Optimized 13C-TrEnDi Enhances the Sensitivity of Plasmenyl Ether Glycerophospholipids and Demonstrates Compatibility with Other Derivatization Strategies.

The identification and quantitation of plasmalogen glycerophospholipids is challenging due to their isobaric overlap with plasmanyl ether-linked glycerophospholipids, susceptibility to acid degradation, and their typically low abundance in biological samples. Trimethylation enhancement using diazomethane (TrEnDi) can be used to significantly enhance the signal of glycerophospholipids through the creation of quaternary ammonium groups producing fixed positive charges using 13C-diazomethane in complex lipid extracts. Although TrEnDi requires a strong acid for complete methylation, we report an optimized protocol using 10 mM HBF4 with the subsequent addition of a buffer solution that prevents acidic hydrolysis of plasmalogen species and enables the benefits of TrEnDi to be realized for this class of lipids. These optimized conditions were applied to aliquots of bovine liver extract (BLE) to achieve permethylation of plasmalogen lipids within a complex mixture. Treating aliquots of unmodified and TrEnDi-derivatized BLE samples with 80% formic acid and comparing their liquid chromatography mass spectrometry (LCMS) results to analogous samples not treated with formic acid, enabled the identification of 29 plasmalogen species. On average, methylated plasmalogen species from BLE demonstrated 2.81-fold and 28.1-fold sensitivity gains over unmodified counterparts for phosphatidylcholine and phosphatidylethanolamine plasmalogen species, respectively. Furthermore, the compatibility of employing 13C-TrEnDi and a previously reported iodoacetalization strategy was demonstrated to effectively identify plasmenyl-ether lipids in complex biological extracts at greater levels of sensitivity. Overall, we detail an optimized 13C-TrEnDi derivatization strategy that enables the analysis of plasmalogen glycerophospholipids with no undesired cleavage of radyl groups, boosting their sensitivity in LCMS and LCMS/MS analyses.

Isomer-Resolved Mass Spectrometry Imaging of Acidic Phospholipids.

The biological functions of lipids are entirely dependent on their molecular structures with even small changes in structure─such as different sites of unsaturation─providing critical markers for changes in the underlying metabolism. Conventional mass spectrometry imaging (MSI) approaches, however, face the twin challenges of mixture and structural complexity and are typically unable to differentiate lipid isomers that differ only in the position(s) of carbon-carbon double bonds. Recent coupling of ozone-induced dissociation (OzID) with matrix-assisted laser desorption/ionization (MALDI)-MSI has demonstrated the potential to map changes in individual double-bond isomers, thus enabling visualization of the modulation in lipid desaturation in adjacent tissue types. This has, to date, only been performed in positive-ion mode due to a generally higher abundance of phosphatidylcholines (PC) in mammalian tissues and the efficient desorption/ionization of this lipid subclass. Many other glycerophospholipids (GPLs), however, are better detected in negative-ion mode as deprotonated anions. Recently, OzID has been implemented on a traveling-wave ion-mobility mass spectrometer (Waters, SYNAPT G2-Si) that provides a 50-fold increase in the rate of the gas-phase reaction between ionized lipids and ozone and a commensurate increase in sensitivity for isomer-resolved mass spectrometry. These gains are exploited here to interrogate the distributions of anionic GPL isomers in biological tissues, covering the subclasses phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylglycerol (PG), and phosphatidic acid (PA). Exploiting both ozone- and collision-induced dissociation in a single acquisition simultaneously identifies sites of unsaturation and acyl chain composition from the same mass spectrum.

Deep-profiling of phospholipidome via rapid orthogonal separations and isomer-resolved mass spectrometry.

A lipidome comprises thousands of lipid species, many of which are isomers and isobars. Liquid chromatography-tandem mass spectrometry (LC-MS/MS), although widely used for lipidomic profiling, faces challenges in differentiating lipid isomers. Herein, we address this issue by leveraging the orthogonal separation capabilities of hydrophilic interaction liquid chromatography (HILIC) and trapped ion mobility spectrometry (TIMS). We further integrate isomer-resolved MS/MS methods onto HILIC-TIMS, which enable pinpointing double bond locations in phospholipids and sn-positions in phosphatidylcholine. This system profiles phospholipids at multiple structural levels with short analysis time (<10 min per LC run), high sensitivity (nM detection limit), and wide coverage, while data analysis is streamlined using a home-developed software, LipidNovelist. Notably, compared to our previous report, the system doubles the coverage of phospholipids in bovine liver and reveals uncanonical desaturation pathways in RAW 264.7 macrophages. Relative quantitation of the double bond location isomers of phospholipids and the sn-position isomers of phosphatidylcholine enables the phenotyping of human bladder cancer tissue relative to normal control, which would be otherwise indistinguishable by traditional profiling methods. Our research offers a comprehensive solution for lipidomic profiling and highlights the critical role of isomer analysis in studying lipid metabolism in both healthy and diseased states.

Improved Structural Characterization of Glycerophospholipids and Sphingomyelins with Real-Time Library Searching.

In mass spectrometry-based lipidomics, complex lipid mixtures undergo chromatographic separation, are ionized, and are detected using tandem MS (MSn) to simultaneously quantify and structurally characterize eluting species. The reported structural granularity of these identified lipids is strongly reliant on the analytical techniques leveraged in a study. For example, lipid identifications from traditional collisionally activated data-dependent acquisition experiments are often reported at either species level or molecular species level. Structural resolution of reported lipid identifications is routinely enhanced by integrating both positive and negative mode analyses, requiring two separate runs or polarity switching during a single analysis. MS3+ can further elucidate lipid structure, but the lengthened MS duty cycle can negatively impact analysis depth. Recently, functionality has been introduced on several Orbitrap Tribrid mass spectrometry platforms to identify eluting molecular species on-the-fly. These real-time identifications can be leveraged to trigger downstream MSn to improve structural characterization with lessened impacts on analysis depth. Here, we describe a novel lipidomics real-time library search (RTLS) approach, which utilizes the lipid class of real-time identifications to trigger class-targeted MSn and to improve the structural characterization of phosphotidylcholines, phosphotidylethanolamines, phosphotidylinositols, phosphotidylglycerols, phosphotidylserine, and sphingomyelins in the positive ion mode. Our class-based RTLS method demonstrates improved selectivity compared to the current methodology of triggering MSn in the presence of characteristic ions or neutral losses.

Metabolic profiles in the xylem sap of Brassica juncea exposed to cadmium.

Metabolic profiles in xylem sap are considered a fundamental mechanism for Cadmium (Cd) detoxification in plants. However, the metabolic mechanism of Brassica juncea xylem sap in response to Cd is still unclear. Here, we investigated the effects on the metabolomics of B. juncea xylem sap treated with Cd at different times by utilizing a nontargeted liquid chromatography-mass spectrometry (LC-MS)-based metabolomics method for further elucidating the response mechanism of Cd exposure. The findings indicated that 48 h and 7 days Cd exposure caused significant differences in metabolic profiles of the B. juncea xylem sap. Those differential metabolites are primarily involved in amino acids, organic acids, lipids, and carbohydrates, and most of them were downregulated, which played essential roles in response to Cd stress. Furthermore, B. juncea xylem sap resisted 48-h Cd exposure via regulation of glycerophospholipid metabolism, carbon metabolism, aminoacyl-tRNA biosynthesis, glyoxylate and dicarboxylate metabolism, linoleic acid metabolism, C5-branched dibasic acid metabolism, alpha-linolenic acid metabolism, cyanoamino acid metabolism, ABC transporters, biosynthesis of amino acids, and pyrimidine metabolism; whereas alpha-linolenic acid metabolism, glycerophospholipid metabolism, photosynthesis, and oxidative phosphorylation were regulated for resisting 7-day Cd exposure.

Determination of eight phosphatidylethanol homologues in blood by reversed phase liquid chromatography-tandem mass spectrometry - How to avoid co-elution of phosphatidylethanols and unwanted phospholipids.

Phosphatidylethanols (PEths) are specific, direct alcohol biomarkers with a substantially longer half-life than ethanol, and can be used to distinguish between heavy- and social drinking. More than forty PEth homologues have been detected in blood from heavy drinkers, and PEth 16:0/18:1 is the predominant one. Since PEths are phospholipids it can be difficult to isolate them from unwanted phospholipids during sample preparation. To minimize possible matrix effects it is therefore important to separate PEths from other phospholipids during LC-MS/MS analysis. In this study, we have investigated how the retention and chromatographic separation of eight PEth homologues and the phospholipid background are influenced by changes in mobile phase composition using two different LC columns, the Acquity BEH C18 column (50 × 2.1 mm ID, 1.7 µm particles) and the Kinetex biphenyl column (100 × 2.1 mm ID, 1.7 µm particles). Our findings show that the buffer concentration of the aqueous part of the mobile phase had a huge effect on the retention of PEth homologues and separation of PEths from unwanted phospholipids. By using a buffer-free mobile phase consisting of 0.025% ammonia in Type 1 water, pH 10.7, as solvent A and methanol as solvent B, all eight PEth homologues were separated from both the early eluting lyso-phospholipids and the later eluting phospholipids with two fatty chains using the BEH C18 column. The knowledge obtained in this study can be of great importance for those seeking to develop reliable and robust bioanalytical LC-MS/MS methods for determination of PEth homologues.

Detection and characterization of lipids in eleven species of fish by non-targeted liquid chromatography/mass spectrometry.

Fish is an important nutrition source because its lipids, which are rich in ω-3 fatty acids, are beneficial for human health. However, studies focusing on their detection, composition, and nutritional value are limited. In this study, we applied a non-targeted lipidomic approach based on ultra-high performance liquid chromatography coupled with linear-ion trap-Orbitrap mass spectrometry (UHPLC/LTQ-Orbitrap-MS) to comprehensively profile, compare, and detect unknown lipids in eleven types of dietary fish. A total of 287 molecular species from five major lipid classes were characterized by MS/MS analysis. Multivariate principal component analysis revealed the distinct lipid composition in shishamo smelt and Japanese sardine compared to other fish types. The assessment of nutritional indices based on the levels of free fatty acid suggested that among the eleven fish types, shishamo smelt is highly beneficial for health. Further, lipids such as N-acyl lysophosphatidylethanolamine were detected and characterized for the first time in fish fillets. Hierarchical cluster correlations indicated the predominance of glycerophospholipids (GPs) and sphingolipids in sardine, whereas fatty acyls and triacylglycerols (TAGs) were predominant in shishamo smelt. The high levels of polyunsaturated fatty acid-enriched GPs and TAGs in dietary fish endow it with great potential as a health-promoting food for human consumption. This study offers a comprehensive analysis of lipids and their compositions in fish fillets, demonstrating their potential use in the nutritional assessment of functional foods.

Quantitative determination of sn-positional phospholipid isomers in MSn using silver cationization.

Glycerophospholipids are one of the fundamental building blocks for life. The acyl chain connectivity to the glycerol backbone constitutes different sn-positional isomers, which have great diversity and importance for biological function. However, to fully realize their impact on function, analytical techniques that can identify and quantify sn-positional isomers in chemically complex biological samples are needed. Here, we utilize silver ion cationization in combination with tandem mass spectrometry (MSn) to identify sn-positional isomers of phosphatidylcholine (PC) species. In particular, a labile carbocation is generated through a neutral loss (NL) of AgH, the dissociation of which provides diagnostic product ions that correspond to acyl chains at the sn-1 or sn-2 position. The method is comparable to currently available methods, has a sensitivity in the nM-µM range, and is compatible with quantitative imaging using mass spectrometry in MS4. The results reveal a large difference in isomer concentrations and the ion images show that the sn-positional isomers PC 18:1_18:0 are homogeneously distributed, whereas PC 18:1_16:0 and PC 20:1_16:0 show distinct localizations to sub-hippocampal structures.

Maternal and fetal metabolomic alterations in maternal lipopolysaccharide exposure-induced male offspring glucose metabolism disorders.

Maternal lipopolysaccharide (LPS) exposure during pregnancy induces metabolic abnormalities in male offspring, but the underlying mechanisms remain unclear. The purpose of this study was to investigate the effects of maternal LPS exposure during pregnancy on metabolic profiling of maternal serum and male fetal liver using Liquid Chromatograph Mass Spectrometer techniques. From day 15 to day 17 of gestation, pregnant mice were administered intraperitoneal LPS (experimental group) (50 µg/kg/d) or saline (control group). On day 18 of gestation, maternal serum and male fetal liver were collected. After LPS exposure, levels of 38 and 75 metabolites, mainly glycerophospholipid and fatty acid metabolites, were altered in maternal serum and male fetal liver, respectively. It was found that in maternal serum and male fetal livers, the glycerophospholipids containing saturated fatty acids (SFAs) and the SFAs were upregulated, while the glycerophospholipids containing polyunsaturated fatty acids (PUFAs) and the PUFAs were downregulated. This concordance between maternal and fetal alterations in glycerophospholipid and fatty acid metabolites may be a metabolomic signature of the early intrauterine period and may provide insight into the mechanisms by which maternal LPS exposure induces disorders of glucose metabolism in male offspring.

Protective mechanism of Astragalus Polysaccharides against Cantharidin-induced liver injury determined in vivo by liquid chromatography/mass spectrometry metabolomics.

Cantharidin (CTD) is a promising anticancer drug; however, its dosage is limited by hepatotoxicity. We previously showed that Astragalus polysaccharides (APS) effectively improved chemical liver injury. In this study, we established a CTD-induced subacute liver injury mouse model and examined the effects of APS on weight, liver indexes, histopathology, serum biochemical indexes and liver metabolism. Compared with the control group, mice in the CTD model group had obvious liver damage, which was partially prevented by APS. Metabolomics demonstrated that CTD caused liver damage mainly by regulating glycerophospholipid metabolism, ABC transporter pathways and choline metabolism in cancer in vivo. APS regulated primary bile acid biosynthesis and glycerophospholipid metabolism, thus decreasing the liver damage caused by CTD. This study revealed the protective mechanism of APS against CTD-induced liver injury from the perspective of metabolomics. The results provide an important basis for analysing the mechanism of CTD-induced liver toxicity and for assessing clinical treatment options to reduce CTD liver toxicity.

Stability of phosphatidylethanol 16:0/18:1 in authentic and spiked whole blood.

Phosphatidylethanol 16:0/18:1 (PEth) is the most abundant homologue of the phosphatidylethanol group of phospholipids. Formed only in the presence of ethanol, PEth is used as a biomarker in whole blood to provide information about the consumption of alcohol. As information on the storage life of PEth is essential for its beneficial use as a biomarker, this study investigated the stability of PEth in spiked and authentic whole blood samples stored at 4°C. Human whole blood samples (n = 23) and spiked whole blood samples (n = 7) with a concentration range between 5 and 2000 ng/ml were analysed at specific time intervals, up to 90 days. Differences were evident between the stability of authentic and spiked samples. PEth was stable at 4°C for 60 days (concentrations within 15% of initial concentration) in authentic samples, whereas spiked samples were stable for up to 30 days. This study emphasizes the importance of including authentic samples in stability experiments.

Analysis of six different homologues of phosphatidylethanol from dried blood spots using liquid chromatography-tandem mass spectrometry.

Phosphatidylethanol (PEth) is a direct biomarker for alcohol consumption consisting of a fraction of different ethanol-modified, homologue phospholipids. The aim of this study was to validate an ultra-high-performance liquid chromatography-tandem mass spectrometry method to quantitate six different homologues of PEth (16:0/18:1, 16:0/18:2, 16:0/20:4, 18:0/18:1, 18:0/18:2, and 18:1/18:1) from dried blood spots (DBSs). DBSs were prepared volumetrically (20 µL of whole blood) and extracted with 1 mL of methanol (0.02 ng/µL internal standards). PEth homologues were separated on a BEH C18 column (2.1 × 150 mm, 1.7 µm) using methanol and ammonium acetate buffer (25 mM) in a 7 min isocratic run. Multiple reaction monitoring mode was used for the detection of PEth and the internal standards. Calibrators (10-1000 ng/mL) and quality controls (40, 400, and 700 ng/mL) were prepared from spiked whole blood; external control samples were obtained from proficiency testing schemes. After a comprehensive validation of the method, quantitative patterns of the different homologues were investigated in PEth positive samples (n = 57) from patients in a transplant setting. Satisfactory chromatographic separation, sensitive detection, and reliable quantification of the PEth homologues in DBSs can be achieved using the liquid chromatography-tandem mass spectrometry (LC/MS/MS) procedure. Validation results, including accuracy, linearity, recovery, matrix effects, and in-process stability, complied with international standards, and the analytical performance of the procedure was not affected by the hematocrit of the blood samples. Different quantitative patterns of the investigated PEth homologues were observed in authentic samples from liver transplant patients. This method will enable the study of the kinetics of six PEth homologues simultaneously and investigate the meaning of the homologues' distribution in individuals.

Lipid profile of Trichinella papuae muscle-stage larvae.

Outbreaks of trichinellosis caused by Trichinella papuae have been reported in South-East Asia. Mebendazole and thiabendazole are the treatments of choice for trichinellosis; however, both drugs result in significant side effects and are less effective for muscle-stage larvae (L1). An alternative therapeutic agent is needed to improve treatment. Information on lipid composition and metabolic pathways may bridge gaps in our knowledge and lead to new antiparasitics. The T. papuae L1 lipidome was analysed using a mass spectrometry-based approach, and 403 lipid components were identified. Eight lipid classes were found and glycerophospholipids were dominant, corresponding to 63% of total lipids, of which the glycerolipid DG (20:1[11Z]/22:4[7Z,10Z,13Z,16Z]/0:0) (iso2) was the most abundant. Overall, 57% of T. papuae lipids were absent in humans; therefore, lipid metabolism may be dissimilar in the two species. Proteins involved T. papuae lipid metabolism were explored using bioinformatics. We found that 4-hydroxybutyrate coenzyme A transferase, uncharacterized protein (A0A0V1MCB5) and ML-domain-containing protein are not present in humans. T. papuae glycerophospholipid metabolic and phosphatidylinositol dephosphorylation processes contain several proteins that are dissimilar to those in humans. These findings provide insights into T. papuae lipid composition and metabolism, which may facilitate the development of novel trichinellosis treatments.

Unsaturation Elements and Other Modifications of Phospholipids in Bacteria: New Insight from Ultraviolet Photodissociation Mass Spectrometry.

Glycerophospholipids (GPLs), one of the main components of bacterial cell membranes, exhibit high levels of structural complexity that are directly correlated with biophysical membrane properties such as permeability and fluidity. This structural complexity arises from the substantial variability in the individual GPL structural components such as the acyl chain length and headgroup type and is further amplified by the presence of modifications such as double bonds and cyclopropane rings. Here we use liquid chromatography coupled to high-resolution and high-mass-accuracy ultraviolet photodissociation mass spectrometry for the most in-depth study of bacterial GPL modifications to date. In doing so, we unravel a diverse array of unexplored GPL modifications, ranging from acyl chain hydroxyl groups to novel headgroup structures. Along with characterizing these modifications, we elucidate general trends in bacterial GPL unsaturation elements and thus aim to decipher some of the biochemical pathways of unsaturation incorporation in bacterial GPLs. Finally, we discover aminoacyl-PGs not only in Gram-positive bacteria but also in Gram-negative C. jejuni, advancing our knowledge of the methods of surface charge modulation that Gram-negative organisms may adopt for antibiotic resistance.

Localization of Double Bonds in Bacterial Glycerophospholipids Using 193 nm Ultraviolet Photodissociation in the Negative Mode.

The need for detailed structural characterization of glycerophospholipids (GPLs) for many types of biologically motivated applications has led to the development of novel mass spectrometry-based methodologies that utilize alternative ion activation methods. Ultraviolet photodissociation (UVPD) has shown great utility for localizing sites of unsaturation within acyl chains and to date has predominantly been used for positive mode analysis of GPLs. In the present work, UVPD is used to localize sites of unsaturation in GPL anions. Similar to UVPD mass spectra of GPL cations, UVPD of deprotonated or formate-adducted GPLs yields diagnostic fragment ions spaced 24 Da apart. This method was integrated into a liquid chromatography workflow and used to evaluate profiles of sites of unsaturation of lipids in Escherichia coli (E. coli) and Acinetobacter baumannii (A. baumannii). When assigning sites of unsaturation, E. coli was found to contain all unsaturation elements at the same position relative to the terminal methyl carbon of the acyl chain; the first carbon participating in a site of unsaturation was consistently seven carbons along the acyl chain when counting carbons from the terminal methyl carbon. GPLs from A. baumannii exhibited more variability in locations of unsaturation. For GPLs containing sites of unsaturation in both acyl chains, an MS3 method was devised to assign sites to specific acyl chains.

Charge Distribution between Different Classes of Glycerophospolipids in MALDI-MS Imaging.

Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) is widely used to visualize and analyze the distribution of membrane lipids in an increasingly large number of applications. In this context, different lipoforms of glycerophospholipids (GPLs) are among the prime targets of interest. For this group of analytes, however, ion suppression effects have been described to strongly favor the detection of certain GPL classes over others, thereby hampering the analysis of suppressed species and greatly restraining quantitative analysis. These effects are generally attributed to the distribution of available charge carriers during the MALDI process. Here, we present a systematic investigation of charge distribution between different classes of GPL under MALDI-MSI conditions. For this, we constructed arrays of artificial tissues with different formulated lipid composition that contained predefined amounts of only two specific GPL classes and analyzed them with MALDI-MSI in positive- and negative-ion modes. Next to a characterization of expected ion suppression effects, analysis of these binary systems revealed yet undescribed signal intensity enhancement for the combinations of certain GPL classes. Furthermore, the comprehensive data allowed us to compile a hierarchy of charge affinities for the investigated GPL classes in both polarities. Additional experiments revealed that laser post-ionization (MALDI-2) has great potential to overwrite changes in signal intensity caused by charge distribution among different GPL classes observed in standard MALDI-MSI.

Metabolic responses of BV-2 cells to puerarin on its polarization using ultra-performance liquid chromatography-mass spectrometry.

Microglia are the primary immune cells in the central nervous system with functional plasticity. They can be activated into M1 and M2 phenotypes when neuroinflammation-related diseases occur. M1 phenotype cells produce pro-inflammatory mediators that cause neuroinflammation and the M2 phenotype can secrete anti-inflammatory cytokines that protect neurons from damage. Therefore, inhibiting the M1 phenotype while stimulating the M2 phenotype has been suggested as a potential therapeutic approach for treating neuroinflammation-related diseases. Puerarin has been demonstrated to exert anti-inflammatory and neuroprotective effects. However, the role of puerarin in regulating microglia polarization and its reaction mechanism has not been fully elucidated. In this paper, a metabolomics approach with ultra-performance liquid chromatography-mass spectrometry was performed to investigate the metabolic changes of BV-2 cells in different phenotypes and test the effects of puerarin on polarization. Thirty-nine metabolites were identified as the biomarkers related to the polarization of BV-2 cells and puerarin intervention reverted the content of most of the biomarkers. Our study demonstrated that puerarin could play a key role in M1/M2 polarization of BV-2 cells from a perspective of metabolomics, and it could regulate the balance between promotion and suppression of inflammation.

Large-scale lipid analysis with C=C location and sn-position isomer resolving power.

Lipids play a pivotal role in biological processes and lipid analysis by mass spectrometry (MS) has significantly advanced lipidomic studies. While the structure specificity of lipid analysis proves to be critical for studying the biological functions of lipids, current mainstream methods for large-scale lipid analysis can only identify the lipid classes and fatty acyl chains, leaving the C=C location and sn-position unidentified. In this study, combining photochemistry and tandem MS we develop a simple but effective workflow to enable large-scale and near-complete lipid structure characterization with a powerful capability of identifying C=C location(s) and sn-position(s) simultaneously. Quantitation of lipid structure isomers at multiple levels of specificity is achieved and different subtypes of human breast cancer cells are successfully discriminated. Remarkably, human lung cancer tissues can only be distinguished from adjacent normal tissues using quantitative results of both lipid C=C location and sn-position isomers.

An integrated metabolomics strategy to reveal dose-effect relationship and therapeutic mechanisms of different efficacy of rhubarb in constipation rats.

The ambiguity of dose-effect relationship of many traditional Chinese medicines (TCMs) has always influenced their rational use in TCM clinic. Rhubarb, a preferred representative of cathartic TCM, is currently widely used that results in a diversity of its dosage. The aim of this study was to use an integrated metabolomics strategy to simultaneously reveal dose-effect relationship and therapeutic mechanisms of different efficacy of rhubarb in constipation rats. Six doses of rhubarb (0.135, 0.27, 0.81, 1.35, 4.05, and 8.1 g/kg) were examined to elucidate the laxative and fire-purging effects by pathological sections and UPLC-Q-TOF/MSE. The results showed that there existed serious lesions in the stomach and colon of model rats. And conditions were basically improved to some extent in rhubarb-treated groups. Through relative distance calculation based on metabolomics score plots, it suggested that the effective dose threshold (EC20-EC80 range) of rhubarb was from 0.31 to 4.5 g/kg (corresponding to 3.44-50.00 g in the clinic) in rat serum and 0.29-2.1 g/kg (corresponding to 3.22-23.33 g in the clinic) in feces. Then, 33 potential biomarkers were identified in total. Functional pathway analysis revealed that the alterations of these biomarkers were associated with 15 metabolic pathways, mainly including arachidonic acid metabolism, glycerophospholipid metabolism, steroid biosynthesis, primary bile acid biosynthesis and sphingolipid metabolism. Of note, different doses of rhubarb could alleviate endogenous disorders to varying degrees through regulating multiple perturbed pathways to the normal state, which might be in a dose-dependent manner and involved in therapeutic mechanisms. To sum up, integrated serum and fecal metabolomics obtained that rhubarb ranging from 0.31 to 2.1 g/kg is safe and effective for constipation treatment. Also, our findings showed that the robust metabolomics techniques would be promising to be more accurately used in the dose-effect studies of complex TCM, and to clarify syndrome pathogenesis and action mechanisms in Chinese medicine.

Comparative spatial lipidomics analysis reveals cellular lipid remodelling in different developmental zones of barley roots in response to salinity.

Salinity-induced metabolic, ionic, and transcript modifications in plants have routinely been studied using whole plant tissues, which do not provide information on spatial tissue responses. The aim of this study was to assess the changes in the lipid profiles in a spatial manner and to quantify the changes in the elemental composition in roots of seedlings of four barley cultivars before and after a short-term salt stress. We used a combination of liquid chromatography-tandem mass spectrometry, inductively coupled plasma mass spectrometry, matrix-assisted laser desorption/ionization mass spectrometry imaging, and reverse transcription - quantitative real time polymerase chain reaction platforms to examine the molecular signatures of lipids, ions, and transcripts in three anatomically different seminal root tissues before and after salt stress. We found significant changes to the levels of major lipid classes including a decrease in the levels of lysoglycerophospholipids, ceramides, and hexosylceramides and an increase in the levels of glycerophospholipids, hydroxylated ceramides, and hexosylceramides. Our results revealed that modifications to lipid and transcript profiles in plant roots in response to a short-term salt stress may involve recycling of major lipid species, such as phosphatidylcholine, via resynthesis from glycerophosphocholine.