Cysteine Sulfoxide Research Articles

Traces of convergent evolution left in the structure of EgtB-IV

The enzymatically regioselective catalyzed incorporation of cysteine sulfoxide into histidine generates physiologically important antioxidants such as ergothioneine and ovothiol. In this issue of Structure, Ireland etal.1 report the crystal structure of EgtB-IV, which provides insights into the convergent evolution of sulfoxide synthase.

Effects of blanching cultivation on the chemical composition and nutritional quality of Chinese chive

Blanching is an agricultural practice where vegetables are cultivated in darkness to prevent photosynthesis, thereby modifying their colour, texture, and flavor. The technique is popularly employed in Chinese chive (CC). Blanched Chinese chive (BCC) is renowned for its pale-yellow appearance, delicate flavor, and culinary-medicinal values; nonetheless, how blanching alters the chemical composition largely remains intangible. In this study, the physiological, nutritional, and metabolic profiles of BCC and CC were investigated. In BCC, the contents of ascorbic acid, flavonoids, anthocyanins, etc. were decreased markedly, whereas the sugar content and pungency were increased significantly, indicating that blanching shaped the vegetable flavor. UPLC-ESI-MS/MS analysis revealed 366 differential metabolites between BCC and CC, and the metabolism of flavor precursors, S-alk(en)yl cysteine sulfoxides, were stimulated by blanching. Together, these findings give a strong clue that blanching increases the pungency flavor in CC, and is a useful technique for improving other selected vegetables.

Cruciferous vegetables lower blood pressure in adults with mildly elevated blood pressure in a randomized, controlled, crossover trial: the VEgetableS for vaScular hEaLth (VESSEL) study

BackgroundHigher cruciferous vegetable intake is associated with lower cardiovascular disease risk in observational studies. The pathways involved remain uncertain. We aimed to determine whether cruciferous vegetable intake (active) lowers 24-h brachial systolic blood pressure (SBP; primary outcome) compared to root and squash vegetables (control) in Australian adults with mildly elevated BP (SBP 120–160 mmHg inclusive).MethodsIn this randomized, controlled, crossover trial, participants completed two 2-week dietary interventions separated by a 2-week washout. Cruciferous vegetables were compared to root and squash vegetables (~ 300 g/day) consumed with lunch and dinner meals. Participants were blinded to which interventions were the active and control. Adherence was assessed using food diaries and biomarkers (S-methyl cysteine sulfoxide (SMCSO, active) and carotenoids (control)). Twenty-four-hour brachial ambulatory SBP and secondary outcomes were assessed pre- and post each intervention. Differences were tested using linear mixed effects regression.ResultsEighteen participants were recruited (median (IQR) age: 68 (66–70); female: n = 16/18; mean ± SD clinic SBP: 135.9 ± 10.0 mmHg). For both interventions, 72% participants had 100% adherence (IQR: 96.4–100%). SMCSO and carotenoids were significantly different between interventions (mean difference active vs. control SMCSO: 22.93 mg/mL, 95%CI 15.62, 30.23, P < 0.0001; carotenoids: − 0.974 mg/mL, 95%CI − 1.525, − 0.423, P = 0.001). Twenty-four-hour brachial SBP was significantly reduced following the active vs. control (mean difference − 2.5 mmHg, 95%CI − 4.2, − 0.9, P = 0.002; active pre: 126.8 ± 12.6 mmHg, post: 124.4 ± 11.8 mmHg; control pre: 125.5 ± 12.1 mmHg, post: 124.8 ± 13.1 mmHg, n = 17), driven by daytime SBP (mean difference − 3.6 mmHg, 95%CI − 5.4, − 1.7, P < 0.001). Serum triglycerides were significantly lower following the active vs. control (mean difference − 0.2 mmol/L, 95%CI − 0.4, − 0.0, P = 0.047).ConclusionsIncreased intake of cruciferous vegetables resulted in reduced SBP compared to root and squash vegetables. Future research is needed to determine whether targeted recommendations for increasing cruciferous vegetable intake benefits population health.Trial registrationClinical trial registry ACTRN12619001294145. https://www.anzctr.org.au

Brassicaceae Mustards: Phytochemical Constituents, Pharmacological Effects, and Mechanisms of Action against Human Disease.

The Brassicaceae genus consists of many economically important mustards of value for food and medicinal purposes, namely Asian mustard (Brassica juncea), ball mustard (Neslia paniculata), black mustard (B. nigra), garlic mustard (Alliaria petiolata), hedge mustard (Sisymbrium officinale), Asian hedge mustard (S. orientale), oilseed rape (B. napus), rapeseed (B. rapa), treacle mustard (Erysimum repandum), smooth mustard (S. erysimoides), white ball mustard (Calepina irregularis), white mustard (Sinapis alba), and Canola. Some of these are commercially cultivated as oilseeds to meet the global demand for a healthy plant-derived oil, high in polyunsaturated fats, i.e., B. napus and B. juncea. Other species are foraged from the wild where they grow on roadsides and as a weed of arable land, i.e., E. repandum and S. erysimoides, and harvested for medicinal uses. These plants contain a diverse range of bioactive natural products including sulfur-containing glucosinolates and other potentially valuable compounds, namely omega-3-fatty acids, terpenoids, phenylpropanoids, flavonoids, tannins, S-methyl cysteine sulfoxide, and trace-elements. Various parts of these plants and many of the molecules that are produced throughout the plant have been used in traditional medicines and more recently in the mainstream pharmaceutical and food industries. This study relates the uses of mustards in traditional medicines with their bioactive molecules and possible mechanisms of action and provides an overview of the current knowledge of Brassicaceae oilseeds and mustards, their phytochemicals, and their biological activities.

Transcriptome Reveals the Key Genes Related to the Metabolism of Volatile Sulfur-Containing Compounds in Lentinula edodes Mycelium.

Lentinula edodes (L. edodes) is a globally popular edible mushroom because of its characteristic sulfur-containing flavor compounds. However, the formation of the volatile sulfur-containing compounds in the mycelium of L. edodes has not been studied. We found that there were also sulfur-containing aroma compounds in the mycelium of L. edodes, and the content and composition varied at different stages of mycelial growth and development. The γ-glutamyl-transpeptidase (GGT) and cysteine sulfoxide lyase (C-S lyase) related to the generation of sulfur compounds showed the highest activities in the 15-day sample. Candidate genes for the metabolism of volatile sulfur compounds in mycelium were screened using transcriptome analysis, including encoding the GGT enzyme, C-S lyase, fatty acid oxidase, HSP20, and P450 genes. The expression patterns of Leggt3 and Leccsl3 genes were consistent with the measured activities of GGT and C-S lyase during the cultivation of mycelium and molecular dynamics simulations showed that they could stably bind to the substrate. Our findings provide insights into the formation of sulfur-containing flavor compounds in L. edodes. The mycelium of L. edodes is suggested for use as material for the production of sulfur-containing flavor compounds.

Profiling of Organosulfur Compounds in Onions: A Comparative Study between LC-HRMS and DTD-GC-MS

Onions are known not only for their culinary importance but also for their nutritional and health-promoting properties. Both properties are closely linked to their content of organosulfur compounds, which account for up to 5% of the dry weight of an onion. Given the importance of these compounds, suitable analytical methods are required for their study. Two techniques should be highlighted in this context: gas chromatography coupled to mass spectrometry (GC-MS), and liquid chromatography coupled to mass spectrometry (LC-MS). In this study, eight different onion varieties were analyzed using two distinct analytical techniques: direct thermal desorption–gas chromatography–mass spectrometry (DTD-GC-MS) and high-resolution mass spectrometry (HRMS) on an LC-ESI-QqTOF instrument. Each method identified different organosulfur compounds, with LC-HRMS targeting 15 non-volatile compounds, such as cysteine sulfoxides, and GC-MS targeting 18 volatiles, such as disulfides and trisulfides. The results obtained were studied using Pearson correlations and principal component analysis. No precise correlation was found between the initial organosulfur compounds in onions and their hydrolysates. Consequently, although GC is one of the most employed techniques in the scientific literature, the use of LC-HRMS or a combination of both techniques may offer a more comprehensive and accurate description of the metabolomic profile of onions.

Advanced Insulin Synthesis by One‐Pot/Stepwise Disulfide Bond Formation Enabled by S‐Protected Cysteine Sulfoxide

Advanced Insulin Synthesis by One‐Pot/Stepwise Disulfide Bond Formation Enabled by S‐Protected Cysteine Sulfoxide

Advanced Insulin Synthesis by One-pot/Stepwise Disulfide Bond Formation Enabled by S-Protected Cysteine Sulfoxide.

An advanced insulin synthesis is presented that utilizes one-pot/stepwise disulfide bond formation enabled by acid-activated S-protected cysteine sulfoxides in the presence of chloride anion. S-chlorocysteine generated from cysteine sulfoxides reacts with an S-protected cysteine to afford S-sulfenylsulfonium cation, which then furnishes the disulfide or reversely returns to the starting materials depending on the S-protection employed and the reaction conditions. Use of S-acetamidomethyl cysteine (Cys(Acm)) and its sulfoxide (Cys(Acm)(O)) selectively give the disulfide under weak acid conditions in the presence of MgCl2 even if S-p-methoxybenzyl cysteine (Cys(MBzl)) and its sulfoxide (Cys(MBzl)(O)) are also present. In contrast, the S-MBzl pair yields the disulfide under more acidic conditions in the presence of a chloride anion source. These reaction conditions allowed a one-pot insulin synthesis. Additionally, lipidated insulin was prepared by a one-pot disulfide-bonding/lipidation sequence.

Sulfoxide‐Mediated Cys‐Trp‐Selective Bioconjugation that Enables Protein Labeling and Peptide Heterodimerization

AbstractA method was developed that enables the magnesium chloride (MgCl2)‐activated S‐acetamidomethyl cysteine sulfoxide (Cys(Acm)(O)) to induce the sp2(C−H) sulfenylation of the indole of Trp residues. The reaction operates under mild acidic conditions using acetic acid or an ionic liquid to give the Trp‐sulfenylated products. Other than Trp, all other proteinogenic amino acids are unreactive to the sulfenylation conditions. We demonstrated the successful application of this reaction to various peptides, including lysozyme. Furthermore, we achieved the Trp‐modification of a monoclonal antibody by a MgCl2‐mediated reaction in an acidic ionic liquid. The resulting antibody exhibited antibody performance comparable to the parent protein. The amide moiety in the Acm group contributes to the difference in chemical behaviors between S‐Acm and S‐p‐methoxybenzyl (MBzl)‐protected cysteine sulfoxides. This is because the S‐Acm sulfoxide is converted to S‐chlorocysteine responsible for Trp‐sulfenylation under less acidic conditions than those required for the reaction of S‐MBzl sulfoxide. Based on this rationale, we prepared a linker possessing S‐Acm and S‐MBzl oxide moieties and subjected the linker to heterodimerization of DNA‐binding MYC and MAX peptides containing a Trp handle. The one‐pot/stepwise Cys‐Trp conjugation between the linker and DNA‐binding peptides allowed the generation of a heterodimeric MYC/MAX DNA binder.

S-Methyl Cysteine Sulfoxide Does Not Ameliorate Weight Gain or Hyperlipidemia in Mice Fed a High-Fat Diet.

Higher intake of cruciferous and allium vegetables is associated with lower cardiometabolic risk. Little research has investigated the cardiometabolic effects of S-methyl cysteine sulfoxide (SMCSO), found abundant in these vegetables. This study hypothesizes that SMCSO will blunt development of metabolic syndrome features in mice fed high-fat feed. Fifty C57BL/6 male mice are randomly assigned to standard-chow, high-fat, or high-fat supplemented with low-SMCSO (43mgkg-1 body weight [BW]day-1), medium-SMCSO (153mgkg-1 BWday-1), or high-SMCSO (256mgkg-1 BWday-1) for 12-weeks. High-fat with SMCSO did not prevent diet-induced obesity, glucose intolerance, or hypercholesterolemia. Mice fed high-fat with SMCSO has higher hepatic lipids than mice fed standard-chow or high-fat alone. Urinary SMCSO increases at 6- and 12-weeks in the low-SMCSO group, before reducing 46% and 28% in the medium- and high-SMCSO groups, respectively, at 12-weeks, suggesting possible tissue saturation. Interestingly, two SMCSO-fed groups consume significantly more feed, without significant weight gain. Due to limitations in measuring consumed feed, caution should be taken interpreting these results. SMCSO (43-256mgkg-1 BWday-1) does not ameliorate metabolic syndrome features in high-fat fed mice. Substantial knowledge gaps remain. Further studies should administer SMCSO separately (i.e., gavage), with metabolic studies exploring tissue levels to better understand its physiological action.

Development of a food composition database for the estimation of dietary S-methyl cysteine sulfoxide from vegetables

A food composition database estimating S-methyl cysteine sulfoxide (SMCSO) was created following a systematic literature search. SMCSO data (705 entries) from 19 vegetables were summarised: brassicas (n = 10) and alliums (n = 9). The highest SMCSO in brassicas was reported in Brussels sprouts (median [range]: 318 [68−420] mg/100 g fresh weight (FW)) whilst the lowest was in radish (19 [4–45] mg/100 g FW). Brussels sprouts were almost twice as concentrated in SMCSO as cauliflower, followed by cabbage, kale, broccoli, kohlrabi, swede, Chinese cabbage, and turnips. The alliums highest in SMCSO were Chinese chives (271 [185−413] mg/100 g FW) followed by rakkyo and garlic, with substantially less found in shallots, onion, and leek. Literature reporting SMCSO content in food is sparse. Further research is required to quantify SMCSO in commercially available vegetables and other foods, in order to update and expand this database for application to large populations and future intervention studies.

Phenolic Content, Amino Acids, Volatile Compounds, Antioxidant Capacity, and Their Relationship in Wild Garlic (A. ursinum L.).

Allium ursinum L. is a wild relative of garlic, and it is abundant in many antioxidant compounds. Sulfur compounds, primarily cysteine sulfoxides (CSOs), are converted through several reactions into various volatile molecules, which are considered the principal flavor compounds of Alliums. In addition to secondary metabolites, wild garlic is abundant in primary compounds, such as amino acids, which serve not only as building blocks for the health-promoting sulfur compounds but also as antioxidants. The aim of this study was to investigate the link between individual amino acid contents, the total phenolic content, and the profile of volatile compounds as well as their influence on the antioxidant capacity of both the leaves and bulbs of wild garlic populations in Croatia. Both univariate and multivariate methods were used to study the differences in the phytochemical compositions among the wild garlic plant organs and the link between individual compounds and antioxidant capacity. Both the plant organ and location, as well as their interaction, have a significant impact on the content of total phenolic content, amino acids, volatile organic compounds, and the antioxidant capacity of wild garlic.

Isotope-Guided Metabolomics Reveals Divergent Incorporation of Valine into Different Flavor Precursor Classes in Chives.

Plants of the genus Allium such as chives, onions or garlic produce S-alk(en)yl cysteine sulfoxides as flavor precursors. Two major representatives are S-propenyl cysteine sulfoxide (isoalliin) and S-propyl cysteine sulfoxide (propiin), which only differ by a double bond in the C3 side chain. The propenyl group of isoalliin is derived from the amino acid valine, but the source of the propyl group of propiin remains unclear. Here, we present an untargeted metabolomics approach in seedlings of chives (Allium schoenoprasum) to track mass features containing sulfur and/or 13 C from labeling experiments with valine-13 C5 guided by their isotope signatures. Our data show that propiin and related propyl-bearing metabolites incorporate carbon derived from valine-13 C5 , but to a much lesser extent than isoalliin and related propenyl compounds. Our findings provide new insights into the biosynthetic pathways of flavor precursors in Allium species and open new avenues for future untargeted labeling experiments.

Cover Feature: Residue‐Selective C−H Sulfenylation Enabled by Acid‐Activated S‐Acetamidomethyl Cysteine Sulfoxide with Application to One‐Pot Stapling and Lipidation Sequence (Chem. Eur. J. 26/2023)

The aromatic (C−H) sulfenylation reaction with S-acetamidomethyl cysteine sulfoxide (Cys(Acm)(O)) can be Trp- or Tyr-selective under acidic conditions. The red chloride anion team kicks the Cys(Acm)(O) ball into the Trp goal, whereas the blue trimethylsilyl team kicks the ball into the Tyr goal. The proton scoreline in the stands supports both teams. More information can be found in the Research Article by A. Otaka and co-workers (DOI: 10.1002/chem.202300799).

Novel simultaneous determination of alliin and allicin in Allium sp. using digital subtraction HPTLC

Allicin is a major thiosulfinate found in garlic and other Allium sp. and it is responsible for their pungent aroma. It is formed during the tissue lysis of garlic, by the initial action of alliinase upon alliin, the major cysteine sulfoxide. Simultaneous detection of these two analytes is usually performed using HPLC. Contrary to the most important phytoconstituents in other samples, allicin is scarcely detected using the simple HPTLC technique, due to challenges caused by its unique structure, despite its simplicity and high needs in the analytical monitoring of the Allium sp. In this work, a cost-effective, simple, sensitive and accurate method was developed for the determination of allicin together with alliin, using HPTLC. Allicin is quickly pre-derivatised with cysteine in excess to the stable S-allylmercaptocysteine that is then simultaneously detected with alliin, using ninhydrin reagent. The method was validated in terms of accuracy (recoveries of 90–120 %), precision (RSD% of 4–12 %), selectivity, robustness, peak purity and limit of detection (LOD = 0.05 μg/band for allicin and LOD = 0.10 μg/band for alliin). The method was successfully applied using real Allium sp. samples and the results were in good agreement with HPLC data.

Residue-selective C-H sulfenylation enabled by acid-activated S-acetamidomethyl cysteine sulfoxide with application to one-pot stapling and lipidation sequence.

A tyrosine (Tyr)- or tryptophan (Trp)-selective metal-free C-H sulfenylation reaction using an acid-activated S-acetamidomethyl cysteine (Cys) sulfoxide, Cys(Acm)(O), has been achieved. The dually protonated intermediate produced from the Cys(Acm)(O) under acidic conditions allows the sulfenylation of Tyr. Significantly, the reaction in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) mainly affords a Cys-Tyr-linked peptide even in the presence of Trp residues. In contrast, a Cys-Trp-linked peptide was selectively obtained from the reaction in the presence of guanidine hydrochloride (Gn·HCl) under acidic conditions. Established Tyr- and Trp-selective sulfenylation methods were used in the Cys-Tyr stapling and Trp-lipidation of glucagon-like peptides in a one-pot/stepwise manner. Investigation of the mechanism showed that orbital- and charge-controlled reactions are responsible for the Trp and Tyr selectivity, respectively.

A global phylogenomic analysis of the shiitake genus Lentinula

Lentinula is a broadly distributed group of fungi that contains the cultivated shiitake mushroom, L. edodes. We sequenced 24 genomes representing eight described species and several unnamed lineages of Lentinula from 15 countries on four continents. Lentinula comprises four major clades that arose in the Oligocene, three in the Americas and one in Asia-Australasia. To expand sampling of shiitake mushrooms, we assembled 60 genomes of L. edodes from China that were previously published as raw Illumina reads and added them to our dataset. Lentinula edodes sensu lato (s. lat.) contains three lineages that may warrant recognition as species, one including a single isolate from Nepal that is the sister group to the rest of L. edodes s. lat., a second with 20 cultivars and 12 wild isolates from China, Japan, Korea, and the Russian Far East, and a third with 28 wild isolates from China, Thailand, and Vietnam. Two additional lineages in China have arisen by hybridization among the second and third groups. Genes encoding cysteine sulfoxide lyase (lecsl) and γ-glutamyl transpeptidase (leggt), which are implicated in biosynthesis of the organosulfur flavor compound lenthionine, have diversified in Lentinula. Paralogs of both genes that are unique to Lentinula (lecsl 3 and leggt 5b) are coordinately up-regulated in fruiting bodies of L. edodes. The pangenome of L. edodes s. lat. contains 20,308 groups of orthologous genes, but only 6,438 orthogroups (32%) are shared among all strains, whereas 3,444 orthogroups (17%) are found only in wild populations, which should be targeted for conservation.

Metabolomic based approach to identify biomarkers of broccoli intake.

It is well-established that consumption of cruciferous and brassica vegetables has a correlation with reduced rates of many negative health outcomes. There is an increased interest in identifying food intake biomarkers to address limitations related to self-reported dietary assessment. The study aims to identify biomarkers of broccoli intake using metabolomic approaches, examine the dose-response relationship, and predict the intake by multimarker panel. Eighteen volunteers consumed cooked broccoli in A-Diet Discovery study and fasting and postprandial urine samples were collected at 2, 4 and 24 hours. Subsequently the A-Diet Dose-response study was performed where volunteers consumed different portions of broccoli (49, 101 or 153 g) and urine samples were collected at the end of each intervention week. Urine samples were analysed by 1H-NMR and LC-MS. Multivariate data analysis and one-way ANOVA were performed to identify discriminating biomarkers. A panel of putative biomarkers was examined for its ability to predict intake through a multiMarker model. Multivariate analysis revealed discriminatory spectral regions between fasting and fed metabolic profiles. Subsequent time-series plots revealed multiple features increased in concentration following the consumption. Urinary S-methyl cysteine sulfoxide (SMCSO) increased as broccoli intake increased (0.17-0.24 μM per mOSM per kg, p < 0.001). Similarly from LC-MS data genipin, dihydro-β-tubaic acid and sinapic acid increased with increasing portions of intake. A panel of 8 features displayed good ability to predict intake from biomarker data only. In conclusion, urinary SMCSO and several LC-MS features appeared as potentially promising biomarkers of broccoli consumption and demonstrated dose-response relationship. Future work should focus on validating these compounds as food intake biomarkers.

Non-thermal treatments for the control of endogenous formaldehyde from Auricularia auricula and their effects on its nutritional characteristics

To control endogenous formaldehyde (EFA) from Auricularia auricula and preserve its nutritional properties, we selected various non-thermal treatments and evaluated their effects on the removal of EFA, inhibition of γ-glutamyl transpeptidase and l -cysteine sulfoxide lyase activities, and bioactive ingredients (i.e., principal nutrients, including vitamins and taste substances). The results showed that single and co-non-thermal treatments (US-EW, IPL-EW) reduced the EFA content of A. auricula to varying degrees. Correlation and principal component analyses showed that synergistic treatment with ultrasound and electrolyzed water (US-EW) significantly reduced EFA (removal rate = 40.54%), with relatively small losses of other chemical components. The second best was treatment with intense pulsed light and electrolyzed water (IPL-EW) (removal rate = 36.27%). We constructed and validated a kinetic model for EFA removal using the US–EW treatment, and fitted a second-order kinetic equation. The optimal process parameters were as follows: ultrasound (US) frequency: 50 kHz, US power: 100 W, and available chlorine concentration of EW: 35 mg/L. These results were verified and can serve as a reliable technical reference to improve safety during the processing and preservation of edible fungi. • US-EW has the highest removal rate of EFA (40.54%). • The removal of EFA via US-EW confirmed the second-order reaction kinetic. • The optimal processing parameters for US-EW removal of EFA have been obtained. • US-EW causes the least loss in nutritional quality of A. auricula .

Comparing the effect of several pretreatment steps, selected to steer (bio)chemical reactions, on the volatile profile of leek (Allium ampeloprasum var. porrum)

Volatile compounds in foods can witness the occurrence of (bio)chemical reactions, comprising both enzymatic and non-enzymatic reactions, which can be influenced by processing. This study investigated the effect of different pretreatments aimed at either minimizing, realized by a heat treatment, or inducing, realized by a tissue disruptive treatment, enzymatic reactivities, on the volatile profile of leek. The volatile profiles obtained were then linked to possible (bio)chemical reactions that could have occurred during the treatments. The study showed that different pretreatments led to markedly different volatile profiles, characterized by different (abundances of) volatile compounds. Partial and extensive tissue disruption was achieved by pulsed electric fields at low electric field strength and mixing, respectively. After these tissue disruptive treatments, the volatile compounds could mainly be related to the occurrence of several enzyme-substrate interactions, including conversions of alk(en)yl cysteine sulfoxides by alliinase and of unsaturated fatty acids by lipoxygenase and hydroperoxide lyase. Thermally-induced reactions were also observed to impact the resultant volatile profile. Present study revealed that targeted (pre)treatment allows to steer (bio)chemical reactions towards specific volatile compounds in leek products.