recently reviewed by Herr and Büchler (2010) . Sulforaphane belongs to isothiocyanates that are formed by the hydrolysis of their parent compounds, the glucosinolates (primarily glucoraphanin in broccoli). It has the most important anticarcinogenic
Zoltán Pék, Hussein Daood, Magdolna Gasztonyi Nagyné, Mária Berki, Marianna Márkus Tóthné, András Neményi and Lajos Helyes
Craig S. Charron and Carl E. Sams
Crops of the Brassicaceae contain glucosinolates(GSs), which when hydrolyzed by the enzyme myrosinase, generate products involved in cancer chemoprotection, plant defense, and plant-insect interactions. A rapid-cycling base population of B. oleracea L. was grown in a hydroponic system in a controlled environment to determine the roles of temperature, photosynthetic photon flux (PPF), and photoperiod in GS concentration and myrosinase activity. The concentration of total GSs in leaves was 44% and 114% higher at 12 and 32 °C respectively than at 22 °C under constant light of 300 μmol·m-2·s-1. The concentration of glucoraphanin, the precursor to sulforaphane, a compound with chemoprotective properties, was 5-fold higher at 32 than at 22 °C. Total GSs were ≈50% lower in roots at 12 °C and 32 than at 22 °C. Total GSs in leaves decreased 20% when PPF was increased from 200 to 400 μmol·m-2·s-1. Myrosinase activity on a fresh weight basis (activity-FW) was ≈30% higher in leaves and stems at 12 and 32 °C than at 22 °C, and ≈30% higher in leaves grown at 200 and 400 μmol·m-2·s-1 than at 300 μmol·m-2·s-1. Consideration of climatic factors that influence the glucosinolate-myrosinase system may be necessary to optimize the planting and cultivation of Brassica crops for maximum health benefits.
Mark W. Farnham, Katherine K. Stephenson and Jed W. Fahey
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).
Honghui Gu, Jiansheng Wang, Huifang Yu, Zhenqing Zhao, Xiaoguang Sheng, Jisuan Chen and Yingjun Xu
and Mithen, 2009 ). Among the hydrolysis products, many ITCs, particularly sulforaphane (SF), derived from the hydrolysis of aliphatic GSs, have shown high anticarcinogenic activity in mammalian cells ( Traka and Mithen, 2009 ). SF has been studied
John A. Juvik
Extensive epidemiological evidence suggests that carotenoids (including vitamin A), ascorbate (vitamin C), tocols (including vitamin E), and glucosinolate breakdown products exert anticarcinogenic effects in a range of human tissues. Consumption of fresh and processed vegetables with enhanced levels of these phytochemicals could reduce human risk of cancer. The vitamins play a major role as antioxidants, offering protection against cancer by preventing or reversing oxidative damage to DNA and other cellular components. Cruciferous vegetables contain glucosinolates (GSs), which, during mastication, are hydrolyzed by the enzyme myrosinase into bioactive breakdown products (BBPs), including sulforaphane. BBPs appear to induce synthesis of drug metabolism enzymes resulting in increased detoxification rates of carcinogens. This paper describes an interdisciplinary investigation designed to develop vegetable cultivars that offer chemoprotection from cancer at doses commensurate with a normal American diet. Initial work has focused on surveying sweet corn and Brassicae oleraceae germplasm for variation in vitamin and glucosinolate content in conjunction with in vitro and in vivo bioassays to determine which compounds and concentrations optimize chemoprotectant activity. Segregating populations from crosses between sweet corn and Brassica lines that vary in vitamin and GS concentrations will be assayed for chemical content and chemoprotectant activity, and genetically characterized using DNA marker technology to identify and map genes controlling these traits. This information will improve selection methodology in a breeding program aimed to develop brassica and sweet corn germplasm with enhanced cancer chemoprevention.
Zhi-Rong Li, Kang-Di Hu, Fen-Qin Zhang, Shi-Ping Li, Lan-Ying Hu, Yan-Hong Li, Song-Hua Wang and Hua Zhang
Broccoli (Brassica oleracea var. italica) is an important vegetable crop rich in vitamins and sulforaphane. However, the floral heads of broccoli experience rapid postharvest senescence. Here we found that hydrogen sulfide (H2S) treatment alleviated dark-promoted senescence in broccoli florets. H2S delayed the symptoms of senescence and maintained higher levels of chlorophyll and Rubisco and lower protease activity compared with water control. Gene expression analysis showed that H2S down-regulated the expression of chlorophyll degradation-related genes BoSGR, BoNYC, BoCLH1, BoPPH, and BoRCCR. Expression of lipoxygenase gene BoLOX1 and the genes involved in the ethylene synthesis pathway, BoACS2 and BoACS3, were also down-regulated by H2S. The reduced expression level in cysteine protease gene BoCP3 and aspartic protease gene BoLSC807 suggested the role of H2S in alleviating protein degradation during broccoli senescence. H2S up-regulated the expression of sulfur metabolism genes BoSR and BoOASTL, and the antioxidant gene BoCAT. These results show that H2S plays a vital role in alleviating broccoli senescence through a broad regulation on gene expression of reactive oxygen species (ROS) metabolism genes, ethylene synthesis genes, and protease genes.
Mark W. Farnham, Jed W. Fahey and Katherine K. Stephenson
Broccoli (Brassica oleracea L. Italica Group) is a rich source of the aliphatic glucosinolate glucoraphanin. The glucoraphanin breakdown product, sulforaphane, has been shown to induce Phase II detoxication enzymes (e.g., Quinone Reductase) and has attracted attention as a potential chemoprotector against cancer. The objectives of this research were to evaluate the concentration of glucoraphanin in an array of diverse broccoli inbreds (doubled-haploids) largely derived from commercial germplasm and to determine if expression of glucoraphanin level in this initial evaluation is correlated with expression in a subsequent environment. In 1996, individual florets from single broccoli heads were sampled from 75 inbred lines grown in the field at Charleston, S.C., and glucoraphanin concentration was assayed. In this test, concentrations ranged from 0.04 to 2.94 μmol glucoraphanin per g fresh weight of florets and the mean concentration was 0.86. In 1997, a subset of 22 inbreds analyzed the first year were grown again in a replicated field trial. This inbred subset was made up of lines with diverse pedigrees and with high, low, or intermediate glucoraphanin concentrations. In this second year, glucoraphanin concentration had a range from 0.24 to 2.99 μmol per g fresh weight of florets and a mean of 1.37. Correlation of entry mean glucoraphanin concentration in 1997 with that in 1996 was positive (r = 0.79) and highly significant (P < 0.001) indicating that floret glucoraphanin concentration was relatively consistent between years. These observations provide evidence that floret glucoraphanin concentration has a significant genetic component.
Mark W. Farnham, Katherine K. Stephenson and Jed W. Fahey
Broccoli (Brassica oleracea L., Italica Group) seed and resulting sprouts can contain high levels of glucoraphanin, a glucosinolate, which can be converted to sulforaphane, a compound with cancer protective and antioxidant properties. This observation has stimulated interest in broccoli seed production. In this study, inbred lines, which produce relatively high yields of homogeneous, selfed-seed across different environments in the absence of insect pollinators, were used to evaluate the relative importance of genotype versus environment as a determinant of glucoraphanin concentration in broccoli seed. Glucoraphanin and glucoiberin were measured in broccoli seed lots generated from ten broccoli inbred lines grown in two greenhouse and two screen cage environments. Typically, seed glucoraphanin level ranged from 5 to 100 μmol·g-1 seed and glucoiberin ranged from 0 to about 40 μmol·g-1 seed, regardless of the environment in which seed was produced. Analysis of variance indicated that genotype was the most significant factor influencing levels of the two glucosinolates. Although significant environmental and genotype × environment effects were observed for glucoraphanin and a significant genotype × environment effect was observed for glucoiberin, these effects were small compared to the genotype effects. Results indicate that it is possible to identify broccoli inbreds that consistently produce relatively high yields of seed with a high glucoraphanin content across different environments.
Mark W. Farnham and Howard F. Harrison
The discovery that broccoli (Brassicaoleracea L., Italica Group) sprouts contain high levels of sulforaphane, a constituent that may provide chemoprotection against certain carcinogens, has stimulated much interest in seed production of this crop. Studies were undertaken to determine the potential for producing broccoli seed using self-compatible selections from open-pollinated (OP) populations or doubled-haploid (DH) programs. In all outdoor and greenhouse trials, three OP selections and seven DH lines produced selfed seed, but seed weight per plant and number per plant varied significantly among the entries. In all environments there were individuals with relatively high (i.e., >3 g/plant) production that were significantly different from low (i.e., <2 g/plant) producers. The relative productivity of some lines varied greatly between experiments, which indicates that seed production of particular genotypes is affected differently by environmental conditions. This indicates the importance of identifying lines that are high producers of selfed seed across different environments. Two OP cultivar-derived lines (USVL102 and USVL104) and two DH lines (USVL062 and USVL093) were identified that consistently produced relatively high yields in greenhouse and screen cage trials. These lines are good candidates for evaluating seed production in field tests and as possible sources of seed for sprouting.
Hyoung Seok Kim and John A. Juvik
., 2004 ), but high concentration of Se fertilization resulted in a decrease in GS concentrations, especially in aliphatic GSs, including glucoraphanin, the parent GS of the isothiocyanate sulforaphane in broccoli florets ( Robbins et al., 2005 ). Similar