Glucosinolates in <Emphasis Type="Italic">Brassica</Emphasis> foods: bioavailability in food and significance for human health

Glucosinolates are sulphur compounds that are prevalent in Brassica genus. This includes crops cultivated as vegetables, spices and sources of oil. Since 1970s glucosinolates and their breakdown products, have been widely studied by their beneficial and prejudicial biological effects on human and animal nutrition. They have also been found to be partly responsible for the characteristic flavor of Brassica vegetables. In recent years, considerable attention has been paid to cancer prevention by means of natural products. The cancer-protective properties of Brassica intake are mediated through glucosinolates. Isothyocianate and indole products formed from glucosinolates may regulate cancer cell development by regulating target enzymes, controlling apoptosis and blocking the cell cycle. Nevertheless, variation in content of both glucosinolates and their bioactive hydrolysis products depends on both genetics and the environment, including crop management practices, harvest and storage, processing and meal preparation. Here, we review the significance of glucosinolates as source of bioactive isothiocyanates for human nutrition and health and the influence of environmental conditions and processing mechanisms on the content of glucosinolate concentration in Brassica vegetables. Currently, this area is only partially understood. Further research is needed to understand the mechanisms by which the environment and processing affect glucosinolates content of Brassica vegetables. This will allow us to know the genetic control of these variables, what will result in the development of high quality Brassica products with a health-promoting activity.     

Phylloplane location of glucosinolates in Barbarea spp. (Brassicaceae) and misleading assessment of host suitability by a specialist herbivore

Glucosinolates are plant secondary metabolites used in host plant recognition by insects specialized on Brassicaceae, such as the diamondback moth (DBM), Plutella xylostella. Their perception as oviposition cues by females would seem to require their occurrence on the leaf surface, yet previous studies have reached opposite conclusions about whether glucosinolates are actually present on the surface of crucifer leaves. DBM oviposits extensively on Barbarea vulgaris, despite its larvae not being able to survive on this plant because of its content of feeding-deterrent saponins. Glucosinolates and saponins in plant tissue and mechanically removed surface waxes from leaves of Barbarea spp. were analyzed with high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). Surface waxes from leaves of Barbarea spp. contained glucosinolates, but not feeding-deterrent saponins. Our research is the first to show that glucosinolates are present on the leaf surface of Barbarea spp., but not in other crucifers investigated, resolving some conflicting results from previous studies. Our research is also the first to quantify glucosinolates on the leaf surface of a crucifer, and to show that the concentrations of glucosinolates found on the leaf surface of Barbarea spp. are sufficient to be perceived by ovipositing DBM.     

芥子油苷在植物-生物环境关系中的作用

芥子油苷是一类含氮、含硫的植物次生代谢物质,主要分布于白花菜目的十字花科植物。芥子油苷及其降解产物具有多种生化活性,近年来人们更多地关注芥子油苷代谢与其它物质代谢途径的相互联系以及与植物生存环境的相互作用。介绍了芥子油苷及其分布、芥子油苷-黑芥子酶系统以及由芥子油苷介导的植物对昆虫、病原体的防御作用和植物与植物之间的化感作用的研究概况。     

Cytochrome p450 CYP79F1 from arabidopsis catalyzes the conversion of dihomomethionine and trihomomethionine to the corresponding aldoximes in the biosynthesis of aliphatic glucosinolates

Glucosinolates are natural plant products that have received rising attention due to their role in interactions between pests and crop plants and as chemical protectors against cancer. Glucosinolates are derived from amino acids and have aldoximes as intermediates. We report that cytochrome P450 CYP79F1 catalyzes aldoxime formation in the biosynthesis of aliphatic glucosinolates in Arabidopsis thaliana. Using recombinant CYP79F1 functionally expressed in Escherichia coli, we show that both dihomomethionine and trihomomethionine are metabolized by CYP79F1 resulting in the formation of 5-methylthiopentanaldoxime and 6-methylthiohexanaldoxime, respectively. 5-methylthiopentanaldoxime is the precursor of the major glucosinolates in leaves of A. thaliana, i.e. 4-methylthiobutylglucosinolate and 4-methylsulfinylbutylglucosinolate, and a variety of other glucosinolates in Brassica sp. Transgenic A. thaliana with cosuppression of CYP79F1 have a reduced content of aliphatic glucosinolates and a highly increased level of dihomomethionine and trihomomethionine. The transgenic plants have a morphological phenotype showing loss of apical dominance and formation of multiple axillary shoots. Our data provide the first evidence that a cytochrome P450 catalyzes the N-hydroxylation of chain-elongated methionine homologues to the corresponding aldoximes in the biosynthesis of aliphatic glucosinolates.     

Genetic control of natural variation in Arabidopsis glucosinolate accumulation

Glucosinolates are biologically active secondary metabolites of the Brassicaceae and related plant families that influence plant/insect interactions. Specific glucosinolates can act as feeding deterrents or stimulants, depending upon the insect species. Hence, natural selection might favor the presence of diverse glucosinolate profiles within a given species. We determined quantitative and qualitative variation in glucosinolates in the leaves and seeds of 39 Arabidopsis ecotypes. We identified 34 different glucosinolates, of which the majority are chain-elongated compounds derived from methionine. Polymorphism at only five loci was sufficient to generate 14 qualitatitvely different leaf glucosinolate profiles. Thus, there appears to be a modular genetic system regulating glucosinolate profiles in Arabidopsis. This system allows the rapid generation of new glucosinolate combinations in response to changing herbivory or other selective pressures. In addition to the qualitative variation in glucosinolate profiles, we found a nearly 20-fold difference in the quantity of total aliphatic glucosinolates and were able to identify a single locus that controls nearly three-quarters of this variation.     

Glucosinolates – biochemistry, genetics and biological activity

This paper provides a brief overview of the biochemistry, genetics andbiological activity of glucosinolates and their degradation products.These compounds are found in vegetative and reproductive tissues of16 plant families, but are most well known as the major secondarymetabolites in the Brassicaceae. Following tissue disruption, theyare hydrolysed to a variety of products of which isothiocyanates(`mustard oils') are the most prominent. The majority of geneticstudies have concentrated on reducing the levels of these compoundsin the seeds of oilseed Brassica crops due to antinutritionalfactors associated with 2-hydroxy-3-butenyl glucosinolate. However,current interest is concerned with the anticarcinogenic activity ofisothiocyanates derived from cruciferous vegetables and salad crops.     

Insect herbivore counteradaptations to the plant glucosinolate-myrosinase system

The glucosinolate-myrosinase system found in plants of the Brassicales order is one of the best studied plant chemical defenses. Glucosinolates and their hydrolytic enzymes, myrosinases, are stored in separate compartments in the intact plant tissue. Upon tissue disruption, bioactivation of glucosinolates is initiated, i.e. myrosinases get access to their glucosinolate substrates, and glucosinolate hydrolysis results in the formation of toxic isothiocyanates and other biologically active products. The defensive function of the glucosinolate-myrosinase system has been demonstrated in a variety of studies with different insect herbivores. However, a number of generalist as well as specialist herbivores uses glucosinolate-containing plants as hosts causing large agronomical losses in oil seed rape and other crops of the Brassicaceae. While our knowledge of counteradaptations in generalist insect herbivores is still very limited, considerable progress has been made in understanding how specialist insect herbivores overcome the glucosinolate-myrosinase system and even exploit it for their own defense. All mechanisms of counteradaptation identified to date in insect herbivores specialized on glucosinolate-containing plants ensure that glucosinolate breakdown to toxic isothiocyanates is avoided. This is accomplished in many different ways including avoidance of cell disruption, rapid absorption of intact glucosinolates, rapid metabolic conversion of glucosinolates to harmless compounds that are not substrates for myrosinases, and diversion of plant myrosinase-catalyzed glucosinolate hydrolysis. One of these counteradaptations, the nitrile-specifier protein identified in Pierid species, has been used to demonstrate mechanisms of coevolution of plants and their insect herbivores.     

芸薹属植物基因组学研究进展

芸薹属是十字花科植物300多个属中最为重要的一个属,是我国栽培面积最大的蔬菜作物。拟南芥和芸薹属在十字花科中两者的亲缘关系最近,通过它们之间的比较作图,两者之间的共线性被大量发现。模式植物拟南芥全基因组测序已经完成,这为芸薹属作物的基因组研究提供了便利条件。芸薹属作物的功能基因组学能够进一步明确不同发育时期基因的功能,为解释芸薹属的进化提供基因证据。就芸薹属植物在比较基因组学、功能基因组学最新进展,特别是芸薹属与模式植物拟南芥在基因组之间的相互关系进行了综述。     

Glucosinolates in the human diet. Bioavailability and implications for health

The glucosinolates are a large group of sulphur-containing glucosides found in brassica vegetables. After physical damage to the plant tissue, glucosinolates are broken down, by the endogenous enzyme myrosinase, releasing glucose and a complex variety of biologically active products. The most important and extensively studied of these compounds are the isothiocyanates. Glucosinolates can be degraded or leached from vegetable tissue during food processing, but thermal inactivation of myrosinase preserves some intact glucosinolates in cooked vegetables. Once ingested, any remaining intact glucosinolates may be broken down by plant myrosinase in the small intestine, or by bacterial myrosinase in the colon. Isothiocyanates are absorbed from the small bowel and colon, and the metabolites are detectable in human urine 2–3 h after consumption of brassica vegetables. Isothiocyanates are potent inducers of Phase II enzymes in vitro, and they have been shown to increase the metabolism and detoxification of chemical carcinogens in vitro and in animal models. Some of these compounds also inhibit mitosis and stimulate apoptosis in human tumour cells, in vitro and in vivo. This second effect raises the possibility that in addition to blocking DNA damage, isothiocyanates may selectively inhibit the growth of tumour cells even after initiation by chemical carcinogens. Epidemiological evidence supports the possibility that glucosinolate breakdown products derived from brassica vegetables may protect against human cancers, especially those of the gastrointestinal tract and lung. To define and exploit these potentially anticarcinogenic effects it is important to understand and manipulate glucosinolate chemistry and metabolism across the whole food-chain, from production and processing to consumption. This revised version was published online in June 2006 with corrections to the Cover Date.     

Phytochemical fingerprinting of vegetable Brassica oleracea and Brassica napus by simultaneous identification of glucosinolates and phenolics

Introduction – Brassica vegetables have been related to the prevention of cancer and degenerative diseases, owing to their glucosinolate and phenolic content. Objective – Identification of glucosinolates, flavonoids and hydroxycinnamic acids in representative varieties of kale, cabbage and leaf rape. Methodology – One local variety of each crop was evaluated in this study using a multi‐purpose chromatographic method that simultaneously separates glucosinolates and phenolics. Chromatograms were recorded at 330 nm for flavonoid glycosides and acylated derivatives and 227 nm for glucosinolates. Results – Eight glucosinolates were identified in kale and cabbage, which exhibited the same glucosinolate profile, and 11 glucosinolates were identified in leaf rape. Furthermore, 20 flavonoids and 10 hydroxycinnamic acids were detected in kale and cabbage, while 17 flavonoids and eight hydroxycinnamic acids were found in leaf rape. Conclusions – This study has provided a deeper and comprehensive identification of health‐promoting compounds in kale, cabbage and leaf rape, thus showing that they are a good source of glucosinolates and phenolic antioxidants. Copyright © 2011 John Wiley & Sons, Ltd.     

In planta side-chain glucosinolate modification in Arabidopsis by introduction of dioxygenase Brassica homolog BoGSL-ALK

Aliphatic glucosinolates and their derived isothiocyanates are important secondary metabolites in crucifers. Some of these compounds have beneficial activities such as carcinogen detoxification, pesticidal and antifungal properties, but others are anti-nutritional; the differences are largely due to side chain modifications. We report the cloning and in planta functionality analysis of BoGSL-ALK, a gene whose protein product influences side-chain modifications in the glucosinolate pathway. Expression of this Brassica gene was demonstrated in Arabidopsis thaliana by assaying RNA activity and monitoring changes in the glucosinolate profiles in leaves and seeds of transformed plants. Dependent on the proposed uses of the crops under development, the ability to regulate BoGSL-ALK expression is a key step towards engineering Brassica crops with specific glucosinolate content.     

华南主要作物和蔬果类现代花粉形态及农业考古研究价值

本文对华南地区主要的19科31种作物和蔬果类花粉进行了形态学研究,包括镜下观察、拍照和特征描述与对比。本研究涉及的花粉包括粮食作物4种,蔬菜类16种,水果类8种,油料和经济作物3种等。结果表明,不同作物的花粉在形态、大小、萌发器官和外壁纹饰等方面有明显的差别,同一科植物花粉的主要形态虽有相似之处,但根据某些细微结构特征,并通过统计学方法在一定程度上可以对相近的种类进行区别。本文对十字花科芸苔属4种蔬菜花粉(油菜、芥菜、菜心和小白菜)的扁率(赤道轴长/极轴长)以及外壁网眼长轴长度分别进行测量,发现外壁网眼长轴长度对于4种蔬菜的区分不明显,而扁率则分异显著,可为十字花科花粉种属判别提供依据。对重庆阿蓬江涪碛口遗址剖面中自明清时期以来的伴人植物十字花科花粉赤道轴长与外壁网眼长轴长度进行了测量,判别出文化层中的十字花科花粉可能为菜心类型。稻田中保存的水稻花粉直径约为34—38μm,结合水稻花粉的其它特征可以应用到全新世地层的水稻花粉鉴定。     

基诺族传统食用植物的民族植物学研究

基诺族是国务院１９７９年确认的我国第５６个民族,至今仍依赖于歇农业即刀耕火种为生,自给自足的自然经济是他们主要经济形式。除在轮歇地内栽培少数几种作物外,基诺族的菜肴绝大部分采自其周围的林地、山野。本文记述了基诺族的传统食用植物１７９种,其中野菜类８６种、野生水果类３７种,栽培植物５４种。     

Fruit trees in a Malaysian rain forest

An inventory was made of 50 ha of primary lowland rain forest in Peninsular Malaysia, in which ca. 340,000 trees 1 cm dbh or larger were measured and identified to species. Out of a total plot tree flora of 820 species, 76 species are known to bear edible fruit. Especially diverse were the wild species of mango (Mangifera, Anacardiaceae, 12 spp.), mangosteen (Garcinia, Clusiaceae, 13 spp.), breadfruit (Artocarpus, Moraceae, 10 spp.) and rambutan (Nephelium, Sapindaceae, 5 spp.). Median population size for all species of fruit trees was 3.0 trees per ha and 0.2 adult trees per ha. Direct economic value of wild fruit trees was small; only one species has been very much collected and sold, Parkia speciosa (Fabaceae), amounting to less than US$20 per ha per year. The potential value of the species as genetic resources is very large: 24 species are cultivated, 38 edible species are congeneric with cultivated crops and at least 10 other species bear inedible fruit but are related to cultivated crops. We conclude that the Peninsular Malaysian rain forest is exceedingly rich in wild fruit trees, that these normally live at low densities, and that their principal economic value is as genetic resources.     

New insight into the biosynthesis and regulation of indole compounds in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

In spite of their silent and sessile life, plants are dynamic organisms that have developed advanced defence strategies in their adaptation to the pressure of herbivores and pathogens. Natural plant products play an important role as chemical weapons in this warfare. Characteristic of cruciferous plants is the synthesis of nitrogen- and sulphur-rich compounds, such as glucosinolates (Mikkelsen et al. 2002) and indole alkaloids (Pedras et al. 2000). Glucosinolates are believed to be largely non-toxic, but upon tissue disruption, they are hydrolyzed by endogenous -thioglucosidases (myrosinases) (Rask et al. 2000) to primarily isothiocyanates and nitriles, which have many biological activities. These include not only important roles as repellents against herbivorous insects and microorganisms, but also as volatile attraction of specialized insects (Wittstock and Halkier 2002). For humans, these compounds serve as cancer-preventive agents, biopesticides, and flavor compounds (Talalay and Fahey 2001). Indole alkaloids are phytoalexins and production of specific alkaloids is usually limited to only a few species. Cruciferous plants include the model plant Arabidopsis, which produces the indole alkaloid camalexin. This review will focus on the central role of indole-3-acetaldoxime (IAOx) in the biosynthesis of indole glucosinolates, camalexin, and the phytohormone IAA.     

Capillary GC of glucosinolate-derived horseradish constituents

The technical requirements of glass capillary GC allowing the separation and identification of a large number of mustard oils and other nitrogenous components in horseradish are presented. Certain of these require support surfaces under the stationary phase which are free from basic sites. The deactivation of adsorptive sites, which is necessary in the case of a number of mustard oils, was accomplished by employing polyglycols as stationary phases. Sampling into conventional vaporizing injectors may cause strong discrimination of high boiling compounds as well as pyrolysis of labile mustard oils within the syringe needle. By employing cold on-column injection these effects could be avoided. Glucosinolates present in horseradish were identified through the corresponding mustard oils using MS. Of the glucosinolates in this species, 30 were identified including at least six compounds that have not been described before as natural products.     

Establishing the occurrence of major and minor glucosinolates in Brassicaceae by LC-ESI-hybrid linear ion-trap and Fourier-transform ion cyclotron resonance mass spectrometry

Glucosinolates (GLSs) are sulfur-rich plant secondary metabolites which occur in a variety of cruciferous vegetables and among various classes of them, genus Brassica exhibits a rich family of these phytochemicals at high, medium and low abundances. Liquid chromatography (LC) with electrospray ionization in negative ion mode (ESI-) coupled to a hybrid quadrupole linear ion trap (LTQ) and Fourier transform ion cyclotron resonance mass spectrometer (FTICRMS) was employed for the selective and sensitive determination of intact GLSs in crude sample extracts of broccoli (Brassica oleracea L. Var. italica), cauliflower (B. oleracea L. Var. Botrytis) and rocket salad (Eruca sativa L.) with a wide range of contents. When LTQ and FTICR mass analyzers are compared, the magnitude of the limit of detection was ca. 5/6-fold lower with the FTICR MS. In addition, the separation and detection by LC-ESI-FTICR MS provides a highly selective assay platform for unambiguous identification of GLSs, which can be extended to lower abundance (minor) GLSs without significant interferences of other compounds in the sample extracts. The analysis of Brassicaceae species emphasized the presence of eight minor GLSs, viz. 1-methylpropyl-GLS, 2-methylpropyl-GLS, 2-methylbutyl-GLS, 3-methylbutyl-GLS, n-pentyl-GLS, 3-methylpentyl-GLS, 4-methylpentyl-GLS and n-hexyl-GLS. The occurrence of these GLSs belonging to the saturated aliphatic side chain families C(4), C(5) and C(6), presumably formed by chain elongation of leucine, homoleucine and dihomoleucine as primary amino acid precursors, is described. Based on their retention behavior and tandem MS spectra, all these minor compounds occurring in plant extracts of B. oleracea L. Var. italica, B. oleracea L. Var. Botrytis and E. sativa L. were tentatively identified.     

植物芥子油苷代谢及其转移

芥子油苷是一类含氮、含硫的植物次生代谢产物,主要分布于十字花科植物。芥子油苷及其降解产物具有多种生化活性,在植物防御方面也有重要作用。简要介绍芥子油苷的分布、合成、降解和在植物体内的转移。