Glucosinolate determination in cruciferous seeds and meals by measurement of enzymatically released glucose

Variation in defence strategies in the metal hyperaccumulator plant Noccaea caerulescens is indicative of synergies and trade-offs between forms of defence

In the metal hyperaccumulator plant Noccaea caerulescens, zinc may provide a defence against pathogens. However, zinc accumulation is a variable trait in this species. We hypothesize that this variability affects the outcome of interactions between metal accumulation and the various constitutive and inducible defences that N. caerulescens shares with non-accumulator plants. We compare zinc concentrations, glucosinolate concentrations and inducible stress responses, including reactive oxygen species (ROS) and cell death, in four N. caerulescens populations, and relate these to the growth of the plant pathogen Pseudomonas syringae, its zinc tolerance mutants and Pseudomonas pathogens isolated from a natural population of N. caerulescens. The populations display strikingly different combinations of defences. Where defences are successful, pathogens are limited primarily by metals, cell death or organic defences; there is evidence of population-dependent trade-offs or synergies between these. In addition, we find evidence that Pseudomonas pathogens have the capacity to overcome any of these defences, indicating that the arms race continues. These data indicate that defensive enhancement, joint effects and trade-offs between different forms of defence are all plausible explanations for the variation we observe between populations, with factors including metal availability and metal-tolerant pathogen load probably shaping the response of each population to infection.

Evaluating extraction conditions of glucosinolate hydrolytic products from seeds of Eruca sativa (Mill.) Thell. using GC-MS

Glucosinolates and their hydrolytic products form an important class of plant secondary metabolites involved in various plant defense-linked mechanisms. The successful isolation of particular glucosinolate hydrolytic products is limited by a number of factors like understanding the parent glucosinolate moiety, solubility, and stability under different drying conditions. The extraction protocols currently available were modified to achieve both an increased yield as well as an increased number of hydrolytic products. Eruca sativa (Mill.) Thell. (called arugula in the U.S.A.), a rich source of varied glucosinolates, was used for the standardization of different extraction protocols. We exploited the volatile nature of the glucosinolates and developed a method that not only enhanced the yield of glucosinolate hydrolytic products, but also reduced undesired compounds. Among all the tested protocols, hydrodistillation using Clevenger apparatus was judged as the best protocol, which was evident from an enhanced yield as well as an increased number of hydrolytic products when compared to the other methods as monitored by gas chromatography-mass spectrometry.

PRACTICAL APPLICATION

Glucosinolate hydrolytic products are important volatile metabolites that are difficult to extract. The different conditions, such as extraction method, solvent, and dryingmethods, are responsible for successful extractions. An improved extraction method will help in a better isolation of these valuable compounds, which may then be used for different biological activities such as anticancer, antimutagenic, bioherbicidal, antimicrobial, antigenotoxic, and antitumor activities.

Low glucosinolate full-fat rapeseed meal in the diets of early-weaned piglets

The potential of using low glucosinolate full-fat rapeseed meal (FFR) in the diets of early-weaned piglets was investigated in this experiment. FFR (containing 17 (xmol total glucosinolates and 2·8 mg erucic acid per g of whole seed) was used on an isonitrogenous basis at either 200 g<kg or 400 g<kg to replace full-fat soya-bean meal. Four replicates of three contemporary pen groups of 10 piglets weaned between 3 and 4 weeks of age were randomly allocated at a mean initial weight of 8·41 (s.e. 1·105) kg to the three dietary treatments. The experimental diets were given for 3 weeks. Inclusion of FFR significantly depressed food intake, daily live-weight gain and food conversion. There were no significant differences between the performance of piglets given either 200 or 400 g FFR per kg. Intakes of the diets containing FFR per unit of metabolic body weight as a proportion of the control diet decreased from about 0·85 to 0·75 from the 1st to the last week of the feeding period. This suggested that the acceptability of diets containing FFR decreased with time, possibly due to the presence of unpalatable and perhaps antinutritive factors which may include glucosinolates although present at relatively low concentrations. It was concluded that the feeding value of FFR would need to be improved by development of oilseed rape varieties with much lower levels of glucosinolates.

Nutritional evaluation of triple low rapeseed products for growing pigs

Ground full-fat rapeseed (FFRS) and the resulting extracted oil (RSO), meal (RSM) and recombined RSO and RSM (ORSM) from a triple-low cultivar containing low levels of erucic acid, glucosinolates and tannins were evaluated. RSO, FFRS and ORSM were included into a basal diet to give levels of added oil of 40, 80 and 120g/kg. RSM was also incorporated into the basal diet at the same rates as in ORSM. The 12 experimental diets together with the basal diet were given to 13 gilts in a metabolism trial conducted over four time periods. A 10-day acclimatization in holding pens preceded a 5-day total collection of faeces and urine in metabolism crates. Rapeseed products, diets, faeces and urine were analysed for gross energy (GE) and all, except urine, for oil content measured by two methods (petroleum ether and acid hydrolysis prior to ether extraction). Apparent digestible energy (DE) and metabolizable energy (ME) of rapeseed products were determined by single-level assay and by regression. Oil DE was also derived indirectly as a product of apparent oil digestibility (AOD) and oil GE. Apparent nitrogen digestibility was estimated for diets and rapeseed products. The response of dietary DE, ME and AOD to rates of test material inclusion was linear (P < 0·001) in all cases except for ORSM and RSM the DE and ME of which, in addition, showed evidence of curvilinearity. Age of pig had no significant effect on dietary AOD and energy values. Linear regression techniques were better than single level assays (particularly at low rates of inclusion) in determining energy values and gave DE values of 42·4, 190, 14·6 and 25·8 MJ/kg dry matter for RSO, FFRS, RSM and ORSM respectively. Oil DE and AOD were not influenced by method of evaluation. The results of this study indicated improved energy values for FFRS and RSM of a triple-low cultivar over published data for high-glucosinolate varieties but not over data for double-low varieties. In addition it appears that AOD is the main factor determining dietary utilization of FFRS and would need to be considered in order to optimize the nutritive value of FFRS in diets for growing pigs.

Antioxidants in hot pepper: variation among accessions

The U.S. Department of Agriculture (USDA) pepper (Capsicum spp.) germplasm collection contains several thousand members or accessions. Many of these species and cultivars have not been analyzed for their concentrations of ascorbic acid, capsaicin, and total phenolic compounds, which are important antioxidants having a number of benefits for human health. The objective of this investigation was to select candidate accessions of hot pepper having high concentrations of ascorbic acid, capsaicin, free sugars, and total phenols for use as parents in breeding for these compounds. Seventeen accessions of pepper from the core Capsicum germplasm collection (four accessions of Capsicum chinense; five accessions of C. baccatum; six accessions of C. annuum; and two of C. frutescens) were field grown and their mature fruits were analyzed for their antioxidant composition. Concentrations of these compounds tended to be higher in C. chinense and C. baccatum, than in C. annuum and C. frutescens. Across all accessions the concentration of total phenols was correlated with ascorbic acid (r = 0.97) and free sugars (r = 0.80). Concentrations of total phenols (1.4, 1.3, and 1.3 mg g-1 fruit) and ascorbic acid (1.6, 1.2, and 1.3 mg g-1 fruit) were significantly greater in PI-633757, PI-387833, and PI-633754, respectively, compared to other accessions analyzed. Total capsaicinoids concentrations were greatest (1.3 mg g-1 fruit) in PI-438622 and lowest (0.002 mg g-1 fruit) in Grif-9320. The great variability within and among Capsicum species for these phytochemicals suggests that these selected accessions may be useful as parents in hybridization programs to produce fruits with value-added traits.

Sustainable soil management practices and quality of potato grown on erodible lands

Land productivity can decline when top soil is lost. In Kentucky, limited resource farmers often produce vegetable crops on erodible lands. The objectives of this study were 1) to quantify the impact of three soil management practices (SMPs) on quantity of potato produced on erodible land, 2) to evaluate the impact of pyrethrin and azadirachtin insecticides on potato tuber quality, and 3) to assess the impact of yard waste compost on the chemical composition (ascorbic acid, free sugars, phenol contents) of potato tubers. Potatoes (Solanum tuberosum L. cv. Kennebec) were grown in a silty loam soil of 10% slope. Plots (n= 18) were 3.7 m wide and 22 m long (10% slope), with metal borders of 20 cm above ground level. Two botanical insecticides, Multi-Purpose Insecticide (containing pyrethrin 0.2%) and Neemix 4EC (containing 0.25% azadirachtin) were sprayed twice on potato foliage during each of two growing seasons (1997 and 1999) at the recommended rates of 6 lbs and 2 gallons.acre(-1), respectively. The SMPs were tall fescue strips (FS) intercropped between each two potato rows, soil mixed with yard waste compost (COM) and no-mulch (NM) treatment (roto-tilled bare soil). The experimental designwas a 2 x 3 x 3 factorial with main factors of two insecticides and three SMPs replicated three times. Average potato yield was lowest in NM and FS and highest in COM treatments. Yield obtained from the bottom of the plots was greater than that obtained from the top of plots. Tuber defects (rot, scab, sun green, hollow heart, necrosis, and vascular discoloration) were significantly different between the two growing seasons. The two insecticidal treatments did not have much influence on potato yield or tuber defects. Tubers obtained from tall fescue treatments had low levels of ascorbic acid and reducing sugars compared to compost treatments.

High-performance liquid-phase separation of glycosides. III. Determination of total glucosinolates in cabbage and rapeseed by capillary electrophoresis via the enzymatically released glucose

A selective and sensitive method for the determination of total glucosinolates (GSs) in plant extracts by capillary electrophoresis-laser-induced fluorescence (LIF) detection was developed. It was based on the enzymatically released glucose from glucosinolates in the presence of the hydrolyzing enzyme myrosinase. The released glucose was converted to gluconic acid (GA) by the action of glucose oxidase. The resulting GA was then labeled selectively with the fluorescent tag 7-aminonaphthalene-1, 3-disulfonic acid (ANDSA). The peak area resulting from the GA-ANDSA derived from free and bound glucose was subtracted from the peak area of the GA-ANDSA resulting from the free glucose in the sample. This gave the total glucosinolates in the sample. The peak areas were normalized to the internal standard, N-acetylneuraminic acid derivatized with ANDSA. The method was validated using four different plant extracts, white cabbage leaves, rapeseed leaves, rapeseed roots, and rapeseed seeds. Furthermore, a capillary electrophoresis-UV detection method for profiling GS in plant extracts was developed. In addition to providing a fingerprint of the glucosinolates in plant extracts, the method allowed the experimenter to rapidly check the various steps involved in the extraction and sample cleanup.

Studies on the toxic effects of crambe meal and two of its constituents, 1-cyano-2-hydroxy-3-butene (CHB) and epi-progoitrin, in broiler chick diets

1. Studies were undertaken to determine a safe inclusion rate for crambe (Crambe abyssinica) meal in broiler chick diets, and to determine the mechanism for adverse effects by investigating its constituents; 1-cyano-2-hydroxy-3-butene (CHB) and 3-butenyl glucosinolate (epi-progoitrin, E-PG). 2. Crambe meals were prepared to differ in E-PG (19, 36 and 40 g/kg) and CHB contents (0.1, 0.7 and 1.9 g/kg), and with either active or inactive thioglucosidase. 3. Meals were fed to 7-d-old broiler chicks at 50 or 100 g/kg of the diet for 12 or 13 d. In separate studies, isolated E-PG or CHB were mixed into the diet or administered by gavage to 7-d-old broiler chicks in amounts equivalent to 50 or 100 g/kg crambe meal diets for 10 and 12 d, respectively. 4. Weight gain decreased (P < 0.05) in chicks fed on the high glucosinolate crambe diets or isolated E-PG. Food consumption decreased (P < 0.05) in chicks fed on the diet containing the high E-PG meal with active enzyme. 5. Mild liver lesions and increased serum aspartate aminotransferase were found in chicks fed on the diet containing the high glucosinolate meal with active enzyme. Other organs, including thyroids, were normal. 6. Commercially-processed crambe meal appeared safe at an inclusion rate of 50 or 100 g/kg diet, but could not be recommended at this point for long term feeding.

Efficacy of feeding glucosinolate-extracted crambe meal to broiler chicks

Glucosinolates and their breakdown products (nitriles) have long been implicated as toxic factors when feeding rapeseed (Brassica napus) meals and crambe (Crambe abyssinica) meals to poultry. Accordingly, various methods have been developed to remove these compounds from the meals to enhance their value as feed supplements. Glucosinolates and nitriles were extracted from commercially processed, defatted crambe meal by washing with water or various solvent-water mixtures: 50% isopropanol, 50% acetone, or 50% ethanol. In addition, crambe seed was extruded and extracted in the laboratory with isopropanol or hexane. Water washing of commercially defatted meal proved to be the most effective method of extraction, removing 95% of the glucosinolates and nitriles. Meals were fed to 7-d-old broiler chicks at 10% of the diet for 14 d. Weight gain decreased (P < .05) in most groups; however a greater decrease (P < .01) was observed in birds fed meals with high glucosinolate content. Feed intake also decreased (P < .05) in most groups; consequently, feed efficiencies were similar for all groups. No changes in serum chemistries, triiodothyronine, thyroxine, or tissue lesions were associated with glucosinolate or nitrile intake. A relationship (P < .05, r = .74) was found between weight gain and glucosinolate intake. No correlation was found between feed intake and meal glucosinolate or nitrile concentrations.