Secoisolariciresinol diglucoside determination in flaxseed (Linum usitatissimum L.) oil and application to a shelf life study

A high-performance liquid chromatographic (HPLC) reliable and sensitive method with diode array detection (DAD) system has been developed for the determination of secoisolariciresinol diglucoside (SDG) in flaxseed oil. An analytical methodology based on the sample extraction with methanol/water (80:20, v/v), subsequent purification of the sample and analysis of the extract by HPLC/DAD is proposed for the determination of SDG in flaxseed oil. The coefficient of determination of the standard calibration curve was 0.999, the limit of detection was 0.08 μg/mL, and the limit of quantification was 0.27 μg/mL. The recovery test was conducted adding four different concentrations of standard solution to the blank sample. The recovery ranged from 90% to 95%. To our knowledge, the presence and quantification of SDG in flaxseed oil has never been reported. The proposed method was tested to study the variation in SDG content in flaxseed oil during a shelf-life test to verify its applicability in quality control for oil industries. The dark and the low temperature of storing together allowed to preserve SDG. A slight pro-oxidant effect was observed for the addition of antioxidant to the flaxseed oil.     

Enhancing lignan biosynthesis by over-expressing pinoresinol lariciresinol reductase in transgenic wheat

Lignans are phenylpropane dimers that are biosynthesized via the phenylpropanoid pathway, in which pinoresinol lariciresinol reductase (PLR) catalyzes the last steps of lignan production. Our previous studies demonstrated that the contents of lignans in various wheat cultivars were significantly associated with anti-tumor activities in APC(Min) mice. To enhance lignan biosynthesis, this study was conducted to transform wheat cultivars ('Bobwhite', 'Madison', and 'Fielder', respectively) with the Forsythia intermedia PLR gene under the regulatory control of maize ubiquitin promoter. Of 24 putative transgenic wheat lines, we successfully obtained 3 transformants with the inserted ubiquitin-PLR gene as screened by PCR. Southern blot analysis further demonstrated that different copies of the PLR gene up to 5 were carried out in their genomes. Furthermore, a real-time PCR indicated approximately 17% increase of PLR gene expression over the control in 2 of the 3 positive transformants at T(0) generation. The levels of secoisolariciresinol diglucoside, a prominent lignan in wheat as determined by HPLC-MS, were found to be 2.2-times higher in one of the three positive transgenic sub-lines at T(2 )than that in the wild-type (117.9 +/- 4.5 vs. 52.9 +/- 19.8 mug/g, p <0.005). To the best of our knowledge, this is the first study that elevated lignan levels in a transgenic wheat line has been successfully achieved through genetic engineering of over-expressed PLR gene. Although future studies are needed for a stably expression and more efficient transformants, the new wheat line with significantly higher SDG contents obtained from this study may have potential application in providing additive health benefits for cancer prevention.     

Thermal degradation kinetics of aqueous anthocyanins and visual color of purple corn (Zea mays L.) cob

Purple corn cob was the byproduct during the corn processing. Thermal degradation kinetics and Hunter color parameters (a, b, C, h° and ΔE) of aqueous anthocyanins from purple corn cob were studied at selected temperatures (70 °C, 80 °C and 90 °C) at pH 4.0. The results indicated that the thermal degradation of anthocyanin and Hunter color C, a and ΔE parameters followed the first-order reaction kinetics, while Hunter color h° and b parameters followed zero-order reaction kinetics. The calculated values of activation energies (Ea) were 18.3, 35.9, 37.1, 31.6, 34.9 and 30.0 kJ/mol for anthocyanins, C, a, ΔE, h° and b parameters, respectively. The higher Ea indicated that greater temperature sensitivity of visual color as compared to anthocyanins content. The degradation of anthocyanins showed positive correlation with C (R² > 0.909), a (R² > 0.860) and ΔE (R² > 0.940), while the degradation of anthocyanins showed negative correlation with h° (R² > 0.828) and b (R² > 0.735) during heating.

Industrial relevance

Purple corn cob was the byproduct during the corn processing. Purple corn cob is dark purple to almost black color due to its high content of anthocyanins, which makes this byproduct a good source of anthocyanins. In this study, the excellent linear correlation between Hunter color parameters (a, b, C, h° and ΔE) and content of anthocyanins showed that the Hunter color parameters may also be used instead of anthocyanins content during heating. The advantage of using the visual Hunter color parameters may be measured as on-line quality control parameters during thermal processing of food industry.     

紫粒小麦麸皮花色苷提取工艺优化及其抗氧化活性研究

以紫粒小麦麸皮为原料,研究其花色苷超声波辅助提取工艺及其体外抗氧化活性。选取超声辅助提取功率、提取温度、提取时间、料液比和乙醇浓度等为考察因素进行了提取工艺的单因素及正交实验。实验结果表明,乙醇浓度为60%、料液比1∶10(g/m L)、提取时间10 min、提取温度60℃、超声波功率160 W。在此条件下,花色苷得率为(1.82±0.23)mg/g,是普通浸提法的2.09倍。体外抗氧化实验显示:紫小麦麸皮花色苷提取物具有一定的清除DPPH自由基和ABTS自由基能力以及铁还原力,其花色苷含量与DPPH自由基、ABTS自由基清除率、铁还原力有显著的相关性(相关系数R2分别为0.9938,0.9737和0.9985),IC50值分别为7.81、12.20、5.18 mg/L。这一结果将为以紫小麦麸皮花色苷为原料的功能性食品的开发提供有益提示和理论基础。      

LC–MS analysis of anthocyanins from purple corn cob

Liquid chromatography coupled with diode array spectrophotometry and mass spectrometry detection (LC–DAS–MS) has been applied to the study of the anthocyanin composition of a commercial extract from purple corn cob used as a colourant additive in the food industry. Nine different anthocyanins were isolated using semipreparative HPLC and identified by LC–MS and hydrolytic techniques. Useful information for the identification of compounds was also obtained from their fragmentation patterns (MS–MS spectra). Six of these anthocyanins seem to be present in the original cob, namely cyanidin‐3‐glucoside, pelargonidin‐3‐glucoside, peonidin‐3‐glucoside and their respective malonyl derivatives. The other three are produced during the industrial extraction process and have been identified as the corresponding ethylmalonyl derivatives. © 2002 Society of Chemical Industry     

Determination of the melatonin content of different varieties of tomatoes (Lycopersicon esculentum) and strawberries (Fragariaananassa)

Melatonin has recently been detected in various plants and foods. However, data regarding the food composition of melatonin are too scarce to evaluate dietary intake. This paper aims to identify melatonin unequivocally using LC–MS in a wide set of varieties of tomatoes (Lycopersicon esculentum) and strawberry (Fragariaananassa). Furthermore, a validated LC fluorescence was developed.     

Bilberry and blueberry anthocyanins act as powerful intracellular antioxidants in mammalian cells

Berry anthocyanins have pronounced health effects, even though they have a low bioavailability. The common mechanism underlying health protection is believed to relate to antioxidant activity. Berry extracts, chemically characterised for their phenolic content, were prepared from bilberries (Vaccinium myrtillus L.) and blueberries (Vaccinium corymbosum L.); the bilberry extract was further purified to obtain the anthocyanin fraction. The antioxidant activity of each extract was examined at the cellular level. For this purpose a specific assay, known as cellular antioxidant activity assay (CAA), was implemented in different cell lines: human colon cancer (Caco-2), human hepatocarcinoma (HepG2), human endothelial (EA.hy926) and rat vascular smooth muscle (A7r5). Here we show for the first time that anthocyanins had intracellular antioxidant activity if applied at very low concentrations (<1 μg/l; nM range), thereby providing a long-sought rationale for their health protecting effects in spite of their unfavorable pharmacokinetic properties.     

Determination of tetracyclines in pig and other meat samples using liquid chromatography coupled with diode array and tandem mass spectrometric detectors

Two high performance liquid chromatographic methods (HPLC–DAD and LC–MS/MS) were developed to analyze tetracycline (TC) residues in pig meat (pork) samples. The method involved a sample preparation using a solid–liquid extraction (SLE) by McIlvaine buffer, followed by a solid-phase extraction (SPE) clean-up using Strata-XL cartridges. The developed sample clean-up resulted in a selective chromatogram in the HPLC–DAD separation and a reduced matrix effect (ME) in LC–MS/MS analysis. Moreover, HPLC columns packed with core–shell particles were tested for separation, which further enhanced the sensitivity and the selectivity of determinations. The validation of the methods for pig samples was carried out according to European Union 2002/657/EC decision. In addition, validation was also performed for bovine, chicken, and turkey meat samples using HPLC–DAD method. The performance characteristics of determinations were evaluated with both spiked and incurred samples, and were systematically compared. LC–MS/MS technique was found to be more accurate for spiked samples; however, HPLC–DAD method resulted in more reliable concentrations for incurred samples.     

Optimization extraction of anthocyanins from purple corn (<Emphasis Type="Italic">Zea mays</Emphasis> L.) cob using tristimulus colorimetry

Optimization of the conditions for extracting anthocyanins from the cob, a byproduct of purple corn (Zea mays L.), was investigated in this paper. A full factorial design (2² × 3²) was used. The factors studied were type of solvent: ethanol or methanol; solvent/water mixture: 100, 90, 80% v/v; type of acid: citric acid or acetic acid; and concentrations of acid: 0.25, 0.5, 1% v/v. Tristimulus colorimetry was employed to evaluate the yield and quality of anthocyanins extracts. The results showed that the maximum yield (5.90 mg/g dw) was obtained with the combination of 80% (v/v) methanol and 1% (v/v) citric acid, and that the relatively high chroma (C* = 23.60) and hue angle (h = 16.63) values of the anthocyanins extract were observed under the same conditions. Eight kinds of anthocyanins in the cob were detected by HPLC–DAD, most the anthocyanins were non-acylated.     

Effect of thermal processing on antioxidant properties of purple wheat bran

Antioxidant activity of purple wheat bran, heat-treated purple wheat bran, and purple wheat bran muffins was evaluated to determine the impact of thermal processing on potential health benefits. The purple wheat bran and muffin samples were analyzed for total phenolic content, anthocyanin content and free radical scavenging activity using peroxyl (oxygen radical absorbance capacity assay) and 2,2-diphenyl-1-picrylhydrazyl (DPPH assay) radicals. Total phenolic content and oxygen radical absorbance capacity (ORAC) values of sample extracts were significantly affected by various extracting solvents. The conditions selected for heat treatment did not markedly change antioxidant activity of purple wheat bran. However, there was a significant reduction in total phenolic contents, ORAC values and total anthocyanins during processing of purple wheat bran- or heat-treated purple wheat bran-enriched muffins. On the contrary, muffin extracts still remained excellent in DPPH radical scavenging activity.     

Characterisation of phenolic phytochemicals and quality changes related to the harvest times from the leaves of Korean purple perilla (Perilla frutescens)

The objective of this study was to investigate the profiles of phenolic phytochemicals in the leaves of Korean purple perilla (cv. Bora, Perilla fructescens) using reversed-phase C₁₈ column chromatography and HPLC with DAD-ESI/MS analysis. Changes in their contents were also the first reported through eight different harvest times during two months. They were characterised as five anthocyanins and three phenolic acids including cyanidin-3,5-di-O-glucoside (1), cyanidin-3-O-glucoside (2), cyanidin-3-O-(6-O-caffeoyl)glucoside-5-O-glucoside (3), cyanidin-3-O-(6-O-coumaroyl)glucoside-5-O-glucoside (4), cyanidin-3-O-(6-O-coumaroyl)glucoside (5), caffeic acid (6), rosmarinic acid (7), and rosmarinic acid methylester (8). Significant differences were observed between individual and total phytochemical contents, especially, cyanidin-3-O-(6-O-coumaroyl)glucoside-5-O-glucoside (4) and rosmarinic acid (7) exhibited the predominant constituents. Among different harvest times, the highest content was found with 82.473 mg/g on 21st September, while the lowest was 39.000 mg/g on 17th August. These results may be useful in determining the optimal harvest time at which phenolic phytochemicals reaches a maximum level in mid-September.     

Analysis of fumonisins B1, B2 and their hydrolysed metabolites in pig liver by LC–MS/MS

A liquid chromatography–tandem mass spectrometry method for the quantitative determination of fumonisin FB1, FB2 and their respective hydrolysed metabolites HFB1 and HFB2 in pig liver has been developed and validated. The method was based on an easy extraction procedure followed by SPE purification. Chromatographic separation of the analytes was performed on a C18 column using 0.3% of formic acid in water and acetonitrile as elution solvent. The mass spectrometer operated in the positive electrospray ionisation mode (ESI+) using multiple reaction monitoring (MRM). An intralaboratory validation was carried out with fortified samples for determining precision, trueness, specificity, limit of detection (LOD) and limit of quantification (LOQ). The method showed good performance characteristics and proved to be sensitive, selective and reliable. The LOD was 0.05 ng g⁻¹ and the LOQ was 10 ng g⁻¹ for all the analytes. The developed method has been applied to seven pig liver samples in order to test its applicability to evaluate exposure of food animals to fumonisins.     

Identification of irradiated meats by determining o- and m-tyrosine as markers

To identify the irradiated meats, various parameters that affect extraction efficiency of tyrosine positional isomers were evaluated. The optimum procedure employed simple extraction by 0.1% formic acid and protein precipitation by acetone. Baseline separation for the extract was carried out on LC–fluorescence detection (FLD) and LC–tandem mass spectrometry (MS/MS). The LC–FLD and LC–MS/MS method had LOD of 1.7–2.1 and 0.3–0.5 ng/mL, respectively, and showed excellent linear correlation over three orders of magnitude, obtained ideal recoveries (78.68–88.90%) and RSD (≤ 8%). The methods were successfully applied in multiple samples. For o- and m-tyrosine, the order of descending trend was: chicken > beef > hairtail > pork and chicken > hairtail > beef > pork, respectively. The radiation dose could be quantitatively evaluated by the nonlinear correlation (y = A₀x² + A₁x + A₂) with coefficients of determination r² > 0.998 in individual meat samples.     

Phenolic compounds in Chinese purple yam and changes during vacuum frying

Phenolic compounds and their changes during vacuum frying were investigated for a Chinese purple yam. Three cyanidin derivatives and one peonidin derivative were tentatively identified by HPLC–DAD–ESIMS analysis; sinapic acid and ferulic acid were identified by HPLC–DAD analysis with authentic chemicals. There were 31.0 mg/100 g (dry weight, DW) of total anthocyanin (ACN) and 478 mg/100 g DW of total phenolic content (TPC) in the fresh yam. Sinapic acid and ferulic acid were 135 and 31.3 mg/100 g DW respectively. The blanching process caused about 60% of ACN, and 30–50% of phenolic acids and TPC to be lost, which showed that anthocyanins were most vulnerable during blanching. The retention rate of the phenolic compounds during vacuum frying was 60–69%, indicating it was a practical technology for purple yam processing, on account of its impact on the phenolic compounds stability.     

小麦中植物化学素的研究进展

综述了小麦中的一些植物化学素如酚类、低聚糖类、植物甾醇等及其生理活性与人类健康的关系。     

Aqueous two-phase extraction,identification and antioxidant activity of anthocyanins from mulberry (Morus atropurpurea Roxb.)

Aqueous two-phase extraction (ATPE), identification and antioxidant activity of anthocyanins from mulberry (Morus atropurpurea Roxb.) were investigated in this study. The optimal differential partitioning of mulberry anthocyanins (MAY) and sugars was achieved in a system (pH 4.5, temperature = 35 ± 1 °C) composed of 30% (w/w) ethanol, 20% (w/w) concentration of ammonium sulphate, 10% (w/w) mulberry juice and 40% (w/w) water. The multiple partitioning indicated a single ATPE step could isolate the majority of anthocyanins, while removing near to 90% of the free sugars. The composition of the MAY extracted by ATPE had no obvious changes, and five anthocyanins were identified by HPLC–ESI-MS/MS. The ATPE extract showed a relatively high antioxidant ability compared to that by the conventional extraction. Our results indicated that ATPE was a valuable method for the removal of the majority of free sugars, which held great promise in the purification of natural anthocyanin pigments.     

小麦粉中神经酰胺类物质的提取及结构分析

从小麦粉中提取纯化了一种神经酰胺类物质,并对其结构进行了分析。实验以小麦粉为材料,首先用索氏提取法以95%乙醇为溶剂进行粗提,粗提物经石油醚萃取、旋转蒸发仪浓缩后,过三次硅胶柱层析提取,再经二次重结晶纯化,得到白色无定型粉末状神经酰胺类物质。使用高效液相色谱/蒸发光散射检测器(HPLC/ELSD)对其进行纯度检测,用红外光谱(IR)和质谱(MS)对其结构进行鉴定。实验结果分析表明该物质为分子量397.3,分子式C24H47NO3的神经酰胺类化合物。     

Composition and colour stability of anthocyanins extracted from fermented purple sweet potato culture

The components and colour stability of anthocyanins in purple sweet potato were investigated. Anthocyanins were extracted from fermented purple sweet potato culture fermented by Suzhou wine starter (Rhizopus 3.851, 3.866 and Saccharomyces cerevisiae). In these purple sweet potato anthocyanins (PSPAs), five major anthocyanins were detected by high performance liquid chromatography (HPLC). Cyanidin and peonidin were found to be the major anthocyanidins in PSPAs by acid hydrolysis of anthocyanins. PSPAs were more stable under the acid conditions (pH 2.0-4.0) than the subacid conditions (pH 5.0-6.0) as per UV-Vis absorption spectra and CIELAB colour coordinates.     

亚麻籽木脂素--开环异落叶松树脂酚二葡萄糖苷分析方法的研究

综合有关文献资料，确定用高效液相色谱法和气相色谱/质谱联用法对亚麻籽木脂素-开环异落叶松树脂酚二葡萄糖苷（SDG）进行分析。