologically active compounds in Brassica vegetables are the breakdown products of glucosinolates, including isothiocyanates, nitriles, thiocyanates, indoles and oxazolidinethiones from which indoles and isothiocyanates in particular have been implicated to have anticarcinogenic properties. The object of the present study was to investigate glucosinolates distribution as well as their losses during blanching and cooking in edible parts of white cabbage, cauliflower, kohlrabi and collard. In all vegetable, only indole glucosinolates as precursors of anticarcinogenic compounds were identified, while glucoraphane was not detected. In cauliflower and collard, proportion of indole glucosinolates was more then 90%, followed by kohlrabi (>70%) and white cabbage (>50%). Analysis of glucosinolates losses during blanching and cooking showed substantial decrease in all vegetables. The major losses were observed for cauliflower, around 60%, for cooked vegetable, followed by white cabbage (55%), kohlrabi (53%) and collard (44%). The losses after blanching were approximately 15% less then in cooked vegetables.

Effect of cooking brassica vegetables on the subsequent hydrolysis and metabolic fate of glucosinolates

The protective effects of brassica vegetables against cancer may be partly related to their glucosinolate content. Glucosinolates are hydrolysed by plant myrosinase following damage of plant tissue. Isothiocyanates are one of the main groups of metabolites of glucosinolates and are implicated in the preventive effect against cancer. During cooking of brassica the glucosinolate-myrosinase system may be modified as a result of inactivation of plant myrosinase, loss of enzymic cofactors such as epithiospecifier protein, thermal breakdown and/or leaching of glucosinolates and their metabolites or volatilisation of metabolites. Cooking brassica affects the site of release of breakdown products of glucosinolates, which is the upper gastrointestinal tract following consumption of raw brassica containing active plant myrosinase. After consumption of cooked brassica devoid of plant myrosinase glucosinolates are hydrolysed in the colon under the action of the resident microflora. Feeding trials with human subjects have shown that hydrolysis of glucosinolates and absorption of isothiocyanates are greater following ingestion of raw brassica with active plant myrosinase than after consumption of the cooked plant with denatured myrosinase. The digestive fate of glucosinolates may be further influenced by the extent of cell rupture during ingestion, gastrointestinal transit time, meal composition, individual genotype and differences in colonic microflora. These sources of variation may partly explain the weak epidemiological evidence relating consumption of brassica to prevention against cancer. An understanding of the biochemical changes occurring during cooking and ingestion of brassica may help in the design of more robust epidemiological studies to better evaluate the protective effects of brassica against cancer.

Cyanide in the Chemical Arsenal of Garlic Mustard, Alliaria petiolata

Cyanide production has been reported from over 2500 plant species, including some members of the Brassicaceae. We report that the important invasive plant, Alliaria petiolata, produces levels of cyanide in its tissues that can reach 100 ppm fresh weight (FW), a level considered toxic to many vertebrates. In a comparative study, levels of cyanide in leaves of young first-year plants were 25 times higher than in leaves of young Arabidopsis thaliana plants and over 150 times higher than in leaves of young Brassica kaber, B. rapa, and B. napus. In first-year plants, cyanide levels were highest in young leaves of seedlings and declined with leaf age on individual plants. Leaves of young plants infested with green peach aphids (Myzus persicae) produced just over half as much cyanide as leaves of healthy plants, suggesting that aphid feeding led to loss of cyanide from intact tissues before analysis, or that aphid feeding inhibited cyanide precursor production. In a developmental study, levels of cyanide in the youngest and oldest leaf of young garlic mustard plants were four times lower than in the youngest and oldest leaf of young Sorghum sudanense (cv. Cadan 97) plants, but cyanide levels did not decline in these leaves with plant age as in S. sudanense. Different populations of garlic mustard varied moderately in the constitutive and inducible expression of cyanide in leaves, but no populations studied were acyanogenic. Although cyanide production could result from breakdown products of glucosinolates, no cyanide was detected in vitro from decomposition of sinigrin, the major glucosinolate of garlic mustard. These studies indicate that cyanide produced from an as yet unidentified cyanogenic compound is a part of the battery of chemical defenses expressed by garlic mustard.

Association between Consumption of Cruciferous Vegetables and Condiments and Excretion in Urine of Isothiocyanate Mercapturic Acids

A high intake of cruciferous vegetables is associated with a reduced risk of cancer and cardiovascular diseases. This protective effect has been linked to isothiocyanates, enzymatic hydrolysis products of glucosinolates. In this study, the metabolic fate of glucosinolates and isothiocyanates after ingestion of 19 different cruciferous vegetables was studied in three male subjects. After the consumption of 13 cruciferous vegetables (glucosinolate content, 0.01-0.94 mmol/kg) and six condiments (isothiocyanate content, 0.06-49.3 mmol/kg), eight different isothiocyanate mercapturic acids were determined in urine samples. Excretion levels after the consumption of raw vegetables and condiments were higher (bioavailability, 8.2-113%) as compared to cooked vegetables (bioavailability, 1.8-43%), but the excretion rate was similar (t1/2=2.1-3.9 h). Isothiocyanates in urine remain longer at a nonzero level after the consumption of glucosinolates from cooked vegetables, as compared to raw vegetables and condiments, and maximal levels in urine were reached about 4 h later. Isothiocyanate mercapturic acids can be used as a biomarker to reflect the active dose of isothiocyanates absorbed.

PRE-HARVEST EFFECTS ON NATURALLY OCCURRED ISOTHIOCYANATES (ITCS) OF CRUCIFEROUS SPROUTS

An anticarcinogenic property of crucifers has been elucidating. Cruciferous vegetables contain glucosinolates. When raw crucifers are grated, chewed or chopped, glucosinolates come into contact with endogenous myrosinase (thioglucoside glucohydrolase EC 3:2:3:1), and isothiocyanates (ITCs), nitriles, etc are released as the breakdown products of glucosinolates. ITCs are responsible for the protection from carcinogen. 4-Methylsulfinylbutyl ITC (L-sulforaphane) of broccoli sprouts is famous for strongly inducing phase 2 detoxication enzymes. 4-Methylthio-3-butenyl ITC (MTB-ITC) of Japanese radish sprouts called kaiware-daikon in Japan has also an anticarcinogenic property. Therefore, preharvest effects on naturally occurred both ITCs content were researched.[...]

Characterisation of recombinant epithiospecifier protein and its over-expression in Arabidopsis thaliana

Epithiospecifier protein (ESP) is a protein that catalyses formation of epithionitriles during glucosinolate hydrolysis. In vitro assays with a recombinant ESP showed that the formation of epithionitriles from alkenylglucosinolates is ESP and ferrous ion dependent. Nitrile formation in vitro however does not require ESP but only the presence of Fe(II) and myrosinase. Ectopic expression of ESP in Arabidopsis thaliana Col-5 under control of the strong viral CaMV 35S promoter altered the glucosinolate product profile from isothiocyanates towards the corresponding nitriles.

Effect of common Brassica vegetables (Brussels sprouts and red cabbage) on the development of preneoplastic lesions induced by 2-amino-3-methylimidazo[4,5- f]quinoline (IQ) in liver and colon of Fischer 344 rats

Aim of the present study was the investigation of effects of juices from commonly consumed Brassica vegetables (two cultivars of Brussels sprouts and two cultivars of red cabbage) on formation and development of preneoplastic lesions in colons (aberrant crypt foci, ACF) and livers (glutathione- S-transferase placental form, GST-P +) in male F344 rats. The foci were induced by 2-amino-3-methylimidazo[4,5- f]quinoline (IQ), a widespread carcinogenic heterocyclic aromatic amine which is found in fried meats. Recently, we reported on pronounced protective effects in the two-organ foci model when the vegetable juices were given during the carcinogen treatment but several findings by other groups indicated that breakdown products of glucosinolates contained in Brassica vegetables cause tumour promotion in various organs of laboratory rodents. In the present study, the animals received the juices in the drinking water (5%) over a period of 20 days after treatment with IQ (100 mg/kg bw on 10 alternate days). To increase the foci yield (which facilitates the detection of modifying effects), the animals were fed with a modified (high fat, fibre free) AIN-76 diet. With exception of the sprout variety “Cyrus”, all juices lowered the number of GST-P + foci as well as the foci area in the liver, but none of these effects was statistically significant. In the colon, none of the juices had an impact on crypt multiplicity (number of crypts/focus), whereas the number of ACF was decreased; only with the sprout variety Maximus the protective effect was significant (reduction 49%). The present findings show that administration of vegetable juices to the animals after the carcinogen does not increase the number and size of IQ-induced preneoplastic lesions in liver and colon.

A Sensory Profile of Turnip Greens as Affected by Variety and Maturity

ABSTRACT: Turnip greens, a Brassica, are characterized by a sulfurous aroma, pungent flavor, and a bitter taste due to isothiocyanates, degradation products of glucosinolates. This study examined the sensory characteristics and preference of turnip greens as affected by variety and maturity. A descriptive analysis panel characterized 16 aromas, flavors, and tastes. The intensity of mustard oil/mustard green aroma and flavor and bitterness was significantly affected (P &lt; 0.05) by variety. Mustard oil/mustard green aroma and flavor, bitterness, and bitter aftertaste increased significantly (P &lt; 0.05) with maturity. Seven Top was preferred significantly (P &lt; 0.05) less than the remaining varieties and as the greens matured, preference decreased.

The role of glucosinolates of Brassica genus in the crop system

Glucosinolates with Brassica genus as secondary metabolites have a&amp;nbsp;lot of functions and effects. Glucosinolates form less than 2% of the overall sulphur content at the beginning of vegetation in different parts of the plants and during growth their content is decreasing and forms less than 0.1%. This low representation doubts their storage function. With its chemical composition, they are ranked among natural pesticides with active and passive resistance against diseases and pests. They show repellent effects and properties of natural biofumigators in soil after ploughing in their biomass as green fertilizing, or after ploughing in after harvest the leftovers of rape. The principle of these effects is decomposition products of glucosinolates &amp;ndash; bioactive isothiocyanates. Very important from this point of view are turnip rape Rex and Brassica juncea, whose content of these compounds is the highest one and they are resistant against the attack of Ceutorrhynchus pleurostigma. The same effect showed also when attacked by Phoma lingam. With other winter Brassicas either hybrid or linea and summer rape is this defensive system suppressed because of their lowered content due to breeding interferences, leading to limitation of their anti-nutritional negative effects. It is possible to state the final result after finding out the production of the above matter, roots, and after evaluation of the sorbal characteristics of the soil and evaluation of the state of health of the following crop or vegetable. After this overall analysis, it will be possible to evaluate the biofumigation properties of accessible varieties of the Brassica genus.

The Cruciferous Nitrile Crambene Has Bioactivity Similar to Sulforaphane When Administered to Fischer 344 Rats but Is Far Less Potent in Cell Culture

The anticarcinogenic properties of broccoli are believed to be due to modification of detoxification enzymes by a group of isothiocyanates, hydrolysis products of glucosinolates, particularly sulforaphane. We previously showed that the nitrile crambene (1-cyano-2-hydroxy-3-butene), present in most Brassica vegetables, induces hepatic quinone reductase activity when administered to rats. In this study, we compared the effects of seven daily oral doses of crambene (50 mg/kg rat/day) and sulforaphane (50 mg/kg rat/day) on induction of hepatic quinone reductase activity in Fischer 344 rats. The two treatments produced similar effects, with crambene and sulforaphane producing 1.5- and 1.7-fold induction in hepatic quinone reductase activity, respectively. Additionally, we evaluated the effect of crambene on quinone reductase activity in Hepa 1c1c7 cells, because this system had been shown to possess high sensitivity to sulforaphane and is commonly used for screening anticarcinogenic compounds. Crambene (5 mM) induced quinone reductase activity and caused cell cycle arrest in the Gsub2;/M phase in mouse Hepa 1c1c7 cells, rat H4IIEC3 cells, and human Hep G2 cells (>95% viability). Doses of crambene needed for induction of quinone reductase in cell culture were ~100-fold greater than effective doses of sulforaphane. These findings indicate that hepatoma cell lines may not accurately reflect relative potency of anticarcinogens in Fischer 344 rats.

Cloning and functional expression of two plant thiol methyltransferases: a new class of enzymes involved in the biosynthesis of sulfur volatiles.

Glucosinolates are defensive compounds found in several plant families. We recently described five distinct isoforms of a novel plant enzyme, thiol methyltransferase (TMT), which methylate the hydrolysis products of glucosinolates to volatile sulfur compounds that have putative anti-insect and anti-pathogen roles. In the work presented here, two cDNAs encoding these enzymes (cTMT1 and cTMT2) were isolated by screening a cabbage cDNA library with an Arabidopsis EST showing high sequence homology to one TMT isoform. The genomic clone of cTMT1 was subsequently amplified by PCR. Both cDNAs encoded polypeptides of identical lengths (227 amino acids) and similar predicted masses (ca. 25 kDa), but differing in 13 residues. The cDNAs contained the typical methyltransferase signatures, but were otherwise distinct from conventionally known N-, O- or S-methyltransferases. A chloride methyl transferase was the only gene with an assigned function that shared significant similarity with the TMT cDNAs. Southern analysis indicated single copy for each TMT gene. The two cDNAs were expressed in Escherichia coli. The substrate range, kinetic properties and molecular sizes of the purified recombinant proteins were comparable to those of the native enzyme. These data, together with the detection of the sequenced amino acid motif of one native TMT peptide in the cDNAs, confirmed that the latter were authentic TMTs. The expression pattern of the TMTs in various cabbage tissues was consistent with their association with glucosinolates. The cloning of this new class of plant genes furnishes crucial molecular tools to understand the role of this metabolic sector in plant defenses against biotic stress.

Glucosinolate breakdown products as insect fumigants and their effect on carbon dioxide emission of insects

BackgroundGlucosinolate breakdown products are volatile, therefore good candidates for insect fumigants. However, although they are insecticidal, the mode of action of such natural products is not clear. We studied the insecticidal effect of these compounds as fumigants, and monitored the production of carbon dioxide by the insects as a probe to the understanding of their mode of action.ResultsThe fumigation 24-h LC50 against the house fly (Musca domestica L.) of allyl thiocyanate, allyl isothiocyanate, allyl cyanide, and l-cyano-2-hydroxy-3-butene was 0.1, 0.13, 3.66, and 6.2 μg cm-3, respectively; they were 0.55, 1.57, 2.8, and > 19.60 μg cm-3, respectively, against the lesser grain borer (Rhyzopertha dominica Fabricius). The fumigation toxicity of some of the glucosinolate products was very close to or better than that of the commercial insect fumigants such as chloropicrin (LC50: 0.08 and 1.3 μg cm-3 against M. domestica and R. dominica, respectively) and dichlorovos (LC50: < 0.02 and 0.29 μg cm-3 against M. domestica and R. dominica, respectively) in our laboratory tests. Significantly increased CO2 expiration was found in insects exposed to the vapor of allyl isothiocyanate, allyl thiocyanate and allyl isocyanate. Allyl isothiocyanate was also found to increase the CO2 expiration of the American cockroach (Periplaneta americana L.).ConclusionsGlucosinolate breakdown products have potential as biodegradable and safe insect fumigants. They may act on the insect respiratory system in their mode of action.

Effects of cruciferous vegetables and their constituents on drug metabolizing enzymes involved in the bioactivation of DNA-reactive dietary carcinogens

Epidemiological studies give evidence that cruciferous vegetables (CF) protect humans against cancer, and also results from animal experiments show that they reduce chemically induced tumor formation. These properties have been attributed to alterations in the metabolism of carcinogens by breakdown products of glucosinolates, which are constituents of CF. The present article gives an overview on the present state of knowledge on the impact of CF and their constituents on enzymes that are involved in the metabolism of DNA-reactive carcinogens. The development of in vitro models with metabolically competent cell lines led to the detection of potent enzyme inducers contained in CF such as sulforaphane. Recently, we showed that Brassica juices induce glutathione- S-transferases (GST) and cytochrome P-450 1A2 in human hepatoma cells (HepG2) and protect against the genotoxic effects of B(a)P and other carcinogens. Earlier in vivo experiments with rodents indicated that indoles and isothiocyanates, two major groups of glucosinolate breakdown products, attenuate the effects of polycyclic aromatic hydrocarbons (PAHs) and nitrosamines via induction of GST and inhibition of cytochrome-P450 isoenzymes, respectively. Our own investigations showed that CF are also protective towards heterocyclic amines (HAs): Brussels sprouts- and garden cress juices attenuated IQ-induced DNA-damage and preneoplastic lesions in colon and liver of rats. These effects were paralleled by induction of uridine-di-phospho-glucuronosyl transferase (UDPGT) which is very probably the mechanism of protection against HAs by cruciferous vegetables. There is also evidence that consumption of CF might protect humans against cancer. In matched control intervention studies with these vegetables, it was shown that they induce GST-activities in humans but overall, results were inconclusive. Recently, we carried out crossover intervention studies and found pronounced GST-induction upon consumption of Brussels sprouts and red cabbage, whereas no effects were seen with white cabbage and broccoli. Furthermore, we found that the isoenzyme induced was GST-π which plays an important role in protection against breast, bladder, colon and testicular cancer. No induction of the GST-α isoform could be detected. Urinary mutagenicity experiments gave further evidence that CF affect drug metabolism in humans. Consumption of red cabbage led to changes in the pattern of meat-derived urinary mutagenicity. Overall, CF are among the most promising chemopreventive dietary constituents and further elucidation of their protective mechanisms and the identification of active constituents may contribute to the development of highly protective Brassica varieties.