Content Of Individual Glucosinolates Research Articles

Analysis of Glucosinolates and Phenolic Content in Sprouts of 7 Brassica rapa Subspecies

Objective: Brassica rapa is an important source of phytochemicals essential for plant defense and human health. To better understand their metabolic characteristics, this study aimed to investigate the glucosinolates and phenolic content from sprouts of 7 B. rapa subspecies. Methods: Glucosinolates and phenolic compounds were extracted using previously reported procedures, with slight modifications. Glucosinolates were identified based on their high-performance liquid chromatography peak area ratios and quantified based on the peak areas, retention time, and response factor and phenolic compounds were identified based on retention times and spiking tests and quantified concerning a corresponding calibration curve. Results: Statistical analysis showed that Choy sum (31.82 ± 2.3 mg/g DW) and Bok choy (31.73 ± 1.49 mg/g DW) presented the highest total glucosinolates content, and the lowest content was observed in Turnip rape (21.75 ± 1.67 mg/g DW). Between the contents of individual glucosinolates, progoitrin presented the highest content in Bok choy (17.84 ± 1.24 mg/g DW). The highest concentration of total phenolic compounds was found in the sprouts of Chinese cabbage (2.7 ± 0.05 mg/g DW), whereas the lowest concentration was found in Choy sum sprouts (2.17 ± 0.05 mg/g DW). The highest individual phenolic content was observed for benzoic acid (0.96 ± 0.03 mg/g DW) and rutin (0.85 ± 0.03 mg/g DW), which were highest in mizuna and Chinese cabbage, respectively. Conclusion: Subspecies may influence the levels of glucosinolates and polyphenols in vegetables. The results of our study showed the distinctive metabolic signatures embedded in the 7 B. rapa subspecies.

A Fast and Simple Solid Phase Extraction-Based Method for Glucosinolate Determination: An Alternative to the ISO-9167 Method.

Glucosinolates (GLSs) are a well-studied sulfur-containing compound found in Brassicaceae plants that play critical roles in plant resistance and human health. Correctly identifying and reliably quantifying the total and individual GLS content is of great importance. An improved method as an alternative to the ISO 9167-1 (ISO) method is developed in the present study. An efficient extraction and purification procedure is proposed with a commercially available dimethylaminopropyl (DEA)-based weak anion exchange solid-phase extraction (SPE) cartridge instead of using the self-prepared ion-exchange columns in the ISO method. The GLSs are identified and quantified by ultra high-performance liquid chromatography (UHPLC) high-resolution mass spectrometry (HRMS). The method demonstrates a comparable quantification of total and individual GLSs on certified rapeseeds and other Brassicaceae vegetables when compared to the ISO method. The developed SPE method is simpler and more efficient, thus allowing for applications to a large sample size with reduced analysis time, improved repeatability and accuracy, and possible automation.

Building comprehensive glucosinolate profiles for brassica varieties

Brassica plants play an important role in common agricultural practices, such as livestock feed or biofumigation, due to the bioactivity of the natural degradation products of glucosinolate metabolites. Therefore, the ability to survey comprehensive glucosinolate profiles for individual brassicas is essential for informing proper species selection for the intended application. Current methods for glucosinolate identification and quantification involve complex or unconventional procedures, and proper reference materials are not readily available. Therefore, researchers with limited resources that require glucosinolate profiles are at an extreme disadvantage. In this work, a simple and accurate HPLC-MS method was developed and validated to build preliminary glucosinolate profiles for three agriculturally relevant forage brassica varieties [turnip (B. rapa L.), canola (B. napus L.), and rapeseed (B. napus L.)]. The average glucosinolate content across three herbage collection dates for canola, rapeseed and turnip were 2.9 ± 0.9 mg g−1, 6.4 ± 1.3 mg g−1, and 14 ± 3.4 mg g−1, respectively. GLS concentrations are reported in milligrams of glucosinolate, calculated as sinigrin equivalents, per gram of dry plant material. This semi-quantitative approach for reporting total GLS content in brassicas is accurate within 15%. Several minor individual glucosinolates were identified that have not been previously reported in canola, rapeseed and turnip species, including glucotropaeolin and 4-hydroxyglucobrassicin (canola), glucoraphanin and glucoberteroin (rapeseed), and glucosinalbin and glucobarbarin (turnip). This non-targeted screen of several forage brassica varieties demonstrates the inherent variation in both the individual glucosinolate content and the total glucosinolate profile among brassicas, and highlights the importance of such glucosinolate characterization in agricultural practices. Additionally, the method developed in this study can be used as a tool for researchers with limited resources to build accurate glucosinolate profiles of brassica plants.

Differential glucosinolate profiles of radish leaves in response to postharvest drying treatment

The aboveground parts of radish (Raphanus sativus L.) are typically discarded after harvesting the roots. However, numerous bioactive compounds have been identified in radish leaves, and dried leaf products have garnered attention as a health food owing to their high fiber content. Here, we assessed the morphological and physiological characteristics of the leaves of 14 commercial radish cultivars and the effects of postharvest drying treatment on their glucosinolate (GSL) contents. The morphological and physiological characteristics of radish leaves exhibited considerable variation, depending on the cultivar. ‘Baekbong’ and ‘Baekja’ presented higher values for the assessed morphological and physiological characteristics than other cultivars. ‘Baekja’ had the best growth parameters, including leaf length and fresh and dry weights, among the tested cultivars. The total and individual GSL content was the highest in the cultivars ‘Sincheongilpum’ and ‘Taebaek’ at harvest. However, after 10 d of postharvest drying in a greenhouse at ambient temperature, the GSL content was the highest in the cultivars ‘Cheongbok plus’ and ‘Taebaek’. The results of the multivariate data analyses indicated that ‘Taebaek’ is a highly distinctive cultivar in terms of shoot physiology, morphology, and GSL content. The GSL content and profiles were differentially affected by both radish cultivar and postharvest drying treatment.

The Relationship between Glucosinolates and the Sensory Characteristics of Steamed-Pureed Turnip (Brassica Rapa subsp. Rapa L.).

Glucosinolates (GSLs) are phytochemical compounds that can be found in Brassica vegetables. Seven separate batches of steamed-pureed turnip were assessed for GSL content using liquid chromatography mass spectrometry (LC-MS) and for sensory attributes by sensory profiling (carried out by a trained sensory panel). Twelve individual GSLs, which included 7 aliphatic, 4 indole and 1 arylaliphatic GSL, were identified across all batches. There were significant differences in individual GSL content between batches, with gluconasturtiin as the most abundant GSL. The total GSL content ranged from 16.07 to 44.74 μmol g−1 dry weight (DW). Sensory profiling concluded there were positive correlations between GSLs and bitter taste and negative correlations between GSLs (except glucobrassicanapin) and sweet taste. The batches, which had been purchased across different seasons, all led to cooked turnip that contained substantial levels of GSLs which were subsequently all rated as bitter.

Profiling of Individual Desulfo-Glucosinolate Content in Cabbage Head (Brassica oleracea var. capitata) Germplasm.

Individual glucosinolates (GSLs) were assessed to select cabbage genotypes for a potential breeding program. One hundred forty-six cabbage genotypes from different origins were grown in an open field from March to June 2019; the cabbage heads were used for GSL analyses. Seven aliphatics [glucoiberin (GIB), progoitrin (PRO), epi-progoitrin (EPI), sinigrin (SIN), glucoraphanin (GRA), glucoerucin (GER) and gluconapin (GNA)], one aromatic [gluconasturtiin (GNS)] and four indolyl GSLs [glucobrassicin (GBS), 4-hydroxyglucobrassicin (4HGBS), 4-methoxyglucobrassicin (4MGBS), neoglucobrassicin (NGBS)] were found this study. Significant variation was observed in the individual GSL content and in each class of GSLs among the cabbage genotypes. Aliphatic GSLs were predominant (58.5%) among the total GSLs, followed by indolyl GSL (40.7%) and aromatic GSLs (0.8%), showing 46.4, 51.2 and 137.8% coefficients of variation, respectively. GIB, GBS and NGBS were the most common GSLs found in all genotypes. GBS was the most dominant GSL, with an average value of 3.91 µmol g−1 (0.79 to 13.14 µmol g−1). SIN, GIB, PRO and GRA were the other major GSLs, showing average values of 3.45, 1.50, 0.77 and 0.62 µmol g−1, respectively. The genotypes with relatively high contents of GBS, SIN, GIB and GRA warrant detailed studies for future breeding programs since the hydrolysis products of these GSLs have several anti-cancer properties.

Relationship of Glucosinolate Thermal Degradation and Roasted Rapeseed Oil Volatile Odor.

This study aims to investigate the effect of glucosinolate (GSL) degradation on the volatile odor of rapeseed oil (RO) during roasting. Volatile compounds of RO and individual GSL contents in the seeds were identified and measured during roasting, separately. Total GSL content decreased by 30.47-84.44%. Nitriles were the key volatile compounds that were negatively correlated with GSLs for all samples. Results indicate that GSL degradation significantly affects the volatile odor of RO and tends to produce low-carbon nitriles. Furthermore, the thermal degradation pathways of GSLs were explored according to the structure of individual GSLs and nitriles. These results provide information for the thermal degradation pathways of GSLs and the formation mechanism of nitriles during seed roasting.

Growth, Photosynthetic Pigments, Phenolic, Glucosinolates Content and Antioxidant Capacity of Broccoli Sprouts in Response to Nanoselenium Particles Supply

Improving the nutritional quality of plants has emerged from the fact that macro- and micro- nutrients are limited in various agricultural areas. The aim of our study was the biofortification of broccoli sprouts with selenium nanoparticles (NSePs) and evaluation of growth parameters, assimilator pigments content, total phenols, glucosinolates content along with antioxidant capacity, in order to boost value added output, such as improved nutrition and food functionality. NSePs were prepared by reduction of NaHSeO3 using glucose as reducing agent, and characterized from structural and morphological point of view. The growth of broccoli seedlings was dependent on NSePs concentration. The treatment with 10 and 50 ppm NSePs caused a slight increase in total biomass, by contrast with 100 ppm treatment. Chlorophyll content, total carotenoid and total phenols content was not affected by the treatment of broccoli sprouts with different concentrations of NSePs. Instead, the content of individual glucosinolates varied between the samples, depending on the levels of NSePs. The highest antioxidant capacity was obtained for 100 ppm NSePs concentration. The effective uptake of NSePs was further demonstrated by FTIR spectroscopy and Hyperspectral Microscopy. NSePs did not induce any toxicity on broccoli sprouts. Moreover, broccoli supply with NSePs may target higher nutritional impact and health benefits.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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Glucosinolate Profiling and Expression Analysis of Glucosinolate Biosynthesis Genes Differentiate White Mold Resistant and Susceptible Cabbage Lines.

Sclerotinia stem rot (white mold), caused by the fungus Sclerotinia sclerotiorum, is a serious disease of Brassica crops worldwide. Despite considerable progress in investigating plant defense mechanisms against this pathogen, which have revealed the involvement of glucosinolates, the host–pathogen interaction between cabbage (Brassica oleracea) and S. sclerotiorum has not been fully explored. Here, we investigated glucosinolate profiles and the expression of glucosinolate biosynthesis genes in white-mold-resistant (R) and -susceptible (S) lines of cabbage after infection with S. sclerotiorum. The simultaneous rise in the levels of the aliphatic glucosinate glucoiberverin (GIV) and the indolic glucosinate glucobrassicin (GBS) was linked to white mold resistance in cabbage. Principal component analysis showed close association between fungal treatment and cabbage GIV and GBS contents. The correlation analysis showed significant positive associations between GIV content and expression of the glucosinolate biosynthesis genes ST5b-Bol026202 and ST5c-Bol030757, and between GBS content and the expression of the glucosinolate biosynthesis genes ST5a-Bol026200 and ST5a-Bol039395. Our results revealed that S. sclerotiorum infection of cabbage induces the expression of glucosinolate biosynthesis genes, altering the content of individual glucosinolates. This relationship between the expression of glucosinolate biosynthesis genes and accumulation of the corresponding glucosinolates and resistance to white mold extends the molecular understanding of glucosinolate-negotiated defense against S. sclerotiorum in cabbage.

Altered Glucosinolate Profiles and Expression of Glucosinolate Biosynthesis Genes in Ringspot-Resistant and Susceptible Cabbage Lines.

Ringspot, caused by the fungus Mycosphaerella brassicicola, is a serious disease of Brassica crops worldwide. Despite noteworthy progress to reveal the role of glucosinolates in pathogen defense, the host–pathogen interaction between cabbage (Brassica oleracea) and M. brassicicola has not been fully explored. Here, we investigated the glucosinolate profiles and expression of glucosinolate biosynthesis genes in the ringspot-resistant (R) and susceptible (S) lines of cabbage after infection with M. brassicicola. The concomitant rise of aliphatic glucoiberverin (GIV) and indolic glucobrassicin (GBS) and methoxyglucobrassicin (MGBS) was linked with ringspot resistance in cabbage. Pearson’s correlation and principle component analysis showed a significant positive association between GIV contents and the expression of the glucosinolate biosynthesis gene ST5b-Bol026202 and between GBS contents and the expression of the glucosinolate biosynthesis gene MYB34-Bol017062. Our results confirmed that M. brassicicola infection induces the expression of glucosinolate biosynthesis genes in cabbage, which alters the content of individual glucosinolates. This link between the expression of glucosinolate biosynthesis genes and the accumulation of their respective glucosinolates with the resistance to ringspot extends our molecular sense of glucosinolate-negotiated defense against M. brassicicola in cabbage.

Leptosphaeria maculans Alters Glucosinolate Profiles in Blackleg Disease-Resistant and -Susceptible Cabbage Lines.

Blackleg, a fungal disease caused by Leptosphaeria maculans, is one of the most devastating diseases of Brassica crops worldwide. Despite notable progress elucidating the roles of glucosinolates in pathogen defense, the complex interaction between B. oleracea (cabbage) and L. maculans infection that leads to the selective induction of genes involved in glucosinolate production and subsequent modulation of glucosinolate profiles remains to be fully understood. The current study was designed to identify glucosinolate-biosynthesis genes induced by L. maculans and any associated alterations in glucosinolate profiles to explore their roles in blackleg resistance in 3-month-old cabbage plants. The defense responses of four cabbage lines, two resistant and two susceptible, were investigated using two L. maculans isolates, 03–02 s and 00–100 s. A simultaneous increase in the aliphatic glucosinolates glucoiberverin (GIV) and glucoerucin (GER) and the indolic glucosinolates glucobrassicin (GBS) and neoglucobrassicin (NGBS) was associated with complete resistance. An increase in either aliphatic (GIV) or indolic (GBS and MGBS) glucosinolates was associated with moderate resistance. Indolic glucobrassicin (GBS) and neoglucobrassicin (NGBS) were increased in both resistant and susceptible interactions. Pearson correlation showed positive association between GER content with GSL-OH (Bol033373) expression. Expressions of MYB34 (Bol007760), ST5a (Bol026200), and CYP81F2 (Bol026044) were positively correlated with the contents of both GBS and MGBS. Our results confirm that L. maculans infection induces glucosinolate-biosynthesis genes in cabbage, with concomitant changes in individual glucosinolate contents. In resistant lines, both aliphatic and indolic glucosinolates are associated with resistance, with aliphatic GIV and GER and indolic MGBS glucosinolates particularly important. The association between the genes, the corresponding glucosinolates, and plant resistance broaden our molecular understanding of glucosinolate mediated defense against L. maculans in cabbage.

Exogenous Methyl Jasmonate and Salicylic Acid Induce Subspecies-Specific Patterns of Glucosinolate Accumulation and Gene Expression in Brassica oleracea L.

Glucosinolates have anti-carcinogenic properties. In the recent decades, the genetics of glucosinolate biosynthesis has been widely studied, however, the expression of specific genes involved in glucosinolate biosynthesis under exogenous phytohormone treatment has not been explored at the subspecies level in Brassica oleracea. Such data are vital for strategies aimed at selective exploitation of glucosinolate profiles. This study quantified the expression of 38 glucosinolate biosynthesis-related genes in three B. oleracea subspecies, namely cabbage, broccoli and kale, and catalogued associations between gene expression and increased contents of individual glucosinolates under methyl jasmonate (MeJA) and salicylic acid (SA) treatments. Glucosinolate accumulation and gene expression in response to phytohormone elicitation was subspecies specific. For instance, cabbage leaves showed enhanced accumulation of the aliphatic glucoiberin, progoitrin, sinigrin and indolic neoglucobrassicin under both MeJA and SA treatment. MeJA treatment induced strikingly higher accumulation of glucobrassicin (GBS) in cabbage and kale and of neoglucobrassicin (NGBS) in broccoli compared to controls. Notably higher expression of ST5a (Bol026200), CYP81F1 (Bol028913, Bol028914) and CYP81F4 genes was associated with significantly higher GBS accumulation under MeJA treatment compared to controls in all three subspecies. CYP81F4 genes, trans-activated by MYB34 genes, were expressed at remarkably high levels in all three subspecies under MeJA treatment, which also induced in higher indolic NGBS accumulation in all three subspecies. Remarkably higher expression of MYB28 (Bol036286), ST5b, ST5c, AOP2, FMOGS-OX5 (Bol031350) and GSL-OH (Bol033373) was associated with much higher contents of aliphatic glucosinolates in kale leaves compared to the other two subspecies. The genes expressed highly could be utilized in strategies to selectively increase glucosinolate compounds in B. oleracea subspecies. These results promote efforts to develop genotypes of B. oleracea and other species with enhanced levels of desired glucosinolates.

Comparative analysis of individual glucosinolates, phytochemicals, and antioxidant activities in broccoli breeding lines

The aim of this research was to evaluate the profile and concentration of individual glucosinolates (GSL), and the total phenol content (TPC), total flavonoid content (TFC), ascorbic acid content, and antioxidant activity of broccoli florets and flower stalks (10 commercial cultivars, 19 F1 hybrids, and 20 inbred lines). All broccoli heads were harvested at their marketable stage, and their flower stalks and florets were subjected to phytochemical analysis. GSL, TPC, TFC, and ascorbic acid content varied significantly depending on broccoli genotype. Altogether, nine GSLs were identified, four of which (glucoraphanin, progoitrin, glucoerucin, and glucobrassicin) were the most common in both broccoli flower stalks and florets. In florets, glucobrassicin was the most abundant GSL (4.46 μmol·g-1 DW), followed by glucoraphanin (1.93 μmol·g-1 DW), whereas glucoraphanin was the most abundant in flower stalks (1.47 μmol·g-1 DW). The concentrations of total GSLs, TPC, and TFC in florets were relatively higher than those in the flower stalks, whereas the concentration of ascorbic acid was higher in the flower stalks than the florets. Almost all F1 hybrids and inbred lines exhibited higher TPC, TFC, ascorbic acid concentration, and antioxidant activities than those in the commercial cultivars. Three F1 hybrids; 5075, 5078, and 5079, and one inbred line (5308) had the highest glucoraphanin and total GSL content. Three inbred lines, 5307, 5311, and 5409 had the higher concentration of glucobrassicin and total GSLs, superior antioxidant activity with low PRO+EPI content. These results suggest that these genotype selections had desirable compositions of individual GSLs and higher nutritional value for commercialization as functional vegetables.

Distribution of glucosinolates in camelina seed fractions by HPLC‐ESI‐MS/MS

High glucosinolate concentrations were detected and identified in camelina (Camelina sativa L. Crantz.) seed fractions using reversed phase high performance liquid chromatography‐electrospray ionization‐mass spectrometry (HPLC‐ESI‐MS) in multiple reaction monitoring mode. Total glucosinolate quantitation was performed using proton nuclear magnetic resonance spectrometry using N,N‐dimethylformamide as an internal standard. Individual glucosinolate concentrations were determined by analysis on extracted ion chromatograms generated by a MS detector. Distribution of glucosinolates in C. sativa seed fractions during pressing is reported.Practical applications: HPLC‐ESI‐MS and HPLC‐ESI‐MS/MS using monolithic HPLC columns were used to detect, quantify, and identify the three major glucosinolates in Camelina sativa L. and fractions of C. sativa produced by processing. Quantitative extracted ion MS chromatograms afforded excellent quantitation of individual glucosinolates. The use of monolithic HPLC columns enabled rapid analysis of these samples.Schematic of a proposed dehulling system for Camelina sativa seed.

Plants as Biofactories: Postharvest Stress-Induced Accumulation of Phenolic Compounds and Glucosinolates in Broccoli Subjected to Wounding Stress and Exogenous Phytohormones.

Broccoli contains high levels of bioactive molecules and is considered a functional food. In this study, postharvest treatments to enhance the concentration of glucosinolates and phenolic compounds were evaluated. Broccoli whole heads were wounded to obtain florets and wounded florets (florets cut into four even pieces) and stored for 24 h at 20 °C with or without exogenous ethylene (ET, 1000 ppm) or methyl jasmonate (MeJA, 250 ppm). Whole heads were used as a control for wounding treatments. Regarding glucosinolate accumulation, ET selectively induced the 4-hydroxylation of glucobrassicin in whole heads, resulting in ∼223% higher 4-hydroxyglucobrassicin than time 0 h samples. Additionally, glucoraphanin was increased by ∼53% in whole heads treated with ET, while neoglucobrassicin was greatly accumulated in wounded florets treated with ET or MeJA, showing increases of ∼193 and ∼286%, respectively. On the other hand, although only whole heads stored without phytohormones showed higher concentrations of phenolic compounds, which was reflected in ∼33, ∼30, and ∼46% higher levels of 1,2,2-trisinapoylgentiobose, 1,2-diferulolylgentiobiose, and 1,2-disinapoyl-2-ferulolylgentiobiose, respectively; broccoli florets stored under air control conditions showed enhanced concentrations of 3-O-caffeoylquinic acid, 1,2-disinapoylgentiobiose, and 1,2-disinapoyl-2-ferulolylgentiobiose (∼22, ∼185, and ∼65% more, respectively). Furthermore, exogenous ET and MeJA impeded individual phenolics accumulation. Results allowed the elucidation of simple and effective postharvest treatment to enhance the content of individual glucosinolates and phenolic compounds in broccoli. The stressed-broccoli tissue could be subjected to downstream processing in order to extract and purify bioactive molecules with applications in the dietary supplements, agrochemical and cosmetics markets.

Variation of Glucosinolate Composition during Seedling and Growth Stages of Brassica rapa L. ssp. pekinensis

The objective of this study was to evaluate glucosinolate (GSL) profiles and variation of total and individual GSLs concentrations within seedling (0-14 days) and growth stages (0-15 weeks) of Korean Chinese cabbage (Brassica rapa L. ssp. pekinensis). Ten GSLs (progoitrin, glucoraphanin, glucoalyssin, gluconapin, glucobrassicanapin, 4-hydroxyglucobrassin, glucobrassicin, 4-methoxyglucobrassicin, neoglucobrassicin and gluconasturtiin) were identified from Korean Chinese cabbage. In general, total GSL content significantly decreased during seedling (from 92.89 to <TEX>$35.26{\mu}mol{\cdot}g^{-1}$</TEX> DW) and g rowth stages ( from 74.11 to <TEX>$1.97{\mu}mol{\cdot}g^{-1}$</TEX> DW). Gluconapin was the highest in seeds and in the germination period (<TEX>$73.1{\mu}mol{\cdot}g^{-1}$</TEX> DW) and declined gradually from 73 to 15% during seedling stages. The level of the major aliphatic GSLs, gluconapin and progoitrin, tended to decrease sharply, whereas levels of indolic GSLs (4-methoxyglucobrassicin, glucobrassicin) and aromatic GSLs (gluconasturtiin) were found to increase generally at the beginning of growth stages.

Variations in the most abundant types of glucosinolates found in the leaves of baby leaf rocket under typical commercial conditions

Changes in the concentration of the three most abundant glucosinolates were measured in the leaves of perennial wall rocket [Diplotaxis tenuifolia (L.) DC.], and annual garden rocket (Eruca sativa Mill.). HPLC-MS was used to identify glucoraphanin, 4-hydroxyglucobrassin and glucoerucin from perennial wall rocket, and glucoraphanin, glucobrassicin and 4-methoxyglucobrassicin from annual garden rocket. In separate experiments the responses of glucosinolates to harvest number, seasonal conditions, nitrogen supply and post-harvest storage conditions were measured. For perennial wall rocket, season influenced the concentration of glucoraphanin, which were highest for the spring [379 µg kg(-1) fresh weight (FW)] and summer (317 µg kg(-1) FW) plantings. The concentration of 4-hydroxyglucobrassin was higher in the leaves of first harvest crops. This response was due to this glucosinolate not being detected in the leaves of second harvest crops. Thus, the parent glucosinolate was altered between the first and second harvests in response to the abiotic stresses caused by harvesting. For annual garden rocket, there was an interaction between the harvest number and season for all glucosinolates measured. However, no clear response was observed between these factors. Higher concentrations of glucobrassicin and 4-methoxyglucobrassicin were measured for first harvest leaves when compared to the second harvest. This was due to the absence of detection of these glucosinolates in the leaves of second harvested plants; consequently higher total glucosinolate concentrations were measured for the first harvest winter (1224 µg kg(-1) FW) and summer (864 µg kg(-1) FW) crops. The concentrations of individual glucosinolates vary greatly over typical pre- and post-harvest commercial conditions. The absence of 4-hydroxyglucobrassin for perennial wall rocket, and glucobrassicin and 4-methoxyglucobrassicin for annual garden rocket between harvests, illustrates that abiotic stress from harvesting has the capacity to alter the types of glucosinolates in leaves. Concentrations do not generally decline during a typical storage period, indicating that the potential benefits of these compounds are not lost during post-harvest storage.

Variation of glucosinolates in 62 varieties of Chinese cabbage (Brassica rapa L. ssp. pekinensis) and their antioxidant activity

Glucosinolate (GSL) and antioxidant activity in 62 varieties of Chinese cabbage (Brassica rapa L. ssp. pekinensis) were determined by HPLC and DPPH, HRSA, and FRAP assays. Five aliphatic GSLs: progoitrin, sinigrin, glucoalyssin, gluconapin, and glucobrassicanapin; four indolyl GSLs: 4-hydroxyglucobrassicin, glucobrassicin, 4-methoxyglucobrassicin, and neoglucobrassicin; one aromatic GSL: gluconasturtiin were identified. Glucobrassicanapin and gluconapin documented the most abundant (average 4.52 and 3.72 μmol/g DW, respectively). The contents of total GSLs varied extensively among 62 varieties (range from 2.83 to 48.53 μmol/g DW). Comprehensive differences in total and individual GSL contents have also been observed among different varieties. Indolyl and aromatic GSL together accounted 26% of the total GSLs; but there are few differences among varieties. FC7 and FI17 could be good candidates for future breeding programs since they had a high quantity of glucobrassicin (2.10 and 1.66 μmol/g DW, respectively). Most of the Chinese cabbage varieties showed significant antioxidant activities when compare with positive control. However, three antioxidant assays were not significantly correlated with total GSLs. The presence of significant quantities of glucobrassicin in some varieties should be studied more extensively, since GSL is the precursor of indole-3-carbinol, a potent anticancer isothiocyanate.

Effects of Sulfur Fertilization on the Accumulation of Health-Promoting Phytochemicals in Radish Sprouts

The effects of sulfur fertilization on the growth profile, the contents of glucosinolates, anthocyanins, vitamin C, carotenoids, chlorophylls, total phenolics, and the FRAP value in radish seeds and sprouts were investigated. The concentrations of glucosinolates and antioxidants in sprouts were strongly influenced by the process of germination. Sulfur fertilization induced significant increases in the contents of individual glucosinolates, carotenoids, chlorophylls, and total phenolics. The phenolic contents in sprouts cultivated using 20, 60, or 100 mg/L sulfate were 20.7%, 40.4%, and 40.8% higher, respectively, than those of 7-day-old control sprouts. No detectable effects were observed on the contents of 4-methoxy-glucobrassicin and vitamin C. In addition, the accumulation of anthocyanins in 7-day-old sprouts decreased by 14.8-39.3% upon sulfur fertilization. These findings indicated that the application of sulfur fertilization has the potential to enhance the levels of health-promoting compounds in radish sprouts.

Convenient identification of desulfoglucosinolates on the basis of mass spectra obtained during liquid chromatography–diode array–electrospray ionisation mass spectrometry analysis: Method verification for sprouts of different Brassicaceae species extracts

Over the past decade, glucosinolates (GLs) present in different tissues of Brassicaceae and their breakdown products, especially isothiocyanates formed after myrosinase catalyzed hydrolysis, have been regarded as not only environment friendly biopesticides for controlling soilborne pathogens, but most importantly as promising anticarcinogenic compounds. For these reasons, the identification and quantitative determination of the content of individual glucosinolates in plant material is of great interest. Among the different analytical approaches available today for determining GLs in brassica plant samples, HPLC analysis of their desulfo derivatives (DS–GLs) according to ISO 9167-1, 1992, method is the most widely used. However, the notorious lack of commercially available standards limits its usefulness. To overcome these limitations, liquid chromatography–electrospray ionisation–mass spectrometry was investigated as a potential method for the identification of DS–GLs. The characteristic pattern of fragmentation either in positive or negative ionisation was established based on mass spectra of 11 DS–GL standards, then proposed for additional over 30 most common desulfated GLs. The applicability of MS detection of DS–GLs was verified for real plant samples, the extracts of 14 kinds of brassica sprouts. The results indicated that this methodology combines a convenient identification of DS–GLs with the well established analytical procedure preferred by many researchers. Thus, incorporation of MS detection into popular ISO method seems to result in an improved and more reliable approach to GLs determination.