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We prepared a detoxified rapeseed protein isolate (RPI) by phytase/ethanol treatment based on alkaline extraction and acidic precipitation. Contents of protein, fat, ash, moisture, crude fiber, glucosinolates, phytic acid, and phenolics and color were determined. To evaluate the safety of detoxified RPI, five groups of C57 mice (detoxified RPI [10 and 20 g kg -1 ]; commercial soybean protein isolate (SPI) [10 g kg -1 ]; non-detoxified RPI [10 g kg -1 ]; control) were used in the acute-toxicity test. Bodyweight and pathology parameters were recorded at different time points, followed by macroscopic examination, organ-weight measurement and microstructure examination. After pretreatment of rapeseed meals with phytase (enzyme : substrate ratio, 1 : 5 mg g -1 ) for 1.5 h and two-time ethanol extraction for precipitated protein, the chemical characteristics in RPI were protein (88.26%), fat (0.57%), ash (2.72%), moisture (1.90%), crude fiber (0.77%), glucosinolates (0 μmol g -1 ), phytic acid (0.17%), phenolics (0.36%) and whiteness (73.38). Treatment resulted in significant removal of anti-nutritional factors (ANFs) and increased whiteness in detoxified RPI compared with non-detoxified RPI, and lower than in cruciferin-rich canola protein isolate (Puratein®). Experimental-related effects on bodyweight, clinical observations, or clinicopathology, in mice treated with detoxified RPI were not observed except for a decreased thyroid gland/parathyroid gland index in mice treated with non-detoxified RPI. Furthermore, the no-observed-effect level (NOEL) was 10 g kg -1 of detoxified RPI, whereas the no-observed-adverse-effect-level (NOAEL) was the highest fed level of 20 g kg -1 of detoxified RPI. Overall, detoxified RPI prepared by the combined treatment of phytase and ethanol was considered safe under the conditions tested, in which the contents of the main ANFs were reduced significantly.

Zinc oxide nanoparticles (ZnO NPs) are widely used to manufacture textile fibers, synthetic rubber, and paint. However, crop yields and quality are threatened by the increased use of metallic NPs in industry, which has resulted in their accumulation in agricultural land. Many studies have shown that plants defend against biotic and abiotic stresses through the activities of metabolites and hormones. However, whether glucosinolates (GSs) are involved in plant responses to ZnO NP-related stress remains unknown. In this study, wild-type (WT) and GS mutant (myb28/29 and cyp79B2/B3) Arabidopsis plants were subjected to ZnO NP stress to address this question. Our results showed that exposure to ZnO NPs promoted GS accumulation and induced the relative messenger RNA (mRNA) expression levels of GS biosynthesis-related genes. Moreover, ZnO NP treatment adversely affected root length, the number of lateral roots, chlorophyll contents, and plant biomass. Importantly, our results showed that root growth, chlorophyll contents, and plant biomass were all decreased in the GS mutants compared with those in WT plants. Overall, our results showed that WT plants tolerated ZnO NP-induced stress more efficiently than the GS mutants, suggesting that GSs are involved in plant resistance to ZnO NP-induced toxicity.

In the past few decades, there has been a lot of interest in plant constituents for their antioxidant, anti-inflammatory, anti-microbial and anti-proliferative properties. However, concerns have been raised on their potential toxic effects particularly when consumed at high dose. The anti-thyroid effects of some plant constituents have been known for some time. Indeed, epidemiological observations have shown the causal association between staple food based on brassicaceae or soybeans and the development of goiter and/or hypothyroidism. Herein, we review the main plant constituents that interfere with normal thyroid function such as cyanogenic glucosides, polyphenols, phenolic acids, and alkaloids. In detail, we summarize the in vitro and in vivo studies present in the literature, focusing on the compounds that are more abundant in foods or that are available as dietary supplements. We highlight the mechanism of action of these compounds on thyroid cells by giving a particular emphasis to the experimental studies that can be significant for human health. Furthermore, we reveal that the anti-thyroid effects of these plant constituents are clinically evident only when they are consumed in very large amounts or when their ingestion is associated with other conditions that impair thyroid function., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Cattle occasionally develop brassica-associated liver disease (BALD) and photosensitisation when grazing turnip or swede ( Brassica spp.) forage crops. The liver toxin in these brassica varieties has yet to be discovered. Progoitrin is the dominant glucosinolate in incriminated crops. Apart from goitrin, progoitrin hydrolysis yields the nitrile, 1-cyano-2-hydroxy-3-butene (CHB), and the epithionitrile, 1-cyano-2-hydroxy-3,4-epithiobutane (CHEB). The two compounds were custom-synthesised. In a small pilot trial, New Zealand White rabbits were given either CHB or CHEB by gavage. Single doses of 0.75 mmol/kg of CHB or 0.25 mmol/kg of CHEB were subtoxic and elicited subclinical effects. Higher doses were severely hepatotoxic, causing periportal to massive hepatic necrosis associated with markedly elevated serum liver biomarkers often resulting in severe illness or death within 24 h. The possibility that one or both of these hepatotoxic nitriles causes BALD in cattle requires further investigation.

A study was conducted to determine effects of reducing hindgut pH through dietary inclusion of high-amylose cornstarch (HA-starch) on growth performance, organ weights relative to live body weight (BW), blood thyroid hormone levels, and glucosinolate degradation products of nursery pigs fed cold-pressed canola cake (CPCC). A total of 240 pigs (initial BW: 7.1 kg), which had been weaned at 21 d of age, were housed in 40 pens (6 pigs per pen) and fed 4 diets (10 pens per diet) in a randomized complete block design for 28 d. Four diets were a basal diet with CPCC at 0 or 40%, and with HA-starch at 0 or 40% in a 2 × 2 factorial arrangement. The diets were fed in two phases: Phase 1 from day 0 to 14 and Phase 2 from day 14 to 28 and were formulated to have the same net energy, standardized ileal digestible AA, Ca, and standardized total tract digestible P contents. Dietary inclusion of CPCC and HA-starch was achieved by a partial or complete replacement of corn, soybean meal, and soy protein. At the end of the study, one pig from each pen was euthanized to determine organ weights, blood parameters, hindgut pH, and glucosinolate degradation products. Dietary CPCC reduced (P < 0.05) overall average daily gain (ADG) by 15%; increased (P < 0.05) relative weights of liver and thyroid gland by 27% and 64%, respectively; and reduced (P < 0.05) serum tetraiodothyronine (T4) level from 30.3 to 17.8 ng/mL. Heart, kidney, and gastrointestinal tract weights; serum triiodothyronine level; and hindgut pH of pigs were unaffected by dietary CPCC. Dietary HA-starch reduced (P < 0.05) overall ADG, relative weight of thyroid gland, cecal, and colonic pH; but increased (P < 0.05) relative weight of colon; tended to increase (P = 0.062) serum T4 level. Dietary CPCC and HA-starch interacted (P = 0.024) on relative weight of thyroid gland such that dietary CPCC increased (P < 0.05) weight of thyroid gland for HA-starch-free diet (120 vs. 197 mg/kg of BW) but not for HA-starch-containing diet (104 vs. 130 mg/kg of BW). Dietary CPCC and HA-starch interacted (P = 0.001) on cecal isothiocyanate content such that dietary CPCC increased (P < 0.05) level of isothiocyanates for HA-starch-containing diet but not for HA-starch-free diet. In conclusion, dietary CPCC reduced growth performance, increased liver, size and interfered with thyroid gland functions of pigs. However, the negative effects of dietary CPCC on thyroid gland functions of nursery pigs were alleviated by dietary HA-starch., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Toxins and nutrients interact and define herbivores' experiences with toxic plants. However, there are still open questions about the mechanisms by which nutrient-toxin interactions affect experience and as a consequence foraging decisions by consumers. This study provides a deeper insight into such mechanisms by using supplemental nutrients, a toxic plant typically avoided by herbivores (wild rocket; Diplotaxis tenuifolia), and a small ruminant (sheep; Ovis aries) as models. Thirty-six sheep were randomly assigned to four treatments (n=9) where animals consumed: wild rocket ("DT"), wild rocket followed by a protein supplement ("DT+P"), wild rocket followed by a protein supplement+a mineral supplement containing iodine and copper ("DT+P+M"), or alfalfa pellets in amounts that paired the ingestion of wild rocket by DT ("CTRL"). Towards the end of the phase of exposure (day 35), DT showed the lowest intake of wild rocket, as well as reduced levels of plasma thyroid hormones (T3 and T4), alanine aminotransferase, and a trend towards reduced hemoglobin relative to DT+P and DT+P+M. Total concentration of serum proteins and albumins were greater in sheep fed the protein supplements, which have probably elicited a protective effect on toxin ingestion. Foraging behavior was then evaluated in an experimental arena where animals could select among randomly distributed buckets containing a fixed amount of wild rocket or variable amounts of barley grain (a preferred food). Regardless of barley grain availability, DT showed lower intake and lower times spent eating wild rocket than DT+P and DT+P+M. Unexpectedly, CTRL (without previous experience with wild rocket) ingested amounts of wild rocket comparable to those observed by DT+P and DT+P+M. A negative feeding experience with wild rocket is needed for animals to display the typical pattern of aversion commonly observed in grazing conditions., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The vast number of plant secondary metabolites (PSMs) produced by higher plants has generated many efforts to exploit their potential for pest control. We performed a systematic literature search to retrieve relevant publications, and we evaluated these according to PSM groups to derive information about the potential for developing plant-derived rodent repellents. We screened a total of 54 publications where different compounds or plants were tested regarding rodent behavior/metabolism. In the search for widely applicable products, we recommend multi-species systematic screening of PSMs, especially from the essential oil and terpenoid group, as laboratory experiments have uniformly shown the strongest effects across species. Other groups of compounds might be more suitable for the management of species-specific or sex-specific issues, as the effects of some compounds on particular rodent target species or sex might not be present in non-target species or in both sexes. Although plant metabolites have potential as a tool for ecologically-based rodent management, this review demonstrates inconsistent success across laboratory, enclosure, and field studies, which ultimately has lead to a small number of currently registered PSM-based rodent repellents.

Glucosinolates are activated plant defenses common in the order Brassicales that release isothiocyanates (ITCs) and other hydrolysis products upon tissue damage. The reactive ITCs are toxic to insects resulting in reduced growth, delayed development and occasionally mortality. Generalist lepidopteran larvae often detoxify ingested ITCs via conjugation to glutathione (GSH) and survive on low glucosinolate diets, but it is not known how this process influences other aspects of metabolism. We investigated the impact of the aliphatic 4-methylsulfinylbutyl-ITC (4msob-ITC, sulforaphane) on the metabolism of Spodoptera littoralis larvae, which suffer a significant growth decline on 4msob-ITC-containing diets while excreting ITC-glutathione conjugates and their derivatives in the frass. The most striking effects were a decrease of GSH in midgut tissue and hemolymph due to losses by conjugation to ITC during detoxification, and a decline of the GSH biosynthetic precursor cysteine. Protein content was likewise reduced by ITC treatment suggesting that protein is actively catabolized in an attempt to supply cysteine for GSH biosynthesis. The negative growth and protein effects were relieved by dietary supplementation with cystine. Other consequences of protein breakdown included deamination of amino acids with increased excretion of uric acid and elevated lipid content. Thus metabolic detoxification of ITCs provokes a cascade of negative effects on insects that result in reduced fitness., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Turnip (Brassica rapa ssp. rapa) and rape (Brassica napus ssp. biennis) and other brassica forage crops are regarded as "safe" feed for cattle during late summer and fall in the North Island of New Zealand when high Pithomyces chartarum spore counts in pastures frequently lead to sporidesmin toxicity (facial eczema). Sporadic acute severe cases of turnip photosensitization in dairy cows characteristically exhibit high γ-glutamyl transferase and glutamate dehydrogenase serum enzyme activities that mimic those seen in facial eczema. The two diseases can, however, be distinguished by histopathology of the liver, where lesions, in particular those affecting small bile ducts, differ. To date, the hepato-/cholangiotoxic phytochemical causing liver damage in turnip photosensitization in cattle is unknown. Of the hydrolysis products of the various glucosinolate secondary compounds found in high concentrations in turnip and rape, work has shown that nitriles and epithionitriles can be hepatotoxic (and nephro- or pancreatotoxic) in rats. These derivatives include β-hydroxy-thiiranepropanenitrile and 3-hydroxy-4-pentenenitrile from progoitrin; thiiranepropanenitrile and 4-pentenenitrile from gluconapin; thiiranebutanenitrile and 5-hexenenitrile from glucobrassicanapin; phenyl-3-propanenitrile from gluconasturtiin; and indole-3-acetonitrile from glucobrassicin. This perspective explores the possibility of the preferential formation of such derivatives, especially the epithionitriles, in acidic conditions in the bovine rumen, followed by absorption, hepatotoxicity, and secondary photosensitization.

Species diversity in terrestrial ecosystems is influenced by plant defense compounds that alter the behavior, physiology, and host preference of insect herbivores. Although it is established that insects evolved the ability to detoxify specific allelochemicals, the mechanisms by which polyphagous insects cope with toxic compounds in diverse host plants are not well understood. Here, we used defended and non-defended plant genotypes to study how variation in chemical defense affects midgut responses of the lepidopteran herbivore Trichoplusia ni, which is a pest of a wide variety of native and cultivated plants. The genome-wide midgut transcriptional response of T. ni larvae to glucosinolate-based defenses in the crucifer Arabidopsis thaliana was characterized by strong induction of genes encoding Phase I and II detoxification enzymes. In contrast, the response of T. ni to proteinase inhibitors and other jasmonate-regulated defenses in tomato (Solanum lycopersicum) was dominated by changes in the expression of digestive enzymes and, strikingly, concomitant repression of transcripts encoding detoxification enzymes. Unbiased proteomic analyses of T. ni feces demonstrated that tomato defenses remodel the complement of T.ni digestive enzymes, which was associated with increased amounts of serine proteases and decreased lipase protein abundance upon encountering tomato defense chemistry. These collective results indicate that T. ni adjusts its gut physiology to the presence of host plant-specific chemical defenses, and further suggest that plants may exploit this digestive flexibility as a defensive strategy to suppress the production of enzymes that detoxify allelochemicals., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Cruciferous vegetables have the reputation to protect against cancer, an effect attributed to glucosinolates (GLS) and their breakdown products. However, some GLS are mutagenic, an activity associated with cancer initiation rather than chemoprevention. We show that juices from steamed pak choi sprouts are strongly mutagenic in Salmonella typhimurium TA100 upon addition of fresh myrosinase. Growth of the plants in the presence of methyl jasmonate, a hormone eliciting defence factors, led to 20-fold enhanced mutagenic activity. The level of 1-methoxy-3-indolylmethyl (1-MIM)-GLS was similarly increased, whereas those of other GLS were only elevated 0.8- to 3.2-fold. 1-MIM-GLS is a potent mutagen, whose activity is further enhanced by human sulphotransferase 1A1 (hSULT1A1), an activation not observed with other GLS. The mutagenicity of the pak choi juices was increased 20-fold in bacteria expressing hSULT1A1. A tiny level of juice from elicitated sprouts, 0.04% in the mutagenicity assay, was sufficient to double the number of revertants above the spontaneous level. We conclude that pak choi juice is mutagenic, an activity that can be strongly affected by the growth conditions. It is owed essentially to a single component, 1-MIM-GLS. We recommend using cultivars, growth conditions and/or food preparations that keep the level of this GLS congener low., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Glucosinolates are compounds produced by commercial crops which can hydrolyse in a range of natural toxins that may exert detrimental effects on beneficial soil organisms. This study examined the effects of 2-phenylethyl isothiocyanate and 3-phenylpropionitrile on the survival and growth of the woodlouse Porcellio scaber exposed for 28 d. 2-Phenylethyl isothiocyanate dissipated from the soil with half-lives ranging from 19 to 96 h. Exposure through soil showed toxic effects only on survival. The LC50s after 28 d were significantly different at 65.3 mg kg(-1) for 2-phenylethyl isothiocyanate and 155 mg kg(-1) for 3-phenylpropionitrile. A toxicokinetic-toxicodynamic (TKTD) approach, however, revealed that both compounds in fact have very similar effect patterns. The TKTD model was better suited to interpret the survival data than descriptive dose-response analysis (LC(x)), accounting for the fast dissipation of the compounds in the soil. Found effects were within environmentally relevant concentrations. Care should therefore be taken before allowing these natural toxins to enter soil ecosystems in large quantities., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Chemopreventive effects of broccoli, a highly valued vegetable, have been known for a long time. Several studies have demonstrated that broccoli might be beneficial by reducing the risk for the development of certain forms of cancer. These effects are generally attributed to glucosinolate-derived degradation products like isothiocyanates and indoles which are formed by the hydrolytic action of plant myrosinase and/or glucosidases deriving from the human microbial flora. However, recent in vitro and experimental animal studies indicate that broccoli, its extracts and the glucosinolate-derived degradation products might also have undesirable effects, especially genotoxic activities. However, the relevance of the genotoxic activities to human health is not known yet. This paper gives an overview on genotoxic, anti-genotoxic/chemopreventive, nutritive and antinutritive properties of broccoli, its ingredients and their degradation products. A qualitative comparison of the benefit and risk of broccoli consumption benefit-risk assessment shows that the benefit from intake in modest quantities and in processed form outweighs potential risks. For other preparations (fortified broccoli-based dietary supplements, diets with extraordinary high daily intake, consumption as a raw vegetable) further studies both for potential risks and beneficial effects are needed in order to assess the benefit and risk in the future., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

1-Methoxy-3-indolylmethyl (1-MIM) glucosinolate, contained in many Brassica vegetables, is strongly mutagenic in Salmonella typhimurium TA100 when activated by myrosinase. Here, we describe the synthesis and evaluation of two breakdown products, 1-MIM nitrile and 1-MIM alcohol. 1-MIM nitrile was not mutagenic and 1-MIM alcohol showed low direct mutagenicity in TA100, indicating that other breakdown products mediated the mutagenicity of 1-MIM glucosinoate/myrosinase in this strain. However, 1-MIM alcohol was strongly mutagenic to a TA100-derived strain expressing human sulphotransferase SULT1A1. Likewise, 1-MIM glucosinolate (with myrosinase) showed 10 times higher mutagenic activity in TA100-SULT1A1 than in strain TA100. Identical adducts, N(2)-(1-MIM)-dG and N(6)-(1-MIM)-dA, were detected in both strains, but the levels were higher in TA100-hSULT1A1. A similar influence of SULT1A1 was observed in recombinant V79-hSULT1A1 cells compared to parental SULT-deficient Chinese hamster V79 cells. 1-MIM glucosinolate (with myrosinase) as well as 1-MIM alcohol induced sister chromatid exchange in both cell lines, but with clearly higher efficiency in V79-hSULT1A1 cells. Gene mutation assays were conducted at the HPRT locus with 1-MIM alcohol in V79-hSULT1A1 cells, and with 1-MIM glucosinolate/myrosinase in V79 parental cells. In both cases, the result was clearly positive. Thus, 1-MIM glucosinolate is mutagenic in bacterial and mammalian cells via at least two different metabolites., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

Some plants use electrophilic metabolites as a defence against biological enemies. Some of them may react with DNA. We devised a new model to test this hypothesis. Plant tissue was homogenised. After incubation of the homogenate at 37°C for varying periods, the plant DNA was analysed for the presence of adducts using the (32)P-postlabelling technique. Adducts were detected with all Brassicales studied. Broccoli was investigated in detail. Adducts were absent in DNA isolated immediately after homogenisation of the plant. Subsequently, five characteristic adduct spots were formed in the homogenate, the maximum being reached after nearly 4 h. Adduct formation was low when broccoli was steamed before homogenisation, but was re-established when myrosinase was added to the homogenate, indicating that the active constituents were glucosinolates. Broccoli juice was mutagenic to Salmonella typhimurium, forming the same adduct spots in these target cells as in plant homogenate, but the relative intensity of the individual spots varied between both models. The patterns of adduct spots formed in homogenates of 15 other Brassicales species and tissues were similar to those detected with broccoli florets heads. However, the relative intensities of the spots varied. Sporadically, some spots were missing or additional spots appeared. These results, therefore, suggest that several different glucosinolates contribute to the adduct formation.

Scope: Juices from Brassicales are mutagenic in Salmonella typhimurium and characteristic adducts are formed with the endogenous DNA in Brassicales homogenates. These effects require myrosinase activity, suggesting an involvement of breakdown products of glucosinolates (GLs). We aimed to identify GLs congeners producing these effects., Methods and Results: We investigated twelve individual GLs for mutagenicity in S. typhimurium TA104 and TA100 and for adduct formation with herring sperm DNA using the 32P-postlabelling/thin-layer chromatography method. All bacteriotoxic and mutagenic effects observed required the presence of myrosinase. Neoglucobrassicin, 4-methoxyglucobrassicin and sinalbin showed mutagenicity over wide concentration ranges, with neoglucobrassicin being the most potent congener. Six other GLs led to modest increases in the number of revertants in a small concentration range, before toxicity overshadowed this effect. The remaining three GLs showed some toxicity, but no mutagenicity. However, all twelve GLs formed DNA adducts. Clearly the highest adduct levels were detected with the indole GLs tested. They matched the major adduct spots formed in Brassicales homogenates., Conclusion: The observation that GLs are genotoxic demands follow-up studies on possible genotoxic and carcinogenic effects of these common food compounds in animal models and humans. Our study may be used to prioritize the congeners in further studies., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The currently accepted view is that the chemopreventive activity of glucosinolates is exclusively mediated by their degradation products, such as isothiocyanates. In the present study, evidence is presented for the first time that intact glucosinolates can modulate carcinogen-metabolising enzyme systems. The glucosinolates glucoraphanin and glucoerucin were isolated from cruciferous vegetables and incubated with precision-cut rat liver slices. Both glucosinolates elevated the O-dealkylations of methoxy- and ethoxyresorufin, markers for CYP1 activity; supplementation of the incubation medium with myrosinase, the enzyme that converts glucosinolates to their corresponding isothiocyanates, abolished these effects. Moreover, both glucoerucin and glucoraphanin increased the apoprotein levels of microsomal CYP1A1, CYP1A2 and CYP1B1. At higher concentrations, both glucosinolates enhanced quinone reductase activity, whereas glucoraphanin also elevated glutathione S-transferase; in this instance, however, supplementation of the incubation medium with myrosinase exacerbated the inductive effect. Finally, both glucosinolates increased modestly cytosolic quinone reductase, GSTα and GSTμ protein levels, which became more pronounced when myrosinase was added to the incubations with the glucosinolate. It may be inferred that intact glucosinolates can modulate the activity of hepatic carcinogen-metabolising enzyme systems and this is likely to impact on the chemopreventive activity linked to cruciferous vegetable consumption., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

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., (Copyright 2009 SETAC.)

Invasive plants are by definition excellent competitors, either indirectly through competition for resources or directly through allelopathic inhibition of neighboring plants. Although both forms of competition are commonly studied, attempts to explore the interactions between direct and indirect competition are rare. We monitored the effects of several doses of extracts of Alliaria petiolata, a Eurasian invader in North America, on the growth of Impatiens pallida, a North American native, at several planting densities. The density-dependent phytotoxicity model predicts that as plant density increases, individual plant size will decrease, unless a toxin is present in the soil. In this case, individual plant size is predicted to increase as plant density increases, as plants share a limited toxin dose. We tested this model using fractions of an A. petiolata extract enriched in flavonoids or glucosinolates, as well as a combined fraction. The flavonoid-enriched fraction and the combined fraction suppressed I. pallida growth but only when applied at a dose eight times higher than that expected in the field. When treated with a dose equivalent to estimated field exposure levels, I. pallida growth was not distinguishable from that of control plants that received no extract, showing that indirect competition for resources was more important for determining the growth of I. pallida than direct allelopathic inhibition by A. petiolata. This is an important reminder that, even though many plants have the demonstrated potential to exert strong allelopathic effects, those effects may not always be apparent when other forms of competition are considered as well.

Desert locusts (Schistocerca gregaria) occasionally feed on Schouwia purpurea, a plant that contains tenfold higher levels of glucosinolates than most other Brassicaceae. Whereas this unusually high level of glucosinolates is expected to be toxic and/or deterrent to most insects, locusts feed on the plant with no apparent ill effects. In this paper, we demonstrate that the desert locust, like larvae of the diamondback moth (Plutella xylostella), possesses a glucosinolate sulfatase in the gut that hydrolyzes glucosinolates to their corresponding desulfonated forms. These are no longer susceptible to cleavage by myrosinase, thus eliminating the formation of toxic glucosinolate hydrolysis products. Sulfatase is found throughout the desert locust gut and can catalyze the hydrolysis of all of the glucosinolates present in S. purpurea. The enzyme was detected in all larval stages of locusts as well as in both male and female adults feeding on this plant species. Glucosinolate sulfatase activity is induced tenfold when locusts are fed S. purpurea after being maintained on a glucosinolate-free diet, and activity declines when glucosinolates are removed from the locust diet. A detoxification system that is sensitive to the dietary levels of a plant toxin may minimize the physiological costs of toxin processing, especially for a generalist insect herbivore that encounters large variations in plant defense metabolites while feeding on different species.

Secondary plant metabolites (allelochemicals) play a major role in plant-insect interactions. Glucosinolates (GLS) and their degradation products from Brassica species are attractants and feeding stimulants for Brassicaceae specialist insects but are generally repellent and toxic for generalist herbivores. The impact of these compounds on crucifer specialist insects are well known but their effect on generalist predators is still not well documented. Prey host plant influence on reproduction of an aphidophagous beneficial, the two spot ladybird, was determined using the cabbage aphid, Brevicoryne brassicae reared on a crucifer plant, namely Brassica napus containing low GLS levels. As ladybird developmental and reproductive parameters were already shown to be strongly affected by the allelochemical presence in its preys, the unsuitable aphid and host plant combination was only momentary used to feed the A. bipunctata adults. A strong impact of the diet was observed on the beetle fecundity and the emerging offspring. Changing B. brassicae aphid to a suitable prey slowly improved the temporary negative effect of the former diet. These results enhance the food environmental effect and the importance of tritrophic relations in pest management strategies by predators. Indeed, more than the choice of the beneficial species, the prey host plant has a major influence on the potential efficacy of biological agent to control herbivore species such as aphids.

The influence of dietary fibre on the biological effects of glucosinolates was investigated in gnotobiotic rats harbouring a human whole faecal flora. Animals were fed for 6 wk with diets containing 12% rapeseed meal (RSM) supplemented or not supplemented with 10% inulin (INL) or oat fibre. Both fibre types enhanced the liver hypertrophy due to RSM to equal extents, but had different effects on the other glucosinolate-related toxic effects. INL partially restored a normal thyroid hormone status whereas kidney weight, goitre and growth deficit were increased on exposure to the diet containing oat fibre. Oat fibre and, to a lesser extent, INL modulated the alterations of digestive xenobiotic-metabolizing enzymes (XME) induced by RSM. They counter-balanced the induction of hepatic cytochrome P-450 and lessened the induction of uridine diphosphate-glucuronosyltransferase in the liver but did not modify depletion of its activity in the small intestine. On the other hand, they enhanced the induction of glutathione S-transferase in the liver and the large intestine but not in the small intestine. These findings give new evidence that the biological effects of naturally occurring non-nutrient compounds are closely dependent on the composition of the diet. Two mechanisms are proposed to explain the different influence of INL and oat fibre on RSM toxicity. Their different fermentative characteristics could lead to a modulation of the bacterial metabolism of glucosinolates in the caecum. Alternatively, their own action on the digestive XME could modify the subsequent metabolism of bacterial glucosinolate derivatives.

Four compounds commonly found in the human diet, allyl isothiocyanate (AITC), phenethyl isothiocyanate (PEITC) and their parent glucosinolates sinigrin and gluconasturtiin, were tested for cytotoxic and genotoxic effects in a Chinese hamster ovary cell line (CHO). The isothiocyanates were found to be more than one thousand times more cytotoxic than the glucosinolates, showing significant cytotoxic activity at concentrations below 1.0 microgram/ml. AITC was unable to induce either chromosome aberrations or sister chromatid exchanges (SCEs) even at highly cytotoxic doses. In contrast, PEITC was found to induce both aberrations and SCE at concentrations of 0.9-1.2 micrograms/ml whilst sinigrin and gluconasturtiin induced aberrations at concentrations above 2 mg/ml.

Sulfur-containing phytochemicals of two different kinds are present in all Brassica oleracea (Cruciferae) vegetables (cabbage, broccoli, etc.). They are glucosinolates (previously called thioglucosides) and S-methyl cysteine sulfoxide. These compounds, which are derived in plant tissue by amino acid biosynthesis, show quite different toxicological effects and appear to possess anticarcinogenic properties. Glucosinolates have been extensively studied since the mid-nineteenth century. They are present in plant foods besides Brassica vegetables with especially high levels in a number of seed meals fed to livestock. About 100 different kinds of glucosinolates are known to exist in the plant kingdom, but only about 10 are present in Brassica. The first toxic effects of isothiocyanates and other hydrolytic products from glucosinolates that were identified were goitre and a general inhibition of iodine uptake by the thyroid. Numerous studies have indicated that the hydrolytic products of at least three glucosinolates, 4-methyl-sulfinylbutyl (glucoraphanin), 2-phenylethyl (gluconasturtiin) and 3-indolylmethyl (glucobrassicin), have anticarcinogenic activity. Indole-3-carbinol, a metabolite of glucobrassicin, has shown inhibitory effects in studies of human breast and ovarian cancers. Kale poisoning, or a severe haemolytic anaemia, was discovered in cattle in Europe in the 1930s, but its link with the hydrolytic product of S-methyl cysteine sulfoxide was only shown about 35 years later. S-methyl cysteine sulfoxide and its metabolite methyl methane thiosulfinate were shown to inhibit chemically-induced genotoxicity in mice. Thus, the cancer chemopreventive effects of Brassica vegetables that have been shown in human and animal studies may be due to the presence of both types of sulfur-containing phytochemicals (i.e. certain glucosinolates and S-methyl cysteine sulfoxide).

Many plant secondary metabolites exhibit a wide range of dose-related physiological properties when included in the diet of animals and man. Within the brassica family, the glucosinolates, a group of sulphur-containing glucosides have been the subject of a vast amount of study and the effects of dietary inclusion of such compounds or their metabolites on the health of animals and man are briefly reviewed. Although excessive amounts of glucosinolates in animal feed formulations may reduce growth and performance as well as affecting thyroid, liver, and kidney function, there is little evidence of such effects in man. On the contrary, compounds derived from glucosinolates as a consequence of enzymic breakdown or metabolism have been shown to activate mechanisms which moderate or reverse carcinogenic processes. Such effects may contribute to the net anti-carcinogenic benefit attributed to these vegetables in numerous epidemiological studies.

This paper surveys the literature concerning biological properties of rapeseed glucosinolates, chiefly the goitrogenic activity of these compounds and their influence on the morphological and histological abnormalities of internal organs in animals. An attempt has been made to establish threshold glucosinolate levels in diet which trigger the onset or increase of internal organs impairment in animals depending on their species and breeding.

Glucosinolates are present in kale but also in rapeseed meal. Rapeseed meal diets with 0.2 to 8 g (0.5-19 mmol) glucosinolates/kg were tested with a total of 197 growing pigs. The iodine supply was different. In case of lacking iodine pigs consumed less of feed with rapeseed meal. The growth was strongly lowered. Clinical hypothyroidism had occurred. In the serum T4 was not detectable. The strongly enlarged thyroid contained only little iodine. The Zn status was impaired. The serum vitamin A concentration was increased and Cu has been accumulated in the liver. Giving iodine the glucosinolates were without any effect or the effects were weakened. In case of < 2 g glucosinolates/kg diet the feed intake was not impaired. 1 g glucosinolates/kg diet had not affected thyroid weight (reference range: 80-120 mg/kg body weight). However iodine dosage was above requirement. In people an estimated daily intake of 0.1 g glucosinolates may be a health risk only under iodine deficiency conditions.

To examine the possible harmful effects of feeding Brussels sprouts to rats, groups of 10 male, weanling rats received the non-dehydrated vegetable in moist diets at levels providing 2.5-30% of the dry matter for 4 wk. A first study comprised test diets with 15 and 30% of the dry matter as uncooked or cooked Brussels sprouts and control diets without and with 0.2% potassium thiocyanate (KSCN) for comparison. The second study comprised diets with 0, 2.5, 5, 10 and 20% of the cooked vegetable and diets with 0 and 20% of the cooked vegetable with extra iodine. Diets with the uncooked vegetable contained considerably less intact glucosinolates than did diets with the cooked product, probably as a result of more extensive enzymatic degradation in the uncooked product. Growth depression and decreased food intake, not accompanied by decreased food efficiency, occurred in rats fed 10% or more dry matter as Brussels sprouts. These findings were less marked with the cooked than with the uncooked vegetable, probably because of unpalatability. Decreased levels of blood haemoglobin and plasma thyroxin were found with 15% or more Brussels sprouts. Prothrombin times were increased if 2.5% or more was fed. Thyroid stimulating hormone was increased by feeding potassium thiocyanate, but not by feeding the vegetable. Increased kidney weights and impaired kidney function not accompanied by microscopic renal changes were observed in rats fed 10% or more Brussels sprouts. Increased liver weights, which occurred from the 5% level, were accompanied by microscopic hepatic changes only at feeding levels from 10% of the cooked vegetable. 'Morphological activation' of the thyroid was increased with 10% or more of the cooked vegetable and with 0.2% KSCN. Iodine supplementation of the diets did not influence the results obtained with the vegetable. These studies indicated that 2.5% Brussels sprouts dry matter in the diet was not without effect, and that the thyroid characteristics were less sensitive to Brussels sprouts than were other criteria examined.

1. Glucosinolate-rich diet (RM) in growing rats increased liver (a), kidneys (b), and thyroid (c) weights and depleted feed intake (d), growth curve (e) and T4 and T3 plasma levels (f). 2. Oral administration of phenobarbital enhanced the toxic effect of RM on (b), (d) and (e) and did not modify the toxic effect of RM on (a), (c) and (f). 3. RM had a depleting effect on hepatic microsomal P-450 specific activity. 4. RM had an enhancing effect on hepatic glutathione S-transferase and UDP-glucuronyltransferase specific activities. 5. These results indicate that some glucosinolate derivatives released by gut microflora metabolism are further metabolized by the hepatic detoxification system, and that they could play the role of co-toxic or co-detoxic molecules.

Glucosinolates were removed from whole rapeseed by a hot-water extraction procedure or depleted by heat treatment. When laying hens were maintained for three months on diets containing about 300 g kg-1 of these rapeseed cakes, the incidence of liver haemorrhages detected at post mortem examination was similar to that in birds maintained on 300 g kg-1 commercial rapeseed meal and significantly greater than in control birds fed soya-based diets. The effectiveness of glucosinolate extraction or depletion was determined by chemical analysis and by histological examination of the thyroid glands. Histologically the haemorrhages were similar after feeding extracted and commercial rapeseed meals. Diets containing mixtures of nitriles and glucosinolates severely depressed food intake and egg production but did not cause a greater incidence of haemorrhages than the other rapeseed products tested. Mortality from causes other than liver haemorrhage was higher with the diets containing rapeseed and this suggests that rapeseed has a more generalised effect on the body's defence mechanisms. These observations suggest that other factors in rapeseed meal, alone or acting with glucosinolates, may be responsible for inducing liver haemorrhages in laying hens.

The composition of rapeseed meal and hulls is reviewed with emphasis on components of nutritional interest. Carbohydrates in rapeseed meal are mainly pectins, pentosans and cellulose and comprise nearly one-half the gross energy. The digestibility of energy is lower for rapeseed than for soybean meal. Protein is well digested, but the protein digestion coefficient and the availability of amino acids are lower than for soybean meal. Data on digestible and metabolizable energy are summarized. The kinds of glucosinolates present in high (HG) and low (LG) glucosinolate rapeseed meal and the nature of their hydrolytic products are discussed. The toxic effects of oxazolidinethione , isothiocyanates, thiocyanates and nitriles, and their relationship to their parent glucosinolates , to myrosinase action and to conditions during rapeseed processing are reviewed briefly. The effects of glucosinolates in animal tissues and products and the effects of converting to LG rapeseed meal are presented. Finally, a brief review is given of the responses of swine and cattle to the feeding of HG and LG rapeseed meal. The nutritional advantages of LG rapeseed meal, over the older type HG meal, are clearly evident from the feeding trials.