Characterization of phenolic extracts from olives (Olea europaea cv. Pisciottana) by electrospray ionization mass spectrometry

Olives are a potential source of natural anti-oxidants; unfortunately, a complete characterization of olive fruit phenolic profile is still to be achieved, as it is characterized by great complexity and variability.     

Investigation of proanthocyanidins by HPLC with electrospray ionization mass spectrometry

Received: 1 June 1999     

Antioxidant activity of Annona crassiflora: Characterization of major components by electrospray ionization mass spectrometry

The polar components of Annona crassiflora pulp, peel and seeds ethanolic extracts were investigated by direct infusion electrospray ionization mass spectrometry (ESI-MS) both in the negative ion mode. Characteristic ESI mass spectra with many diagnostic ions were obtained for the extracts, serving for fast and reliable information. The technique provided information of component structures revealing the presence of important bioactive components widely reported as potent antioxidants such as ascorbic acid, caffeic acid, quinic acid, ferulic acid, xanthoxylin, rutin, caffeoyltartaric acid, caffeoyl glucose and [quercetin+hexose+pentose−H]⁻¹ This is the first report on the composition by ESI-MS of araticum peel and seed ethanolic extracts demonstrating excellent antioxidant activity.     

Electrospray ionization mass spectrometry fingerprinting of essential oils: Spices from the Labiatae family

Polar components of the methanolic extracts of the essential oils of the spices Origanum dictamnus, Origanum vulgare, Origanum majorana and Rosmarinus officinalis, all four belonging to the Labiatae family, were investigated by direct infusion electrospray ionisation mass spectrometry (ESI-MS) both in the negative and positive ion modes. Characteristic ESI mass spectra with many diagnostic ions were obtained for the extracts of all four spices, serving for fast and reliable identification of these species. Tandem mass spectrometry (ESI-MS/MS), which often forms a series of fragment ions, and this additional MS dimension increases selectivity for authenticity and adulteration tests for spice essential oils. The MS technique also provides complementary information of component structures revealing the presence of important bioactive components.     

Antioxidant activity of Caryocar brasiliense (pequi) and characterization of components by electrospray ionization mass spectrometry

The Caryocar brasiliense known commonly as pequi is a tropical fruit of Brazilian Cerrado and is considered an important option of income and food for the populations living in this biome. Our previous study indicated that C. brasiliense had high total phenol content (209 g as gallic acid equivalent kg⁻¹) and excellent scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical (IC₅₀ of 9.44 μg ml⁻¹). In this study, we evaluated the highly efficient antioxidant activity of C. brasiliense using the biological relevant method of chemically induced lipid peroxidation. The half inhibition concentration did not exceed 0.8 μg ml⁻¹. In addition, polar components of pequi ethanolic extract were investigated by direct infusion electrospray ionization mass spectrometry (ESI-MS). The technique revealed the presence of important bioactive components widely reported as potent antioxidants such as gallic acid, quinic acid, quercetin, and quercetin 3-O-arabinose possibly explaining its higher antioxidant activity. This is the first report on the composition by ESI-MS of pequi extract demonstrating excellent antioxidant activity.     

Molecular mass distribution of dextran in Brazilian sugar and insoluble deposits of cachaça

The dextran molecular mass distribution profile in 77 sugar samples from Brazil and twelve insoluble deposits (alcoholic flocks) samples from sugared cachaças (Brazilian sugar cane spirit) is described in terms of number-average molecular mass M_n, weight-average molecular mass M_w, Z-average molecular mass M_z, and polydispersity. The analyses were performed by size-exclusion chromatography, using a refractive index detector. In most of the sugar samples, it was possible to identify two major groups of dextrans with M_w averages of 5 × 10⁶ and 5 × 10⁴ Da. Based on the evaluated parameters, the dextran distribution profile is about the same in samples analyzed over five seasons, and, therefore, it is likely that the Brazilian product pattern will not change very much over the years. In insoluble deposits from sugared cachaças, dextrans with M_w values in the order of the 10⁵ Da were the most frequent ones, being present in 58% of the samples.     

Application of electrospray ionization ion trap/time-of-flight mass spectrometry for chemically-synthesized small RNAs

In this study, we have demonstrated an accurate and rapid small RNA analytical method with both sequence determination and detailed modification analysis by electrospray ionization-ion trap/time-of-flight mass spectrometry (ESI-IT/TOFMS). To develop this ideal method, we have examined the performance of ESI-IT/TOFMS using various chemically-synthesized model sequences of modified or unmodified microRNAs (miRNAs). The deconvoluted mass of a 22-nucleotide (nt) miRNA was obtained from a multiply charged precursor ion (MS(1)). The ion exhibited high mass accuracy (< 7 ppm) and high mass resolution (a value of m/Δm=10,000) and was therefore very useful in RNA composition assignment. The optimized MS(2) method using ion trap collision-induced dissociation, as well as automatic annotation analysis of product ions based on the accurate mass information, enabled the precise sequencing determination of intact miRNAs. Further, the detailed structural analysis of 3'-terminal modified nucleic acid in intact methylated miRNA was carried out using the MS(3) capability of the hybrid IT/TOFMS. The direct infusion method also provided a high throughput and good sensitivity because the analytical time and sample concentration needed in a series of experiments with reliable data were only 3 min and 100 nM, respectively. This study provides a novel approach for characterizing the intact chemically-synthesized small RNA without chemical and enzymatic digestions and would be widely applicable for the structural analysis of complicated modified small RNAs.     

Survey of bottled waters for perchlorate by electrospray ionization mass spectrometry (ESI‐MS) and ion chromatography (IC)

Perchlorate has been identified in ground and surface waters around the USA including some that serve as supplies for drinking water. Because perchlorate salts are used as solid oxidants in rockets and ordnance, water contamination may occur near military or aerospace installations or defense industry manufacturing facilities. This ion has been added to the Environmental Protection Agency's Contaminant Candidate List and the Unregulated Contaminant Monitoring Rule. Concern over perchlorate has prompted many residents in affected areas to switch to bottled water; however, bottled waters have not previously been examined for perchlorate contamination. Should the EPA promulgate a regulation for municipal water systems, US law requires the Food and Drug Administration to take action on bottled water. Methods will therefore be required to determine perchlorate concentrations not only in tap water, but also in bottled waters. Ion chromatography (IC) is the primary technique used for its analysis in drinking water, but it does not provide a unique identification. Confirmation by electrospray ionization mass spectrometry (ESI‐MS) can serve in this capacity. The ESI‐MS method can be applied to these products, but it requires an understanding of matrix effects, especially of high ionic strength that can suppress electrospray. When using methyl isobutyl ketone (MIBK) as the extraction solvent, the ESI‐MS method can reach lower limits of detection of 6 ng ml ⁻¹ for some bottled waters. However, dilution required to negate ionic strength effects in mineral waters can raise this by a factor of 10 or more, depending on the sample. Decyltrimethylammonium cation (added as the bromide salt) is used to produce an ion pair that is extracted into MIBK. After extraction, the sum of the peak areas of the ions C₁₀H₂₁NMe₃(Br)(ClO₄)⁻ (m/z = 380) and C₁₀H₂₁NMe₃(ClO₄)₂⁻ (m/z = 400) is used to quantitate perchlorate. Standard additions are used to account for most of the matrix effects. In this work, eight domestic brands and eight imported brands of bottled water were comparatively analyzed by the two techniques. For comparison, a finished potable water known to contain perchlorate was also tested. None of the bottled waters were found to contain any perchlorate within the lower limit of detection for the IC method. Recoveries on spiked samples subjected to the IC method were ≥98%. Published in 2000 for SCI by John Wiley & Sons, Ltd     

Isolation and identification of antioxidative peptides from porcine collagen hydrolysate by consecutive chromatography and electrospray ionization–mass spectrometry

The porcine skin collagen was hydrolyzed by different protease treatments to obtain antioxidative peptides. The hydrolysate of collagen by cocktail mixture of protease bovine pancreas, protease Streptomyces and protease Bacillus spp. exhibited the highest antioxidant activities on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, metal chelating and in a linoleic acid peroxidation system induced by Fe²⁺. And degree of hydrolysis highly affected the antioxidant properties of the hydrolysates. Four different peptides showing strong antioxidant activity were isolated from the hydrolysate using consecutive chromatographic methods including gel filtration chromatography, ion-exchange chromatography and high-performance liquid chromatography. The molecular masses and amino acid sequences of the purified antioxidant peptides were determined using electrospray ionization (ESI) mass spectrometry. One of the antioxidative peptides, Gln-Gly-Ala-Arg, was then synthesized and the antioxidant activities measured using the aforementioned methods. The results confirmed the antioxidant activity of this peptide, and adds further support to its feasibility as a provider of natural antioxidants from porcine skin collagen protein.     

Molecular characterization of edible vegetable oils via free fatty acid and triacylglycerol fingerprints by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Free fatty acids (FFAs) and triacylglycerols (TAGs) are the main components of edible vegetable oils. In this work, electrospray ionisation (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was employed to characterise the molecular composition of FFAs and TAGs in various vegetable oils, including soybean, rapeseed, corn, sunflower, peanut, linseed and olive oils. Semiquantitative analysis of FFAs and structural analysis of TAGs by MS/MS were further conducted to reveal the differences in the molecular compositions of the various vegetable oils. It was found that each vegetable oil has characteristic fingerprints of FFAs and TAGs. MS/MS measurements showed that the high-abundance TAGs in each vegetable oil were mainly composed of their abundant FFAs and glycerol. FFA and TAG fingerprints of genetically modified (GM) and nongenetically modified (non-GM) vegetable oils were similar, exhibiting only subtle differences, as confirmed by principal component analysis (PCA).     

亲水作用色谱-质谱法同时检测鱼肉中 链霉素和双氢链霉素残留

目的 建立一种亲水作用色谱串联质谱技术同时检测鱼肉中链霉素和双氢链霉素残留的分析方法。方法 以鱼肉为原料, 样品经磷酸盐缓冲溶液提取, 固相萃取柱净化后, 采用亲水作用色谱柱分离, 在正离子模式下以电喷雾电离串联质谱进行测定, 外标法定量。结果 链霉素和双氢链霉素在2.0?50 μg/L质量浓度范围内线性关系良好, 在10、20、50 μg/kg三个加标水平下, 方法的回收率为80.2%?97.1%, 相对标准偏差为3.3%?7.2%。结论 该方法简便、快速、实用、准确, 各项技术指标满足国内外法规的要求, 可用于鱼肉中链霉素和双氢链霉素残留的确证检测。     

C NMR and electrospray ionization mass spectrometric study of sucrose aqueous solutions at high pH: NMR measurement of sucrose dissociation constant

The ¹³C NMR technique is used for the measurement of the first dissociation constant of sucrose (HL) in highly alkaline solutions. In 1.0 M NaCl/NaOH medium and for 25 °C, the concentration dissociation constant (pK₁) was 13.1 ± 0.3; and, for 60 °C, pK₁ = 12.30 ± 0.05. The β-d-fructofuranosyl ring was found to be responsible for dissociation. The NMR data reveal no clear evidence of the second dissociation step below pH 14, either at 25 °C or at 60 °C. In the solutions with 4–10 mol dm⁻³ NaOH content the ¹³C NMR technique indicated the chemical shift changes, treated as the second dissociation step of sucrose and a sodium complex formation. A very rough estimation, for variable ionic strength, gives the value: pK₂ ∼ 15.8 ± 0.8. The anionic species L⁻ and NaH₋₁L⁻ have been registered by electrospray ionization time-of-flight mass spectrometry (ESI-ToF MS) for 0.01 M sucrose solutions with initial pH 13.     

快速蒸发电离质谱法在食品质量安全快速检测中的应用

快速蒸发电离质谱技术(rapid evaporation ionization mass spectrometry, REIMS)是环境电离-质谱技术迅速发展的最新成果, 也是近几年质谱检测领域的热点。通过电离切割组织或其他生物样品产生的含丰富特定区域生物特征的气溶胶, 借助高分辨率质谱对其进行原位、在线、实时、快速分析。随后进行计算机数据建模与可视化, 实现目标物质的快速检测。本文综述了REIMS技术的发展概况、主要结构组成、检测原理、采用的常规数据处理方法及其在食品检测领域中的具体应用, 包括肉品掺假鉴别、风味物质检测、品种鉴别、干果真实性评估、果汁风味物质鉴别等。主要通过对当前快速蒸发电离质谱技术在不同食品检测领域的应用研究进展进行综述, 以期为食品安全快速检测等相关研究领域科研工作者提供一定的思路与参考。     

几种不同血清型沙门氏菌生化结果及基质辅助激光解吸电离飞行时间质谱离子峰的差异性分析

目的了解不同血清型沙门氏菌生化结果差异及飞行质谱离子峰的差异性。方法选取10种不同血清型的沙门氏菌,确认其血清种类,使用VITEK2全自动微生物鉴定仪迚行生化分析,采用基质辅助激光解吸电离飞行时间质谱法(matrix-assisted laserdesorption ionization time-of-flight mass spectrometry, MALDI-TOFMS)获得蛋白质指纹图谱,幵迚行离子峰差异性分析。结果 10株不同血清型沙门氏菌尿素酶、赖氨酸、H_2S等33种生化结果无差异,而L-脯氨酸芳胺酶、乳酸盐产碱、O/129耐受等14个反应结果有个别差异;建立了10株沙门氏菌鉴定分型主要差异的离子峰数据库,幵収现菌株存在完全不同的离子峰:Sal-01具有8370.144离子峰, Sal-03具有5462.553、10927.51离子峰, Sal-06具有3013.925、6035.049离子峰, Sal-07具有3030.747、6026.629、6067.12离子峰。结论不同血清型沙门氏菌在生化结果上有一定的差异,通过MALDI-TOF-MS分析能够获得不同血清型的沙门氏菌具有差异性离子峰基础数据。     

Ethyl carbamate in pot still cachaças (Brazilian sugar cane spirits): Influence of distillation and storage conditions

Ethyl carbamate (EC), a known genotoxic carcinogen, was studied in 25 brands of pot still cachaças from 19 distilleries in Paraíba State, Brazil. A concentration range of 55–700 μg/l was found with most brands (∼70%) exceeding the international EC limit for spirits (150 μg/l). Brand characteristics (colour, distillation [single or double], and bottle colouration) showed no consistent connection with EC levels. However, when EC levels of yellowish (cask matured) and colourless single-distiled cachaças from the same distillery were compared, the yellowish type was much more heavily contaminated. Eleven distilleries were visited and information regarding the distillation scale, kettle heating system, kettle’s shape, and cooling system of the column was collected. A close connection between EC levels and cooling system was found, with the non-cooled and cooled columns dominating the brands with high (200–700 μg/l range) and low (55–100 μg/l range) contamination levels, respectively.     

Analysis of isopropyl para‐toluenesulphonate in palm‐based esters by gas chromatography with flame ionization detection and confirmed with mass spectrometry

A simple and rapid gas chromatography (GC) method with flame ionization detector was developed for detection of isopropyl para‐toluenesulphonate (IPTS) in palm‐based isopropyl palmitate (IPP) and isopropyl myristate (IPM). The method involved spiking the IPP/IPM samples with IPTS and directly injecting the spiked samples into GC without undergoing clean‐up steps. The calibration curves for IPTS showed good linearity with coefficient correlation of 0.9999 for six‐point calibration from 0.5 to 50 μg mL^?1 and 0.9996 for six‐point calibration from 0.5 to 200 μg mL^?1. IPTS recoveries from IPP were 98.6–103.5% with relative standard deviation (RSD) of 0.40–2.80%, whereas recoveries from IPM were 97.0–107.2% with RSD of 0.42–4.21%. The identity of IPTS recovered from the isopropyl esters was confirmed by a GC‐mass spectrometer detector. The method was successfully applied to the analyses of IPTS in commercial samples. It was found that there were IPTS in the range of 34.8–1303.0 μg g^?1 in the palm‐based esters for some of the samples analysed.     

Studies on structures and activities of initial Maillard reaction products by electrospray ionisation mass spectrometry combined with liquid chromatography in processing of red ginseng

Electrospray ionisation-mass spectrometry (ESI-MS) was applied to analyse the water-soluble extract of red ginseng (RG). Several new compounds were produced from the Maillard reaction during the steaming and drying process for preparing RG. Both the tandem electrospray ionisation (ESI-MS(n)) and Fourier transform ion cyclotron resonant mass spectrometric (FT-ICR-MS) data of these products proved that they were the initial Maillard reaction products (MRPs) of maltose with glutamic acid/aspartic acid, which were specific components in RG. In addition, their anti-diabetic and antioxidant activities were examined in vitro. The anti-diabetic activities were evaluated by studying the α-glucosidase inhibition using ultrafiltration LC-MS/MS techniques, while the antioxidant activities were investigated by UPLC-ESI-MS method. The results demonstrated that four initial MRPs in RG were identified as α-glucosidase inhibitors, and showed marked scavenging effect on the hydroxyl radical ((·)OH). Based on these studies, the processing method of RG was improved to generate more active compounds.     

Determination of diquat and paraquat in olive oil by ion-pair liquid chromatography–electrospray ionization mass spectrometry (MRM)

For the first time a method for determination of herbicides diquat (DQ) and paraquat (PQ) in olive oil was developed utilising liquid chromatography–electrospray ionization mass spectrometry (MRM). n-Hexane/10 mM HFBA aqueous solution partitioning was used as the extraction method. Separation was carried out in an Xterra C8 column (100 × 21 mm, 3 μm), using the gradient mode. Solvent A was a HFBA aqueous solution (5 mM, pH 2) and solvent B acetonitrile/methanol 75/25 (v/v). Peaks used for quantification were m/z = 157 (diquat) and m/z = 158 (paraquat). Detection limit found for both diquat and paraquat was 4 μg kg⁻¹. The method can also be applied for determination of chlormequat (CQ, quantification peak m/z = 58), the detection limit being 0.3 μg kg⁻¹. Such limits are clearly lower than the MCLs commonly applied to olive oil as reference criteria (5 times MCLs in olives). Good reproducibilities (day to day and run to run) were obtained.     

Short communication: Evaluation of MALDI-TOF mass spectrometry and a custom reference spectra expanded database for the identification of bovine-associated coagulase-negative staphylococci

This study evaluated MALDI-TOF mass spectrometry and a custom reference spectra expanded database for the identification of bovine-associated coagulase-negative staphylococci (CNS). A total of 861 CNS isolates were used in the study, covering 21 different CNS species. The majority of the isolates were previously identified by rpoB gene sequencing (n = 804) and the remainder were identified by sequencing of hsp60 (n = 56) and tuf (n = 1). The genotypic identification was considered the gold standard identification. Using a direct transfer protocol and the existing commercial database, MALDI-TOF mass spectrometry showed a typeability of 96.5% (831/861) and an accuracy of 99.2% (824/831). Using a custom reference spectra expanded database, which included an additional 13 in-house created reference spectra, isolates were identified by MALDI-TOF mass spectrometry with 99.2% (854/861) typeability and 99.4% (849/854) accuracy. Overall, MALDI-TOF mass spectrometry using the direct transfer method was shown to be a highly reliable tool for the identification of bovine-associated CNS.