Retention of Phytochemicals in Fresh and Processed Broccoli

Optimization of extraction and nanoencapsulation of kimchi cabbage by-products to enhance the simulated in vitro digestion of glucosinolates

Kimchi cabbage is a well-known glucosinolate (GLS)-containing vegetable, but its by-products are discarded despite the presence of GLS. The aim of this study was the optimization of the extraction and nanoencapsulation of GLS from kimchi cabbage by-products to enhance the intestinal absorption of GLS. The optimal GLS extraction conditions included steaming thrice as pretreatment, utilizing 70% methanol, and ultrasonication at 20% amplitude for 15 min. Under these conditions, 80.11 ± 4.40 mg/100 g of GLS extraction was obtained and the extraction yield was 81.70 ± 4.73%. The optimized kimchi cabbage by-product extract (KCE) was coated with chitosan-lipid nanoparticles (KCE-NPs) and their stability and release under simulated in vitro gastrointestinal conditions were evaluated. KCE-NPs protected the encapsulated GLS under acidic gastric conditions and released 91.63 ± 0.76% of GLS in the simulated intestinal medium. Therefore, the proposed KCE-NPs are a promising delivery system for increasing GLS absorption.

Interplay of broccoli/broccoli sprout bioactives with gut microbiota in reducing inflammation in inflammatory bowel diseases

Inflammatory Bowel Diseases (IBD) are chronic, reoccurring, and debilitating conditions characterized by inflammation in the gastrointestinal tract, some of which can lead to more systemic complications and can include autoimmune dysfunction, a change in the taxonomic and functional structure of microbial communities in the gut, and complicated burdens in a person's daily life. Like many diseases based in chronic inflammation, research on IBD has pointed towards a multifactorial origin involving factors of the person's lifestyle, immune system, associated microbial communities, and environmental conditions. Treatment currently exists only as palliative care, and seeks to disrupt the feedback loop of symptoms by reducing inflammation and allowing as much of a return to homeostasis as possible. Various anti-inflammatory options have been explored, and this review focuses on the use of diet as an alternative means of improving gut health. Specifically, we highlight the connection between the role of sulforaphane from cruciferous vegetables in regulating inflammation and in modifying microbial communities, and to break down the role they play in IBD.

A steamed broccoli sprout diet preparation that reduces colitis via the gut microbiota

Sulforaphane is a bioactive metabolite with anti-inflammatory activity and is derived from the glucosinolate glucoraphanin, which is highly abundant in broccoli sprouts. However, due to its inherent instability its use as a therapeutic against inflammatory diseases has been limited. There are few studies to investigate a whole food approach to increase sulforaphane levels with therapeutic effect and reduce inflammation. In the current study, using a mouse model of inflammatory bowel disease, we investigated the ability of steamed broccoli sprouts to ameliorate colitis and the role of the gut microbiota in mediating any effects. We observed that despite inactivation of the plant myrosinase enzyme responsible for the generation of sulforaphane via steaming, measurable levels of sulforaphane were detectable in the colon tissue and feces of mice after ingestion of steamed broccoli sprouts. In addition, this preparation of broccoli sprouts was also capable of reducing chemically-induced colitis. This protective effect was dependent on the presence of an intact microbiota, highlighting an important role for the gut microbiota in the metabolism of cruciferous vegetables to generate bioactive metabolites and promote their anti-inflammatory effects.

Are non-animal systemic safety assessments protective? A toolbox and workflow

An important question in toxicological risk assessment is whether non-animal new approach methodologies (NAMs) can be used to make safety decisions that are protective of human health, without being overly conservative. In this work, we propose a core NAM toolbox and workflow for conducting systemic safety assessments for adult consumers. We also present an approach for evaluating how protective and useful the toolbox and workflow are by benchmarking against historical safety decisions. The toolbox includes physiologically based kinetic (PBK) models to estimate systemic C_max levels in humans, and 3 bioactivity platforms, comprising high-throughput transcriptomics, a cell stress panel, and in vitro pharmacological profiling, from which points of departure are estimated. A Bayesian model was developed to quantify the uncertainty in the C_max estimates depending on how the PBK models were parameterized. The feasibility of the evaluation approach was tested using 24 exposure scenarios from 10 chemicals, some of which would be considered high risk from a consumer goods perspective (eg, drugs that are systemically bioactive) and some low risk (eg, existing food or cosmetic ingredients). Using novel protectiveness and utility metrics, it was shown that up to 69% (9/13) of the low risk scenarios could be identified as such using the toolbox, whilst being protective against all (5/5) the high-risk ones. The results demonstrated how robust safety decisions could be made without using animal data. This work will enable a full evaluation to assess how protective and useful the toolbox and workflow are across a broader range of chemical-exposure scenarios.

Approaches for enhancing the stability and formation of sulforaphane

The isothiocyanate sulforaphane (SF) is one of the most potent naturally occurring Phase 2 enzymes inducers derived from brassica vegetables like broccoli, cabbage, brussel sprouts, etc. Ingestion of broccoli releases SF via hydrolysis of glucoraphanin (GRP) by plant myrosinase and/or intestinal microbiota. However, both SF and plant myrosinase are thermal-labile, and the epithiospecifier protein (ESP) directs the hydrolysis of GRP toward formation of sulforaphane nitrile instead of SF. In addition, bacterial myrosinase has low hydrolyzing efficiency. In this review, we discuss strategies that could be employed to improve the stability of SF, increase SF formation during thermal and non-thermal processing of broccoli, and enhance the myrosinase-like activity of the gut microbiota. Furthermore, new cooking methods or blanching technologies should be developed to maintain myrosinase activity, and novel thermostable myrosinase and/or microbes with high SF producing abilities should also be developed.

Aryl hydrocarbon Receptor activation during in vitro and in vivo digestion of raw and cooked broccoli (brassica oleracea var. Italica)

Broccoli is rich in glucosinolates, which can be converted upon chewing and processing into Aryl hydrocarbon Receptor (AhR) ligands. Activation of AhR plays an important role in overall gut homeostasis but the role of broccoli processing on the generation of AhR ligands is still largely unknown. In this study, the effects of temperature, cooking method (steaming versus boiling), gastric pH and further digestion of broccoli on AhR activation were investigated in vitro and in ileostomy subjects. For the in vitro study, raw, steamed (t = 3 min and t = 6 min) and boiled (t = 3 min and t = 6 min) broccoli were digested in vitro with different gastric pH. In the in vivo ileostomy study, 8 subjects received a broccoli soup or a broccoli soup plus an exogenous myrosinase source. AhR activation was measured in both in vitro and in vivo samples by using HepG2-Lucia™ AhR reporter cells. Cooking broccoli reduced the AhR activation measured after gastric digestion in vitro, but no effect of gastric pH was found. Indole AhR ligands were not detected or detected at very low levels both after intestinal in vitro digestion and in the ileostomy patient samples, which resulted in no AhR activation. This suggests that the evaluation of the relevance of glucosinolates for AhR modulation in the gut cannot prescind from the way broccoli is processed, and that broccoli consumption does not necessarily produce substantial amounts of AhR ligands in the large intestine.

Effects of Nonthermal Plasma Technology on Functional Food Components

Understanding the impact of nonthermal plasma (NTP) technology on key nutritional and functional food components is of paramount importance for the successful adoption of the technology by industry. NTP technology (NTPT) has demonstrated marked antimicrobial efficacies with good retention of important physical, chemical, sensory, and nutritional parameters for an array of food products. This paper presents the influence of NTPT on selected functional food components with a focus on low-molecular-weight bioactive compounds and vitamins. We discuss the mechanisms of bioactive compound alteration by plasma-reactive species and classify their influence on vitamins and their antioxidant capacities. The impact of NTP on specific bioactive compounds depends both on plasma properties and the food matrix. Induced changes are mainly associated with oxidative degradation and cleavage of double bonds in organic compounds. The effects reported to date are mainly time-dependent increases in the concentrations of polyphenols, vitamin C, or increases in antioxidant activity. Also, improvement in the extraction efficiency of polyphenols is observed. The review highlights future research needs regarding the complex mechanisms of interaction with plasma species. NTP is a novel technology that can both negatively and positively affect the functional components in food.

Potential effects of sulforaphane to fight obesity

Obesity is linked to the onset of many diseases such as diabetes mellitus, cardiovascular diseases and cancer, among others. The prevalence of obesity nearly doubled worldwide between 1980 and 2014. Simultaneously, in the last decade, the effects of sulforaphane as a potential treatment for obesity have been investigated, with promising results. Fruits and vegetables and their processed agri-food co-products are good sources of natural health-promoting compounds. Brassica crops are among the most produced crops in the world and are a good source of glucoraphanin, which, following hydrolysis, releases sulforaphane. The Brassicaceae family generates large amounts of co-products with no intended use, causing negative economic and environmental impact. Valorization of these co-products could be achieved through their exploitation for the extraction of bioactive compounds such as sulforaphane. However, the extraction process still needs further improvement for its economic feasibility. This article reviews the potential effects of sulforaphane in the treatment of obesity, linked to the relevance of giving Brassica co-products added value, which is of key importance for the competitiveness of farmers and the agri-food industry. © 2018 Society of Chemical Industry.

Hydrolysis before Stir-Frying Increases the Isothiocyanate Content of Broccoli

Broccoli is found to be a good source of glucosinolates, which can be hydrolyzed by endogenous myrosinase to obtain chemopreventive isothiocyanates (ITCs); among them, sulforaphane (SF) is the most important agent. Studies have shown that cooking greatly affects the levels of SF and total ITCs in broccoli. However, the stability of these compounds during cooking has been infrequently examined. In this study, we proved that the half-lives of SF and total ITCs during stir-frying were 7.7 and 5.9 min, respectively, while the myrosinase activity decreased by 80% after stir-frying for 3 min; SF and total ITCs were more stable than myrosinase. Thus, the contents of SF and total ITCs decreased during stir-frying largely because myrosinase was destroyed. Subsequently, it was confirmed that compared to direct stir-frying, hydrolysis of glucosinolates in broccoli for 90 min followed by stir-frying increased the SF and total ITC concentration by 2.8 and 2.6 times, respectively. This method provides large quantities of beneficial ITCs even after cooking.

High resolution mass spectrometry studies of sulforaphane and indole-3-carbinol in broccoli

Broccoli is a rich source of bioactive compounds. Among them, sulforaphane and indole-3-carbinol have attracted a lot of attention, since their consumption is associated with reduced risk of cancer. In this work, the development of an efficient and direct method for the simultaneous determination of sulforaphane and indole-3-carbinol in broccoli using UPLC-HRMS/MS is described. The correlation coefficient, and limits of detection (LOD) and quantification (LOQ) were 0.993, 0.77mg/L and 2.35mg/L for sulforaphane and 0.997, 0.42mg/L, 1.29mg/L for indole-3-carbinol, respectively. The content of sulforaphane and indole-3-carbinol varied between 72±9-304±2mg and 77±1-117±3mg per 100g of fresh florets, respectively. Taking into consideration the differences in cultivar, geography, season and environmental factors, the results agreed with values published in the literature using other techniques.

Effect of broccoli extract enriched diet on liver cholesterol oxidation in rats subjected to exhaustive exercise

The effect of broccoli extract (BE)-enriched diet was studied in order to evaluate its ability to counteract liver cholesterol oxidation products (COPs) induced by acute strenuous exercise in rats. Thirty-two female Wistar rats were randomly divided into four groups: control diet without exercise (C), BE-enriched diet without exercise (B), control diet with acute exhaustive exercise (S) and BE-enriched diet with acute exhaustive exercise (BS). The study lasted 45days and on the last day, rats of S and BS groups were forced to run until exhaustion on a treadmill. Glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT) and cholesterol oxidation products (COPs) were determined in liver. Exhaustive exercise was clearly responsible for tissue damage, as evidenced by the increase of lactate dehydrogenase (LDH) plasma activity in the S group. Moreover, the exercise protocol reduced CAT activity in liver, while it did not affect GST, GR and GPx. BE-enriched diet raised GST, GR and CAT activities in rats of BS group. The main COPs found were 7α-hydroxycholesterol, 7β-hydroxycholesterol, 7-ketocholesterol, cholestanetriol, 24-hydroxycholesterol and 27-hydroxycholesterol. The BE-enriched diet led to reduced cholesterol oxidation following exhaustive exercise; the highest level of COPs was found in the S group, whereas the BS rats showed the lowest amount. This study indicates that the BE-enriched diet increases antioxidant enzyme activities and exerts an antioxidant effect towards cholesterol oxidation in rat liver, suggesting the use of phytochemicals in the prevention of oxidative damage and in the modulation of the redox environment.

Effect of industrial freezing on the stability of chemopreventive compounds in broccoli

Broccoli (Brassica oleracea L. var. Italica) is largely consumed all over the world and has a high economic importance. Likewise, broccoli contains high levels of glucosinolates, carotenoids and total phenols, which are related with the prevention of chronic diseases. The present project's objective was to evaluate the effect of industrial freezing on the stability of bioactive molecules in seven commercial broccoli cultivars (Tlaloc®, Endurance®, Florapack®, Domador®, Steel®, Iron Man® and Avenger®). In general, industrial freezing increased the extractability of total glucosinolates, whereas total phenols remained constant in most broccoli cultivars. Likewise, broccoli subjected to industrial freezing showed higher levels of total carotenoids (∼60-300% higher) as compared with fresh broccoli. Results suggest that bioactive compounds in frozen broccoli would be more bioavailable than in raw.

Chemical composition and antioxidant activity in different tissues of brassica vegetables

This research was conducted to evaluate glucosinolate profiles, vitamin C, total phenol, total flavonoid, and free sugar (glucose, fructose, and sucrose) content, fatty acid composition, and antioxidant activity in floret and leaf of six cauliflower and broccoli cultivars. The level of chemical constituents as well as antioxidants significantly varied among crop types, cultivars, and their different parts, in that phytochemicals such as glucosinolate were statistically higher in florets compared with leaves in both broccoli and cauliflower cultivars. In contrast, total flavonoid and free sugar were found at higher levels in the leaf parts. The Asia purple cultivar exhibited statistically higher vitamin C (649.7 mg·100 g-1), total phenol (1345.2 mg·GAE 100 g-1), and total flavonoid (632.7 mg·CE 100 g-1) contents and consequently had the highest antioxidant activity (1.12 mg·mL-1) in its florets, while Baeridom and Bridal had the highest total glucosinolate (9.66 µmol·g-1) and free sugar (318.6 mg·g-1) contents, respectively compared with other cultivars. Likewise, the major fatty acids were palmitic (23.52%-38.42%), linoleic (13.09%-18.97%), and linolenic (26.32%-51.80%) acids, which comprised the highest compositional ratio (more than 50%) of polyunsaturated fatty acids (PUFAs) in most cultivars. Among the antioxidants, total phenol exhibited the most significant positive correlation (r = 0.698 **) with antioxidant activity, followed by vitamin C (r = 0.522 **) and total flavonoid (r = 0.494 **), indicating their significant contributions to total antioxidant activity.

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. This review highlights 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. This paper collates the research that has been conducted to date in rocket and summarizes all glucosinolate and flavonol compounds identified in the species. The paper emphasizes 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. This review also stresses that collaboration with industrial partners is becoming essential for long-term plant breeding goals through research.

The effect of cooking on the phytochemical content of vegetables

Cooking induces many chemical and physical modifications in foods; among these the phytochemical content can change. Many authors have studied variations in vegetable nutrients after cooking, and great variability in the data has been reported. In this review more than 100 articles from indexed scientific journals were considered in order to assess the effect of cooking on different phytochemical classes. Changes in phytochemicals upon cooking may result from two opposite phenomena: (1) thermal degradation, which reduces their concentration, and (2) a matrix softening effect, which increases the extractability of phytochemicals, resulting in a higher concentration with respect to the raw material. The final effect of cooking on phytochemical concentration depends on the processing parameters, the structure of food matrix, and the chemical nature of the specific compound. Looking at the different cooking procedures it can be concluded that steaming will ensure better preservation/extraction yield of phenols and glucosinolates than do other cooking methods: steamed tissues are not in direct contact with the cooking material (water or oil) so leaching of soluble compounds into water is minimised and, at the same time, thermal degradation is limited. Carotenoids showed a different behaviour; a positive effect on extraction and the solubilisation of carotenes were reported after severe processing.

Optimization of a blanching step to maximize sulforaphane synthesis in broccoli florets

A blanching step was designed to favor sulforaphane synthesis in broccoli. Blanching was optimised through a central composite design, and the effects of temperature (50-70 °C) and immersion time in water (5-15 min) on the content of total glucosinolates, glucoraphanin, sulforaphane, and myrosinase activity were determined. Results were analysed by ANOVA and the optimal condition was determined through response surface methodology. Temperature between 50 and 60 °C significantly increased sulforaphane content (p<0.05), whilst blanching at 70 and 74 °C diminished significantly this content, compared to fresh broccoli. The optimal blanching conditions given by the statistical model were immersion in water at 57 °C for 13 min; coinciding with the minimum glucosinolates and glucoraphanin content, and with the maximum myrosinase activity. In the optimal conditions, the predicted response of 4.0 μmol sulforaphane/g dry matter was confirmed experimentally. This value represents a 237% increase with respect to the fresh vegetable.

Maintaining quality and bioactive compounds of broccoli by combined treatment with 1-methylcyclopropene and 6-benzylaminopurine

BACKGROUND

Broccoli deteriorates very quickly after harvest at ambient temperature due to the loss of green colour and the consequent yellowing of florets. To search for an effective method to control quality deterioration, the effect of 1-methylcyclopropene (1-MCP) combined with 6-benzylaminopurine (6-BA) treatment on visual quality, antioxidant enzymes and bioactive compounds in broccoli florets were investigated.

RESULTS

A combined treatment of 2.5 µL L⁻¹ 1-MCP and 200 mg L⁻¹ 6-BA significantly reduced the increase of lightness (L*) value, and retained a high level for the hue value (H) and chlorophyll content. Superoxide dismutase, ascobate peroxidase and catalase activities increased while the activity of peroxidase decreased during storage in treated samples in comparison with the controls. The combined treatment enhanced the biosynthesis of glucosinolate and the formation of the anticarcinogen sulforaphane, which improved the health benefit of broccoli.

CONCLUSION

These results indicate that a combined treatment of 1-MCP and 6-BA could be a good candidate for maintaining the visual quality and enhancing the nutritional value in broccoli during storage at 15 °C.

An overview of health-promoting compounds of broccoli (Brassica oleracea var. italica) and the effect of processing

Broccoli offers many heath-promoting properties owing to its content of antioxidant and anticarcinogenic compounds. The concentration and bioavailability of polyphenols, glucosinolates, sulforaphane and selenium depend on plant biochemistry, cultivation strategy and type of processing. In this article, the main biochemical properties of broccoli are reviewed regarding their health-promoting effects. Additionally, the way these properties are affected by processing is discussed. Steaming and drying result in an apparent increment of sulforaphane content as well as antioxidant activity, most likely due to an increase of the extractability of antioxidants and sulforaphane. Freezing and boiling diminish polyphenols concentration, mainly due to volatilization and leaching into the cooking water. In view of these results, the optimization of broccoli processing in order to maximize the content of bioactive compounds should be possible. The effect of processing on selenium compounds has been poorly studied so far, and therefore this topic should be investigated in the future. Finally, the effect of operating conditions in different drying processes on the content of bioactive compounds in broccoli should be investigated in a greater depth.

Food as a source for quorum sensing inhibitors: iberin from horseradish revealed as a quorum sensing inhibitor of Pseudomonas aeruginosa

Foods with health-promoting effects beyond nutritional values have been gaining increasing research focus in recent years, although not much has been published on this subject in relation to bacterial infections. With respect to treatment, a novel antimicrobial strategy, which is expected to transcend problems with selective pressures for antibiotic resistance, is to interrupt bacterial communication, also known as quorum sensing (QS), by means of signal antagonists, the so-called QS inhibitors (QSIs). Furthermore, QSI agents offer a potential solution to the deficiencies associated with use of traditional antibiotics to treat infections caused by bacterial biofilms and multidrug-resistant bacteria. Several QSIs of natural origin have been identified, and in this study, several common food products and plants were extracted and screened for QSI activity in an attempt to isolate and characterize previously unknown QSI compounds active against the common opportunistic pathogen Pseudomonas aeruginosa. Several extracts displayed activity, but horseradish exhibited the highest activity. Chromatographic separation led to the isolation of a potent QSI compound that was identified by liquid chromatography-diode array detector-mass spectrometry (LC-DAD-MS) and nuclear magnetic resonance (NMR) spectroscopy as iberin-an isothiocyanate produced by many members of the Brassicaceae family. Real-time PCR (RT-PCR) and DNA microarray studies showed that iberin specifically blocks expression of QS-regulated genes in P. aeruginosa.

Kinetic changes in glucosinolate-derived volatiles by heat-treatment and myrosinase activity in nakajimana (Brassica rapa L. cv. nakajimana)

Nakajimana (Brassica rapa L. cv. nakajimana), of the family Brassicaceae, is a traditional vegetable in Japan. Three isothiocyanates and five cyanides in the leaves of nakajimana were identified by gas chromatography (GC) and GC-mass spectrometry (GC-MS), and their kinetic changes using heat-treatment (temperature and time) were investigated. In addition, myrosinase activity of extracts prepared from fresh nakajimana leaf was determined. In crushed heat-treated leaves of nakajimana (70 °C for 30 s), formation of isothiocyanates and myrosinase activity increased, whereas formation of 1-cyano-3,4-epithiobutane and 1-cyano-4,5-epithiopentane decreased. Heat-treatment can significantly alter the content of potentially beneficial compounds in nakajimana, and ingestion of suitable isothiocyanates for human health may be better facilitated by mild boiling.

Health benefits and possible risks of broccoli - an overview

Chemopreventive effects of broccoli, a highly valued vegetable, have been known for a long time. Several studies have demonstrated that broccoli might be beneficial by reducing the risk for the development of certain forms of cancer. These effects are generally attributed to glucosinolate-derived degradation products like isothiocyanates and indoles which are formed by the hydrolytic action of plant myrosinase and/or glucosidases deriving from the human microbial flora. However, recent in vitro and experimental animal studies indicate that broccoli, its extracts and the glucosinolate-derived degradation products might also have undesirable effects, especially genotoxic activities. However, the relevance of the genotoxic activities to human health is not known yet. This paper gives an overview on genotoxic, anti-genotoxic/chemopreventive, nutritive and antinutritive properties of broccoli, its ingredients and their degradation products. A qualitative comparison of the benefit and risk of broccoli consumption benefit-risk assessment shows that the benefit from intake in modest quantities and in processed form outweighs potential risks. For other preparations (fortified broccoli-based dietary supplements, diets with extraordinary high daily intake, consumption as a raw vegetable) further studies both for potential risks and beneficial effects are needed in order to assess the benefit and risk in the future.

HPLC method validation for measurement of sulforaphane level in broccoli by-products

A simple and specific analytical method was developed and tested for the determination of sulforaphane in broccoli by-products. The method includes the optimization of the conversion of glucoraphanin to sulforaphane, followed by purification of extracts using solid-phase extraction and high-performance liquid chromatography (HPLC) analysis. The response surface methodology was used to find optimum conditions for the preparation and purification procedure. Chromatographic conditions for reversed-phase HPLC with UV photodiode array detection were as follows: column, Exil ODS C(18), 25 x 0.46 cm, 5 microm; column temperature, 36 degrees C; mobile phase, a 30 : 70 (v/v) mixture of acetonitrile:water; flow rate, 0.6 mL/min. The detection wavelength was UV 202 nm. Under these conditions, excellent linearity was obtained (r(2) = 1), and the overall recovery was 97.5 and 98.1% for fresh florets and lyophilized florets, respectively. The precision results showed that the relative standard deviation of the repeatability for florets fresh and lyophilized was 3.0 and 4.0%, respectively. Sulforaphane contents were determined in the edible portion of fresh broccoli, and broccoli crop remains.

Variation of glucoraphanin metabolism in vivo and ex vivo by human gut bacteria

Glucosinolates, phytochemicals found in cruciferous vegetables, are metabolised to bioactive isothiocyanates (ITC) by certain bacteria in the human gut. Substantial individual variation in urinary ITC excretion has been observed in previous cruciferous vegetable-feeding studies. We hypothesised that individual differences in gut microbial community contribute to the observed variation in glucosinolate metabolism, i.e. gut microbiota composition between high- and low-ITC excreters differs. We recruited twenty-three healthy individuals and fed them a standardised meal containing 200 g of cooked broccoli. After the meal, 24 h urinary ITC excretion was measured. Study participants with the highest (n 5) and lowest (n 5) ITC excretion provided faecal samples for ex vivo bacterial cultivation with 50 μm-glucoraphanin, the major glucosinolate found in broccoli. When grown ex vivo, faecal bacteria from the selected high-ITC excreters were able to degrade more glucoraphanin than those from the low-ITC excreters (P = 0·05). However, bacterial fingerprints of faecal and ex vivo culture microbiota revealed no statistically significant differences between the high- and low-ITC excreters in terminal restriction fragment length polymorphism analysis of the bacterial 16S ribosomal RNA gene. In conclusion, glucosinolate degradation by faecal bacteria ex vivo may be associated with in vivo bacterial glucosinolate metabolism capacity, but no direct link to specific bacterial species could be established, possibly due to the complexity and functional redundancy of the gut microbiota.

Modulation of rat hepatic and pulmonary cytochromes P450 and phase II enzyme systems by erucin, an isothiocyanate structurally related to sulforaphane

Administration of dietary doses of the isothiocyanate erucin had no effect on rat hepatic cytochrome P450 activity or protein levels, but at higher doses a rise in CYP1A/B1 protein levels was evident. In lung, treatment with erucin, as well as sulforaphane, failed to modulate cytochrome P450 activities but elevated CYP1A/B1 protein levels. In liver, erucin stimulated quinone reductase activity accompanied by a rise in protein. Glutathione S-transferase activity was unaffected, but GSTalpha and GSTmu protein levels increased. In lung, both isothiocyanates increased quinone reductase paralleled by a rise in protein levels; at the higher dose both isothiocyanates elevated moderately GSTalpha levels. Hepatic microsomes converted both isothiocyanates to metabolites that impaired cytochrome P450 activity, which was antagonized by reduced glutathione. It may be concluded that erucin may protect against carcinogens by stimulating the detoxication of quinones but is unlikely to significantly influence reactive intermediate generation through modulation of cytochrome P450 activity.

Absolute bioavailability and dose-dependent pharmacokinetic behaviour of dietary doses of the chemopreventive isothiocyanate sulforaphane in rat

Sulforaphane is a naturally occurring isothiocyanate with promising chemopreventive activity. An analytical method, utilising liquid chromatography-MS/MS, which allows the determination of sulforaphane in small volumes of rat plasma following exposure to low dietary doses, was developed and validated, and employed to determine its absolute bioavailability and pharmacokinetic characteristics. Rats were treated with either a single intravenous dose of sulforaphane (2·8 μmol/kg) or single oral doses of 2·8, 5·6 and 28 μmol/kg. Sulforaphane plasma concentrations were determined in blood samples withdrawn from the rat tail at regular time intervals. Following intravenous administration, the plasma profile of sulforaphane was best described by a two-compartment pharmacokinetic model, with a prolonged terminal phase. Sulforaphane was very well and rapidly absorbed and displayed an absolute bioavailability of 82 %, which, however, decreased at the higher doses, indicating a dose-dependent pharmacokinetic behaviour; similarly,Cmaxvalues did not rise proportionately to the dose. At the highest dose used, the rate of absorption constantkab, biological half-lifet½and apparent volume of distribution decreased significantly. It is concluded that in the rat orally administered sulforaphane is rapidly absorbed, achieving high absolute bioavailability at low dietary doses, but dose-dependent pharmacokinetics was evident, with bioavailability decreasing with increasing dose.

The influence of processing and preservation on the retention of health-promoting compounds in broccoli

In this work the effects of common household practices such as chilling, freezing, and cooking on vitamin C retention in broccoli (Marathon cv.), as well as their influence on the release of sulforaphane upon enzymatic hydrolysis of glucoraphanin by the endogenous enzyme myrosinase, were investigated. When chilled at 6 degrees C and 95% R.H. for 35 d, broccoli showed a vitamin C and sulforaphane loss of about 39% and 29%, respectively, while storage at -18 degrees C for 60 d resulted in similar losses, but mainly due to the blanching step. Boiling, steaming, microwaving, pressure-cooking, and the combined use of pressure and microwaves were the cooking methods investigated. Boiling and steaming caused significant vitamin C losses, 34% and 22%, respectively, while with the other treatments more than 90% retention was observed. Sulforaphane was no more detectable after boiling or steaming, while pressure/microwave cooking did not cause any significant loss. The quantitative distribution of these moieties in the florets and stems of fresh and chilled broccoli was also investigated.

Effect of storage, processing and cooking on glucosinolate content of Brassica vegetables

Epidemiological studies have shown that consumption of Brassica vegetables decrease the risk of cancer. These associations are linked to dietary intake of glucosinolates and their metabolism to cancer preventive isothiocyanates. Bioavailability of glucosinolates and related isothiocyanates are influenced by storage and culinary processing of Brassica vegetables. In this work, the content of the 7 major glucosinolates in broccoli, Brussels sprouts, cauliflower and green cabbage and their stability under different storage and cooking conditions is examined. Glucosinolates and isothiocyanates were quantified by liquid chromatography with tandem mass spectrometric detection (LC-MS/MS). Isothiocyanates were detected with high sensitivity as the corresponding thiourea derivatives. Storage at ambient temperature and in a domestic refrigerator showed no significant difference and a minor loss (9-26%) of glucosinolate levels over 7 days. Vegetables shredded finely showed a marked decline of glucosinolate level with post-shredding dwell time - up to 75% over 6h. Glucosinolate losses were detected partly as isothiocyanates. Cooking by steaming, microwaving and stir-fry did not produce significant loss of glucosinolates whereas boiling showed significant losses by leaching into cooking water. Most of the loss of the glucosinolates (approximately 90%) was detected in the cooking water. Increased bioavailability of dietary isothiocyanates may be achieved by avoiding boiling of vegetables.

Changes in the content of health-promoting compounds and antioxidant activity of broccoli after domestic processing

The effect of water- and steam-cooking on the content of vitamin C, polyphenols, carotenoids, tocopherols and glucosinolates, as well as on the antioxidant activity of broccoli, are reported. Flavonoids, phenolic acids, vitamins C and E, beta-carotene, lutein, and glucosinolates in domestically processed broccoli were quantified using high-performance liquid chromatography (HPLC) methods; total polyphenols were determined with Folin-Ciocalteu reagent. The antioxidant capacities of broccoli extracts were evaluated using the Trolox equivalent antioxidant capacity (TEAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods. The results indicated that steam-cooking of broccoli results in an increase in polyphenols, as well as the main glucosinolates and their total content as compared with fresh broccoli, whereas cooking in water has the opposite effect. Steam-cooking of broccoli has no influence on vitamin C, whereas cooking in water significantly lowers its content. Both, water- and steam-cooking of broccoli results in an increase in beta-carotene, lutein, and alpha- and gamma-tocopherols as compared with fresh broccoli. Similar effects of steaming and water-cooking of broccoli on their antioxidant activity were observed.

Modulation of hepatic cytochromes P450 and phase II enzymes by dietary doses of sulforaphane in rats: Implications for its chemopreventive activity

The principal objectives of our study were to ascertain whether sulforaphane, at dietary levels of intake, modulates rat hepatic cytochrome P450 and phase II enzyme systems and to evaluate the impact of such changes in the chemopreventive activity of this isothiocyanate. Animals were exposed to sulforaphane in their drinking water for 10 days, equivalent to daily doses of 3 and 12 mg/kg. Depentylation of pentoxyresorufin decreased and was paralleled by a decline in CYP2B apoprotein levels. At the higher dose, erythromycin N-demethylase activity declined and was accompanied by a similar decrease in CYP3A2 apoprotein levels. However, sulforaphane treatment upregulated CYP1A2 levels, determined immunologically, but the dealkylations of methoxy- and ethoxyresorufin were not similarly increased. Hepatic S9 preparations from sulforaphane-treated rats were less effective than control preparations in converting IQ (2-amino-3-methylimidazo-[4,5-f]quinoline) to mutagenic intermediates in the Ames test. To clarify the underlying mechanism, in vitro studies were undertaken. In beta-naphthoflavone-treated rats, the inhibition by sulforaphane of the O-dealkylations of methoxy- and ethoxyresorufin was enhanced if the isothiocyanate was preincubated in the presence of NADPH. It may be inferred that sulforaphane induces hepatic CYP1A2 but the enzyme is not catalytically competent because of bound sulforaphane metabolite(s). Finally, sulforaphane stimulated, in a dose-dependent fashion, quinone reductase but failed to influence glutathione S-transferase, epoxide hydrolase and glucuronosyl transferase activities. It is concluded that, even at dietary doses, sulforaphane can modulate the xenobiotic-metabolising enzyme systems, shifting the balance of carcinogen metabolism toward deactivation, and this may be an important mechanism of its chemopreventive activity.

The effect of post-harvest and packaging treatments on glucoraphanin concentration in broccoli (Brassica oleracea var. italica)

The effects of post-harvest and packaging treatments on glucoraphanin (4-methylsulfinylbutyl glucosinolate), the glucosinolate precursor of anticancer isothiocyanate sulforaphane [4-methylsulfinylbutyl isothiocyanate], were examined in broccoli (Brassica oleracea var. italica) during storage times. The results showed that at 20 degrees C, 55% loss of glucoraphanin concentration occurred in broccoli stored in open boxes during the first 3 days of the treatment and 56% loss was found in broccoli stored in plastic bags by day 7. Under both air and controlled atmosphere (CA) storage, glucoraphanin concentration appeared to fluctuate slightly during 25 days of storage and the concentrations under CA was significantly higher than those stored under air treatment. In modified atmosphere packaging (MAP) treatments, glucoraphanin concentration in air control packaging decreased significantly whereas there were no significant changes in glucoraphanin concentration in MAP with no holes at 4 degrees C and two microholes at 20 degrees C for up to 10 days. Decreases in glucoraphanin concentration occurred when the broccoli heads deteriorated. In the present study, the best method for preserving glucoraphanin concentration in broccoli heads after harvest was storage of broccoli in MAP and refrigeration at 4 degrees C. This condition maintained the glucoraphanin concentration for at least 10 days and also maintained the visual quality of the broccoli heads.

Urinary excretion of dithiocarbamates and self-reported Cruciferous vegetable intake: application of the 'method of triads' to a food-specific biomarker

OBJECTIVE

Greater intake of Cruciferous vegetables (e.g. broccoli) may prevent cancer at several sites. Urinary excretion of isothiocyanate conjugates (dithiocarbamates, DTC) provides a specific biomarker of Cruciferous vegetable consumption suitable for epidemiological investigations. However, no gold-standard referent is available for evaluating urinary DTC levels as an estimator of Cruciferous vegetable consumption. We compared urinary DTC levels to intake as measured by two self-reported dietary assessment techniques.

DESIGN

Cruciferous vegetable consumption was measured before and after a behavioural dietary intervention using multiple 24-hour recalls (24HR), a food-counting questionnaire (VFQ) and urinary DTC excretion levels. Analysis included a structural equation approach (Method of Triads) combining these three assessment techniques to estimate the relationship between DTC level and the study population's 'true' Cruciferous vegetable intake.

SETTING

The intervention curriculum assisted participants in consuming about 2 servings per day for a 6-week period. Participants attended four classes emphasising problem-solving skills, dietary counselling and vegetable preparation skills. There were no dietary restrictions.

SUBJECTS

Thirty-three healthy, free-living, post-menopausal women.

RESULTS

Although few participants reported Cruciferae consumption prior to the intervention, 30 participants reported Cruciferae consumption after the intervention (Post-intervention). Urinary DTC levels were correlated with estimated intake derived from either the 24HR (r = 0.57; 95% confidence interval (95% CI) 0.28, 0.76) or VFQ (r =0.49; 95% CI 0.17, 0.71). The validity coefficient (Method of Triads) between urinary DTC excretion and an index of true Cruciferous intake was stronger than the Pearson correlation (r(v) = 0.65; 95% CI 0.35, 0.90), and comparable to estimates derived from the 24HR (r(v) = 0.82; 95% CI 0.65, 1.00) or VFQ (r(v) = 0.76; 95% CI 0.47, 0.92) method. These associations were not affected by adjustment for body mass index, energy intake, or social approval or desirability response sets.

CONCLUSIONS

Food-frequency questionnaires (FFQ) suitable for large epidemiological studies may not be designed to measure all Cruciferae, and cannot capture exposure to phytochemicals derived from those vegetables. Urinary DTC measurement was significantly correlated with Cruciferae intake derived from two dietary assessment approaches, and urinary DTC levels could supplement traditional FFQ data by providing an index of recent Cruciferous vegetable intake not susceptible to reporting biases.