Glucosinolates in Food

Direct seeding compromised the vitamin C content of baby vegetables and the glucosinolate content of mature vegetables in Asian leafy brassicas

This study hypothesised that direct seeding may compromise the nutritional quality of crops, as they may not release the nutrients that are triggered by the stress of transplantation. To that end, the effect of direct seeding on the nutrient content of bok choy (Brassica rapa subsp. chinensis), choy sum (Brassica rapa subsp. chinensis var. parachinensis) and mao bai (Brassica oleracea var. capitata) was investigated at the baby- and commercially-mature stages. Direct seeding had distinct effects on each stage. Directly seeded baby vegetables had 39 to 51 % less ascorbic acid and 21 to 30 % less vitamin K than transplanted baby vegetables (p < 0.05). For mature crops, direct seeding decreased the total glucosinolate content by 12 to 40 % (p < 0.05). Thus, while direct seeding may profit vegetable producers, its impact on nutrient quality merits careful consideration.

Glucosinolates in cancer prevention and treatment: experimental and clinical evidence

Glucosinolates are naturally occurring β-d-thioglucosides that mainly exist in the Brassicaceae family. The enzyme myrosinase hydrolyzes glucosinolates to form isothiocyanates, which are chemical protectors. Phenethyl isothiocyanate, sulforaphane, and benzyl isothiocyanate are potential isothiocyanate with efficient anti-cancer effects as a protective or treatment agent. Glucosinolate metabolites exert the cancer-preventive activity through different mechanisms, including induction of the Nrf2 transcription factor, inhibition of expression of tumor necrosis factor-α (TNFα) and interleukin-1β (IL-1β), induction of apoptosis through inhibiting phase I enzymes and inducting phase II enzymes, interruption of caspase pathways, STAT1/STAT2, inhibition of sulfotransferases. Moreover, glucosinolates and their metabolites are effective in cancer treatment by inhibiting angiogenesis, upregulating natural killers, increasing expression of p53, p21, caspase 3 and 9, and modulating NF-κB. Despite the mentioned cancer-preventing effects, some isothiocyanates can increase the risk of tumors. So, further studies are needed to obtain an accurate and effective dose for each glucosinolates to treat different types of tumors.

Anticancer activity of broccoli, its organosulfur and polyphenolic compounds

The use of natural bioactive constituents from various food sources for anticancer purposes has become increasingly popular worldwide. Broccoli (Brassica oleracea var. italica) is on the top of the consumed vegetables by the masses. Its raw matrix contains a plethora of phytochemicals, such as glucosinolates and phenolic compounds, along with rich amounts of vitamins, and minerals. Consumption of broccoli-derived phytochemicals provides strong antioxidant effects, particularly due to its sulforaphane content, while modulating numerous molecules involved in cell cycle regulation, control of apoptosis, and tuning enzyme activity. Thus, the inclusion of broccoli in the daily diet lowers the susceptibility to developing cancers. Numerous studies have underlined the undisputable role of broccoli in the diet as a chemopreventive raw food, owing to the content in sulforaphane, an isothiocyanate produced as a result of hydrolysis of precursor glucosinolates called glucoraphanin. This review will provide evidence supporting the specific role of fresh florets and sprouts of broccoli and its key bioactive constituents in the prevention and treatment of different cancers; a number of studies carried out in the in vitro and in vivo conditions as well as clinical trials were analyzed.

Food processing to reduce antinutrients in plant-based foods

Antinutrients such as phytic acids, tannins, saponin, and enzyme inhibitors are phytochemicals that can decrease the bioavailability of micro- and macronutrients, thus causing them to be unavailable for absorptions in the digestive system. Antinutrients are a major concern especially in countries where plant-based commodities such as wheat, legumes, and cereals are staple foods, for the antinutrients can cause not only mineral deficiencies, but also lead to more serious health issues. Although various thermal and non-thermal processing methods such as cooking, boiling, and fermentation processes have been practiced to decrease the level of antinutrients, these processes may also undesirably influence the final products. More advanced practices, such as ozonation and cold plasma processing (CPP), have been applied to decrease the antinutrients without majorly affecting the physicochemical and nutritional aspects of the commodities post-processing. This review will cover the types of antinutrients that are commonly found in plants, and the available processing methods that can be used, either singly or in combination, to significantly decrease the antinutrients, thus rendering the foods safe for consumption.

Cruciferous Vegetables and Their Bioactive Metabolites: from Prevention to Novel Therapies of Colorectal Cancer

The Brassicaceae family, known as cruciferous vegetables, includes many economically important species, mainly edible oil plants, vegetable species, spice plants, and feed plants. Cruciferous vegetables are foods rich in nutritive composition and are also a good source of dietary fiber. Besides, cruciferous vegetables contain various bioactive chemicals known as glucosinolates and S-methyl cysteine sulfoxide, including sulphur-containing cancer-protective chemicals. Numerous studies have reported that daily intake of sulphurous vegetables helps prevent cancer formation and reduces cancer incidence, especially in colorectal cancer, through various mechanisms. The potential mechanisms of these compounds in preventing cancer in experimental studies are as follows: protecting cells against DNA damage, inactivating carcinogenic substances, showing antiviral and antibacterial effects, triggering apoptosis in cells with disrupted structure, inhibiting tumour cell migration causing metastasis and the development of tumour-feeding vessels (angiogenesis). These beneficial anticancer effects of cruciferous vegetables are generally associated with glucosinolates in their composition and some secondary metabolites, as well as other phenolic compounds, seed oils, and dietary fiber in the literature. This review aims to examine to the roles of cruciferous vegetables and their important bioactive metabolites in the prevention and treatment of colorectal cancer.

Facile fabricating of rGO and Au/rGO nanocomposites using Brassica oleracea var. gongylodes biomass for non-invasive approach in cancer therapy

In this study, we report a facile green-synthesis route for the fabrication of reduced graphene oxide (rGO) using biomass of Brassica oleracea var. gongylodes (B. oleracea). In addition, we have attempted to provide a green synthesis approach to prepare Gold nanoparticles (Au NPs) on the surface of rGO by using stem extract of B. oleracea. The synthesized Au/rGO nanocomposite was evaluated using UV-visible and FTIR spectroscopy, XRD, Raman, FE-SEM, EDX, AFM and DLS techniques. The obtained results demonstrated that the synthesized Au NPs on the surface of rGO was spherical with sizes ranging about 12-18 nm. The Au/rGO NC was, also, developed as photo-synthesizer system for the photothermal therapy (PTT) of MCF7 breast cancer cells. The near-infrared (NIR) photothermal properties of Au/rGO NCs was evaluated using a continuous laser at 808 nm with power densities of 1 W.cm-2. Their photothermal efficacy on MCF7 breast cancer cells after optimizing the proper concentration of the NCs were evaluated by MTT assay, Cell cycle and DAPI staining. In addition, the potential of the synthesized Au/rGO NCs on reactive oxygen species generating and antioxidant activity were assessed by DPPH. Au/rGO NCs possess high capacity to light-to-heat conversion for absorption in range NIR light, and it is able to therapeutic effects on MCF7 cells at a low concentration. The maximum amount of cell death is 40.12% which was observed in treatment groups that received a combination of Au/rGO NCs and laser irradiation. The results demonstrate that the nanomaterials synthesized by green approach lead to efficient destruction of cancer cell and might thus serve as an excellent theranostic agent in Photothermal therapy applications.

Effect of short-term high temperature on the accumulation of glucosinolates in Brassica rapa

Glucosinolates, an important class of secondary metabolites in cruciferous vegetables, play a crucial role in protecting plants from stress-related damage. The mechanism of glucosinolate synthesis under short-term high temperature stress has not been sufficiently studied. In this work, we investigated the changes in transcription factors, synthetic genes, and related metabolites involved in glucosinolate synthesis by pakchoi seedlings under short-term high temperature stress (40 °C for 8 h). Short-term high temperature stress inhibited the primary sulfur assimilation and the contents of methionine, cysteine and glutathione. The contents of aliphatic and indolic glucosinolates were increased by short-term high temperature stress, whereas the content of 4-methoxy-glucobrassicin increased significantly. During the stress period, the transcript level of glucosinolate related MYB transcription factors had been basically significantly up-regulated, whereas the transcript level of aliphatic and indolic glucosinolate synthetic genes were predominantly up-regulated and down-regulated respectively. In the early recovery period, primary sulfur assimilation up-regulated rapidly, and decreased during the late recovery process. The glucosinolate content and synthesis gene expression act similar to the primary sulfur assimilation, a short up-regulated in early recovery, then all go down at 40 and 48 h after short-term high temperature treatment.

Glucosinolate Biosynthesis and the Glucosinolate–Myrosinase System in Plant Defense

Insect pests represent a major global challenge to important agricultural crops. Insecticides are often applied to combat such pests, but their use has caused additional challenges such as environmental contamination and human health issues. Over millions of years, plants have evolved natural defense mechanisms to overcome insect pests and pathogens. One such mechanism is the production of natural repellents or specialized metabolites like glucosinolates. There are three types of glucosinolates produced in the order Brassicales: aliphatic, indole, and benzenic glucosinolates. Upon insect herbivory, a “mustard oil bomb” consisting of glucosinolates and their hydrolyzing enzymes (myrosinases) is triggered to release toxic degradation products that act as insect deterrents. This review aims to provide a comprehensive summary of glucosinolate biosynthesis, the “mustard oil bomb”, and how these metabolites function in plant defense against pathogens and insects. Understanding these defense mechanisms will not only allow us to harness the benefits of this group of natural metabolites for enhancing pest control in Brassicales crops but also to transfer the “mustard oil bomb” to non-glucosinolate producing crops to boost their defense and thereby reduce the use of chemical pesticides.

Glucosinolate structural diversity, identification, chemical synthesis and metabolism in plants

The glucosinolates (GSLs) is a well-defined group of plant metabolites characterized by having an S-β-d-glucopyrano unit anomerically connected to an O-sulfated (Z)-thiohydroximate function. After enzymatic hydrolysis, the sulfated aglucone can undergo rearrangement to an isothiocyanate, or form a nitrile or other products. The number of GSLs known from plants, satisfactorily characterized by modern spectroscopic methods (NMR and MS) by mid-2018, is 88. In addition, a group of partially characterized structures with highly variable evidence counts for approximately a further 49. This means that the total number of characterized GSLs from plants is somewhere between 88 and 137. The diversity of GSLs in plants is critically reviewed here, resulting in significant discrepancies with previous reviews. In general, the well-characterized GSLs show resemblance to C-skeletons of the amino acids Ala, Val, Leu, Trp, Ile, Phe/Tyr and Met, or to homologs of Ile, Phe/Tyr or Met. Insufficiently characterized, still hypothetic GSLs include straight-chain alkyl GSLs and chain-elongated GSLs derived from Leu. Additional reports (since 2011) of insufficiently characterized GSLs are reviewed. Usually the crucial missing information is correctly interpreted NMR, which is the most effective tool for GSL identification. Hence, modern use of NMR for GSL identification is also reviewed and exemplified. Apart from isolation, GSLs may be obtained by organic synthesis, allowing isotopically labeled GSLs and any kind of side chain. Enzymatic turnover of GSLs in plants depends on a considerable number of enzymes and other protein factors and furthermore depends on GSL structure. Identification of GSLs must be presented transparently and live up to standard requirements in natural product chemistry. Unfortunately, many recent reports fail in these respects, including reports based on chromatography hyphenated to MS. In particular, the possibility of isomers and isobaric structures is frequently ignored. Recent reports are re-evaluated and interpreted as evidence of the existence of "isoGSLs", i.e. non-GSL isomers of GSLs in plants. For GSL analysis, also with MS-detection, we stress the importance of using authentic standards.

A high-density genetic map and QTL mapping of leaf traits and glucosinolates in Barbarea vulgaris

Background

Barbarea vulgaris is a wild cruciferous plant and include two distinct types: the G- and P-types named after their glabrous and pubescent leaves, respectively. The types differ significantly in resistance to a range of insects and diseases as well as glucosinolates and other chemical defenses. A high-density linkage map was needed for further progress to be made in the molecular research of this plant.

Results

We performed restriction site-associated DNA sequencing (RAD-Seq) on an F₂ population generated from G- and P-type B. vulgaris. A total of 1545 SNP markers were mapped and ordered in eight linkage groups, which represents the highest density linkage map to date for the crucifer tribe Cardamineae. A total of 722 previously published genome contigs (50.2 Mb, 30% of the total length) can be anchored to this high density genetic map, an improvement compared to a previously published map (431 anchored contigs, 38.7 Mb, 23% of the assembly genome). Most of these (572 contigs, 31.2 Mb) were newly anchored to the map, representing a significant improvement. On the basis of the present high-density genetic map, 37 QTL were detected for eleven traits, each QTL explaining 2.9–71.3% of the phenotype variation. QTL of glucosinolates, leaf size and color traits were in most cases overlapping, possibly implying a functional connection.

Conclusions

This high-density linkage map and the QTL obtained in this study will be useful for further understanding of the genetic of the B. vulgaris and molecular basis of these traits, many of which are shared in the related crop watercress.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5769-z) contains supplementary material, which is available to authorized users.

Atypical Myrosinase as a Mediator of Glucosinolate Functions in Plants

Glucosinolates (GLSs) are a well-known class of specialized plant metabolites, distributed mostly in the order Brassicales. A vast research field in basic and applied sciences has grown up around GLSs owing to their presence in important agricultural crops and the model plant Arabidopsis thaliana, and their broad range of bioactivities beneficial to human health. The major purpose of GLSs in plants has been considered their function as a chemical defense against predators. GLSs are physically separated from a specialized class of beta-thioglucosidases called myrosinases, at the tissue level or at the single-cell level. They are brought together as a consequence of tissue damage, primarily triggered by herbivores, and their interaction results in the release of toxic volatile chemicals including isothiocyanates. In addition, recent studies have suggested that plants may adopt other strategies independent of tissue disruption for initiating GLS breakdown to cope with certain biotic/abiotic stresses. This hypothesis has been further supported by the discovery of an atypical class of GLS-hydrolyzing enzymes possessing features that are distinct from those of the classical myrosinases. Nevertheless, there is only little information on the physiological importance of atypical myrosinases. In this review, we focus on the broad diversity of the beta-glucosidase subclasses containing known atypical myrosinases in A. thaliana to discuss the hypothesis that numerous members of these subclasses can hydrolyze GLSs to regulate their diverse functions in plants. Also, the increasingly broadening functional repertoires of known atypical/classical myrosinases are described with reference to recent findings. Assessment of independent insights gained from A. thaliana with respect to (1) the phenotype of mutants lacking genes in the GLS metabolic/breakdown pathways, (2) fluctuation in GLS contents/metabolism under specific conditions, and (3) the response of plants to exogenous GLSs or their hydrolytic products, will enable us to reconsider the physiological importance of GLS breakdown in particular situations, which is likely to be regulated by specific beta-glucosidases.

Effects of thermal and non-thermal processing of cruciferous vegetables on glucosinolates and its derived forms

Brassica vegetables, which include broccoli, kale, cauliflower, and Brussel sprouts, are known for their high glucosinolate content. Glucosinolates and their derived forms namely isothiocyanates are of special interest in the pharmaceutical and food industries due to their antimicrobial, neuroprotective, and anticarcinogenic properties. These compounds are water soluble and heat-sensitive and have been proved to be heavily lost during thermal processing. In addition, previous studies suggested that novel non-thermal technologies such as high pressure processing, pulsed electric fields, or ultraviolet irradiation can affect the glucosinolate content of cruciferous vegetables. The objective of this paper was to review current knowledge about the effects of both thermal and non-thermal processing technologies on the content of glucosinolates and their derived forms in brassica vegetables. This paper also highlights the importance of the incorporation of brassica vegetables into our diet for their health-promoting properties beyond their anticarcinogenic activities.