Radish sprouts versus broccoli sprouts: A comparison of anti-cancer potential based on glucosinolate breakdown products

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Radish sprouts and broccoli sprouts have been implicated in having a potential chemoprotective effect against certain types of cancer. Each contains a glucosinolate that can be broken down to an isothiocyanate capable of inducing chemoprotective factors known as phase 2 enzymes. In the case of broccoli, the glucosinolate, glucoraphanin, is converted to an isothiocyanate, sulforaphane, while in radish a similar glucosinolate, glucoraphenin, is broken down to form the isothiocyanate, sulforaphene. When sprouts are consumed fresh (uncooked), however, the principal degradation product of broccoli is not the isothiocyanate sulforaphane, but a nitrile, a compound with little anti-cancer potential. By contrast, radish sprouts produce largely the anti-cancer isothiocyanate, sulforaphene. The reason for this difference is likely to be due to the presence in broccoli (and absence in radish) of the enzyme cofactor, epithiospecifier protein (ESP). In vitro induction of the phase 2 enzyme, quinone reductase (QR), was significantly greater for radish sprouts than broccoli sprouts when extracts were self-hydrolysed. By contrast, boiled radish sprout extracts (deactivating ESP) to which myrosinase was subsequently added, induced similar QR activity to broccoli sprouts. The implication is that radish sprouts have potentially greater chemoprotective action against carcinogens than broccoli sprouts when hydrolysed under conditions similar to that during human consumption.

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... Unlike in broccoli, breakdown of glucoraphenin (GRE), the GSL corresponding to GRA in broccoli, results in the production of SFE, rather than SFE nitrile, in radish plant. This process occurs because radish seeds and sprouts lack the epithiospecifier protein (ESP), which promotes nitrile formation during the breakdown of GSLs by myrosinase [18]. The anticancer properties of SFA from broccoli have been well documented, but research on the potential biological activities of SFE from radish is limited to a few recent studies. ...
... Compared with broccoli, kale, and other cruciferous vegetables, the radish is a better source of the ITC SFE because it lacks ESP, which inhibits the formation of ITCs. When fresh broccoli containing active ESP is consumed, the major hydrolysis product of GRA is predominantly SFA nitrile, which is an inactive form of SFA[18]. The ...
Sulforaphene (SFE), a major isothiocyanate in radish seeds, is a close chemical relative of sulforaphane (SFA) isolated from broccoli seeds and florets. The anti-proliferative mechanisms of SFA against cancer cells have been well investigated, but little is known about the potential anti-proliferative effects of SFE. In this study, we showed that SFE purified from radish seeds inhibited the growth of six cancer cell lines (A549, CHO, HeLa, Hepa1c1c7, HT-29, and LnCaP), with relative half maximal inhibitory concentration (IC50) values ranging from 1.37 to 3.31 g/mL. Among the six cancer cell lines evaluated, SFE showed the greatest growth inhibition against A549 lung cancer cells. In A549 cells, SFE induced apoptosis via changes in the levels of poly (adenosine diphosphate ribose) polymerase and caspase-3, -8, and -9. Our results indicate that SFE from radish seeds may have significant anti-proliferative potency against a broad range of human cancer cells via induction of apoptosis.
... botrytis), and radish (Raphanus sativus), is associated with a decreasing risk of developing many cancers and cardiovascular diseases (Higdon, Delage, Williams, & Dashwood, 2007;Joseph et al., 2004;Lam et al., 2010;Truong, Baron-Dubourdieu, Rougier, & Guenel, 2010). This chemoprotective effect is related to isothiocyanates, a type of hydrolysis products of glucosinolates, which are relatively unique into cruciferous vegetables (Beevi, Mangamoori, Subathra, & Edula, 2010;Force, O'Hare, Wong, & Irving, 2007;O'Hare et al., 2009;Williams, Critchley, Pun, Chaliha, & O'Hare, 2010). When cruciferous vegetables are ground or chopped, glucosinolates are hydrolyzed by myrosinase enzyme (b-thioglucoside glucohydrolase, EC3.2.3.1) to a variety of biological products such as isothiocyanates, thiocyanates, nitriles, oxazolidine-thiones and epithionitriles (Bones & Rossiter, 2006;Vaughn & Berhow, 2005). ...
... Radish sprouts have been shown to be capable of inducing the phase II enzyme, quinone reductase, in vitro in murine hepatoma cell line O'Hare et al., 2009), and activating the antioxidant response element in a stably transfected hepatoma cell line (Hanlon & Barnes, 2011). These biological activities have been remarkably attributed to the radish sprouts' glucosinolate composition. ...
Glucosinolates are sulphur-containing glycosides found in brassicaceous plants that can be hydrolysed enzymatically by plant myrosinase or non-enzymatically to form primarily isothiocyanates and/or simple nitriles. From a human health perspective, isothiocyanates are quite important because they are major inducers of carcinogen-detoxifying enzymes. Two of the most potent inducers are benzyl isothiocyanate (BITC) present in garden cress (Lepidium sativum), and phenylethyl isothiocyanate (PEITC) present in watercress (Nasturtium officinale). Previous studies on these salad crops have indicated that significant amounts of simple nitriles are produced at the expense of the isothiocyanates. These studies also suggested that nitrile formation may occur by different pathways: (1) under the control of specifier protein in garden cress and (2) by an unspecified, non-enzymatic path in watercress. In an effort to understand more about the mechanisms involved in simple nitrile formation in these species, we analysed their seeds for specifier protein and myrosinase activities, endogenous iron content and glucosinolate degradation products after addition of different iron species, specific chelators and various heat treatments. We confirmed that simple nitrile formation was predominantly under specifier protein control (thiocyanate-forming protein) in garden cress seeds. Limited thermal degradation of the major glucosinolate, glucotropaeolin (benzyl glucosinolate), occurred when seed material was heated to >120 degrees C. In the watercress seeds, however, we show for the first time that gluconasturtiin (phenylethyl glucosinolate) undergoes a non-enzymatic, iron-dependent degradation to a simple nitrile. On heating the seeds to 120 degrees C or greater, thermal degradation of this heat-labile glucosinolate increased simple nitrile levels many fold.
The chemical nature of the hydrolysis products from the glucosinolate-myrosinase system depends on the presence or absence of supplementary proteins, such as epithiospecifier proteins (ESPs). ESPs (non-catalytic cofactors of myrosinase) promote the formation of epithionitriles from terminal alkenyl glucosinolates and as recent evidence suggests, simple nitriles at the expense of isothiocyanates. The ratio of ESP activity to myrosinase activity is crucial in determining the proportion of these nitriles produced on hydrolysis. Sulphoraphane, a major isothiocyanate produced in broccoli seedlings, has been found to be a potent inducer of phase 2 detoxification enzymes. However, ESP may also support the formation of the non-inductive sulphoraphane nitrile. Our objective was to monitor changes in ESP activity during the development of broccoli seedlings and link these activity changes with myrosinase activity, the level of terminal alkenyl glucosinolates and sulphoraphane nitrile formed. Here, for the first time, we show ESP activity increases up to day 2 after germination before decreasing again to seed activity levels at day 5. These activity changes paralleled changes in myrosinase activity and terminal alkenyl glucosinolate content. There is a significant relationship between ESP activity and the formation of sulforaphane nitrile in broccoli seedlings. The significance of these findings for the health benefits conferred by eating broccoli seedlings is briefly discussed.
Broccoli (Brassica oleracea L., Italica Group) has been recognized as a source of glucosinolates and their isothiocyanate metabolites that may be chemoprotective against human cancer. A predominant glucosinolate of broccoli is glucoraphanin and its cognate isothiocyanate is sulforaphane. Sulforaphane has been shown to be a potent inducer of mammalian detoxication (Phase 2) enzyme activity and to inhibit chemical-induced tumorigenesis in animal models. Little is known about phenotypic variation in broccoli germplasm for Phase 2 enzyme (e.g., quinone reductase) induction potential. Thus, this study was undertaken to evaluate: 1) quinone reductase induction potential (QRIP) diversity among a population of broccoli inbreds; 2) QRIP levels in selected lines; 3) correlation of QRIP with other horticultural characteristics; and 4) QRIP expression in a sample of synthesized hybrids. In 1996, 71 inbreds and five hybrid checks (all field-grown), ranged from a QRIP of nearly zero to 150,000 units/g fresh weight (FW) (mean of 34,020 units/g FW). These values were highly correlated with methylsulphinylalkyl glucosinolate (MSAG; primarily glucoraphanin) concentrations that ranged from 0.04 to 2.94 μmol·g-1 FW. A select subset of lines evaluated in 1996 were reevaluated in 1997. QRIP and MSAG values in this second year were similar to and correlated with those observed in 1996 (r = 0.73, P < 0.0001 and r = 0.79, P < 0.0001, respectively). In addition, both QRIP and MSAG concentration were highly correlated with days from transplant to harvest. Average F1 hybrid values for QRIP and MSAG in 1997 fell typically between their parental means, but were often closer to the mean of the low parent. Results of this study indicate that divergent QRIP expression can effectively be used to select enhanced inbred lines to use in development of value-added hybrids. Evidence is also provided that there is a significant genetic component to both QRIP and MSAG concentration, and that selection for either one may provide an effective means for developing broccoli hybrids with enhanced chemoprotective attributes. Chemical names used: 4-methylsulphinylbutyl glucosinolate (glucoraphanin) and 4-methylsulphinylbutyl isothiocyanate (sulforaphane).
An epithiospecifier protein present in turnip tissue gives rise to 1-cyano-epithioalkanes during autolysis. Volatile hydrolysis products are produced from glucosinolates during autolysis of seeds, seedlings and plant tissue more than 6 weeks after sowing.
The activity of a methanol extract of radish sprouts for the induction of nicotinamide adenine dinucleotide (phosphate) NAD(P)H/quinone reductase (QR), which plays critical roles in protection against chemical carcinogens and other toxic xenobiotics, was examined in murine Hepa1c1c7 cells. The methanol extract induced QR activity in a dose-dependent manner in the concentration range of 0.2 to 1.6 mg/mL with a maximum of a 3.5-fold increase in induction. The induction of QR by the extract was regulated at the transcriptional level. Using a Western blotting analysis and Ah-receptor-defective mutant of Hepa1c1c7 cells (BPrc1 cells), the extracts at a concentration of 0.8 mg/mL or lower was found to be a monofunctional inducer and caused no elevation in cytochrome P-450 level that may activate carcinogens. The dichloromethane (CH2Cl2) fraction of the extract showed the highest induction potency while the other fractions were less potent. These results indicate that radish sprouts can be regarded as a safe and promising new dietary source for decreasing the risk of developing cancer.
An in vitro biochemical assay using induction of a phase II enzyme, NADPH-quinone reductase (NADPH-QR) for selection and identification of potential chemopreventive agents is described. A normal human liver cell line (Chang liver cells) or a rodent rat liver cell line (buffalo rat liver cells) was selected as the candidate cell line for induction of QR by a known chemopreventive agent, genistein. The choice of a liver cell line is based on the fact that liver being a major metabolic organ, phase II enzymes are commonly elaborated in liver tissues and is therefore appropriate for enzyme induction studies.
Ion-pair and hydrophilic interaction chromatographies are considered to be complementary methods of choice for analyzing intact glucosinolates from broccoli. Ion-pair chromatography resolves non-polar glucosinolates, such as those containing indole moieties, while hydrophilic interaction chromatography is superior for separating polar glucosinolates, such as glucoraphanin and glucoiberin. Reversed-phase separations using hydrophilic endcapped C18-bonded silica and a 50 mM ammonium acetate-methanol gradient mobile phase resolve both polar and non-polar glucosinolates negating the need for switching columns.