Cytotoxic and genotoxic potential of food-borne nitriles in a liver in vitro model

Unravelling Glucoraphanin and Glucoerucin Metabolism across Broccoli Sprout Development: Insights from Metabolite and Transcriptome Analysis

Variations in the concentration of glucoraphanin (GRA) and glucoerucin (GER), as well as the corresponding breakdown products, isothiocyanates (ITCs) and nitriles, were investigated during the growth of broccoli sprouts. The concentrations of GRA and GER decreased sharply from 33.66 µmol/g to 11.48 µmol/g and 12.98 µmol/g to 8.23 µmol/g, respectively, after seed germination. From the third to the seventh day, both GRA and GER were maintained as relatively stable. The highest concentrations of sulforaphane (17.16 µmol/g) and erucin (12.26 µmol/g) were observed on the first day. Hereafter, the concentrations of nitrile hydrolyzed from GRA or GER were higher than those of the corresponding ITCs. Moreover, the ratio of sulforaphane to sulforaphane nitrile decreased from 1.35 to 0.164 from 1 d to 5 d, with a similar trend exhibited for erucin/erucin nitrile after 2 d. RNA-seq analysis showed that BolMYB28 and BolCYP83A1, involved in aliphatic glucosinolate (GSL) biosynthesis, remained largely unexpressed until the third day. In contrast, the genes operating within the GSL-myrosinase hydrolysis pathway were highly expressed right from the beginning, with their expression levels increasing significantly after the third day. Additionally, we identified two BolESPs and six BolNSPs that might play important roles in promoting the production of nitriles during the development of broccoli sprouts.

Degradation of glucosinolates and formation of isothiocyanates, nitriles, amines, and N,N'-dialk(en)yl thioureas during domestic boiling of red cabbage

Red cabbage is a popular vegetable in Central Europe and a rich source of glucosinolates (GLSs). Upon hydrolysis, GLSs form health-promoting isothiocyanates (ITCs), but also nitriles and epithionitriles. Recently, ITCs were shown to undergo further hydrolysis, yielding amines. Here, we analyzed the degradation of GLSs and the formation of ITCs, nitriles, epithionitriles, and amines during domestic-like cooking of red cabbage with addition of vinegar or baking soda. Both additives strongly affected the stability of GLSs and the formation of nitriles during boiling. Primary amines were found as a major degradation product of GLSs. In control and vinegar samples, formation of methylsulfinylalkyl amines increased during boiling. Additionally, for the first time, the formation of several N,N'-dialk(en)yl thioureas during boiling of Brassica vegetables was demonstrated, resulting from the reaction of GLS-derived ITCs and amines, and they were subsequently quantified. As references, five N,N'-dialk(en)yl thioureas were synthesized and characterized by NMR and HRMS.

Thermal degradation and oxidation of glucosinolates in model systems and Brassica vegetable broth is mediated by redox-active compounds

Glucosinolates (GLSs) are secondary plant metabolites with health-promoting effects found in Brassica vegetables. Recently, next to non-enzymatic degradation yielding nitriles, 4-(methylthio)butyl GLS (4MTB-GLS) was shown to undergo side chain oxidation during thermal treatment, forming 4-(methylsulfinyl)butyl GLS (4MSOB-GLS). Here, we investigated natural plant components and artificial analogs on their capability of altering the thermal reactivity of 4MTB-GLS in vegetable broths and model systems using buffers. Addition of ascorbic acid and dehydroascorbic acid caused varying effects: in broth samples, it increased nitrile formation, while in buffer, 4MSOB-GLS was formed. In further experiments, the antioxidant compounds quercetin and Trolox triggered the side chain oxidation of 4MTB-GLS, while H2S terminated its degradation. A synergistic effect of ascorbic acid and Fe2+ was observed, degrading 98% of 4MTB-GLS to the nitrile after 60 min of boiling. Deepening the understanding of factors that influence the non-enzymatic degradation of GLSs will help to preserve their health-promoting effects.

Metabolic profiling of Ochradenus baccatus Delile. utilizing UHPLC-HRESIMS in relation to the in vitro biological investigations

Ochradenus baccatus Delile (Resedaceae) is a desert plant with edible fruits native to the Middle East. Few investigators have reported antibacterial, antiparasitic and anti-cancer activities of the plant. Herein we evaluated the cytotoxic activity of O. baccatus using four cell lines and a zebrafish embryo model. Additionally, liquid chromatography coupled with mass spectroscopy was performed to characterize the extract's main constituents. The highest cytotoxicity was observed against human cervical adenocarcinoma (HeLa), with CC₅₀ of 39.1 µg/mL and a selectivity index (SI) of 7.23 (p < 0.01). Metabolic analysis of the extract resulted in the annotation of 57 metabolites, including fatty acids, flavonoids, glucosinolates, nitrile glycosides, in addition to organic acids. The extract showed an abundance of hydroxylated fatty acids (16 peaks). Further, 3 nitrile glycosides have been identified for the first time in Ochradenus sp., in addition to 2 glucosinolates. These identified phytochemicals may partially explain the cytotoxic activity of the extract. We propose O. baccatus as a possible safe food source for further utilization to partially contribute to the increasing food demand specially in Saharan countries.

Functional metagenomics uncovers nitrile-hydrolysing enzymes in a coal metagenome

Introduction: Nitriles are the most toxic compounds that can lead to serious human illness through inhalation and consumption due to environmental pollution. Nitrilases can highly degrade nitriles isolated from the natural ecosystem. In the current study, we focused on the discovery of novel nitrilases from a coal metagenome using in silico mining.

Methods: Coal metagenomic DNA was isolated and sequenced on the Illumina platform. Quality reads were assembled using MEGAHIT, and statistics were checked using QUAST. Annotation was performed using the automated tool SqueezeMeta. The annotated amino acid sequences were mined for nitrilase from the unclassified organism. Sequence alignment and phylogenetic analyses were carried out using ClustalW and MEGA11. Conserved regions of the amino acid sequences were identified using InterProScan and NCBI-CDD servers. The physicochemical properties of the amino acids were measured using ExPASy’s ProtParam. Furthermore, NetSurfP was used for 2D structure prediction, while AlphaFold2 in Chimera X 1.4 was used for 3D structure prediction. To check the solvation of the predicted protein, a dynamic simulation was conducted on the WebGRO server. Ligands were extracted from the Protein Data Bank (PDB) for molecular docking upon active site prediction using the CASTp server.

Results and discussion:In silico mining of annotated metagenomic data revealed nitrilase from unclassified Alphaproteobacteria. By using the artificial intelligence program AlphaFold2, the 3D structure was predicted with a per-residue confidence statistic score of about 95.8%, and the stability of the predicted model was verified with molecular dynamics for a 100-ns simulation. Molecular docking analysis determined the binding affinity of a novel nitrilase with nitriles. The binding scores produced by the novel nitrilase were approximately similar to those of the other prokaryotic nitrilase crystal structures, with a deviation of ±0.5.

Role of Sulfur Compounds in Vegetable and Mushroom Aroma

At the base of the food pyramid is vegetables, which should be consumed most often of all food products, especially in raw and unprocessed form. Vegetables and mushrooms are rich sources of bioactive compounds that can fulfill various functions in plants, starting from protection against herbivores and being natural insecticides to pro-health functions in human nutrition. Many of these compounds contain sulfur in their structure. From the point of view of food producers, it is extremely important to know that some of them have flavor properties. Volatile sulfur compounds are often potent odorants, and in many vegetables, belonging mainly to Brassicaeae and Allium (Amaryllidaceae), sulfur compounds determine their specific flavor. Interestingly, some of the pathways that form volatile sulfur compounds in vegetables are also found in selected edible mushrooms. The most important odor-active organosulfur compounds can be divided into isothiocyanates, nitriles, epithionitriles, thiols, sulfides, and polysulfides, as well as others, such as sulfur containing carbonyl compounds and esters, R-L-cysteine sulfoxides, and finally heterocyclic sulfur compounds found in shiitake mushrooms or truffles. This review paper summarizes their precursors and biosynthesis, as well as their sensory properties and changes in selected technological processes.

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.

Current Methods for the Extraction and Analysis of Isothiocyanates and Indoles in Cruciferous Vegetables

Cruciferous vegetables are characterized by the presence of sulfur-containing secondary plant metabolites known as glucosinolates (GLS). The consumption of cruciferous vegetables such as broccoli, cabbage, rocket salad, and cauliflower has been related to the prevention of non-communicable diseases. Their beneficial effects are attributed to the enzymatic degradation products of GLS, e.g., isothiocyanates and indoles. Owing to these properties, there has been a shift in the last few years towards the research of these compounds and a wide range of methods for their extraction and analytical determination have been developed. The aim of this review is to present the sample preparation and extraction procedures of isothiocyanates and indoles from cruciferous vegetables and the analytical methods for their determination. The majority of the references that have been reviewed are from the last decade. Although efforts towards the application of eco-friendly non-conventional extraction methods have been made, the use of conventional solvent extraction is mainly applied. The major analytical techniques employed for the qualitative and quantitative analysis of isothiocyanates and indoles are high-performance liquid chromatography and gas chromatography coupled with or without mass spectrometry detection. Nevertheless, the analytical determination of isothiocyanates presents several problems due to their instability and the absence of chromophores, making the simultaneous determination of isothiocyanates and indoles a challenging task.

Modulation of IR as a therapeutic target to prevent NASH using NRF from Diceratella elliptica (DC.) jonsell. Strong Nrf2 and leptin inducer as well as NF-kB inhibitor

BACKGROUND

Insulin resistance (IR) and lipotoxicity were evidenced as the major nonalcoholic steatohepatitis (NASH) initiators. However, absence of the effective treatment against NASH progression raised our aim to discover a new promising insulin modulator and NSH preventer.

PURPOSE

Our study aimed to extract and prepare a nitriles rich fraction (NRF) from Diceratella elliptica (DC.) Jonsell, investigate its insulin-sensitizing & anti-NASH potentialities and address its molecular targets in IR-NASH pathogenesis.

STUDY DESIGN

NRF was prepared using natural autolysis method and compounds were identified. Then, seventy male Wistar rats were feed high fat diet (HFD) or normal pellets for 35 days. In day 14th, HFD rats were injected by Streptozotocin (STZ) once and treatment was started in day 21st with either NRF (30, 60 and 120 mg/kg; orally) or pioglitazone (PioG) (10 mg/kg; i.p) beside HFD. While, NRF-alone rats were treated with NRF (120 mg/kg; orally) beside the normal pellets. Body weight, glucose homeostasis, hepatopathological examinations were performed.

METHODS

Gas liquid chromatography-mass spectrophotometry (GLC/MS) was used for compounds' identification while spectrophotometer was used for total glucosinolates (GLS) quantification. Also, the biochemical and molecular investigations concerned with liver lipotoxicity, oxidative stress, inflammation and insulin signaling pathway were investigated and confirmed with the computational prediction of the major compounds' targets.

RESULTS

Butenyl and benzyl GLS were the major along with other volatile compounds. NRF had significantly increased the insulin sensitivity and improved NASH-hisptopathology showing hepatoprotective effect. While, the fraction's anti-NASH potentiality was evidenced in the normalized hepatic steatosis markers, inflammation and oxidative stress key transcriptional factors resulting in induction of insulin receptor substrates (IRSs) phosphorylation and its downstream effectors.

CONCLUSION

NRF has reversed IR, stimulated leptin secretion and prevented NASH initiation showing promising anti-NASH and anti-fibrotic effects.

Mild heat combined with lactic acid fermentation: a novel approach for enhancing sulforaphane yield in broccoli puree

This study evaluated for the first time the feasibility of mild preheating treatment of broccoli florets combined with lactic acid bacteria fermentation for enhancing sulforaphane yield in broccoli puree. The optimum preheating condition for in-pack processing of broccoli florets was 3 min treatment at 65 °C increasing sulforaphane yield in broccoli puree by ∼5 times compared to untreated broccoli. Preheating of broccoli florets in-pack (65 °C per 3 min) combined with lactic acid bacteria fermentation further enhanced the sulforaphane content by ∼16 times compared to untreated broccoli. The sulforaphane content of the preheated-fermented puree remained stable (∼94% retention) for two weeks at 4 °C. The results indicate that a combination of judicious heat treatment of broccoli florets with lactic acid bacteria fermentation enables production of safe and high sulforaphane content broccoli products with potential health benefits.

Natural Variation of Glucosinolates and Their Breakdown Products in Broccoli (Brassica oleracea var. italica) Seeds

Seeds of 32 pure lines and 6 commercial broccoli cultivars were used to investigate variation in glucosinolates and their breakdown products. The aliphatic glucosinolate content was 54.5-218.7 μmol/g fresh weight, accounting for >90% of the total glucosinolates. The major glucosinolates found were glucoraphanin and glucoerucin in 27 samples and progoitrin in 7 samples. A gas chromatography-flame ionization detector (GC-FID) method was used to identify glucosinolate breakdown products; nine products were directly determined using standards. Using Arabidopsis thaliana lines myb28myb29 and Landsberg erecta to hydrolyze each reference glucosinolate, seven products were tentatively identified. 4-(Methylsulfinyl)butyl isothiocyanate and 5-(methylsulfinyl)pentanenitrile contents were 2.6-91.1 μmol/g fresh weight and 0-35.4 μmol/g fresh weight, respectively, with epithionitriles being more common than nitriles in accessions rich in alkenyl glucosinolate. Additionally, (S)-5-vinyl-1,3-oxazolidine-2-thione was detected in accessions rich in progoitrin. Specific lines with altered glucosinolate profiles and breakdown products were obtained and discussed according to the putative glucosinolate metabolism pathway.

Modulation of hepatic ABC transporters by Eruca vesicaria intake: Potential diet-drug interactions

The aim of this work was to evaluate whether oral administration of Eruca vesicaria, a species of rocket cultivated in Argentina, could modify cyclophosphamide (CP)-induced genotoxicity through modulation of hepatic ABC transporters. Daily oral administration of E. vesicaria fresh leaves juice (1.0, 1.4 and 2.0  g/kg) for 14 days did not alter genotoxicity biomarkers -alkaline comet assay and micronucleus test -in neither male nor female mice. Instead, repeated intake of this cruciferous decreased CP-induced DNA damage dose-dependently and it caused hepatic overexpression of P-glycoprotein (P-gp; 1.4 and 2.0  g/kg) and multidrug resistance protein 2 (MRP2; 2.0  g/kg), but not breast cancer resistance protein (Bcrp). The antigenotoxic effect of E. vesicaria was prevented by 50 mg/kg verapamil (P-gp inhibitor) or 10 mg/kg indomethacin (MRP2 inhibitor). In turn, CP-induced cytotoxicity (10 mM, 24 h) on human hepatoma cells (HepG2/C3A) was significantly reduced by preincubation with E. vesicaria (1.4 mg/ml; 48 h); this effect was absent when CP was coincubated with 35 μM verapamil, 80 μM indomethacin or 10 μM KO-143 (BCRP inhibitor). Altogether, these results allow us to demonstrate that repeated intake of E. vesicaria exhibited antigenotoxicity, at least in part, by induction of hepatic ABC transporters in vivo in mice as well as in vitro in human liver cells. This could account for other diet-drug interactions.

Organ-Specific Expression of IL-1 Receptor Results in Severe Liver Injury in Type I Interferon Receptor Deficient Mice

Upon treatment with polyinosinic:polycytidylic acid [poly(I:C)], an artificial double-stranded RNA, type I interferon receptor-deficient (IFNAR^−/−) mice develop severe liver injury seen by enhanced alanine aminotransferase (ALT) activity in the serum that is not observed in their wildtype (WT) counterparts. Recently, we showed that liver injury is mediated by an imbalanced expression of interleukin (IL)-1β and its receptor antagonist (IL1-RA) in the absence of type I IFN. Here we show that despite comparable expression levels of IL-1β in livers and spleens, spleens of poly(I:C)-treated IFNAR^−/− mice show no signs of injury. In vitro analyses of hepatocytes and splenocytes revealed that poly(I:C) had no direct toxic effect on hepatocytes. Furthermore, expression levels of cytokines involved in other models for liver damage or protection such as interferon (IFN)-γ, transforming growth factor (TGF)-β, IL-6, IL-10, IL-17, and IL-22 were comparable for both organs in WT and IFNAR^−/− mice upon treatment. Moreover, flow cytometric analyses showed that the composition of different immune cells in livers and spleens were not altered upon injection of poly(I:C). Finally, we demonstrated that the receptor binding IL-1β, IL1R1, is specifically expressed in livers but not spleens of WT and IFNAR^−/− mice. Accordingly, mice double-deficient for IFNAR and IL1R1 developed no liver injury upon poly(I:C) treatment and showed ALT activities comparable to those of WT mice. Collectively, liver injury is mediated by the organ-specific expression of IL1R1 in the liver.

Intake of glucosinolates and risk of coronary heart disease in three large prospective cohorts of US men and women

Importance

Glucosinolates, a group of phytochemicals abundant in cruciferous vegetables, may have cardioprotective properties. However, no prospective study has evaluated the association of intake of glucosinolates with the risk of coronary heart disease (CHD).

Objective

The objective of the study was to evaluate the association between the intake of glucosinolates and incident CHD in US men and women.

Design

Prospective longitudinal cohort study.

Setting

Health professionals in the USA.

Participants

We followed 74,241 women in the Nurses’ Health Study (NHS; 1984–2012), 94,163 women in the NHSII (1991–2013), and 42,170 men in the Health Professionals Follow-Up Study (1986–2012), who were free of cardiovascular disease and cancer at baseline.

Exposure

Glucosinolate intake was assessed using validated semi-quantitative food frequency questionnaires at baseline and updated every 2–4 years during follow-up.

Main outcome measures

Incident cases of CHD were confirmed by medical record review.

Results

During 4,824,001 person-years of follow-up, 8,010 cases of CHD were identified in the three cohorts. After adjustment for major lifestyle and dietary risk factors of CHD, weak but significantly positive associations were observed for glucosinolates with CHD risk when comparing the top with bottom quintiles (hazard ratio [HR]:1.09; 95% CI: 1.01, 1.17; P_trend<0.001). Higher intakes of three major subtypes of glucosinolates were consistently associated with a higher CHD risk, although the association for indolylglucosinolate did not achieve statistical significance. Regarding cruciferous vegetable intake, participants who consumed one or more servings per week of Brussels sprouts (HR: 1.16; 95% CI: 1.06, 1.26; P<0.001) and cabbage (HR: 1.09; 95% CI: 1.02, 1.17; P=0.009) had a significantly higher CHD risk than those who consumed these cruciferous vegetables less than once per month.

Conclusion and relevance

In these three prospective cohort studies, dietary glucosinolate intake was associated with a slightly higher risk of CHD in US adults. These results warrant replications in further studies including biomarker-based studies. Further studies are needed to confirm these findings and elucidate mechanistic pathways that may underlie these associations.

The major glucosinolate hydrolysis product in rocket (Eruca sativa L.), sativin, is 1,3-thiazepane-2-thione: Elucidation of structure, bioactivity, and stability compared to other rocket isothiocyanates

Rocket is rich in glucosinolates and valued for its hot and spicy taste. Here we report the structure elucidation, bioactivity, and stability of the mainly formed glucosinolate hydrolysis product, namely sativin, which was formerly thought to be 4-mercaptobutyl isothiocyanate. However, by NMR characterization we revealed that sativin is in fact 1,3-thiazepane-2-thione, a tautomer of 4-mercaptobutyl isothiocyanate with 7-membered ring structure and so far unknown. This finding was further substantiated by conformation sampling using molecular modeling and total enthalpy calculation with density functional theory. During aqueous heat treatment sativin in general was quite stable, while the isothiocyanates erucin and sulforaphane were labile, having half-lives of 132 min and 56 min (pH 5, 100 °C), respectively. Moreover, using a WST-1 assay, we found that sativin did not reduce cell viability of HepG2 cells in a range of 0.3-30 µM, and, therefore, exhibited no cytotoxic effects in this cell line.

Optimizing isothiocyanate formation during enzymatic glucosinolate breakdown by adjusting pH value, temperature and dilution in Brassica vegetables and Arabidopsis thaliana

Consumption of glucosinolate-rich Brassicales vegetables is associated with a decreased risk of cancer with enzymatic hydrolysis of glucosinolates playing a key role. However, formation of health-promoting isothiocyanates is inhibited by the epithiospecifier protein in favour of nitriles and epithionitriles. Domestic processing conditions, such as changes in pH value, temperature or dilution, might also affect isothiocyanate formation. Therefore, the influences of these three factors were evaluated in accessions of Brassica rapa, Brassica oleracea, and Arabidopsis thaliana. Mathematical modelling was performed to determine optimal isothiocyanate formation conditions and to obtain knowledge on the kinetics of the reactions. At 22 °C and endogenous plant pH, nearly all investigated plants formed nitriles and epithionitriles instead of health-promoting isothiocyanates. Response surface models, however, clearly demonstrated that upon change in pH to domestic acidic (pH 4) or basic pH values (pH 8), isothiocyanate formation considerably increases. While temperature also affects this process, the pH value has the greatest impact. Further, a kinetic model showed that isothiocyanate formation strongly increases due to dilution. Finally, the results show that isothiocyanate intake can be strongly increased by optimizing the conditions of preparation of Brassicales vegetables.

Isothiocyanates, Nitriles, and Epithionitriles from Glucosinolates Are Affected by Genotype and Developmental Stage in Brassica oleracea Varieties

Vegetables of the Brassica oleracea group, such as broccoli, cauliflower, and cabbage, play an important role for glucosinolate consumption in the human diet. Upon maceration of the vegetable tissue, glucosinolates are degraded enzymatically to form volatile isothiocyanates, nitriles, and epithionitriles. However, only the uptake of isothiocyanates is linked to the cancer-preventive effects. Thus, it is of great interest to evaluate especially the isothiocyanate formation. Here, we studied the formation of glucosinolates and their respective hydrolysis products in sprouts and fully developed vegetable heads of different genotypes of the five B. oleracea varieties: broccoli, cauliflower as well as white, red, and savoy cabbages. Further, the effect of ontogeny (developmental stages) during the head development on the formation of glucosinolates and their respective hydrolysis products was evaluated at three different developmental stages (mini, fully developed, and over-mature head). Broccoli and red cabbage were mainly rich in 4-(methylsulfinyl)butyl glucosinolate (glucoraphanin), whereas cauliflower, savoy cabbage and white cabbage contained mainly 2-propenyl (sinigrin) and 3-(methylsulfinyl)propyl glucosinolate (glucoiberin). Upon hydrolysis, epithionitriles or nitriles were often observed to be the main hydrolysis products, with 1-cyano-2,3-epithiopropane being most abundant with up to 5.7 μmol/g fresh weight in white cabbage sprouts. Notably, sprouts often contained more than 10 times more glucosinolates or their hydrolysis products compared to fully developed vegetables. Moreover, during head development, both glucosinolate concentrations as well as hydrolysis product concentrations changed and mini heads contained the highest isothiocyanate concentrations. Thus, from a cancer-preventive point of view, consumption of mini heads of the B. oleracea varieties is recommended.