Liquid Chromatography-electrospray Mass Research Articles

Simple liquid chromatography-electrospray ionization ion trap mass spectrometry method for the quantification of galacto-oxylipin arabidopsides in plant samples

A simple and sensitive method to quantify five different arabidopsides by HPLC—ion trap mass spectrometry in complex plant samples was developed and validated. Arabidopsides are oxidized galactolipids first described in Arabidopsis thaliana but also produced by other plant species under stress conditions. External calibration was performed using arabidopsides purified from freeze-thawed Arabidopsis leaves. Lipids were extracted and pre-purified on an SPE silica column before HPLC–MS analysis. Arabidopsides were separated on a C18 column using a gradient of mQ water and acetonitrile:mQ water (85:15) supplemented with formic acid (0.2%) and ammonium formate (12 mM). The method was validated according to European commission decision 2002/657/CE. LOD, LOQ, linearity, intra-day and inter-day precision and accuracy, selectivity, matrix effects and recoveries were determined for the five metabolites. The established method is highly selective in a complex plant matrix. LOD and LOQ were, respectively, in the range 0.098–0.78 and 0.64–1.56 µM, allowing the arabidopside quantification from 25.6–62.4 nmol/g fresh weight. Calibration curve correlation coefficients were higher than 0.997. Matrix effects ranged from -2.09% to 6.10% and recoveries between 70.7% and 109%. The method was successfully applied to complex plant matrixes: Arabidopsis thaliana and Nasturtium officinale.

Exploring the Chemoselectivity towards Cysteine Arylation by Cyclometallated AuIII Compounds: New Mechanistic Insights.

To gain more insight into the factors controlling efficient cysteine arylation by cyclometallated AuIII complexes, the reaction between selected gold compounds and different peptides was investigated by high‐resolution liquid chromatography electrospray ionization mass spectrometry (HR‐LC‐ESI‐MS). The deduced mechanisms of C−S cross‐coupling, also supported by density functional theory (DFT) and quantum mechanics/molecular mechanics (QM/MM) calculations, evidenced the key role of secondary peptidic gold binding sites in favouring the process of reductive elimination.

Systematic Evaluation of Normalization Methods for Glycomics Data Based on Performance of Network Inference.

Glycomics measurements, like all other high-throughput technologies, are subject to technical variation due to fluctuations in the experimental conditions. The removal of this non-biological signal from the data is referred to as normalization. Contrary to other omics data types, a systematic evaluation of normalization options for glycomics data has not been published so far. In this paper, we assess the quality of different normalization strategies for glycomics data with an innovative approach. It has been shown previously that Gaussian Graphical Models (GGMs) inferred from glycomics data are able to identify enzymatic steps in the glycan synthesis pathways in a data-driven fashion. Based on this finding, here, we quantify the quality of a given normalization method according to how well a GGM inferred from the respective normalized data reconstructs known synthesis reactions in the glycosylation pathway. The method therefore exploits a biological measure of goodness. We analyzed 23 different normalization combinations applied to six large-scale glycomics cohorts across three experimental platforms: Liquid Chromatography-ElectroSpray Ionization-Mass Spectrometry (LC-ESI-MS), Ultra High Performance Liquid Chromatography with Fluorescence Detection (UHPLC-FLD), and Matrix Assisted Laser Desorption Ionization-Furier Transform Ion Cyclotron Resonance-Mass Spectrometry (MALDI-FTICR-MS). Based on our results, we recommend normalizing glycan data using the ‘Probabilistic Quotient’ method followed by log-transformation, irrespective of the measurement platform. This recommendation is further supported by an additional analysis, where we ranked normalization methods based on their statistical associations with age, a factor known to associate with glycomics measurements.

Antifungal effect of bioprocessed surplus bread as ingredient for bread-making: Identification of active compounds and impact on shelf-life

Bread is one of the most consumed food products in the world and one of the most discarded, due to its intrinsic short shelf-life and susceptibility to mold spoilage. Additionally, bread waste is generated during production and distribution, leading to the disposal of bread otherwise still fit for consumption. To avoid generating huge amount of bread waste, strategies to enable its reutilization should be sought. In this study, surplus bread, still suitable for consumption, was bioprocessed with enzymes and fermented by selected lactic acid bacteria generating an ingredient with antifungal properties. Bread hydrolysate fermented by Lactobacillus brevis AM7 showed broad inhibitory spectrum against the fungal species tested and antifungal activity ranging from 20 to 70%. Nine antifungal peptides were identified via Liquid Chromatography-Electrospray Ionisation-Mass Spectra/Mass Spectra (nano-LC-ESI-MS/MS), having 10–17 amino acid residues and mass ranging from 1083.6 to 1980.7 Da, all of them encrypted in wheat proteins sequences. Bread hydrolysate fermented by Lb. brevis AM7, non-fermented bread hydrolysate and a slurry consisting of water-bread mixture were used as ingredients in bread making and compared to regular wheat bread. Breads containing the fermented hydrolysate (18 and 22% of the dough weight) showed the longest mold-free shelf-life compared to the other breads, lasting up to 10 days before mold appearance. Additionally, the fermented hydrolysate was the least detrimental on bread quality, emphasizing the positive impact and potential of the studied biotechnology.

Rapid detection and identification of dioscorine compounds in Dioscorea hispida tuber plants by LC-ESI-MS

Studies have revealed that Dioscorea hispida tubers contain a poisonous substance called alkaloid dioscorine. The method for removing alkaloid dioscorine in Dioscorea hispida is explored in this research through a soaking process. The tubers were peeled, washed, sliced, and soaked for 5 days in either 1.0 M sodium chloride (NaCl) or distilled water. The aim of this study was to firstly identify the amount of toxic dioscorine remaining after soaking for 5 days, and then determine the best solution for removing dioscorine compounds in the tubers that were obtained from a tropical area in Peninsular Malaysia. The liquid chromatography electrospray ionization mass spectrometric (LC-ESI-MS) systems were used to identify the presence of alkaloid dioscorine compounds within Dioscorea hispida tubers. The analysis showed that no dioscorine compounds were present in day 5 for samples soaked in the NaCl solution. However, the relative abundance in the distilled water solution at day 5 was 281000, indicating a 95% decrease of the relative abundance value of the dioscorine compounds. This work aimed to determine the minimum days needed to remove the poisonous element before Dioscorea hispida tubers could be used for food consumption or for any other applications.

Controlling formation of metal ion adducts and enhancing sensitivity in Liquid Chromatography Mass Spectrometry

Formation of metal ion adducts in mass spectrometry, particularly in electrospray ionization liquid chromatography mass spectrometry (ESI-LC-MS), is a nightmare scenario for an analyst dealing with quantitative analysis. We have studied in detail the metal adduct formation and concluded that the use of fluorinated alkanoic acids along with formic acid and volatile ammonium salts was extremely useful in suppressing metal adduct formation in positive ion mode of ESI-LC-MS. The extremely high electronegativity of fluorine atom and unique electrostatic nature of C—F bond coupled with stereo-electronic interactions with neighboring bonds or lone pairs enables the polyfluorinated alkanoic acids in trapping highly electropositive ions (Na+, K+) thereby letting proton do its job efficiently. Addition of formic acid, trifluoroacetic acid, heptafluorobutyric acid and ammonium acetate was found to be extremely effective in controlling metal ion adducts and producing [M+H]+ ions almost exclusively resulting in significant increase in the sensitivity. This technique has been successfully used in our laboratory for the estimation of targeted and nontargeted analysis of pesticides, marine toxins, drugs and pharmaceuticals etc. in various matrices including environmental waters using liquid chromatography-time of flight mass spectrometer operated in all ion acquisition mode and triple quadruples (QQQ) in multiple reaction monitoring (MRM) mode.

Contamination Level, Distribution Characteristics, and Ecotoxicity of Tetrabromobisphenol A in Water and Sediment from Weihe River Basin, China.

Tetrabromobisphenol A (TBBPA) is a brominated flame retardant, which is widely present in the various environmental and biological media. The knowledge on the contamination of TBBPA in Weihe River Basin is still limited. In order to know the pollution level and distribution of tetrabromobisphenol A (TBBPA) in the Weihe River Basin, a total of 34 sediment samples and 36 water samples were collected from the main stream and tributaries of the WeiHe River Basin, and the concentration of TBBPA in the samples was analyzed by high-performance liquid chromatography–electrospray ionization–mass spectrometry (HPLC-ESI-MS). The detection frequency of TBBPA in sediments and water samples was 61.8% and 27.8%, respectively; the TBBPA concentrations in sediments and water samples were in the range of not detected (N.D.)–3.889 ng/g (mean value of 0.283 ng/g) and N.D—12.279 ng/L (mean value of 0.937 ng/L), respectively. Compared with other areas in China, the residues of TBBPA in the Weihe River Basin were at a relatively low level. The spatial distributions of TBBPA in surface sediments and water indicated that the local point-input was their major source. This is related to the proximity of some sampling sites to industrial areas and domestic sewage discharge areas. The insignificant correlation between TBBPA and total organic carbon (TOC) indicated that TBBPA in sediments is not only influenced by TOC but also affected by atmosphere and land input, wet deposition, and long-distance transmission. The potential risks posed by TBBPA in water and sediment were characterized using the risk quotient (RQ) method. The calculated RQ for TBBPA was less than 0.01, showing that the ecological risk due to TBBPA was quite low for aquatic organisms.

Determination of 5-HT3 Receptor Antagonists in Human Urine by Porous Graphitic Carbon (PGC) Solid Phase Extraction (SPE) Coupled with High Performance Liquid Chromatography-Tandem Mass Spectrometry (HPLC-MS/MS)

The quantitative determination of drugs in urine by high performance liquid chromatography electrospray-ionization mass spectrometry (HPLC-ESI-MS) is challenging due to complex matrix interferences and the relatively low concentrations of analytes in urine. In this study, porous graphitic carbon (PGC) was investigated as solid phase extraction (SPE) sorbent before HPLC-ESI-MS determination of three 5-hydroxytryptamine (3) (5-HT3) receptor antagonists from human urine. The factors affecting extraction of the target antagonists were investigated and optimized systematically by using single-factor tests. The optimized SPE procedure was developed for the simultaneous extraction and sample pretreatment of tropisetron, ondansetron, and granisetron in urine by HPLC-ESI-MS/MS. Using the optimized conditions, the matrix effects were reduced by the PGC-based SPE clean-up procedure, with acceptable matrix effects for tropisetron, ondansetron, and granisetron from 96.53% to 98.42%, 93.19% to 94.36%, and 94.48% to 95.60%, respectively. The reported method significantly removes matrix interferences from the urine samples and exhibited satisfactory recovery and process efficiency for the determination of tropisetron, ondansetron, and granisetron. The established pretreatment method provides a promising strategy for the removal of interferences from hydrophilic basic drugs in biological fluids.

Characterization and bioactivity of proanthocyanidins during Malay cherry (Lepisanthes alata) fruit ripening

Bioactive proanthocyanidins are the main inhibitors of starch hydrolases in unripe and ripe Malay cherry fruits. Proanthocyanidins from both unripe and ripe fruits showed stronger inhibition of α-amylase with IC50 values of 3.54 ± 0.03 and 1.19 ± 0.02 μg/mL, respectively, than that of α-glucosidase. The structural fingerprints of proanthocyanidins were identified using high-performance liquid chromatography electrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses. Results showed the subunits of proanthocyanidins were (epi)catechins and (epi)gallocatechins, and they formed tetramers to dodecamers in unripe fruits and tetramers to hexadecamers in ripe fruits. The mean degree of polymerization (mDP) of proanthocyanidins was found to increase from 8 to 18 as fruit ripened. Larger proanthocyanidins (higher mDP values) in ripe fruits exerted significantly stronger inhibition of α-amylase and α-glucosidase than less polymerized proanthocyanidins in unripe fruits, indicating the dependence of inhibition on mDP. Total phenolics and total proanthocyanidins significantly decreased as fruit ripened.

Optimization of Ultra-High-Performance Liquid Chromatography-Electrospray Ionization-Mass Spectrometry Detection of Glutamine-FMOC Ad-Hoc Derivative by Central Composite Design

Glutamine (Gln) is converted to excitatory (glutamate, aspartate) and inhibitory (γ-amino butyric acid) amino acid neurotransmitters in brain, and is a source of energy during glucose deprivation. Current research utilized an Analytical Quality by Design approach to optimize levels and combinations of critical gas pressure (sheath, auxiliary, sweep) and temperature (ion transfer tube, vaporizer) parameters for high-sensitivity mass spectrometric quantification of brain tissue glutamine. A Design of Experiments (DOE) matrix for evaluation of relationships between these multiple independent variables and a singular response variable, e.g. glutamine chromatogram area, was developed by statistical response surface methodology using central composite design. A second-order polynomial equation was generated to identify and predict singular versus combinatory effects of synergistic and antagonistic factors on chromatograph area. Predicted versus found outcomes overlapped, with enhanced area associated with the latter. DOE methodology was subsequently used to evaluate liquid chromatographic variable effects, e.g. flow rate, column temperature, and mobile phase composition on the response variable. Results demonstrate that combinatory AQbD-guided mass spectrometric/liquid chromatographic optimization significantly enhanced analytical sensitivity for Gln, thus enabling down-sized brain tissue sample volume procurement for quantification of this critical amino acid.

Simultaneous analysis of polyethylene glycol in dietary supplement tablets using high-performance liquid chromatography and verification with liquid chromatography–electrospray ionization mass spectrometry

Polyethylene glycol (PEG) are widely applied in detergents, cosmetics, and food additives. A simultaneous analytical method was developed to detection the polyethylene glycol (100–10000 Da). High-performance liquid chromatography (HPLC) with evaporative light scattering detector (ELSD) could analyze successively PEG products. The method was verified with liquid chromatography–electrospray ionization mass spectrometry (LC-ESI-MS/MS). The retention times of PEG 200–8000 ranged from 1.97 to 12.33 min. Method validation was performed to the International Conference on Harmonization (ICH) guidelines and the Korea Ministry of Food and Drug Safety (MFDS); linearity: R2 > 0.997, LOD: 7.47–16.24 µg/mL, LOQ: 22.40–75 µg/mL, repeatability (%RSD): 0.2–2.5, recovery (%): 90.4–104.9% for film-coated tablet, 80.1–95.9% for sugar-coated tablet. A total of 115 PEG could be identified by extracted ion chromatography in mass analysis, based on the charge state represented as [M+Na++H3O+n-1]. This method can be applied for successive identification of PEGs in PEG-containing products.

In Vitro Antifungal Activity of Peltophorum dubium (Spreng.) Taub. extracts against Aspergillus flavus.

Aspergillus flavus is a filamentous, saprophytic fungus, whose colonization occurs mainly in cereal grains and oilseeds once harvested. Under certain conditions, it could produce mycotoxins called aflatoxins, known as powerful human liver carcinogens. The aim of the present study was to describe the antifungal activity of extracts of Peltophorum dubium, a species from northern Argentina (Oriental Chaco), against A. flavus. The antifungal activities of different collection sites are reported. The extracts exhibited a minimum inhibitory concentration of 125 µg/mL, and the differences between the treatments and the inoculum control were 11 mm of P. dubium A and 10 mm of P. dubium F in colony growth. Moreover, hyphae treated with the extracts stained blue with Evans blue showed alterations in the membrane and/or cell wall, allowing the dye income. Bio-guided fractionation, High Performance Liquid Chromatography diode array ultraviolet/visible (HPLC UV/VIS DAD), and Ultra-High Performance Liquid Chromatography Electrospray Ionization Mass Spectrometry (UPLC ESI-MS) analyses were conducted to characterize the extracts and their active fractions. The HPLC UV/VIS DAD analysis allowed the determination of the presence of flavonoids (flavonols and flavones), coumarins, terpenes, and steroids. UPLC ESI/MS analysis of active fractions revealed the presence of Kaempferol, Apigenin, Naringenin, Chrysin and Daidzein.

Nickel(I) salen-catalyzed reduction of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113): CO2-mediated carbon–fluorine bond cleavage

Cyclic voltammetry, controlled-potential (bulk) electrolysis, gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and high-performance liquid chromatography–electrospray ionization–mass spectrometry (HPLC–ESI–MS) have been used to investigate the direct and nickel(I) salen-catalyzed reduction of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113) in both Ar- and CO2-saturated dimethylformamide (DMF) containing 0.10 M tetra-n-butylammonium tetrafluoroborate (TBABF4). Cyclic voltammograms show one irreversible cathodic peak for direct reduction of CFC-113 in CO2-saturated DMF to afford 1-chloro-1,2,2-trifluoroethene (CFC-1113), whereas cyclic voltammograms in Ar-saturated DMF exhibit two irreversible cathodic peaks. Bulk electrolyses of CFC-113 in CO2-saturated DMF at a potential 400 mV more negative than the resolved cathodic peak cause partial reduction of CFC-1113 to yield di-, tri-, and tetrafluoro species. Cyclic voltammograms for reduction of nickel(II) salen in the presence of CFC-113 in CO2-saturated DMF show two cathodic peaks attributable to formation of CFC-1113 and HFC-1123; cyclic voltammograms in Ar-saturated DMF exhibit similar behavior. Bulk electrolyses involving electrogenerated nickel(I) salen in CO2-saturated DMF yield mixtures of HFC-1123, isomers of difluoroethene, and traces of other species. No electrocarboxylation of CFC-113 or its derivatives was seen in the presence of CO2; however, excess CO2 increases the extent of dechlorination of CFC-113 during bulk electrolyses when compared with analogous electrolyses in an Ar-saturated medium. Structural modification of nickel(II) salen during catalytic reduction of CFC-113 in the presence of CO2 was determined with the aid of HPLC–ESI–MS.

Nutritional component analyses of kiwifruit in different development stages by metabolomic and transcriptomic approaches.

Metabolites in kiwifruit greatly influence nutritional values; however, the dynamic changes in nutrient composition and the gene expression level of yellow kiwifruit have not been studied so far. To investigate the types and accumulation patterns of metabolites, a metabolomics approach utilizing liquid chromatography-electrospray ionization mass spectrometry and transcriptomics were used to analyze the yellow flesh of kiwifruit cultivar 'jinshi 1' collected at different stages of days after full bloom. In total, 285 metabolites were identified over the kiwifruit developmental stages. The composition of the metabolites of kiwifruit at different stages of development was different. The organic acids contents and their derivatives were higher at the initial stage of development and then gradually decreased. The lipids and amino acids contents fluctuated at different stages of development but did not change significantly. Transcript profiles throughout yellow kiwifruit development were constructed and analyzed, with a focus on the biosynthesis and metabolism of compounds such as sugars, organic acids and ascorbic acid, which are indispensable for the development and formation of quality fruit. The transcript levels of genes involved in sucrose and starch metabolism were consistent with the change in soluble sugar and starch content throughout kiwifruit development. The metabolism of ascorbic acid was primarily through the l-galactose pathway. Our metabolome and transcriptome approach identified dynamic changes in five types of nutrient metabolite levels, and correlations among such levels, in developing fruit. The results provide information that can be used by metabolic engineers and molecular breeders to improve kiwifruit quality. © 2020 Society of Chemical Industry.

Alternative Sweeteners Modify the Urinary Excretion of Flavanones Metabolites Ingested through a New Maqui-Berry Beverage.

Dietary sugar has been largely related to the onset of metabolic diseases such as type 2 diabetes and obesity, among others. The growing awareness on the close relationship between the dietary habits and this health disturbance has encouraged the development of new beverages using alternative sweeteners that could contribute to combat the above referred pathophysiological disorders. To gain further insight into this issue, the present work, upon an acute dietary intervention, evaluated the urinary excretion of flavanones ingested through polyphenols-rich beverages composed of maqui berry and citrus, with the aim of establishing the highest urinary excretion rate and metabolite profiles. The functional beverages evaluated were supplemented with a range of sweeteners including sucrose (natural and high caloric), stevia (natural and non-caloric), and sucralose (artificial and non-caloric) as an approach that would allow reducing the intake of sugars and provide bioactive phenolics (flavanones). The juices developed were ingested by volunteers (n = 20) and the resulting flavanones and their phase II metabolites in urine were analyzed by Ultra-High Performance Liquid Chromatography ElectroSpray Ionization Mass Spectrometry (UHPLC-ESI-MS/MS). A total of 16 metabolites were detected: eriodyctiol, naringenin, and homoeriodyctiol derivatives, where peak concentrations were attained 3.5 h after beverage intake. Sucralose and stevia were the sweeteners that provided the highest urinary excretion for most compounds. Sucrose did not provide a remarkable higher elimination through urine of any compounds in comparison with sucralose or stevia. These results propose two alternative sweeteners to sucrose (sucralose and stevia), an overused, high caloric sweetener that promotes some metabolic diseases.

Effect of ultrasound treatment on the extraction of antioxidants from Ardisia compressa Kunth fruits and identification of phytochemicals by HPLC-ESI-MS

The influence of ultrasound-assisted extraction of phytochemicals from Ardisia compressa Kunth on the antioxidant capacity was investigated. The factors evaluated were: ultrasound extraction time (10, 20 and 30 min), ethanol concentration (0, 35, 70 %) and solid/liquid ratio (1:4, 1:8 and 1:12 g mL−1). The L9 (3)3 array was applied, and the DPPH• scavenging capacity of treatments was evaluated to obtain optimal extraction conditions. Finally, the phytochemicals were characterized by high-performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS). Ten minutes of ultrasound extraction using 0 % of ethanol and solid/liquid ratio 1:12 g mL−1 were the optimal conditions of extraction. The HPLC-ESI-MS analysis revealed the presence of gluconic acid, quercetin-3-O-glucoside, isorhamnetin-3-O-rutinoside, demethylligstroside, ponicidin, 4-caffeoylquinic acid, rosmarinic acid, and galloyl-hexoside. The optimal ultrasound-assisted extraction conditions were defined by applying the Taguchi methodology. The phytochemicals identified in A. compressa fruits suggest its use as a potential source of bioactive compounds.

Acute Toxicity of the Hydroethanolic Extract of the Flowers of Acmella oleracea L. in Zebrafish (Danio rerio): Behavioral and Histopathological Studies.

Hydroethanolic preparations of the botanical species Acmella oleracea L. are used in the north of Brazil for the treatment of various diseases. However, few studies have been conducted to evaluate the toxicity of this species. The objective of this study was to evaluate the acute toxicity of the hydroethanolic extract of A. oleracea L. (EHFAo) flowers in zebrafish by immersion and oral administration. The extract was analyzed by ultra-performance liquid chromatography–mass spectrometry (UPLC–MS). EHFAo was administered orally (44.457, 88.915, 199.94, 281.83, and 448.81 mg/kg) and by immersion (250, 300, 350, 400, and 450 µg/L). Behavioral and histopathological analysis of gills, liver, intestine, and kidney were performed. The presence of (2E,6Z,8E)-N-isobutyl-2,6,8-decatrienamide (spilanthol) in EHFAo was identified by ultra-high-re.solution liquid chromatography–electrospray ionization mass spectrometry (UHPLC–ESI-MS). Treatment with EHFAo caused significant behavioral changes and death. The calculated median lethal dose (LD50) was 148.42 mg/kg, and the calculated median lethal concentration (LC50) was 320 μg/L. In the histopathological study, it was observed that upon oral treatment, the tissue alterations that compromised the normal functioning of the organism occurred with EHFAo doses of 88.915, 199.53, and 281.83 mg/kg, the intestine being the most affected. When the treatment was performed by immersion, the most toxic EHFAo concentrations according to the histopathological evaluation were 300, 350, and 400 μg/L, with the most affected organ being the gills. Finally, EHFAo in this study was shown to be more toxic to the liver, intestine, and kidneys when administered orally and to gills, liver, and kidneys when administered by immersion in water. Therefore, considering the results obtained and the chemical characteristics of the main phytochemical marker of EHFAo, spilanthol, it can be suggested that, depending on the dose, this compound can lead to histopathological damages in the organs highlighted in this study.

A comparative metabolomics analysis of the components of heartwood and sapwood in Taxus chinensis (Pilger) Rehd.

Taxus chinensis is a well-known gymnosperm with great ornamental and medicinal value. Its purple red brown heartwood (HW) has many attributes such as straight texture, high density, mechanical strength, rich elasticity and corrosion resistance that is highly prized commercially. T. chinensis sapwood (SW), in comparison, lacks these important traits. At present, little is known about the differences of metabolites between the SW and HW in T. chinensis. Widely targeted metabolic profiling was performed to analyze the metabolic profiles of HW and SW in T. chinensis using Liquid Chromatography-Electrospray Ionization-Mass Spectrometry (LC-EI-MS). A total of 607 metabolites were detected in HW and SW. Among them, 146 metabolites were significantly higher, and 167 metabolites significantly lower, in HW as compared to SW. These differential metabolites were mainly involved in metabolic pathways and biosynthesis of secondary metabolites, such as flavonoids, flavone and flavonol, phenylpropanoids and antibiotics. Moreover, 71 flavonoids and isoflavones were found to be significantly different between HW and SW. Our results show the difference of components between the HW and SW, which has potential significance to further elucidate the mechanism of HW color formation. The results will provide insight into the metabolites associated with wood color formation and useful information for understanding the metabolites associated with wood quality.

Dynamic distribution of azoxystrobin residues in strawberry (Fragaria x ananassa Duchesne) using liquid chromatography tandem mass spectrometry: Putative evaluation of dietary intake

ABSTRACT A simple, rapid and environmentally compatible method involving quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction technique for simultaneous detection of azoxystrobin residues in strawberry was optimised and validated. Liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS) was also used for quantitative and confirmatory analysis of azoxystrobin residues in strawberry. Recoveries ranged between 96% and 111% and repeatability (expressed as percentage relative standard deviation, % RSD) typically <11% has been well achieved. The dissipation pattern of azoxystrobin in different treatments level, based on the most critical field use patterns was reported utilising the method developed in this study. The results revealed that the degradation of azoxystrobin in strawberry followed first-order kinetics (R2 > 0.974) with estimated half-life value of 8.45 days. Considering the terminal residues and the maximum residue limit (MRL, 10 mg kg−1) in strawberry, and based on this study, it is safe to harvest strawberry 3 days after applying azoxystrobin even at rated higher the recommended one with exaggerated, suggesting that the use of this compound is safe for humans. The results could provide a guidance to fully evaluate the risks of azoxystrobin to consumers.

Isolation and characterization of zinc-binding peptides from mung bean protein hydrolysates

The aim of this study was to isolate, purify, and characterize a novel peptide with zinc-binding ability from mung bean protein hydrolysates obtained by alcalase. The peptide purification process was performed using ultrafiltration, TSK-GEL size-exclusion chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC). The molecular weight of the isolated peptide was determined by liquid chromatography–electrospray ionization mass spectrometry (LC–ESI/MS) and found to be 1192.56 Da with amino acid sequence SSEDQPFNLR. The identified peptide showed zinc-binding capacity of 80.82 mg/g, which is 55.09% higher than that of the original mung bean protein hydrolyzate. Moreover, UV–vis and FTIR spectra indicated that the zinc-binding sites on the peptide were nitrogen atoms of amide, terminal amino group, and oxygen atoms on the carboxyl group. Moreover, zinc-releasing experiments showed that the peptide–zinc chelate is highly soluble under both acidic and alkaline conditions. Furthermore, the identified peptide significantly promoted the transportation and absorption of zinc ions in Caco-2 cell model. These findings indicate a potential for production of zinc-binding peptide from mung bean protein for the utilization as ingredient in functional foods.