Determination of the absolute configuration of the glucosinolate methyl sulfoxide group reveals a stereospecific biosynthesis of the side chain

Sulforaphane and bladder cancer: a potential novel antitumor compound

Bladder cancer (BC) is a common form of urinary tract tumor, and its incidence is increasing annually. Unfortunately, an increasing number of newly diagnosed BC patients are found to have advanced or metastatic BC. Although current treatment options for BC are diverse and standardized, it is still challenging to achieve ideal curative results. However, Sulforaphane, an isothiocyanate present in cruciferous plants, has emerged as a promising anticancer agent that has shown significant efficacy against various cancers, including bladder cancer. Recent studies have demonstrated that Sulforaphane not only induces apoptosis and cell cycle arrest in BC cells, but also inhibits the growth, invasion, and metastasis of BC cells. Additionally, it can inhibit BC gluconeogenesis and demonstrate definite effects when combined with chemotherapeutic drugs/carcinogens. Sulforaphane has also been found to exert anticancer activity and inhibit bladder cancer stem cells by mediating multiple pathways in BC, including phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), mitogen-activated protein kinase (MAPK), nuclear factor kappa-B (NF-κB), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), zonula occludens-1 (ZO-1)/beta-catenin (β-Catenin), miR-124/cytokines interleukin-6 receptor (IL-6R)/transcription 3 (STAT3). This article provides a comprehensive review of the current evidence and molecular mechanisms of Sulforaphane against BC. Furthermore, we explore the effects of Sulforaphane on potential risk factors for BC, such as bladder outlet obstruction, and investigate the possible targets of Sulforaphane against BC using network pharmacological analysis. This review is expected to provide a new theoretical basis for future research and the development of new drugs to treat BC.

(R)-8-Methylsulfinyloctyl isothiocyanate from Nasturtium officinale inhibits LPS-induced immunoinflammatory responses in mouse peritoneal macrophages: chemical synthesis and molecular signaling pathways involved

The aim of this study was to develop an optimal synthetic route to obtain natural (R)-8-methylsulfinyloctyl isothiocyanate ((R)-8-OITC), present in watercress, based on the "DAG methodology" as well as to evaluate its potential antioxidant and immunomodulatory effects, exploring possible signaling pathways that could be involved in an ex vivo model of murine peritoneal macrophages stimulated with LPS. Treatment with (R)-8-OITC inhibited the levels of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-17 and IL-18), intracellular ROS production and expression of pro-inflammatory enzymes (COX-2, iNOS and mPGES-1) through modulation of the expression of Nrf2, MAPKs (p38, JNK and ERK) and JAK/STAT, and the canonical and non-canonical pathways of the inflammasome. Taking all these together, our results provide a rapid and cost-effective synthetic route to obtain natural (R)-8-OITC and demonstrate that it could be a potential nutraceutical candidate for managing immuno-inflammatory pathologies. Therefore, further in vivo trials are warranted.

Immunomodulatory Effects of (R)-Sulforaphane on LPS-Activated Murine Immune Cells: Molecular Signaling Pathways and Epigenetic Changes in Histone Markers

The aim of this study was to explore the immunomodulatory effects of the natural enantiomer (R)-Sulforaphane (SFN) and the possible signaling pathways involved in an ex vivo model of LPS-stimulated murine peritoneal macrophages. Furthermore, we studied the epigenetic changes induced by (R)-SFN as well as the post-translational modifications of histone H3 (H3K9me3 and H3K18ac) in relation to the production of cytokines in murine splenocytes after LPS stimulation. (R)-SFN was able to modulate the inflammatory response and oxidative stress induced by LPS stimulation in murine peritoneal macrophages through the inhibition of reactive oxygen species (ROS), nitric oxide (NO) and cytokine (IL-1β, IL-6, IL-17, IL-18 and TNF-α) production by down-regulating the expression of pro-inflammatory enzymes (iNOS, COX-2 and mPGES-1). We also found that activation of the Nrf-2/HO-1 axis and inhibition of the JAK2/STAT-3, MAPK, canonical and non-canonical inflammasome signaling pathways could have been responsible for the immunomodulatory effects of (R)-SFN. Furthermore, (R)-SFN modulated epigenetic modifications through histone methylation (H3K9me3) and deacetylation (H3K18ac) in LPS-activated spleen cells. Collectively, our results suggest that (R)-SFN could be a promising epinutraceutical compound for the management of immunoinflammatory diseases.

Assessment of Methodological Pipelines for the Determination of Isothiocyanates Derived from Natural Sources

Isothiocyanates are biologically active secondary metabolites liberated via enzymatic hydrolysis of their sulfur enriched precursors, glucosinolates, upon tissue plant disruption. The importance of this class of compounds lies in their capacity to induce anti-cancer, anti-microbial, anti-inflammatory, neuroprotective, and other bioactive properties. As such, their isolation from natural sources is of utmost importance. In this review article, an extensive examination of the various parameters (hydrolysis, extraction, and quantification) affecting the isolation of isothiocyanates from naturally-derived sources is presented. Overall, the effective isolation/extraction and quantification of isothiocyanate is strongly associated with their chemical and physicochemical properties, such as polarity-solubility as well as thermal and acidic stability. Furthermore, the successful activation of myrosinase appears to be a major factor affecting the conversion of glucosinolates into active isothiocyanates.

The Role of Brassica Bioactives on Human Health: Are We Studying It the Right Way?

Brassica vegetables and their components, the glucosinolates, have been suggested as good candidates as dietary coadjutants to improve health in non-communicable diseases (NCDs). Different preclinical and clinical studies have been performed in the last decade; however, some concerns have been posed on the lack of established and standardized protocols. The different concentration of bioactive compounds used, time of intervention or sample size, and the lack of blinding are some factors that may influence the studies' outcomes. This review aims to analyze the critical points of the studies performed with Brassica-related biomolecules and propose some bases for future trials in order to avoid biases.

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.

Protective Effect of Glucosinolates Hydrolytic Products in Neurodegenerative Diseases (NDDs)

Crucifer vegetables, Brassicaceae and other species of the order Brassicales, e.g., Moringaceae that are commonly consumed as spice and food, have been reported to have potential benefits for the treatment and prevention of several health disorders. Though epidemiologically inconclusive, investigations have shown that consumption of those vegetables may result in reducing and preventing the risks associated with neurodegenerative disease development and may also exert other biological protections in humans. The neuroprotective effects of these vegetables have been ascribed to their secondary metabolites, glucosinolates (GLs), and their related hydrolytic products, isothiocyanates (ITCs) that are largely investigated for their various medicinal effects. Extensive pre-clinical studies have revealed more than a few molecular mechanisms of action elucidating multiple biological effects of GLs hydrolytic products. This review summarizes the most significant and up-to-date in vitro and in vivo neuroprotective actions of sulforaphane (SFN), moringin (MG), phenethyl isothiocyanate (PEITC), 6-(methylsulfinyl) hexyl isothiocyanate (6-MSITC) and erucin (ER) in neurodegenerative diseases.

Advanced NMR-Based Structural Investigation of Glucosinolates and Desulfoglucosinolates

Glucosinolates (GLs) constitute a class of plant secondary metabolites that are characteristic of the order Brassicales. They each contain a common hydrophilic moiety connected to a mostly hydrophobic side chain whose constitution is the most frequent structural variant. Their transformations by myrosinases lead to intensively studied and highly reactive compounds of biological relevancy. In other respects, the enzymatic desulfation of GLs produces derivatives (DS-GLs) that are useful for GL analysis. A collection of 31 compounds, GLs and DS-GLs, representing 17 different side chains was established in order to report accurate descriptions of the molecules' ¹H-, ¹³C-, and ¹⁵N-NMR parameters. The descriptions of the ¹H-NMR spectra were achieved using the PERCH software, which accurately analyzed the complex coupling patterns that arose from strongly coupled nuclei. The chemical shift assignments were supported by 2D COSY, HSQC, and HMBC spectra. The impact of desulfation and the influence of the nature of the side chains on the chemical shift values are discussed. The results of the spectroscopic analysis and the 3D chemical-structure models of the studied molecules were grouped in structure-and-data-format (SDF) files. The NMR parameters were also collected in a simple text file, a spreadsheet file, and a relational database.

HPLC Separation of Sulforaphane Enantiomers in Broccoli and Its Sprouts by Transformation into Diastereoisomers Using Derivatization with (S)-Leucine

Racemic sulforaphane, which was derivatized with (S)-leucine (l-leucine), was resolved by reversed phase HPLC with UV detection. The optimum mobile phase conditions were found to be 10 mM citric acid (pH 2.8) containing 22% methanol at 35 °C using detection at 254 nm. Sulforaphane enantiomers in florets and stems of five brands of broccoli and leaves and stems of three brands of broccoli sprouts were analyzed by the proposed HPLC method. Both sulforaphane enantiomers were detected in all of the samples. The S/R ratios of sulforaphane in broccoli samples were 1.5-2.6/97.4-98.5% for florets and 5.0-12.1/87.9-95.0% for stems. The S/R ratios in broccoli sprout samples were higher than those in broccoli samples and were found to be 8.3-19.7/80.3-91.7% for leaves and 37.0-41.8/58.2-63.0% for stems. (S)-Sulforaphane detected in the broccoli and its sprout samples was positively identified by separately using an HPLC with a chiral column (Chiralpak AD-RH) and mass spectrometry.

Natural Phytochemicals in the Treatment and Prevention of Dementia: An Overview

The word dementia describes a class of heterogeneous diseases which etiopathogenetic mechanisms are not well understood. There are different types of dementia, among which, Alzheimer's disease (AD), vascular dementia (VaD), dementia with Lewy bodies (DLB) and frontotemporal dementia (FTD) are the more common. Currently approved pharmacological treatments for most forms of dementia seem to act only on symptoms without having profound disease-modifying effects. Thus, alternative strategies capable of preventing the progressive loss of specific neuronal populations are urgently required. In particular, the attention of researchers has been focused on phytochemical compounds that have shown antioxidative, anti-amyloidogenic, anti-inflammatory and anti-apoptotic properties and that could represent important resources in the discovery of drug candidates against dementia. In this review, we summarize the neuroprotective effects of the main phytochemicals belonging to the polyphenol, isothiocyanate, alkaloid and cannabinoid families in the prevention and treatment of the most common kinds of dementia. We believe that natural phytochemicals may represent a promising sources of alternative medicine, at least in association with therapies approved to date for dementia.

Identification of a flavin-containing S-oxygenating monooxygenase involved in alliin biosynthesis in garlic

S-Alk(en)yl-l-cysteine sulfoxides are cysteine-derived secondary metabolites highly accumulated in the genus Allium. Despite pharmaceutical importance, the enzymes that contribute to the biosynthesis of S-alk-(en)yl-l-cysteine sulfoxides in Allium plants remain largely unknown. Here, we report the identification of a flavin-containing monooxygenase, AsFMO1, in garlic (Allium sativum), which is responsible for the S-oxygenation reaction in the biosynthesis of S-allyl-l-cysteine sulfoxide (alliin). Recombinant AsFMO1 protein catalyzed the stereoselective S-oxygenation of S-allyl-l-cysteine to nearly exclusively yield (RC SS )-S-allylcysteine sulfoxide, which has identical stereochemistry to the major natural form of alliin in garlic. The S-oxygenation reaction catalyzed by AsFMO1 was dependent on the presence of nicotinamide adenine dinucleotide phosphate (NADPH) and flavin adenine dinucleotide (FAD), consistent with other known flavin-containing monooxygenases. AsFMO1 preferred S-allyl-l-cysteine to γ-glutamyl-S-allyl-l-cysteine as the S-oxygenation substrate, suggesting that in garlic, the S-oxygenation of alliin biosynthetic intermediates primarily occurs after deglutamylation. The transient expression of green fluorescent protein (GFP) fusion proteins indicated that AsFMO1 is localized in the cytosol. AsFMO1 mRNA was accumulated in storage leaves of pre-emergent nearly sprouting bulbs, and in various tissues of sprouted bulbs with green foliage leaves. Taken together, our results suggest that AsFMO1 functions as an S-allyl-l-cysteine S-oxygenase, and contributes to the production of alliin both through the conversion of stored γ-glutamyl-S-allyl-l-cysteine to alliin in storage leaves during sprouting and through the de novo biosynthesis of alliin in green foliage leaves.

An overview on neuroprotective effects of isothiocyanates for the treatment of neurodegenerative diseases

The discovery of new natural compounds with pharmacological properties is a field of interest widely growing, especially for the management of neurodegenerative diseases. As no pharmacological treatment is available to prevent the development of these disorders, dietary intake of foods or plant-based extracts with antioxidant properties might have beneficial effects on human health and improve brain functions. Isothiocyanates (ITCs), derived from the hydrolysis of the corresponding glucosinolates (GLs), mainly found in Brassica vegetables (Brassicaceae) and, to a lesser extent, in Moringaceae plants, have demonstrated to exert neuroprotective properties. Specifically, strong evidences suggest that antioxidant effects may be ascribed mainly to their peculiar ability to activate the Nrf2/ARE pathway, but alternative mechanisms of action have also been suggested. This review summarizes the current knowledge about the neuroprotective effects of ITCs in counteracting oxidative stress as well as inflammatory and apoptotic mechanisms, using in vitro and in vivo models of acute and chronic neurodegenerative disease. Therefore, ITCs could be regarded as a promising source of alternative medicine for the prevention and/or treatment of neurodegenerative diseases.

Sulforaphane homologues: Enantiodivergent synthesis of both enantiomers, activation of the Nrf2 transcription factor and selective cytotoxic activity

Reported is an enantiodivergent approach for the synthesis of both enantiomers of sulforaphane (SFN) homologues with different chain lengths between the sulfinyl sulfur and the isothiocyanate groups and different substituents on the sulfinyl sulfur. The homologues were designed in order to unravel the effect of all the diversity elements included in sulforaphane's structure. The key step of the approach is the diastereoselective synthesis of both sulfinate ester epimers at sulfur, using as single chiral auxiliary the sugar derived diacetone-d-glucose. The approach allows the first synthesis of both enantiomers of 5-methylsulfinylpentyl isothiocyanate, and the biologically important 6-methylsulfinylhexyl isothiocyanate (6-HITC) found in Japanese horseradish, wasabi (Wasabia japonica). The ability of the synthesized compounds as inductors of phase II detoxifying enzymes has been studied by determining their ability to activate the cytoprotective transcription factor Nrf2. The cytotoxic activity of all the synthesized compounds against human lung adenocarcinoma (A549) and foetal lung fibroblasts (MRC-5) is also reported.

Novel gram-scale production of enantiopure R-sulforaphane from Tuscan black kale seeds

Dietary R-sulforaphane is a highly potent inducer of the Keap1/Nrf2/ARE pathway. Furthermore, sulforaphane is currently being used in clinical trials to assess its effects against different tumour processes. This study reports an efficient preparation of enantiopure R-sulforaphane based on the enzymatic hydrolysis of its natural precursor glucoraphanin. As an alternative to broccoli seeds, we have exploited Tuscan black kale seeds as a suitable source for gram-scale production of glucoraphanin. The defatted seed meal contained 5.1% (w/w) of glucoraphanin that was first isolated through an anion exchange chromatographic process, and then purified by gel filtration. The availability of glucoraphanin (purity ≈ 95%, weight basis) has allowed us to develop a novel simple hydrolytic process involving myrosinase (EC 3.2.1.147) in a biphasic system to directly produce R-sulforaphane. In a typical experiment, 1.09 g of enantiopure R-sulforaphane was obtained from 150 g of defatted Tuscan black kale seed meal.

Extraction, chemical characterization and biological activity determination of broccoli health promoting compounds

Broccoli (Brassica oleracea L. var. Italica) contains substantial amount of health-promoting compounds such as vitamins, glucosinolates, phenolic compounds, and dietary essential minerals; thus, it benefits health beyond providing just basic nutrition, and consumption of broccoli has been increasing over the years. This review gives an overview on the extraction and separation techniques, as well as the biological activity of some of the above mentioned compounds which have been published in the period January 2008 to January 2013. The work has been distributed according to the different families of health promoting compounds discussing the extraction procedures and the analytical techniques employed for their characterization. Finally, information about the different biological activities of these compounds has been also provided.

FT-IR and NMR study of seed coat dissected from different colored progenies of Brassica napus-Sinapis alba hybrids

BACKGROUND

Yellow-seeded Brassica napus is preferred by breeders for economic reasons, and seed coat is the most obvious comparable character between yellow and black rapeseed.

RESULTS

Owing to an incomplete understanding of chemical components in yellow rapeseed coat, here we optimized a technique based on attenuated total reflectance-Fourier transform infrared (FT-IR) microspectroscopy to screen differences in chemical compositions of Brassica napus, Sinapis alba and four progeny lines with different yellow seed color derived from somatic hybrids between B. napus and S. alba. Nuclear magnetic resonance (NMR) analysis of seed coat from B. napus and S. alba represented two specific peaks representing components of lignin in B. napus, which were absent in the progenies. Also, the intensity of peaks related to fiber were stronger in B. napus than S. alba and yellow seed lines, indicating the differences of fiber and lignin contents in yellow-seeded lines and parent lines. Differences in the lipid, protein and carbohydrate features were identified between B. napus and S. alba, some of which were specifically inherited in progenies of the somatic hybrids.

CONCLUSION

FT-IR spectrometry and NMR provide a rapid, direct bioanalytical technique for exploring the changes in molecular chemistry within the canola seed coat and for selecting rapeseed materials with high quality, which can be further used for breeding or nutrition of human and animals.

Flavin-dependent enzymes in cancer prevention

Statistical studies have demonstrated that various agents may reduce the risk of cancer's development. One of them is activity of flavin-dependent enzymes such as flavin-containing monooxygenase (FMO)(GS-OX1), FAD-dependent 5,10-methylenetetrahydrofolate reductase and flavin-dependent monoamine oxidase. In the last decade, many papers concerning their structure, reaction mechanism and role in the cancer prevention were published. In our work, we provide a more in-depth analysis of flavin-dependent enzymes and their contribution to the cancer prevention. We present the actual knowledge about the glucosinolate synthesized by flavin-containing monooxygenase (FMO)(GS-OX1) and its role in cancer prevention, discuss the influence of mutations in FAD-dependent 5,10-methylenetetrahydrofolate reductase on the cancer risk, and describe FAD as an important cofactor for the demethylation of histons. We also present our views on the role of riboflavin supplements in the prevention against cancer.

Glucosinolate structures in evolution

By 2000, around 106 natural glucosinolates (GSLs) were probably documented. In the past decade, 26 additional natural GSL structures have been elucidated and documented. Hence, the total number of documented GSLs from nature by 2011 can be estimated to around 132. A considerable number of additional suggested structures are concluded not to be sufficiently documented. In many cases, NMR spectroscopy would have provided the missing structural information. Of the GSLs documented in the past decade, several are of previously unexpected structures and occur at considerable levels. Most originate from just four species: Barbarea vulgaris, Arabidopsis thaliana, Eruca sativa and Isatis tinctoria. Acyl derivatives of known GSLs comprised 15 of the 26 newly documented structures, while the remaining exhibited new substitution patterns or chain length, or contained a mercapto group or related thio-functionality. GSL identification methods are reviewed, and the importance of using authentic references and structure-sensitive detection methods such as MS and NMR is stressed, especially when species with relatively unknown chemistry are analyzed. An example of qualitative GSL analysis is presented with experimental details (group separation and HPLC of both intact and desulfated GSLs, detection and structure determination by UV, MS, NMR and susceptibility to myrosinase) with emphasis on the use of NMR for structure elucidation of even minor GSLs and GSL hydrolysis products. The example includes identification of a novel GSL, (R)-2-hydroxy-2-(3-hydroxyphenyl)ethylglucosinolate. Recent investigations of GSL evolution, based on investigations of species with well established phylogeny, are reviewed. From the relatively few such investigations, it is already clear that GSL profiles are regularly subject to evolution. This result is compatible with natural selection for specific GSL side chains. The probable existence of structure-specific GSL catabolism in intact plants suggests that biochemical evolution of GSLs has more complex implications than the mere liberation of a different hydrolysis product upon tissue disruption.

The natural chemopreventive phytochemical R-sulforaphane is a far more potent inducer of the carcinogen-detoxifying enzyme systems in rat liver and lung than the S-isomer

The chemopreventive activity of the phytochemical sulforaphane, (-)1-isothiocyanato-4R-(methylsulfinyl)-butane, present in cruciferous vegetables in substantial amounts in the form of glucosinolate, was demonstrated in animal models of cancer using the racemate, despite the fact that humans are exposed only to the R-enantiomer through the diet. Since a principal mechanism of the chemopreventive activity of sulforaphane is modulation of the carcinogen-metabolising enzyme systems, a study was conducted in precision-cut rat liver and lung slices, and in FAO cells comparing the ability of R- and S-sulforaphane to modulate these enzyme systems. R-sulforaphane elevated hepatic glutathione S-transferase and quinone reductase whereas the S-enantiomer had no effect; moreover, the R-enantiomer was more effective in up-regulating GSTα, GSTμ and quinone reductase protein levels. In the lung, both enantiomers increased the same enzyme activities with the R-enantiomer being more potent; in addition, the R-enantiomer was more effective in up-regulating GSTα and quinone reductase protein levels. Both isomers increased glutathione levels in both tissues, with R-sulforaphane being more potent. Finally, R-sulforaphane was the more effective of the two isomers in up-regulating CYP1A1/1B1 apoprotein levels in both liver and lung, and CYP1A2 in the liver. Similarly, in FAO cells the R-enantiomer was far more effective in up-regulating quinone reductase and glutathione S-transferase activities and protein levels compared with the S-isomer. These studies demonstrate clearly the superiority of R-sulforaphane, when compared with the S-enantiomer, in stimulating detoxification enzymes, and raises the possibility that the animal studies that employed the racemate may have underestimated the chemopreventive activity of this isothiocyanate.