A time-course study of glucosinolates in the ontogeny of forage rape (Brassica napus L)

One cultivar and two breeding lines of forage rape, grown in a glasshouse, were sampled at weekly intervals from 9 to 22 weeks after sowing. Separate determinations of glucosinolate content were made on leaves and stems by HPLC. There were differences in the proportion and concentration of individual glucosinolates between the rapes and between leaves and stems, showing that levels of individual glucosinolates cannot be predicted from total glucosinolate content. Of particular interest was the variation with harvest date in the levels of individual glucosinolates. This has considerable implications for the comparison of levels of individual glucosinolates between cultivars and crops, and suggests that detailed agronomic field studies are required to determine whether the intake by animals of potentially toxic glucosinolates, in particular progoitrin, can be minimised by exploiting these seasonal differences in glucosinolate concentrations. Progress has been made in lowering the level of this glucosinolate, and the possibility of breeding forage rape with very low or zero levels of progoitrin is indicated.     

A time-course study of the effect of sulphur on glucosinolates in oilseed rape (Brassica napus) from the vegetative stage to maturity

Samples consisting of the whole above-ground part of the oilseed rape plant (Brassica napus L), were taken every 2 weeks from before stem extension to maturity. The plants were separated into vegetative tissue, floral tissue, pods and seeds (when these components appeared), and the individual glucosinolates present were quantified by high performance liquid chromatography. A high glucosinolate variety (Rafal) and a low glucosinolate variety (Cobra) were compared. The effect of sulphur (32 kg ha^?1 elemental sulphur applied at the beginning of stem extension) on the various parts of the plant was investigated. Total glucosinolate concentration in all plant parts was higher in Rafal than in Cobra. Glucosinolate concentration in the vegetation declined over time, most noticeably when the flowers and seeds were produced, and glucosinolate concentration of the pods also fell as that of the seeds rose. It is suggested that there may have been some redistribution of glucosinolates or glucosinolate precursors within the plant as maturity approached. Changes occurred in the proportions that individual glucosinolates contributed to the total glucosinolate content, and this may be relevant to plant/pathogen relationships. Sulphur application increased the glucosinolate concentration of the vegetative tissue by mid April and also increased the glucosinolate concentration of the flowers. It is suggested that this could affect the plant's resistance to disease.     

Glucosinolates in isaño (Tropaeolum tuberosum) tubers: qualitative and quantitative content and changes after maturity

Six varieties of isaño (Tropaeolum tuberosum), an Andean edible tuber, were analysed. The aim was to characterise qualitatively and quantitatively their content of glucosinolates and to determine concentration changes of these compounds upon delayed harvest. Additionally, exploratory assays were carried out on the effect of postharvest cold storage of the tubers as well as of a drying process imposed on blanched tuber slices. Only one glucosinolate (p‐methoxybenzyl glucosinolate) was found in the six domestic varieties analysed. Its concentration varied between 36.5 and 90.0 µmol g^?1 dry matter. This range is relatively high when compared with other edible glucosinolate‐containing vegetables. ‘Dark’ coloured tuber varieties showed higher levels than ‘light’ coloured tuber varieties at normal harvest time. Of the two varieties on which the effect of delayed harvest was studied, one showed increasing and then decreasing changes until 44 days after maturity, while the other did not show any significant change with time. Postharvest cold stored samples showed similar changes to tubers kept in soil, and glucosinolate levels in dried blanched tubers did not differ significantly from those in fresh samples. Taken together, the data indicate that the glucosinolate content of isaño is highly dependent on both the variety and the time of harvest. These parameters should be taken into account when considering isaño as a promising food source with medicinal properties for humans and animals, but also with possible adverse biological effects, all related to the presence of glucosinolates. Copyright © 2004 Society of Chemical Industry     

Glucosinolate profiles of international rapeseed lines (Brassica napus and Brassica campestris)

Seed samples from a range of international rapeseed lines (Brassica napus L and B campestris L) were analysed for glucosinolate content using high performance liquid chromatography (HPLC). This analytical method provided a total profile consisting of eight different glucosinolates, including those used to define the Canola standard. The data indicated that broad categories of distinct glucosinolate profiles existed among the seed lines analysed. Indole glucosinolate content, expressed as a percentage of total glucosinolate content, was higher in the low glucosinolate lines of B napus. The actual contents of all eight glucosinolates in the seed were variable, particularly gluconapin, glucobrassicanapin and progoitrin. The importance of this HPLC procedure in facilitating selection for high or low contents of individual glucosinolates is discussed.     

Genotypic variation of glucosinolates in broccoli (Brassica oleracea var. italica) florets from China

Five main cultivars from China and 143 parent materials grown in a greenhouse were used to investigate the glucosinolates in broccoli florets. Eight aliphatic glucosinolates, four indole glucosinolates, and one aromatic glucosinolate were identified and quantified using high-performance liquid chromatography (HPLC). The results showed that glucoraphanin, glucobrassicin, 4-methoxyglucobrassicin and neoglucobrassicin were present in all samples. However, the predominant type of glucosinolate was different among pure lines. The anti-cancer glucoraphanin concentration ranged from 0.06 to 24.17 μmol/g in pure lines and from 1.57 to 5.95 μmol/g in commercial cultivars. The progoitrin concentration in commercial cultivars varied from 1.77 to 6.07 μmol/g with a mean value of 3.20 μmol/g. Significant variations were observed in the concentration of individual glucosinolates and in each class of glucosinolates among broccoli populations. Dozens of specific lines with altered glucosinolate profiles, as well as ten good candidates for breeding high-chemoprotective glucosinolate cultivars, were obtained according to the putative glucosinolate pathway in broccoli.     

Influence of nitrogen and sulphur on the glucosinolate profile of rapeseed (brassica napus l)

Clear influence of N and S applications on the profile of individual glucosinolates in the seeds of winter oilseed rape (Brassica napus L) was found in field experiments. The major effect of N was on the relative abundance of the four alkenyl glucosinolates. Increasing the N rate increased the relative proportion of 2-hydroxybut-3-enyl at the expense of pent-4-enyl, and to a lesser extent, 2-hydroxypent-4-enyl, in the double-low (low erucic acid and low glucosinolates) variety Cobra, but at the expense of but-3-enyl in the single-low (low erucic acid) variety Bienvenu. The results strongly suggest that a high N supply favours the hydroxylation step from but-3-enyl to 2-hydroxybut-3-enyl. In contrast, the major effect of S appeared to be on the relative abundance of the alkenyl and indole groups as a whole. Sulphur deficiency decreased the concentrations of the alkenyl glucosinolates more than those of the indole glucosinolates, whereas S application to a S-deficient crop resulted in a larger response in the alkenyl group than in the indole group. The more sensitive response of alkenyl glucosinolates to the plant S status is probably due to the requirement of methionine in their biosynthesis, as compared with the indole glucosinolates which are derived from tryptophan. Implications for changes in the glucosinolate profile in rapeseed are discussed.     

Changes in forage and oilseed rape (Brassica napus) root glucosinolates in response to attack by turnip root fly (Delia floralis)

Three genotypes of forage rape and two of winter oilseed rape (Brassica napus L), grown in a glasshouse, were inoculated with Delia floralis Fall eggs at 5 weeks and their roots were sampled after a further 6 weeks of larval attack. Individual and total glucosinolates were examined in seed and roots using HPLC. No clear relationship was found between seed and root total or individual glucosinolate content. Major differences in glucosinolate composition were found between uninoculated control roots. In two doublezero oilseed rapes, phenylethyl glucosinolate was predominant whereas, in the three forage rapes, 2-hydroxy-but-3-enyl was the major glucosinolate. Attack by D floralis larvae considerably modified both concentrations and relative proportions of individual glucosinolates in roots. The total glucosinolate content decreased for all of the rapes except double-zero oilseed rape WRG35. In all rapes the proportion of aromatic to aliphatic glucosinolates increased after attack, largely due to increased levels of indolebased glucosinolates; 1-methyoxy-3-indole methyl glucosinolate increased by over 88%. The total aliphatic glucosinolate content of all rape roots with the exception of WRG35 was reduced by 39–56% after attack. Possible causes for altered glucosinolate metabolism are discussed in relation to observed differences in levels of susceptibility to turnip root fly attack.     

Sulphur turnover in the developing pods of single and double low varieties of oilseed rape (Brassica napus L)

Changes in the sulphur (S) concentrations in pod walls and seeds of the double low variety Cobra and single low variety Bienveou of winter oilseed rape (Brassica napus L) were studied during pod development. The S concentration in the seeds of Cobra increased between 47 and 61 days after flowering and thereafter remained stable, whereas in Bienvenu seed S concentration was much higher initially and continued to increase throughout the sampling period (from 57 to 108 days after flowering). These differences in S concentration reflect different patterns of glucosinolate accumulation in the seeds. In contrast, there was a large and progressive build-up of S in the pod walls of Cobra, such that at maturity the S concentration in the pod walls of Cobra was approximately double that of Bienvenu. A large and progressive accumulation of inorganic sulphate was found to be responsible for the build-up of S in the pod walls of the double low variety. Short-term feeding experiments with terminal racemes showed that a smaller proportion of ³⁵S was translocated from the pod walls to the seeds in Cobra than in Bienvenu. However, the build-up of S in the pod walls of Cobra did not seem to result from a restricted translocation of glucosinolates, since in both varieties exogenously supplied allylglucosinolate was translocated rapidly from the pod walls to the seeds. These results are therefore consistent with the hypothesis that pod walls are a major site for the biosynthesis of glucosinolates present in the seeds, and a metabolic block in the pathway of glucosinolate biosynthesis is responsible for the low glucosinolate concentration in the seeds of double low varieties, which consequently results in a large build-up of sulphate in the pod walls.     

Glucosinolates in brassica vegetables. Analysis of 22 varieties of brussels sprout (Brassica oleracea var. gemmifera)

The glucosinolate content of 22 cultivars of Brussels sprout have been determined. The levels of total glucosinolates, determined by methods based on glucose release and gas chromatography, were substantially higher than those reported by other workers for cabbage and Chinese cabbage. The major glucosinolates in Brussels sprout leaf material were identified as gluconapin, progoitrin, sinigrin and glucobrassicin, with the latter two generally predominating. Detailed analysis of the material from five different growing sites has shown considerable variation in the total content but surprisingly little difference in the relative proportions of the individual glucosinolates within each cultivar. The glucosinolates of the corresponding seed material differ significantly from that in leaf; in particular glucobrassicin is found in trace amounts only, and glucoerucin, glucotropaeolin and neoglucobrassicin are all present, in addition to sinigrin, progoitrin and gluconapin.     

Nutritive value of rapeseed meal: Effects of individual glucosinolates

In the first of a series of studies on the nutritional value of rapeseed meal, rats were fed diets containing six individual glucosinolates over a period of 29 days. The diets included progoitrin and gluconapin both of which are major components of high glucosinolate rapeseed cultivars. No reduction of feed intake or growth rate was noted and thyroid weights were significantly affected only by the progoitrin diet, which also produced small increases in the weights of the livers and kidneys. There was no depression of plasma thyroid hormone levels.     

Variation of glucosinolates in vegetable crops of Brassica rapa L. ssp. pekinensis

Glucosinolates of Chinese cabbage (Brassica rapa L. ssp. pekinensis) from Korea were characterised to determine the total glucosinolate content and the diversity amongst glucosinolates; 24 varieties were analysed. The profiles of 14 glucosinolates identified from the leaves were subjected to principal component analysis (PCA) to evaluate the differences among varieties. The Kori, Sandun and e-Norang varieties separated from the others based on glucosinolate concentration. Genetically modified Chinese cabbage containing the bar gene could not be separated from non-genetically modified varieties. Glucobrassicanapin, 4-methoxyglucobrassicin, gluconapin and glucobrassicin in Chinese cabbage were confirmed as the main glucosinolate compounds. The Kori, Sandun and e-Norang varieties appear to be good candidates for future breeding programmes since they have a high glucosinolate content. The presence of indolic glucosinolates in all varieties should be studied more extensively because they are the precursor of indole-3-carbinol, a potent cancer chemopreventive agent.     

INDIVIDUAL GLUCOSINOLATES IN SIX CANOLA VARIETIES

The glucosinolate composition of canola varieties ofAltex, Candle, Regent, Tower, Triton and Westar were determined by gas chromatography (GC) and high-performance liquid chromatography (HPLC). Twelve glucosinolates were detected and their identities confirmed by comparison with the retention times of known glucosinolates and by mass spectrometry (MS). The major glucosinolates present in canola meals were gluconapin (3-butenyl), progoitrin (2-hydroxy-3-butenyl), glucobrassicanapin (4-pentenyl), glucobrassicin (3-indolylmethyl) and 4-hydroxyglucobrassicin (4-hydroxy-3-indolylmethyl). Indole glucosinolates were quantified better by HPLC than GC method of analysis. Sulphinyl glucosinolates were determined only by the HPLC methodology due to the yield of multiple peaks by GC.     

The glucosinolate content of the leaf and stem of fodder kale (Brassica oleracea L.), rape (Brassica napus L.) and radicole (Raphanobrassica)

The glucosinolate content of three fodder kales, one fodder rape, one semi-artificial rape and one radicole were determined. The major glucosinolates (mmol kg^?1 dry matter) were: in kale leaf, glucobrassicin (3.21) and sinigrin (3.12); in kale stem, sinigrin (5.82); in rape leaf, gluconapin (3.14) and progoitrin (13.99); in rape stem, gluconapin (3.29) and progoitrin (20.18); in semi-artificial rape leaf, gluconapin (25.64) and progoitrin (9.00); in semi-artificial rape stem, gluconapin (35.33) and progoitrin (12.08); in radicole leaf, progoitrin (4.74) and glucobrassicin (3.28); and in radicole stem, gluconapin (3.26) and progoitrin (5.53). The implications for plant breeding are discussed.     

Effects of storage condition on the bioactive compound contents of Korean cabbage

The influence of common storage condition (i.e., temperature and period) on the phytochemical contents of Korean cabbage was investigated. The total polyphenol and flavonoid contents of fresh Korean cabbage extract were 308.48 μg gallic acid equivalent/g d.w. and 5.33 μg quercetin equivalent/g d.w., respectively. Seven glucosinolate peaks were detected in Korean cabbage representing progoitrin, glucoalyssin, gluconapin, glucobrassicanapin, glucobrassicin, 4-methoxyglucobrassicin, and neoglucobrassicin based on HPLC and LC-MS analysis. The concentration of total glucosinolates in fresh Korean cabbage was 13.55 μmol/g d.w. Our results suggest that the total glucosinolate content in Korean cabbage did not much change more over 7 days of storage at 4°C but a little bit decreased in stored at ambient temperature. The extractable β-carotene, lutein as well as tocopherol contents in Korean cabbage were decreased by increasing storage period at both temperatures of 4°C and ambient temperature. Longer storage period at ambient temperature may reduce the levels of health promoting compounds. Based on our results refrigeration at 4°C can help preserve the nutritive value of Korean cabbage by maintaining high levels of glucosinolates and other bioactive compounds.     

Variation of glucosinolates in three edible parts of Chinese kale (Brassica alboglabra Bailey) varieties

Glucosinolates in Chinese kale (Brassica alboglabra Bailey) were analysed by liquid chromatography–mass spectrometry (LC–MS), and the variation of glucosinolates in three edible parts (sprout, rosette leaf and bolting stem) of 27 Chinese kale varieties was investigated. Thirteen glucosinolates, including eight aliphatic glucosinolates, four indole glucosinolates and one aromatic glucosinolate, were identified in Chinese kale. The contents of total glucosinolate varied extensively among the different edible parts, and the total glucosinolate contents in the sprouts were obviously higher than those in rosette leaves and bolting stems. Obvious differences in the total and individual glucosinolate contents were also observed in each edible part among the different varieties. Gluconapin was the most abundant glucosinolate among all the edible parts of the 27 varieties except for the sprout of JL-26. The JL-26, JL-25 and JL-16 varieties are good candidates for future breeding programs since they contain high levels of methylsulphinylalkyl glucosinolates (glucoiberin and glucoraphanin) in certain edible parts.     

Changes in Glucosinolate Concentrations in BrassicaCrops (BoleraceaandBnapus) Throughout Growing Seasons

In the Iberian Peninsula, Brassica crops are grown throughout the year and may be consumed at immature stages or leaves may be harvested by ‘picking-over’ during plant growth. Consumption of Brassicas in Portugal is high but there is no information on the levels of glucosinolates in such material. Changes in the total and individual glucosinolate concentrations of four Brassica oleracea types (two cultivars of Portuguese cabbage, one Portuguese kale type and one hybrid white cabbage) and one Portuguese Brassica napus type were monitored throughout two growing seasons, spring/summer (SS) and summer/winter (SW). Glucosinolates were determined between sowing and maturity corresponding to nine sampling dates in the leaves and five harvests in the heads. The main glucosinolates in B oleracea types were 3-methylsulphinylpropyl-, allyl- and indol-3-ylmethyl- whereas in the B napus type pent-4-enyl-, 2-hydroxybut-3-enyl- and but-3-enylglucosinolate predominated. In the leaves of B oleracea types, the highest concentration of total glucosinolates and of most of the individual glucosinolates was observed at 14 days after sowing whilst, in the heads the highest levels were noted at the start of head formation. In the B napus , the highest total and individual glucosinolate concentration was generally observed at the end of the growing season. Both for the total and for the main individual glucosinolates there were significant differences ( P< 0·001) between the nine harvest dates and between growing seasons. Between the two seasons, the glucosinolate levels in SS were generally higher than in SW. A comparison of cultivars showed the hybrid cabbage to have generally higher glucosinolate levels than the Portuguese types, except for B napus .     

Glucosinolates in Rutabaga Grown in Soil Capped over Coal Fly Ash

Nine glucosinolates were measured by HPLC analysis in rutabaga grown on soil capped over a coal fly ash landfill or on normal clay and silt loam soil. Progoitrin (2-hydroxybut-3-enyl glucosinolate) and neoglucobrassicin (1-methoxy-3-indolylmethyl glucosinolate) were the most abundant glucosinolates found. Progoitrin and three other minor glucosinolates were present in the natural soil-grown rutabaga in greater amounts than in that grown in fly-ash soil. However, fly ash grown rutabaga contained comparatively greater levels of glucobrassicin (3-indolylmethyl glucosinolate) and neoglucobrassicin, the major glucosinolate present.     

CHEMICAL AND SENSORY QUALITY OF BROCCOLI (BRASSICA OLERACEA L. VAR ITALICA)

Five cultivars of broccoli (Brassica oleracea L. var. italica) were analyzed for individual glucosinolates, S-methylcysteine sulfoxide (SMCSO), aroma volatiles and sensory quality. Total glucosinolate content ranged from 47 to 93 μmol μmol·g dry weight¹, and SMCSO ranged from 22 to 57 μmol μmol·g dry weight¹. A total of 11 glucosinolates were identified in the broccoli cultivars. The major glucosinolates were: progoitrin, glucoiberin, glucoraphanin, glucobrassicin and neo-glucobrassicin and they accounted for more than 95% of the total content. Glucoiberin was only found in appreciable amounts in purple-headed broccoli. Pentanol, pentanal, hexanal, heptanal and nonanal were the most abundant higher boiling volatiles isolated from cooked broccoli using dynamic headspace trapping on Porapak and solvent desorption with diethyl ether. Sensory analysis by a trained panel showed that scores for cooked vegetable odor (‘hay’ and ‘green peapod’) were significantly different between cultivars. In contrast, scores related to Brassica odor (‘cauliflower’ and ‘mustard’) were not significantly different. The content of individual glucosinolates, SMCSO and higher boiling volatiles in the cultivars is discussed in relation to the sensory quality of the cooked product.     

Rapeseed meal-Glucosinolates and their antinutritional effects Part 6. Taint in end-products

From the present review it is clear that glucosinolates and their breakdown products may pass in small amounts into such products as meat, milk or eggs without noticeable deterioration in their taste. When applying low glucosinolate rapeseed meal (LG-RSM) as the sole high protein component of concentrate mixture for cows, the level of rapeseed glucosinolates breakdown products should not exceed 0.1 μmol/1 oxazolidinethione, 10 μmol/1 unsaturated nitriles and 100 μmol/1 thiocyanate. At these levels no evidence has been found to indicate the negative influence of glucosinolates breakdown products on the sensory properties of milk or threat for consumers. No published information appears to be available suggesting that glucosinolates have any deleterious effect on the carcass flavour in cattle. Even at a 20% inclusion of LG-RSM in diets no impairment on visual scores or sensory evaluation was found in pig's or broiler's carcass. Glucosinolated, chiefly progoitrin, which depress trimethylamine oxidation thus clearly affect the taint in eggs. In birds with genetically conditioned susceptibility (brown layers) fishy taint can be observed even at 0.3 μM progoitrin, i.e. approximately 0.5 μM total glucosinolates in 1 g diet. Assuming a threefold higher threshold for white layers (1 μM progoitrin in 1 g diet) fishy taint can be expected at a 10% LG-RSM level in diet, and only very low glucosinolate rapeseed meals can be fed to layers without the risk of fishy taint in eggs.     

Glucosinolates in seed of rape and turnip rape as affected by variety and environment

Seed meals of winter and summer types of varieties of Brassica napus and B. campestris, grown at different localities and in different years, have been analysed for content of glucosinolates which produce oxazolidinethiones and volatile isothiocyanates upon enzymic hydrolysis. Considerable differences existed in amounts of glucosinolates between species and between winter and summer types of the same species. Varietal differences were relatively small in most of the material studied. Samples of the Polish summer rape variety Bronowski and selections from this variety, however, exhibited very low glucosinolate contents; this is probably genetically determined. Environmental variation generally amounted to ±15% of the average value. Under certain environments, however, 65% lower values than average were obtained. Lack of sulphur in the growth medium of soil-free cultures resulted in seeds low in glucosinolates. In practical farming low glucosinolate content has been found in rape seed as a result of low sulphate content in the soil.