Profiles of phenolic compounds in modern and old common wheat varieties determined by liquid chromatography coupled with time-of-flight mass spectrometry

The health-promoting properties of common wheat (Triticum aestivum L.) have been largely attributed to the presence of unique phytochemicals of whole grains. The aim of this study was to profile the phenolic content of 16 old and 6 modern Italian wheat varieties, cropped in the same location and growing season. High variability was observed among the investigated wheat genotypes, both in the free and bound phenolic extracts. The total polyphenol content ranged from 885.5 to 1715.9 μmol GAE/100 g of grain and, on average, the bound fraction contributed for 72.0% to the total phenolic content. As regards the flavonoid content, the free fraction ranged from 50.7 to 106.1 μmol CE/100 g of grain and the bound fraction from 78.3 to 148.9 μmol CE/100 g of grain. Moreover, the interpretation of the mass spectra allowed the characterization of 34 phenolic compounds (104 including isomer forms) belonging to the phenolic acid, flavonoid, coumarin, stilbene, proanthocyanidin and lignan chemical classes. HPLC-ESI-TOF-MS analysis highlighted remarkable differences in the phytochemical fingerprints of old and modern wheat varieties. Six ancient wheat genotypes (Bianco Nostrale, Frassineto, Gentil Rosso, Gentil Rosso Mutico, Marzuolo d'Aqui, Verna) showed phenolic profiles with a number of total compounds and isomer forms much higher than that identified in the modern cultivars. The present findings confirm that ancient wheat may represent a valuable source of biodiversity, especially as regards phenolic compounds. The investigated old wheat genotypes may be successfully used in breeding programs for developing bread wheat varieties with added value in terms of health-promoting phytochemicals.     

Evaluation of the free radical scavenging capability of wheat extracts by capillary electrophoresis and multivariate curve resolution

In the current work, phenolic acids were analysed and their radical scavenging activity evaluated by CE, including the quantification of overlapping peaks by applying the multivariate curve resolution (MCR) method. To investigate radical scavenging activity, the solution of phenolic acids was treated with a stable free 2,2-diphenyl-1-picrylhydrazyl radical of different concentrations and the radical scavenging activity of the reaction mixture was monitored. The radical scavenging reaction was also applied to wheat bran extracts. The overlapping peaks on the electropherograms of both mixtures of standard compounds and extracts of different wheat bran varieties were resolved by using the MCR method, assuming that the overlapping compounds have different UV spectra. MCR enabled the insufficient resolution between syringic and ferulic acids to be effectively resolved.     

Determination of deoxynivalenol in whole wheat flour and wheat bran

A liquid chromatographic (LC) method was developed for determining deoxynivalenol (DON) in whole wheat flour and wheat bran. A 15 g test sample was extracted with acetonitrile-water (84 + 16, v/v) and applied to a Romer MycoSep cleanup column. The eluate was dried and then reconstituted in a 0.1 M phosphate buffer, pH 7.0, and applied to a Vicam DONtest-LC cleanup column. The methanol eluate was chromatographed with a methanol-water (17 + 83, v/v) mobile phase on a C18 column with UV detection at 220 nm. Five replicates at each of 5 fortification levels (0.25, 0.50, 1.0, 2.0, and 4.0 ppm), plus 5 controls, were determined for both whole wheat flour and wheat bran. For flour, the average recoveries were 72.2-91.5% with relative standard deviations (RSDs) of 4.9-18.4%. The intra-assay flour recovery was 82.4% with 9.8% RSD. A 5 replicate sample of naturally incurred wheat had an average of 1.1 ppm DON with 6.7% RSD. For bran, average recoveries of fortified samples were 69.5-99.7% with RSDs of 1.7-18.8%. The intra-assay bran recovery was 81.5% with 8.9% RSD. The limit of detection (about 3x noise) for the method is 0.05 ppm; the correlation coefficient (linearity) was >0.9995. The DON peak was clearly identified and easily integrated in the chromatograms.     

Slurry atomization of wheat-milled fractions for electrothermal atomic absorption spectrometric determination of nickel and chromium.

A slurry electrothermal atomic absorption spectrometric technique was used to determine Ni and Cr in wheat flour and its by-products. Slurries (3%, w/v) were prepared in a mixture of 15% HNO3-10% H2O2 as suspended medium. Differences in Ni and Cr contents due to origin and texture of the wheat and to the effects of the milling process were studied. Ni and Cr levels were more markedly influenced by the geographical origin of the wheat than by its texture. Both metals were related to the amount of bran present in each milled fraction and varied over the ranges of 212-298 ng/g (Ni) and 34-85 ng/g (Cr) in flours (with minimal bran contents); 297-460 ng/g (Ni) and 67-118 ng/g (Cr) in shorts; and 424-723 ng/g (Ni) and 106-165 ng/g (Cr) in brans. The Ni and Cr contents were not significantly affected by the technological processes typically performed in a flour-producing factory.     

基于手性固定相的超高效液相色谱-串联质谱法检测小麦及其加工制品中的腈菌唑对映体

建立了手性超高效液相色谱-串联质谱检测小麦及其加工制品中腈菌唑对映体残留的分析方法。样品经乙腈提取,N-丙基乙二胺(PSA)和C18净化,手性色谱柱Lux Cellulose-1(150 mm×2.0 mm, 3 μm)分离,质谱电喷雾正离子扫描(ESI⁺),多反应监测(MRM)模式进行检测。为准确定量,考察了小麦籽粒及其加工制品的基质效应,最终采用基质匹配校准法来补偿基质效应,并进行样品中腈菌唑对映体残留的校准定量。结果表明,腈菌唑的两个对映体得到良好的拆分。S-(+)-腈菌唑先出峰,R-(-)-腈菌唑后出峰,保留时间分别为4.34 min和5.13 min。S-(+)-腈菌唑和R-(-)-腈菌唑在小麦及其加工制品中的检出限均为0.2 μg/kg,定量限均为0.5 μg/kg。在0.5~25 μg/L范围内,腈菌唑对映体的峰面积与其质量浓度呈现良好的线性关系,相关系数(R²)均大于0.99。在对映体添加水平为5、50、100 μg/kg时,在小麦籽粒、麸皮、面粉、面团、馒头、面条、煮面水中,S-(+)-腈菌唑的平均回收率在82%~110%之间,RSD在0.9%~6.8%之间;R-(-)-腈菌唑的平均回收率在80%~109%之间,RSD在0.9%~6.8%之间。将该方法应用于实际样品的检测,在5份面粉、2份面条及2份馒头样品中均未检出腈菌唑对映体。该方法为手性农药腈菌唑对映体在初级农产品及其加工制品中的残留分析提供了有效的方法。     

Cadmium and other metals in Swedish wheat and rye flours: longitudinal study, 1983-1997.

Wheat flour (sifted), wheat bran, and rye flour were sampled annually in several different areas in Sweden for 15 consecutive years (1983-1997) for a total of 105, 90, and 30 samples, respectively. These samples were analyzed for their content of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn by atomic absorption spectrophotometry with background correction after dry ashing at 450 degrees C. As part of the quality control procedures, an in-house reference material was analyzed in parallel to the samples to ensure reliability of the results. In addition, a certified reference material was analyzed to monitor accuracy of the results. The Cd level in wheat and rye flours (mean 0.029 and 0.017 mg/kg dry wt, respectively) correlated significantly with time (p < 0.05) in 2 phases, tending to increase during the first half of the period and decrease during the latter half. In wheat bran, Cd (mean 0.15 mg/kg) levels did not correlate significantly with time. In wheat flour, Cu, Mn, and Zn (means 1.7, 6.2, and 7.6 mg/kg, respectively) showed a significant linear increase (p < 0.05) in concentration over time. In rye flour, the levels of Cu, Fe, Mn, and Zn (means 3.8, 36, 30, and 28 mg/kg, respectively) all decreased significantly (p < 0.05) over time. Similarly, in wheat bran Cu (mean 14 mg/kg) increased and Pb (mean 0.027 mg/kg) decreased significantly (p < 0.05) over time, whereas Ni and Zn showed a significant curved correlation with time and peaked at about the middle of the measurement period.     

Survey of selected materials for use as an organic nutrient standard

Summary There is a need for food based reference materials characterized for organic nutrient content, since very few are presently available. A series of twelve food matrices has been prepared by Agriculture Canada as Candidate Reference Materials. This paper reports a survey of the organic nutrient content of these twelve materials which include bovine muscle powder, corn starch, hard red spring wheat flour, soft winter wheat flour, white granulated sugar, whole milk powder, wheat gluten, potato starch, corn bran, durum wheat flour, whole egg powder, and microcrystalline cellulose. Whole egg, bovine muscle and whole milk powder appear to be best suited for further development as organic nutrient standards.

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Überblick über ausgewählte Materialien zur Verwendung als Standards für organische Nährstoffe

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Contribution Number 88-65 from Land Resource Research Center     

Distribution of deoxynivalenol in wheat,wheat flour,bran, and gluten,and variability associated with the test procedure

Analytical data obtained on deoxynivalenol (DON) concentration in naturally contaminated wheat during processing in an industrial mill were statistically analyzed, and the distribution functions of DON concentration in lots of wheat, bran, wheat flour, and gluten were estimated. The analytical method had acceptable precision (HORRAT 0.25-0.32) for each test sample. The total variance combined sampling, sample preparation, and analytical variances were 0.188, 0.033, 0.42, and 0.0014 ppm2 for wheat, 1.93; flour, 0.99; bran, 4.68; and gluten, 0.29, respectively. The distribution function of DON contamination presented an asymmetric tail for high values of concentration in wheat grains and wheat flour; in bran it seemed to be bimodal with 2 separated peaks of different concentrations; in gluten the normal distribution function gave a reasonably good fit to empirical data. The function eta(c) = -In(-Inp), where p (c) is the cumulative distribution function was linear with c in the so-called extreme-value type I distribution and could be fitted by a cubic polynomial in c in the distributions determined for all the products. This variability and distributional information contributes to the design of better sampling plans in order to reduce the total variability and to estimate errors in the evaluation of DON concentration in lots of wheat and wheat products.     

Determination of phenolic compounds in modern and old varieties of durum wheat using liquid chromatography coupled with time-of-flight mass spectrometry

An evaluation of the grain functional components of Italian durum wheat cultivars was conducted. The raw material was obtained from the field trial performed in 2006–2007 at the Experimental Farm of the University of Bologna, (Bologna, Italy). The aim of this study was to define the phytochemical profile of ten varieties, comprised of old and modern durum wheat genotypes, including quantitative and qualitative phenolic and flavonoid content (free and bound forms). The results showed that mean values of total phenolic compound and total flavonoid content in old wheat varieties (878.2 ± 19.0 μmol gallic acid equivalent/100 g of grain and 122.6 ± 25.4 μmol catechin equivalent/100 g of grain, respectively) did not differ significantly from those detected in modern genotypes (865.9 ± 128.9 μmol gallic acid equivalent/100 g and 123.5 ± 20.6 μmol catechin equivalent/100 g, respectively). However, the HPLC–ESI-TOF-MS analysis highlighted remarkable differences between modern and old cultivars. The interpretation of the mass spectra allowed the identification of 70 phenolic compounds, including coumarins, phenolic acids, anthocyanins, flavones, isoflavones, proanthocyanidins, stilbenes and lignans. The free extracts of ancient wheat varieties showed the presence of a mean number of phenolic compounds and isomer forms (8.7 ± 2.5 and 7.7 ± 4.7 respectively) significantly higher than in modern genotypes (4.4 ± 2.9 and 2.0 ± 2.4, respectively). A similar trend was observed also for the bound phenolic fraction. Moreover, the phytochemical profiles showed the presence of unique phenolic compounds in both free and bound fractions of some of the investigated wheat genotypes. Results highlighted that investigated old wheat cultivars may offer unique nutraceutical values for their peculiar contents in bioactive phytochemicals, suggesting their uses into a wide range of regular and specialty products naturally enriched with health-promoting compounds.     

Microwave-assisted dilute acid pretreatment of different agricultural bioresources for fermentable sugar production

Microwave-assisted pretreatment can be used for fermentable sugar production from lignocellulosic biomass. In this study, the optimum hydrolysis conditions of barley husk, oat husk, wheat bran, and rye bran were determined in power level, treatment time, solid-to-liquid ratio and dilute acid ratio as follows: 700 W, 6.92 min, 1:18.26 w/v, and 3.67% for barley husk, 600 W, 6.96 min, 1:17.22 w/v, and 3.47% for oat husk, 600 W, 6.92 min, 1:16.69 w/v, and 1.85% for wheat bran, and 460 W, 6.15 min, 1:17.14 w/v, and 2.72% for rye bran. The fermentable sugar concentrations were 37.21 (0.68 g/g), 38.84 (0.67 g/g), 49.65 (0.83 g/g), and 36.27 g/L (0.62 g/g) under optimum conditions, respectively. The results showed that microwave-assisted pretreatment is a promising technology which can be successfully implemented for the hydrolysis of lignocellulosic biomass for high sugar yield. On the other hand, hydrolysates included some inhibitors such as organic acids, furans, and phenolic compounds. Lignocellulosic biomass used in this study can be employed as good feedstocks for value-added product production in the fermentation process, after the inhibitors have been detoxified/removed with different detoxification methods.     

A fast and reliable method for the quantitative determination of benzimidazoles and metabolites in milk by LC-MS/MS with on-line sample treatment

A method to detect the presence of common wheat in durum wheat flour samples was developed and tested. Flour samples, or ground wheat samples, were digested by pepsin and chymotrypsin, and the peptide mixture obtained was analyzed by LC/ESI-MS and LC/ESI-MS/MS, which led to the identification of two marker peptides. One peptide was coded only in the DD genome, and thus present only in common wheat; the second was present in all wheat samples (both common and durum), so it was used as marker of the total wheat content. The ratio of the chromatographic areas of these two peptides, as determined by LC/ESI-MS, was related to the proportion of common wheat in the sample using a calibration curve that was constructed with standards of known composition. The proportions of common wheat in samples obtained by mixing different common and durum wheat varieties were accurately determined by this method. Finally, the method was applied in a survey of several durum wheat flour brands present on the Italian market. The results of the survey revealed that contamination of durum wheat flour with common wheat is commonplace.     

高效液相色谱-串联质谱法测定食品中的矮壮素与缩节胺残留

建立了食品中矮壮素和缩节胺2种植物生长调节剂的高效液相色谱-电喷雾电离串联质谱(HPLC-ESI MS/MS)分析方法.样品经甲醇-水(1:1,体积比)提取后,采用Strata-X-C萃取小柱净化,再经Agilent ZORBAX RX-SIL(1.8μm,3.0 mm×100 mm)色谱柱分离,以乙腈和10 mmol...     

Multielement determination in wheat and bran

Instrumental neutron activation analysis was employed to measure 26 elements in three wheat varieties and in bran retained on U.S. standard sieve#e40. It was observed that the mineral content of bran was much higher than whole wheat and more than 90% of the elemental content was retained in the bran. The concentrations of As, Ce, Cr, Cs, Eu, Hf, Hg, La, Sb, Sc, Sr, Th and V in whole wheat and bran were below the detection limit.     

Investigation of free and conjugated seleno‐amino acids in wheat bran by hydrophilic interaction liquid chromatography with tandem mass spectrometry

An analytical method for determining seleno‐methionine, methyl‐seleno‐cysteine, and seleno‐cystine in wheat bran was developed and validated. Four different extraction procedures were evaluated to simultaneously extract endogenous free and conjugated seleno‐amino acids in wheat bran in order to select the best extraction protocol in terms of seleno amino acid quantitation. The extracted samples were subjected to a clean‐up by a reversed phase/strong cation exchange solid‐phase extraction and analyzed by chiral hydrophilic interaction liquid chromatography‐tandem mass spectrometry. The optimized extraction protocol was employed to validate the methodology. Process efficiency ranged from 58 to 112% and trueness from 73 to 98%. Limit of detection and limit of quantification were lower than 1 ng/g. Four wheat bran samples were analyzed for both total Se and single seleno‐amino acids determination. The results showed that Se‐ seleno‐methyl‐l selenocysteine was the major seleno‐amino acid in wheat bran while seleno‐methionine and seleno‐cysteine were both minor species.     

Use of a multifunctional column for the determination of deoxynivalenol in grains, grain products, and processed foods

Deoxynivalenol (DON), also known as vomitoxin, belongs to a class of naturally occurring mycotoxins produced by Fusarium spp. DON, 12, 13-epoxy-3,7 trihydroxytrichothec-9-en-8-one, is one of the most frequently detected mycotoxins in agricultural commodities worldwide. A method consisting of extraction, filtration, column cleanup, and RP-HPLC-UV separation and quantitation was validated for the determination of DON in grains (rice and barley), grain products (whole wheat flour, white flour, wheat germ, and wheat bran), and processed foods (bread, breakfast cereals, and pretzels). A 25 g test portion was extracted with 100 mL acetonitrile-water (84 + 16, v/v). After blending for 3 min, the supernatant was applied to a multifunctional column (MycoSep 225). The purified filtrate (2 mL) was evaporated to dryness and redissolved in the mobile phase. The toxins were then subjected to RP-HPLC-UV analysis. The accuracy and repeatability characteristics of the method were determined. Recoveries of DON added at levels ranging from 0.5 to 1.5 microg/g for all test matrixes were from 75 to 98%. SD and RSD(r) ranged from 0.7 to 11.6% and 0.9 to 12.7%, respectively. Within-laboratory HorRat values were from 0.1 to 0.7 for all matrixes analyzed. The method was found to meet AOAC method performance criteria for grains, grain products, and processed foods. The identity of DON in naturally contaminated test sample extracts was confirmed by HPLC/MS/MS analysis.     

Profiling of phenolic compounds and antioxidant activity of dry extracts from the selected Sorbus species

The antioxidant efficiency of dry extracts from inflorescences and/or leaves of seven Sorbus species was studied using four in vitro tests of SET (single electron transfer) and HAT-type (hydrogen atom transfer) mechanisms. The 70% methanol extracts and its diethyl ether, ethyl acetate, n-butanol and water fractions were tested in parallel with the phenolic standards, e.g., caffeic acid, quercetin, BHA, BHT, and Trolox. The SET-type activity of the extracts depended primarily on the extraction solvent. The most valuable extracts were n-butanol and ethyl acetate ones, which activity was high in the DPPH (EC(50) = 3.2-5.2 μg/mL), TEAC (2.8-4.0 mmol Trolox/g), and FRAP (9.8-13.7 mmol Fe2+/g) tests, and strongly correlated with the total phenolic levels (39.6-58.2% of gallic acid equivalents). The HPLC-PDA analysis of the extracts led to the identification of chlorogenic acid, isoquercitrin, hyperoside, rutin, quercetin 3-O-sophoroside, and sexangularetin 3-O-β-D-glucopyranoside as the main components. Apart from flavonoids and hydroxycinnamic acids, proanthocyanidins have also a significant impact on the SET-type activity. The HAT-reactivity of the extracts in the linoleic acid peroxidation test (IC(50) = 36.9-228.3 μg/mL) depended more strongly on the plant tissue than on the extraction solvent, and its correlation with the phenolic content was weak. Both SET and HAT-type activity of the most potent Sorbus extracts was comparable with the activity of the standards, indicating their great potential as effective sources for health products.     

Summary of preparation and homogeneity characterization of ten agricultural food reference materials for elemental composition

Summary Preparation and development has been completed of ten agricultural/food reference materials (RMs): bovine muscle powder, corn starch, hard red spring wheat flour, soft winter wheat flour, whole milk powder, wheat gluten, corn bran, durum wheat flour, whole egg powder and microcrystalline cellulose. Homogeneity tests for 14 elements, Al, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr and Zn were performed by the initiating laboratories by application of precise and reliable analytical methods based on flame atomic absorption spectrometry and graphite furnace atomic absorption spectrometry. An extensive set of analytical results obtained from the interlaboratory cooperative characterization campaign was assessed to provide homogeneity estimates for other elements. Estimates of homogeneity from within-laboratory precision indicated that all materials exhibited acceptable homogeneity for virtually all 29 elements (Al, As, B, Ba, Br, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, I, K, Mg, Mn, Mo, N, Na, Ni, P, Pb, Rb, S, Se, Sr, V, Zn) for which best estimate concentration values are available. Two thirds of all homogeneity coefficients of variation were below 5%.     

Simultaneous determination of phenolic acids and flavonoids in rice using solid-phase extraction and RP-HPLC with photodiode array detection

An analytical method based on an optimized solid-phase extraction procedure and followed by high-performance liquid chromatography (HPLC) separation with diode array detection was developed and validated for the simultaneous determination of phenolic acids (gallic, protocatechuic, 4-hydroxy-benzoic, vanillic, caffeic, syringic, p-coumaric, ferulic, sinapic, and cinnamic acids), flavanols (catechin and epicatechin), flavonols (myricetin, quercetin, kaempferol, quercetin-3-O-glucoside, hyperoside, and rutin), flavones (luteolin and apigenin) and flavanones (naringenin and hesperidin) in rice flour (Oryza sativa L.). Chromatographic separation was carried out on a PerfectSil Target ODS-3 (250 mm × 4.6 mm, 3 μm) column at temperature 25°C using a mobile phase, consisting of 0.5% (v/v) acetic acid in water, methanol, and acetonitrile at a flow rate 1 mL min(-1) , under gradient elution conditions. Application of optimum extraction conditions, elaborated on both Lichrolut C(18) and Oasis HLB cartridges, have led to extraction of phenolic acids and flavonoids from rice flour with mean recoveries 84.3-113.0%. The developed method was validated in terms of linearity, accuracy, precision, stability, and sensitivity. Repeatability (n = 5) and inter-day precision (n = 4) revealed relative standard deviation (RSD) <13%. The optimized method was successfully applied to the analysis of phenolic acids and flavonoids in pigmented (red and black rice) and non-pigmented rice (brown rice) samples.     

Determination of amino acid ratios in natural products by micellar electrokinetic chromatography

Summary Separation of dansyl and di-dansyl derivatives of amino acids present in natural products (corn seed flour, wheat flour fraction gliadine) is described. Problems with coelution of derivatization by-products and reagent with some dansyl amino acids (DNS-AA) were solved. A preconcentration step after derivatization of real sample is described. DNS-AA peak areas for different varieties of corn seed flour were compared. Di-dansyl histidine is not separated from di-dansyl lysine and didansyl tyrosine. Additional separation mechanisms have to be introduced to achieve separation of these three species.     

Accurate determination of selenium in biological materials without perchloric acid for digestion

Selenium (10–80 μg kg^?1) is determined by hydride-generation atomic absorption spectrometry in mixed diet, faecal and urine samples and in standard reference materials (bovine liver, rice flour, wheat flour and horse kidney) after two digestion procedures. No difference was found in digestion efficiency between a nitric/sulphuric acid mixture and a nitric/sulphuric/perchloric acid mixture. The results suggest that the digestion of most biological materials for the determination of selenium does not require the use of perchloric acid.