Effect of increasing fruit and vegetable intake by dietary intervention on nutritional biomarkers and attitudes to dietary change : a randomised trial

This work was funded by The Scottish Government Rural and Environmental Science and Analytical Sciences Division (RESAS) and supported by the Rank Prize Funds.Peer reviewedPublisher PD

Supplementation of the diet by exogenous myrosinase via mustard seeds to increase the bioavailability of sulforaphane in healthy human subjects after the consumption of cooked broccoli

Broccoli contains the glucosinolate glucoraphanin which, in the presence of myrosinase, can hydrolyse to the isothiocyanate sulforaphane, reported to have anti-carcinogenic activity. However, the myrosinase enzyme is denatured on cooking. Addition of an active source of myrosinase, such as from powdered mustard seed, to cooked brassica vegetables can increase the release of health beneficial isothiocyanates, however this has not previously been proven in-vivo. The concentration of sulforaphane metabolite (sulforaphane N-acetyl-L-cysteine (SF-NAC) in 12 healthy adults after the consumption of 200g cooked broccoli, with and without 1 g powdered brown mustard, was studied in a randomized crossover design. During the 24 hour period following consumption of the study sample all urine was collected. SF-NAC content was assayed by HPLC. When study subjects ingested cooked broccoli alone, mean urinary SF-NAC excreted was 9.8 ± 5.1 µmol per g creatinine, whilst when cooked broccoli was consumed with mustard powder this increased significantly to 44.7 ± 33.9 µmol SF-NAC per g creatinine. These results conclude that when powdered brown mustard is added to cooked broccoli the bioavailability of sulforaphane is over four times greater than that from cooked broccoli ingested alone

Comparison of the effect of raw and blanched-frozen broccoli on DNA damage in colonocytes

Consumption of cruciferous vegetables may protect against colorectal cancer. Cruciferous vegetables are rich in a number of bioactive constituents including polyphenols, vitamins and glucosinolates. Before consumption, cruciferous vegetables often undergo some form of processing that reduces their content of bioactive constituents and may determine whether they exert protective effects. The aim of this study was to compare the ability of raw and blanched-frozen broccoli to protect colonocytes against DNA damage, improve antioxidant status and induce xenobiotic metabolising enzymes (XME). Fifteen Landrace x Large White male pigs were divided into five age and weight matched sets (79 days, SD 3, and 34.7 kg, SD 3.9 respectively). Each set consisted of siblings to minimise genetic variation. Within each set, pigs received a cereal-based diet, unsupplemented (control) or supplemented with 600 g/d of raw or blanched-frozen broccoli for 12 d. The consumption of raw broccoli caused a significant 27% increase in DNA damage in colonocytes (P=0.03) relative to the control diet, whereas blanched-frozen broccoli had no significant effect. Both broccoli diets had no significant effect on plasma antioxidant status or hepatic and colonic XME. This study is the first to report that the consumption of raw broccoli can damage DNA in porcine colonocytes

Benefits and risks of the hormetic effects of dietary isothiocyanates on cancer prevention

The isothiocyanate (ITC) sulforaphane (SFN) was shown at low levels (1-5 µM) to promote cell proliferation to 120-143% of the controls in a number of human cell lines, whilst at high levels (10-40 µM) it inhibited such cell proliferation. Similar dose responses were observed for cell migration, i.e. SFN at 2.5 µM increased cell migration in bladder cancer T24 cells to 128% whilst high levels inhibited cell migration. This hormetic action was also found in an angiogenesis assay where SFN at 2.5 µM promoted endothelial tube formation (118% of the control), whereas at 10-20 µM it caused significant inhibition. The precise mechanism by which SFN influences promotion of cell growth and migration is not known, but probably involves activation of autophagy since an autophagy inhibitor, 3-methyladenine, abolished the effect of SFN on cell migration. Moreover, low doses of SFN offered a protective effect against free-radical mediated cell death, an effect that was enhanced by co-treatment with selenium. These results suggest that SFN may either prevent or promote tumour cell growth depending on the dose and the nature of the target cells. In normal cells, the promotion of cell growth may be of benefit, but in transformed or cancer cells it may be an undesirable risk factor. In summary, ITCs have a biphasic effect on cell growth and migration. The benefits and risks of ITCs are not only determined by the doses, but are affected by interactions with Se and the measured endpoint

Glucosinolates, myrosinase hydrolysis products, and flavonols found in rocket (Eruca sativa and Diplotaxis tenuifolia)

Rocket species have been shown to have very high concentrations of glucosinolates and flavonols, which have numerous positive health benefits with regular consumption. In this review we highlight how breeders and processors of rocket species can utilize genomic and phytochemical research to improve varieties and enhance the nutritive benefits to consumers. Plant breeders are increasingly looking to new technologies such as HPLC, UPLC, LC-MS and GC-MS to screen populations for their phytochemical content to inform plant selections. Here we collate the research that has been conducted to-date in rocket, and summarise all glucosinolate and flavonol compounds identified in the species. We emphasize the importance of the broad screening of populations for phytochemicals and myrosinase degradation products, as well as unique traits that may be found in underutilized gene bank resources. We also stress that collaboration with industrial partners is becoming essential for long-term plant breeding goals through research

The Eruca sativa genome and transcriptome: a targeted analysis of sulfur metabolism and glucosinolate biosynthesis pre and postharvest

Rocket (Eruca sativa) is a source of health-related metabolites called glucosinolates (GSLs) and isothiocyanates (ITCs) but little is known of the genetic and transcriptomic mechanisms responsible for regulating pre and postharvest accumulations. We present the first de novo reference genome assembly and annotation, with ontogenic and postharvest transcriptome data relating to sulfur assimilation, transport, and utilization. Diverse gene expression patterns related to sulfur metabolism, GSL biosynthesis, and glutathione biosynthesis are present between inbred lines of rocket. A clear pattern of differential expression determines GSL abundance and the formation of hydrolysis products. One breeding line sustained GSL accumulation and hydrolysis product formation throughout storage. Multiple copies of MYB28, SLIM1, SDI1 and ESM1 have increased and differential expression postharvest, and are associated with GSLs and hydrolysis product formation. Two glucosinolate transporter gene (GTR2) copies were found to be associated with increased GSL accumulations in leaves. Monosaccharides (which are essential for primary metabolism and GSL biosynthesis, and contribute to the taste of rocket) were also quantified in leaves, with glucose concentrations significantly correlated with the expression of numerous GSL-related genes. Significant negative correlations were observed between the expression of glutathione synthetase (GSH) genes and those involved in GSL metabolism. Breeding line ‘B’ showed increased GSH gene expression and low GSL content compared to two other lines where the opposite was observed. Co-expression analysis revealed senescence (SEN1) and oxidative stress-related (OXS3) genes have higher expression in line B, suggesting that postharvest deterioration is associated with low GSL concentrations

Glucosinolates and isothiocyanates: cancer preventive effects

The anticarcinogenic bioactivity of various isothiocyanates (ITCs) has been demonstrated in various animal models such as rats, mice, and hamsters, and in different target tissues such as lung, esophagus, and forestomach. A major chemopreventive mechanism of ITCs involves suppression of reactive metabolite generation and, therefore, a decrease in DNA adducts formation. Many in vitro studies have reported the effects of ITCs on cell cycle modulation and proapoptotic effects through a number of targets, at different points of the pathways. A comparative study in human subjects showed that the hydrolysis of glucosinolates and the absorption of ITCs are greater following ingestion of raw brassica with active plant myrosinase than after consumption of the cooked plant with denatured myrosinase. Apoptosis is considered a vital component of the cellular mechanisms responsible for the maintenance of homeostasis in multicellular organisms. Understanding the pathways of associated proteins provides an insight into the induction of apoptosis by anticancer agents

The metabolic fate of glucosinolates from processed brassica vegetables after consumption

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