Derivatization Strategy Research Articles

Determination of phenylenediamines in hair colors derivatizated with 5-(4, 6-dichlorotriazinyl)aminofluorescein via micellar electrokinetic chromatography

Phenylenediamines (PDs), which are reported to cause allergic dermatitis and possess genotoxicity and carcinogenicity, are the ingredients used in permanent hair dyes. The fluorescent derivatization strategy coupled with micellar electrokinetic chromatography (MEKC) were established to analyze four PDs, including o-phenylenediamine (OPD), m-phenylenediamine (MPD), p-phenylenediamine (PPD) and toluene-2,5-diamine (PTD). Additionally, 5-(4, 6-dichlorotriazinyl) aminofluorescein (DTAF) was used as a fluorescent reagent derived at amino groups of PDs and underwent nucleophilic substitution reaction to improve the detection sensitivity. The derivatization condition reacted at 90 °C for 10 min in alkaline conditions. The optimized separation conditions were 20 mM borate (pH 8.0) containing 10 mM Brij 35 and 35% (v/v) methanol. The limits of detection (S/N = 3) for MPD, PTD, PPD and OPD were 25, 25, 50 and 100 nM, respectively. Compared to MEKC-UV, the sensitivity enhancements were 30- to 81-fold when PDs were derived with DTAF. The high-sensitivity MEKC-LIF method was successfully established and applied to determine PDs in commercial hair colors for quality control and in real hair samples for evaluating the location of PDs in dyed hair samples, as well as in percutaneous absorption samples for evaluating the ability of PDs to penetrate skin.

Derivatization Strategy for Simultaneous Molecular Imaging of Phospholipids and Low-Abundance Free Fatty Acids in Thyroid Cancer Tissue Sections.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) has been applied in many fields for detecting and imaging a variety of metabolites. In cancer research, this fast-growing imaging method also helps to elucidate the connection between the changes of metabolites in the microenvironment and the proliferation and survival of cancer cells. Free fatty acids (FFAs) are a vital building block of phospholipids (PLs) that can serve as a second cellular messenger and provide nutrients in the cancer microenvironment. The metabolism process of FFAs and PLs is highly relevant to the initiation and progression of different cancers. To better understand the metabolism process in cancer tissues, simultaneously detecting and imaging FFAs and PLs is essential. Despite the crucial developments that have been performed in the field of lipids imaging, FFAs and PLs have rarely been detected and imaged simultaneously in positive ion mode with good detection sensitivity. In this work, an on-tissue derivatization method was used to add a permanently quaternary amine onto FFAs; then, the FFAs and PLs were simultaneously imaged in positive ion mode. The derivatized FFAs are suitable for detection in positive ion mode. In comparison with the traditional matrix and the previous derivatization method, our derivatization reagent has a higher sensitivity for imaging FFAs. In addition, for simultaneous imaging analysis of FFAs and PLs, the number of imaged FFAs and PLs is greater than that with the previous on-tissue derivatization method. This high-sensitivity on-tissue derivatization method was applied to detect and image PLs and fatty acids in thyroid cancer tissues. In the MSI experiment, FFA derivatives and PLs were imaged while molecular localization and tissue integrity were maintained. Meanwhile, the correlation between PLs and FFAs was also studied, and the results showed that the correlations between saturated FFAs of C16:0 and C18:0 and PLs are better than the correlations of unsaturated FFAs with PLs.

Trends in the Design of New Isobaric Labeling Reagents for Quantitative Proteomics.

Modern mass spectrometry is one of the most frequently used methods of quantitative proteomics, enabling determination of the amount of peptides in a sample. Although mass spectrometry is not inherently a quantitative method due to differences in the ionization efficiency of various analytes, the application of isotope-coded labeling allows relative quantification of proteins and proteins. Over the past decade, a new method for derivatization of tryptic peptides using isobaric labels has been proposed. The labels consist of reporter and balanced groups. They have the same molecular weights and chemical properties, but differ in the distribution of stable heavy isotopes. These tags are designed in such a way that during high energy collision induced dissociation (CID) by tandem mass spectrometry, the isobaric tag is fragmented in the specific linker region, yielding reporter ions with different masses. The mass shifts among the reporter groups are compensated by the balancing groups so that the overall mass is the same for all forms of the reagent. Samples of peptides are labeled with the isobaric mass tags in parallel and combined for analysis. Quantification of individual peptides is achieved by comparing the intensity of reporter ions in the tandem mass (MS/MS) spectra. Isobaric markers have found a wide range of potential applications in proteomics. However, the currently available isobaric labeling reagents have some drawbacks, such as high cost of production, insufficient selectivity of the derivatization, and relatively limited enhancement of sensitivity of the analysis. Therefore, efforts have been devoted to the development of new isobaric markers with increased usability. The search for new isobaric markers is focused on developing a more selective method of introducing a tag into a peptide molecule, increasing the multiplexicity of markers, lowering the cost of synthesis, and increasing the sensitivity of measurement by using ionization tags containing quaternary ammonium salts. Here, the trends in the design of new isobaric labeling reagents for quantitative proteomics isobaric derivatization strategies in proteomics are reviewed, with a particular emphasis on isobaric ionization tags. The presented review focused on different types of isobaric reagents used in quantitative proteomics, their chemistry, and advantages offer by their application.

Iron(III) Complexes for Highly Efficient and Sustainable Ketalization of Glycerol: A Combined Experimental and Theoretical Study.

The growing production of biodiesel as a promising alternative and renewable fuel led as the main problem the dramatic increase of its by-product: glycerol. Different strategies for glycerol derivatization have been reported so far, some more efficient or sustainable than others. Herein, we report a very promising and eco-friendly transformation of glycerol in nontoxic solvents and chemicals (i.e., solketal, ketals), proposing three new families of Fe(III) compounds capable of catalysing glycerol acetalization with unpublished turn over frequencies (TOFs), and adhering most of the principles of green chemistry. The comparison between the activity of complexes of formula [FeCl3(1-R)] (1-R = substituted pyridinimine), [FeCl(2-R,R′)] (2-R,R′ = substituted O,O′-deprotonated salens) and their corresponding simple salts reveals that the former are extremely convenient because they are able to promote solketal formation with excellent TOFs, up to 105 h–1. Satisfactory performances were shown with respect to the entire range of substrates, with results being competitive to those reported in the literature so far. Moreover, the experimental activity was supported by an accurate and complete ab initio study, which disclosed the fundamental role of iron(III) as Lewis acid in promoting the catalytic activity. The unprecedented high activity and the low loading of the catalyst, combined with the great availability and the good eco-toxicological profile of iron, foster future applications of this catalytic process for the sustainable transformation of an abundant by-product in a variety of chemicals.

Revisiting the reactive chemistry of FOX-7: cyclization of FOX-7 affords the fused-ring polynitro compounds.

A novel fused-ring polynitro compound (5) and a cyclic compound featuring gem-dinitromethylene and nitroso groups (7) were synthesized from 1,1-diamino-2,2-dinitroethylene (FOX-7). Both compounds exhibit high density, decent thermal stability, high detonation performances, and low mechanical sensitivities. This newly developed derivatization strategy enriches the ever-expanding reactive chemistry of FOX-7.

Determination of Ultraviolet Filters in Domestic Wastewater by LC–MS Coupled with Polydopamine-Based Magnetic Solid-Phase Extraction and Isotope-Coded Derivatization

A selective and accurate liquid chromatography–mass spectrometry (LC-MS) method based on magnetic solid-phase extraction (MSPE) and isotope-coded derivatization was developed and validated. The magnetic polydopamine (Fe3O4@PDA) was prepared as sorbent for enrichment of ten ultraviolet (UV) filters from domestic wastewater samples. The obtained extract and standards were labeled by a pair of isotope-coded derivatization reagents d0-/d3-10-methylacridone-2-sulfonyl chloride (d0-/d3-MASC), respectively. The quantification of UV filters was achieved by calculation of the peak area ratios of d0-MASC/d3-MASC-labeled derivatives. The isotope-coded derivatization strategy was confirmed to be effective in reducing matrix effect and improving sensitivity. Excellent linearity is established with the correlation coefficients > 0.9922. The limits of detection (LODs) were in the range of 0.056–0.128 µg L−1, and the limits of quantitation (LOQs) were in the range of 0.193–0.315 µg L−1. The developed method has been successfully applied to the quantification of UV filters in domestic wastewater samples with recoveries ranging from 95.6 to 103.6%.

Endogenous Anti-Inflammatory Very-Long-Chain Dicarboxylic Acids: Potential Chemopreventive Lipids.

In a paradigm shift, cancer research efforts are being dedicated to the discovery of chemopreventive agents. The goal of this approach is to delay or prevent the progression of augmented cell division to established cancer. Research has focused on dietary supplements, drugs, and endogenous lipids that possess anti-inflammatory properties. We undertook a lipidomics analysis of potential endogenous anti-inflammatory/anti-proliferative lipids in human plasma. We performed high-resolution mass spectrometric lipidomics analyses of plasma samples from controls and patients with colorectal, kidney, pancreatic, glioblastoma, and breast cancers. We present evidence that endogenous very-long-chain dicarboxylic acids (VLCDCA) are anti-inflammatory lipids that possess chemopreventative properties. In a family of VLCDCAs, we characterized VLCDCA 28:4, which is decreased in the plasma of patients with colorectal, kidney, and pancreatic cancers. The structure of this biomarker was validated by derivatization strategies, synthesis of the analytical standard, and tandem mass spectrometry. Our data suggest that VLCDCA 28:4 may be a useful blood biomarker for a number of cancers and that resupplying this lipid, via a prodrug for example, may offer a new anti-inflammatory therapeutic strategy for delaying or preventing the progression of cancer and other inflammatory diseases.

Distinguishing enantiomeric amino acids with chiral cyclodextrin adducts and structures for lossless ion manipulations.

Enantiomeric molecular evaluations remain an enormous challenge for current analytical techniques. To date, derivatization strategies and long separation times are generally required in these studies, and the development and implementation of new approaches are needed to increase speed and distinguish currently unresolvable compounds. Herein, we describe a method using chiral cyclodextrin adducts and structures for lossless ion manipulations (SLIM) and serpentine ultralong path with extended routing (SUPER) ion mobility (IM) to achieve rapid, high resolution separations of d and l enantiomeric amino acids. In the analyses, a chiral cyclodextrin is added to each sample. Two cyclodextrins were found to complex each amino acid molecule (i.e. potentially sandwiching the amino acid in their cavities) and forming host-guest noncovalent complexes that were distinct for each d and l amino acid pair studied and thus separable with IM in SLIM devices. The SLIM was also used to accumulate much larger ion populations than previously feasible for evaluation and therefore allow enantiomeric measurements of higher sensitivity, with gains in resolution from our ultralong path separation capabilities, than previously reported by any other IM-based approach.

Chemical Derivatization Strategy for Extending the Identification of MHC Class I Immunopeptides.

Neoantigen-based therapeutic vaccines have a high potential impact on tumor eradication and patient survival. Mass spectrometry (MS)-based immunopeptidomics has the capacity to identify tumor-associated epitopes and pinpoint mutation-bearing major histocompatibility complex (MHC)-binding peptides. This approach presents several challenges, including the identification of low-abundance peptides. In addition, MHC peptides have much lower MS/MS identification rates than tryptic peptides due to their shorter sequence and lack of basic amino acid at C-termini. In this study, we report the development and application of a novel chemical derivatization strategy that combines the analysis of native, dimethylated, and alkylamidated peptides by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to expand the coverage of the MHC peptidome. The results revealed that dimethylation increases hydrophobicity and ionization efficiency of MHC class I peptides, while alkylamidation significantly improves the fragmentation by producing more y-ions during MS/MS fragmentation. Thus, the combination of dimethylation and alkylamidation enabled the identification of peptides that could not be identified from the analysis of their native form. Using this strategy, we identified 3148 unique MHC I peptides from HCT 116 cell lines, compared to only 1388 peptides identified in their native form. Among these, 10 mutation-bearing peptides were identified with high confidence, indicating that this chemical derivatization strategy is a promising approach for neoantigen discovery in clinical applications.

Speciation of reactive sulfur species and their reactions with alkylating agents: do we have any clue about what is present inside the cell?

Buffered aqueous solutions of inorganic, organic, cysteine, GSH and GAPDH polysulfide species were used. Additional experiments in human plasma and serum revealed that monobromobimane can extract sulfide from the endogenous sulfur pool by shifting speciation equilibria, suggesting caution should be exercised when interpreting experimental results using this tool. In the majority of cases, the speciation of alkylated polysulfide/thiol derivatives depended on the experimental conditions. Alkylation perturbed sulfur speciation in both a concentration- and time-dependent manner and strong alkylating agents cleaved polysulfur chains. Moreover, the labelling of sulfenic acids with dimedone also affected cysteine speciation, suggesting that part of the endogenous pool of products previously believed to represent sulfenic acid species may represent polysulfides. We highlight methodological caveats potentially arising from these pitfalls and conclude that current derivatization strategies often fail to adequately capture physiological speciation of sulfur species. This article is part of a themed section on Chemical Biology of Reactive Sulfur Species. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.4/issuetoc.

Sensitive monitoring of taurine biomarker in unprocessed human plasma samples using a novel nanocomposite based on poly(aspartic acid) functionalized by graphene quantum dots.

The rapid and accurate determination of the level of taurine biomarker in various tissues and body fluids can be of great interest in the early diagnosis of several important pathologies and diseases. For the first time, this study reports on the electropolymerization of a low toxic and biocompatible nanocomposite "poly(aspartic acid)-graphene quantum dots (GQDs)" as a novel strategy for surface modification of glassy carbon electrode and preparation a new interface for measurement of taurine. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs nanostructures on poly(aspartic acid) using cyclic voltammetry techniques in the regime of -1.5 to 2V. The field emission scanning electron microscopy indicated immobilization of uniformly GQDs onto poly(aspartic acid) film. The modified electrode appeared as an effective electroactivity for detection of taurine biomarker using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of poly(aspartic acid) as semiconducting polymer, GQDs as high density of edge plane sites, and subtle electronic characteristics to chemical modification. Under the optimized analysis conditions, the prepared sensor for detection of taurine showed a low limit of quantification 0.001mM. Finally, the resulting prepared sensor allow the quantification of these biomarkers directly in biological samples without need of derivatization schemes or sample pretreatment.

Improved de novo sequencing of heparin/heparan sulfate oligosaccharides by propionylation of sites of sulfation

The structure of heparin and heparan sulfate (Hep/HS) oligosaccharides, as determined by the length and the pattern of sulfation, acetylation, and uronic acid epimerization, dictates their biological function through modulating interactions with protein targets. But fine structural determination is a very challenging task due to the lability of the sulfate modifications and difficulties in separating isomeric HS chains. Previously, we reported a strategy for chemical derivatization involving permethylation, desulfation, and trideuteroperacetylation, combined with standard reverse phase LC-MS/MS that enables the structural sequencing for heparin/HS oligosaccharides of sizes up to dodecasaccharide by positionally replacing all sulfates with more stable trideuteroacetyl groups, allowing for robust MS/MS sequencing. However, isomeric oligosaccharides that contain both N-sulfation and N-acetylation become isotopomers after labeling, differing only in the sites of deuteration. This prevents chromatographic separation of these different mixed domain sequences post-derivatization, and makes sequencing by MS/MS difficult due to co-fragmentation of the isotopomers leading to chimeric product ion spectra. In order to improve chromatographic separation of mixed domain oligosaccharides, we have introduced a propionylation step in place of trideuteroacetylation for labeling of sites of sulfation. HS standard disaccharides have been used to evaluate the efficiency of this improved chemical derivatization. The results show that we can quantitatively replace sulfation with propionyl groups with the same high efficiency as the previously reported trideuteroacetylation. After derivatization, we demonstrate the ability to chromatographically separate two mixed domain tetrasaccharide isomers differing solely by the order of N-sulfation and N-acetylation, allowing for full sequencing of each by MS/MS. These results represent a marked improvement in the ability of our previously reported derivatization strategy to analyze complex mixtures of Hep/HS oligosaccharides without a decrease in sensitivity.

Diversity Driven Decoration and Ligation of Fullerene by Ugi and Passerini Multicomponent Reactions.

Aiming at providing an efficient and versatile method for the diversity-oriented decoration and ligation of fullerenes, we report the first C60 derivatization strategy based on isocyanide-multicomponent reactions (I-MCRs). The approach comprises the use of Passerini and Ugi reactions for assembling pseudo-peptidic scaffolds (i.e., N-alkylated and depsipeptides, peptoids) on carboxylic acid-functionalized fullerenes. The method showed wide substrate scope for the oxo and isocyanide components, albeit the Ugi reaction proved efficient only for aromatic amines. The approach was successfully employed for the ligation of oligopeptides and polyethyleneglycol chains (PEG) to C60 , as well as for the construction of bis-antennary as well as PEG-tethered dimeric fullerenes. The quantum yields for the formation of 1 O2 was remarkable for the selected compounds analyzed.

A comparative analysis of derivatization strategies for the determination of biogenic amines in sausage and cheese by HPLC

The six biogenic amines in sausage and cheese were analyzed by HPLC with UV detection after off-line derivatization with dansyl chloride, 9-fluorenylmethoxycarbonyl chloride, benzoyl chloride and dabsyl chloride, respectively. The results showed that both the off-line 9-fluorenylmethoxycarbonyl and dabsyl derivatization were not suitable for HPLC analysis of biogenic amines when batch injection was used because the derivatives were instable, whereas both the off-line dansyl and benzoyl derivatization were suitable for HPLC analysis of biogenic amines when batch injection was used, but the latter needed to maintain the derivatives at 4 °C to ensure that benzoylated tyramine was not degraded when waiting for the analysis. The off-line dansyl derivatization had an obvious advantage in the analysis of biogenic amines in sausage and cheese samples by HPLC combined with batch injection because the method has a wider linear range and higher sensitivity, accuracy, precision and stability of the derivatives.

Hydrofluoric Acid-Based Derivatization Strategy To Profile PARP-1 ADP-Ribosylation by LC-MS/MS.

Despite significant advances in the development of mass spectrometry-based methods for the identification of protein ADP-ribosylation, current protocols suffer from several drawbacks that preclude their widespread applicability. Given the intrinsic heterogeneous nature of poly(ADP-ribose), a number of strategies have been developed to generate simple derivatives for effective interrogation of protein databases and site-specific localization of the modified residues. Currently, the generation of spectral signatures indicative of ADP-ribosylation rely on chemical or enzymatic conversion of the modification to a single mass increment. Still, limitations arise from the lability of the poly(ADP-ribose) remnant during tandem mass spectrometry, the varying susceptibilities of different ADP-ribose-protein bonds to chemical hydrolysis, or the context dependence of enzyme-catalyzed reactions. Here, we present a chemical-based derivatization method applicable to the confident identification of site-specific ADP-ribosylation by conventional mass spectrometry on any targeted amino acid residue. Using PARP-1 as a model protein, we report that treatment of ADP-ribosylated peptides with hydrofluoric acid generates a specific +132 Da mass signature that corresponds to the decomposition of mono- and poly(ADP-ribosylated) peptides into ribose adducts as a consequence of the cleavage of the phosphorus-oxygen bonds.

EpiProfile 2.0: A Computational Platform for Processing Epi-Proteomics Mass Spectrometry Data.

Epigenetics has become a fundamental scientific discipline with various implications for biology and medicine. Epigenetic marks, mostly DNA methylation and histone post-translational modifications (PTMs), play important roles in chromatin structure and function. Accurate quantification of these marks is an ongoing challenge due to the variety of modifications and their wide dynamic range of abundance. Here we present EpiProfile 2.0, an extended version of our 2015 software (v1.0), for accurate quantification of histone peptides based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. EpiProfile 2.0 is now optimized for data-independent acquisition through the use of precursor and fragment extracted ion chromatography to accurately determine the chromatographic profile and to discriminate isobaric forms of peptides. The software uses an intelligent retention time prediction trained on the analyzed samples to enable accurate peak detection. EpiProfile 2.0 supports label-free and isotopic labeling, different organisms, known sequence mutations in diseases, different derivatization strategies, and unusual PTMs (such as acyl-derived modifications). In summary, EpiProfile 2.0 is a universal and accurate platform for the quantification of histone marks via LC-MS/MS. Being the first software of its kind, we anticipate that EpiProfile 2.0 will play a fundamental role in epigenetic studies relevant to biology and translational medicine. EpiProfile is freely available at https://github.com/zfyuan/EpiProfile2.0_Family .

Increasing the Efficiency of Amino Acids Detection By Electrochemical Methods on Amorphous Carbon Nitride a-CNx Electrodes

The naphthalene-2,3-dicarboxyaldehyde (NDA) label is widely used for the derivatization of amino acids (AAs) to form N-2-substituted-1-cyanobenz-[f]-isoindole derivatives (CBI) which are both fluorescent and electroactive. [1],[2] Optimal conditions for labeling were previously obtained when [NDA]tot/[CN-] ratio =1 and [NDA]tot /[amino acid or peptide]=40 with a buffer pH of 10. [3],[4] The detection step was achieved by using a carbon reference material (glassy carbon electrode ) exhibiting an obvious oxidation peak for CBI-AA observed at 0.5V/SCE [1]. These experiments confirmed that NDA can by used as a derivative agent for non electroactive AA, allowing for simultaneous electrochemical and fluorescence detections. In this work, amorphous carbon nitride a-CN0.26 thin films were elaborated on transparent and conductive glass/indium-tin oxide (ITO) wafers to improve the electroanalytical detection of AAs. The results obtained on as-grown a-CN0.26 were compared to the glassy carbon (GC). It was shown that a soft anodic pre-treatment protocol on glass/ITO/a-CN0.26 electrode in KCl solution drastically improved the CBI-AA oxidation peak performances. The oxidation peak potential for all CBI derivatives varied in the same range that those on GC and pre-treated glass/ITO/a-CN0.26, while no discrimination could be obtained for as-grown glass/ITO/a-CN0.26. For almost all the tested CBI derivatives, the electrochemical properties determined by electrochemical impedance spectroscopy (R ct, charge transfert resistance) and by differential pulse voltammetry (peak areas, full-widths at peak mid-height, peak current density and their SD values) were improved on pre-treated a-CN0.26 in comparison with GC. [1] M. Faure, S. Korchane, I. Le Potier, A. Pallandre, C. Deslouis, A.-M. Haghiri-Gosnet, J. Gamby, Investigating of labeling and detection of transthyretin synthetic peptide derivatized with naphthalene-2,3-dicarboxaldehyde, Talanta, 116 (2013) 8-13. [2] M. Faure, A. Pallandre, S. Chebil, I. Le Potier, M. Taverna, B. Tribollet, C. Deslouis, A.-M. Haghiri-Gosnet, J. Gamby, Improved electrochemical detection of a transthyretin synthetic peptide in the nanomolar range with a two-electrode system integrated in a glass/PDMS microchip, Lab Chip, 14 (2014) 2800-2805. [3] S. Korchane, A. Pallandre, C. Przybylski, C. Poas, F. Gonnet, M. Taverna, R. Daniel, I. Le Potier, Derivatization strategies for CE-LIF analysis of biomarkers: Toward a clinical diagnostic of familial transthyretin amyloidosis, Electrophoresis, 35 (2014) 1050-1059. [4] M. Faure, I. Le Potier, A. Pallandre, S. Chebil, A.-M. Haghiri-Gosnet, C. Deslouis, E. Maisonhaute, J. Gamby, Determination of the isomeric forms proportion of fluorogenic naphthalene-2,3-dicarboxaldehyde in a binary mixture of water:methanol using electrochemical methods, Talanta, 148 (2016) 494-501.

Establishment of a Charge Reversal Derivatization Strategy to Improve the Ionization Efficiency of Limaprost and Investigation of the Fragmentation Patterns of Limaprost Derivatives Via Exclusive Neutral Loss and Survival Yield Method.

Sensitivity is generally an issue in bioassays of prostaglandins and their synthetic analogs due to their extremely low concentration in vivo. To improve the ionization efficiency of limaprost, an oral prostaglandin E1 (PGE1) synthetic analog, we investigated a charge reversal derivatization strategy in electrospray ionization mass spectrometry (ESI-MS). We established that the cholamine derivative exhibits much greater signal intensity in the positive-ion mode compared with limaprost in the negative ion mode. Collision-induced dissociation (CID) involved exclusive neutral mass loss and positive charge migration to form stable cationic product ions with the positive charge on the limaprost residue rather than on the modifying group. This has the effect of maintaining the efficiency and specificity of multiple reaction monitoring (MRM) and avoiding cross talk. CID fragmentation patterns of other limaprost derivatives allowed us to relate the dissociation tendency of different neutral leaving groups to an internal energy distribution scale based on the survival yield method. Knowledge of the energy involved in the production of stabilized positive ions will potentially assist the selection of suitable derivatization reagents for the analysis of a wide variety of lipid acids. Graphical Abstract ᅟ.

Synthesis of Novel Amino Lactose and Evaluation of Its Antioxidant Property

In order to improve the bioactivity of lactose, a novel lactose derivative is designed and synthesized by introducing an amino group to the C‐6 of lactose. The in vitro antioxidant activities of synthesized lactose derivatives are assessed. It shows better scavenging activity against hydrogen peroxide (IC50 < 0.1 mg mL−1), hydroxyl radicals (IC50 0.55 mg mL−1), and DPPH radicals (IC50 0.37 mg mL−1) than lactose. Based on this data, it is reasonable to propose that the introduction of amino group through chemical modification is significant to enhance the free antioxidant activity of lactose. This derivatization strategy might provide an effective tool to broaden utilization of lactose.

HPLC-CUPRAC post-column derivatization method for the determination of antioxidants: a performance comparison between porous silica and core-shell column packing

BackgroundAn HPLC method employing a post-column derivatization strategy using the cupric reducing antioxidant capacity reagent (CUPRAC reagent) for the determining antioxidants in plant-based materials leverages the separation capability of regular HPLC approaches while allowing for detection specificity for antioxidants.MethodsThree different column types, namely core-shell and porous silica including two chemically different core-shell materials (namely phenyl-hexyl and C18), were evaluated to assess potential improvements that could be attained by changing from a porous silica matrix to a core-shell matrix. Tea extracts were used as sample matrices for the evaluation specifically looking at catechin and epigallocatechin gallate (EGCG).ResultsBoth the C18 and phenyl-hexyl core-shell columns showed better performance compared to the C18 porous silica one in terms of separation, peak shape, and retention time. Among the two core-shell materials, the phenyl-hexyl column showed better resolving power compared to the C18 column.ConclusionsThe CUPRAC post-column derivatization method can be improved using core-shell columns and suitable for quantifying antioxidants, exemplified by catechin and EGCG, in tea samples.