Ultrahigh-performance Liquid Chromatography Electrospray Ionization Research Articles

Comprehensive profiling and evaluation of free/conjugated Phytosterols in crops using chemical derivatization coupled with UHPLC-ESI-QTOF-MS/MS

Phytosterols are naturally existed in crops but their detection is constrained by sensitivity and accuracy due to the inefficient analytical approaches. This study hypothesizes that an untargeted analytical method combining chemical derivatization with ultrahigh performance liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry can identify the various composition and contents of phytosterols in different crops. The results showed that chemical derivatization significantly enhanced intensity of phytosterols compared with non-derivatized samples. Using precursor ion scanning (PIS) of m/z 252.0690, dansyl chloride-labeled phytosterols were identified, demonstrating that rapeseeds had the highest content of total phytosterol (3981.2 ± 95.3 mg/kg), followed by sunflower seeds, flaxseeds, corn and rice, respectively. Principal component analysis revealed significant variations in phytosterol distribution among 15 crop samples, suggesting the applicability of phytosterol profile as a marker for phytosterols-contained crops. Hence, the proposed analytic approach proves high efficiency and accuracy in determining phytosterols and advances the study for phytosterol-enriched crops.

Comprehensive analysis of Moringa oleifera leaves’ antioxidant properties in ovine cheese

This study aimed to enhance “Pecorino” type ovine cheese by adding Moringa oleifera leaves powder (MOLP). Cheese-making trials, conducted at industrial level, used raw ewes' milk and two selected Lactococcus lactis strains. The experimental plan included a control production (CTR), and two experimental productions with 1% or 2% MOLP addition (1-MOLP and 2-MOLP, respectively). MOLP did not hinder starters development, which reached about 8.0 Log CFU/g in 2-month ripened cheeses. Illumina results highlighted lactococci dominance in all trials [45.98%–62.48% of relative abundance (RA)]. Physicochemical analysis showed that MOLP-enriched cheeses had higher protein content and lower secondary lipid oxidation. The addition of MOLP increased total phenolic compounds in cheese, reaching 3.64 mg GAE/g in the 2-MOLP sample. MOLP-enriched cheeses showed significantly higher radical scavenging activity than CTR production (p < 0.0001). Ultrahigh-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) revealed increased levels of chlorogenic acid, protocatechuic acid, caffeic acid, and ferulic acid due to MOLP enrichment. In the presence of MOLP, cheese volatile organic compounds were affected by compounds like 2-octanone, 3-hexen-2-one, heptane, nonanol, and linalool. 1-MOLP cheese was comparable to CTR production in overall satisfaction (sensory evaluation). Including MOLP in cheese production offers exciting opportunities for functional Sicilian ewes’ milk products.

Spatial distribution of differential metabolites in different parts of Tetrastigma hemsleyanum Diels et Gilg by ultrahigh-performance liquid chromatography/mass spectrometry and desorption electrospray ionization mass spectrometry imaging

Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) is a homology medicine and food that is rich in bioactive ingredients such as flavonoids and phenolic acids. A strategy that integrates ultrahigh-performance liquid chromatography–electrospray ionization mass spectrometry (UHPLC–ESI/MS) and desorption electrospray ionization mass spectrometry imaging (DESI-MSI) spatial metabolomics analysis was proposed and applied to different parts of T. hemsleyanum for the first time. A total of 132 compounds were tentatively identified, and 3, 7, and 24 components were found only in tuberous roots (TRs), fibrous roots (FRs), and leaves, respectively, using UHPLC–ESI/MS. The DESI-MSI results showed that the spatial distribution of flavonoids between the aerial and underground parts was diverse; for example, vitexin-2″-O-glucoside was largely localized in the epidermis and xylem of TRs, while a small amount was restricted to the xylem of the leaf margin and FRs. There was a higher abundance of most organic acids and flavonoids in the leaves than in the underground parts. Some flavonoids showed the same abundance in FRs and TRs, but the levels of most compounds were considerably higher in FRs. It is possible for leaves and FRs to become new medicinal parts of T. hemsleyanum. Through chemometrics statistics analysis, 19 key differential compounds in different parts of T. hemsleyanum were found, and the pharmacological mechanisms of the main differential metabolites were predicted by network pharmacology. This study provides a novel method for the medicinal development of T. hemsleyanum, showing its great potential in the development of medicinal resources.

Quantitative analysis of erythromycin, its major metabolite and clarithromycin in chicken tissues and eggs via QuEChERS extraction coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry

A simple, rapid and novel method involving ultrahigh-performance liquid chromatography-electrospray ionization tandem triple quadrupole mass spectrometry (UHPLC-ESI–MS/MS) was developed to simultaneously detect erythromycin, its major metabolite and clarithromycin in chicken tissues (muscle, liver and kidney) and eggs (whole egg, albumen and yolk). Samples were extracted using acetonitrile–water (80:20, v/v), and a Cleanert MAS-Q cartridge was used to perform quick, easy, cheap, effective, rugged, and safe (QuEChERS) purification. The average recoveries were 87.78–104.22 %, and the corresponding intraday and interday relative standard deviations were less than 7.10 %. The decision limits and detection capabilities of the chicken tissues and eggs were 2.15–105.21 μg/kg and 2.26–110.42 μg/kg, respectively. For chicken tissues and eggs, the limits of detection and limits of quantification were 0.5 μg/kg and 2.0 μg/kg, respectively. The proposed method was successfully employed to analyse real samples, demonstrating its applicability.

Lipidome characterisation and sex-specific differences in type 1 and type 2 diabetes mellitus

BackgroundIn this study, we evaluated the lipidome alterations caused by type 1 diabetes (T1D) and type 2 diabetes (T2D), by determining lipids significantly associated with diabetes overall and in both sexes, and lipids associated with the glycaemic state.MethodsAn untargeted lipidomic analysis was performed to measure the lipid profiles of 360 subjects (91 T1D, 91 T2D, 74 with prediabetes and 104 controls (CT)) without cardiovascular and/or chronic kidney disease. Ultra-high performance liquid chromatography-electrospray ionization mass spectrometry (UHPLC-ESI-MS) was conducted in two ion modes (positive and negative). We used multiple linear regression models to (1) assess the association between each lipid feature and each condition, (2) determine sex-specific differences related to diabetes, and (3) identify lipids associated with the glycaemic state by considering the prediabetes stage. The models were adjusted by sex, age, hypertension, dyslipidaemia, body mass index, glucose, smoking, systolic blood pressure, triglycerides, HDL cholesterol, LDL cholesterol, alternate Mediterranean diet score (aMED) and estimated glomerular filtration rate (eGFR); diabetes duration and glycated haemoglobin (HbA1c) were also included in the comparison between T1D and T2D.ResultsA total of 54 unique lipid subspecies from 15 unique lipid classes were annotated. Lysophosphatidylcholines (LPC) and ceramides (Cer) showed opposite effects in subjects with T1D and subjects with T2D, LPCs being mainly up-regulated in T1D and down-regulated in T2D, and Cer being up-regulated in T2D and down-regulated in T1D. Also, Phosphatidylcholines were clearly down-regulated in subjects with T1D. Regarding sex-specific differences, ceramides and phosphatidylcholines exhibited important diabetes-associated differences due to sex. Concerning the glycaemic state, we found a gradual increase of a panel of 1-deoxyceramides from normoglycemia to prediabetes to T2D.ConclusionsOur findings revealed an extensive disruption of lipid metabolism in both T1D and T2D. Additionally, we found sex-specific lipidome changes associated with diabetes, and lipids associated with the glycaemic state that can be linked to previously described molecular mechanisms in diabetes.

Distribution of Vicine, Convicine and Levodopa in Faba Bean Plant Tissues Determined by UltraHigh Performance Liquid Chromatography-Electrospray Ionization Mass Spectrometry

Faba bean is an emerging pulse crop for the Canada Prairies and is becoming an increasingly important source of plant sourced protein. It also has a high content of levodopa (up to 0.1 % of the dry seed weight), a nutraceutical compound for treating Parkinson's Disease (PD). The presence of pyrimidine glycosides, vicine and convicine, however, restricts the use of faba due to their potential to cause favism in susceptible individuals. For the rapid separation and quantification of levodopa, vicine and convicine, a 5-min ultrahigh performance liquid chromatography-electrospray ionization mass spectrometry method (UHPLC-ESI MS) was developed. This method provided a wide linear range of quantification (4.8 nM to 60 µM for vicine, and 6.0 nM to 24 µM for convicine and levodopa), and low limit of detection (1.2 to 3.0 nM). The method was applied in the analysis of diverse faba bean samples, from dehulled mature faba bean and seed coat, to fresh plant tissues such as flowers, leaves, stems, roots and pods. The results indicated that fresh faba bean plant tissues, such as leaves and flowers, had the highest concentration of levodopa and low level of VC, which makes them an alternative source of plant-based l-DOPA with potential as a food-based treatment for Parkinson's Disease.

Chemical analysis and bioactive compounds from agrifood by-products of peruvian crops

Many countries face the problem of agroindustrial waste elimination, which is linked to environmental damage caused by improper waste management. These wastes contain bioactive compounds often discarded due to a lack of knowledge. The objective of this study was to analyze five types of agroindustrial waste from Peru, including avocado (Persea americana) seeds, lucuma (Pouteria lucuma) seeds, grape (Vitis vinifera) pomace, mango (Mangifera indica) peel, and cocoa (Theobroma cacao) pods. This study includes proximal analysis, determination of total phenolic compound content, analysis of phenolic compounds by UHPLC– Q/Orbitrap/ESIMS/MS (Ultrahigh-performance liquid chromatography-electrospray ionization Q-Orbitrap mass spectrometry), and the evaluation of antioxidant, antimicrobial, and antifungal activities of different samples. The results showed that lucuma seeds had the highest protein content of 6.59 g/100 g DW. Mango peels showed the highest fat content of 4.89 g/100 g DW, cocoa pods had the highest crude fiber content of 26.91 g/100 g DW, and cocoa pods exhibited the highest ash content of 7.14 g/100 g DW. The highest carbohydrate content was found in avocado seeds at 85.85 g/100 g DW. Mango peels (56.66 mg GAE/g DW), avocado seeds (56.35 mg GAE/g DW), and cocoa pods (51.52 mg GAE/g DW) extracts showed the highest phenolic compound contents. Mango peel extract exhibited the highest antioxidant activities evaluated by the ABTS (995.01 μmol TEAC/g DW), DPPH (953.54 μmol TEAC/g DW), and FRAP (1661.13 μmol TEAC/g DW) assays. Extracts from cocoa pods, grape pomace, and lucuma seeds showed inhibitory activity on the growth of Staphylococcus aureus and Escherichia coli. In contrast, the extract of lucuma seeds was the only one that showed antifungal activity over Penicillium digitatum. As a result, several phenolic compounds were detected in each, indicating their potential use in developing functional foods and food preservation, among other applications.

Metabolomics-derived biomarkers for biosafety assessment of Gd-based nanoparticle magnetic resonance imaging contrast agents.

With the rapid development of nanotechnology and biomedicine, numerous gadolinium (Gd)-based nanoparticle MRI contrast agents have been widely investigated. Due to the unique physicochemical properties of nanoparticles and the complexity of biological systems, the biosafety of Gd-based nanoparticle MRI contrast agents has been paid more and more attention. Herein, for the first time, we employed an ultra-high performance liquid chromatography-electrospray ionization quadrupole time-of-flight/mass spectrometry (UPLC-ESI-QTOF/MS)-based metabolomics approach to investigate the potential toxicity of Gd-based nanoparticle MRI contrast agents. In this work, NaGdF4 and PEG-NaGdF4 nanoparticles were successfully constructed and selected as the representative Gd-based nanoparticle MRI contrast agents for the metabolomics analysis. Based on the results of metabolomics, more metabolic biomarkers and pathways were identified in the NaGdF4 group than those in the PEG-NaGdF4 group. Careful analysis of these metabolic biomarkers and pathways suggested that NaGdF4 nanoparticles induced disturbance of pyrimidine and purine metabolism, inflammatory response, and kidney injury to a certain extent compared with PEG-NaGdF4 nanoparticles. These results indicated that Gd-based nanoparticle contrast agents modified with PEG had better biosafety. Additionally, it was demonstrated that the discovery of characteristic metabolomics biomarkers induced by nanoparticles would provide a new approach for biosafety assessment and stimulate the development of nanomedicine.

Network pharmacology and experimental verification to explore the anti-superficial thrombophlebitis mechanism of Mailuo shutong pill

Ethnopharmacological relevanceMailuo shutong pill (MLST) has been widely used in clinical treatment of superficial thrombotic phlebitis (STP). Nevertheless, the major active components of MLST and the mechanism of synergistic action have not been reported. Aim of the studyThe present study aimed to evaluate the improving effects and the underlying mechanism of MLST on mannitol-induced STP in rabbits. Material and methodsIn this study, Ultrahigh-performance liquid chromatography electrospray ionization quadrupole-exactive orbitrap mass spectrometry (UHPLC-ESI-Q-Exactive-Orbitrap-MS) was used to analyze and identify the chemical composition of MLST and the prototype components absorbed into the blood. Then, according to the prototype components in serum, the targets and mechanisms of MLST were explored by applying network pharmacology. The rabbit model of STP was established by injecting 20% mannitol into bilateral auricular vein. The pathological changes of rabbit ear tissues, inflammatory factors, coagulation function and hemorheology were detected. In addition, molecular docking verified the interaction between the main active ingredient and the key target. Finally, the PI3K/AKT pathway and its regulated downstream pathways were verified by Western blot. ResultsA total of 96 MLST components and 53 prototypical components absorbed into the blood were successfully identified. Based on network pharmacology, PI3K/AKT pathway and 10 chemical components closely related to this pathway were obtained. Hematoxylin-eosin (HE) staining results indicated that MLST effectively improved of the pathological damage of ear tissues. MLST decreased levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and C-reactive protein (CRP). The expression of platelets (PLT) and fibrinogen concentration (FIB) was decreased, while prothrombin time (PT) and activated partial thromboplastin time (APTT) were prolonged. In addition, the plasma viscosity and whole blood viscosity in the MLST groups were significantly decreased. The more important discovery was that the expressions of P-PI3K, VEGF, P-AKT, P-IκB-α, P–NF-κB, NLRP3, ASC, Cleaved IL-1β and Cleaved Caspase-1 were effectively reversed after treatment with MLST. ConclusionsThis study comprehensively analyzed and characterized the chemical composition of MLST and the prototypical components absorbed into the blood. This study strongly confirmed the pharmacodynamic effect of MLST on STP. More importantly, this pharmacodynamic effect was achieved through inhibition of the PI3K/AKT pathway and its regulated NF-κB and NLRP3 pathways.

NMR-based metabolomics and UHPLC-ESI-MS/MS profiling of Syzygium jambos in relation to their antioxidant and anti-hyperglycemic activities

Search for natural sources in disease management especially diabetes has surged recently for its potential health benefits. However, several fruit tree species remained unpopular despite their folkloric usage due to insufficient scientific data. Syzygium jambos (L.) Alston (Myrtaceae) is a fruit-bearing plant that is used as a traditional dietary supplement to treat various diseases including diabetes. This study investigated the correlation between S. jambos leaves’ metabolites and the bioactivities using proton-nuclear magnetic resonance (1H NMR)-based metabolomics approach. In-vitro total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH•) radicals scavenging, nitric oxide (NO•) radicals scavenging, anti-α-amylase and anti-α-glucosidase assays were performed. The findings indicated that 70 % ethanolic extract demonstrated the highest potential in overall bioactivities. A total of 59 and 30 metabolites were tentatively identified using ultrahigh-performance liquid chromatography electrospray ionization Quadrupole-Orbitrap tandem mass spectrometry (UHPLC/ESI Q-Orbitrap MS/MS) and NMR, respectively. The partial least square (PLS) model revealed tannins, triterpenoids, and flavonoids significantly contributed to the separation and bioactivities. This study provides comprehensive insights into S. jambos metabolome and reveals the potential as a reliable source of antioxidant and anti-hyperglycemic compounds.

Dietary risk assessment of benzophenone derivatives using bread consumption estimates in a Taiwanese population.

Listed as endocrine-disrupting chemicals, benzophenone (BP) and its nine analogues (BPs) are an emerging group of contaminants. The migration of BPs from ultraviolet inks to food has been investigated in many studies; however, few studies have investigated BPs in foods and the risks of human exposure to BPs. We validated a trace and multi-residue method for simultaneously determining 10 BPs, including BP, BP-1, BP-2, BP-3, BP-8, 4-MBP, 2-OHBP, 4-OHBP, M2BB, and PBZ. Eighty-one bread samples were analyzed using stable isotope labeling and ultrahigh-performance liquid chromatography-electrospray ionization tandem mass spectrometry with solid-liquid extraction. We determined the estimated daily intake of BPs, non-cancer risks, and lifetime cancer risks (LTCRs) from daily bread consumption for seven age groups using a Monte Carlo simulation. The method demonstrated robust linearity (R2 ≥ 0.991), low limits of detection (0.04-2 ng/g), and satisfactory precision. The intra- and interday relative standard deviation ranges were 0.6%-9% and 3%-20%, respectively. BP, 4-MBP, 2-OHBP, BP-1, and BP-3 were detected in 97%, 67%, 59%, 24%, and 23% of the samples, respectively. 2-OHBP had the highest mean (range) value of 18.3 (<LOD-201.6) ng/g. The results demonstrated that the 0-3 year group had the highest LTCRs (2.6 × 10-6) and hazard indices [HIs] (5.4 × 10-2). The LTCRs were lower than 10-5, and the HIs were lower than 1 in seven age groups. This suggests that exposure to BPs from bread consumption is safe and acceptable.

Suspect Screening of Lupin-Produced Phytotoxins in Environmental Samples

Phytotoxins, secondary metabolites synthesized by plants, are now recognized as a new category of environmental micropollutants. Only a limited number of phytotoxins have been detected and reported in terrestrial and aquatic environments, partially due to analytical challenges. In this article, a robust, reliable, and efficient approach, namely Source Supported Suspect Screening (4S), is introduced for high-throughput analysis of phytotoxins from their plant origin to the downstream environmental compartments. The approach was established on an ultrahigh-performance liquid chromatography–electrospray ionization–quadrupole‑time‑of‑flight-mass spectrometry (UHPLC–ESI–QTOF-MS) analytical platform where optimal sample preparation and chromatographic conditions were investigated and a new suspect screening protocol was suggested.

Catalytic behavior of nitrous acid for acetaminophen transformation during the freezing process

This study demonstrates the transformation of acetaminophen by reactive nitrous acid in a frozen solution and its abnormal stoichiometry. The chemical reaction between acetaminophen and nitrous acid (AAP/NO2− system) was negligible in the aqueous solution; however, the reaction rapidly progressed if the solution started to freeze. The ultrahigh performance liquid chromatography–electrospray ionization tandem mass spectrometry measurements showed that polymerized acetaminophen and nitrated acetaminophen were formed in the proceeding reaction. Electron paramagnetic resonance spectroscopy measurements showed that nitrous acid oxidized acetaminophen via a one-electron transfer reaction producing acetaminophen-derived radical species, which is the cause of acetaminophen polymerization. We demonstrated that a relatively smaller dose of nitrite than acetaminophen caused significant acetaminophen degradation in the frozen AAP/NO2− system and revealed that the dissolved oxygen content notably affected acetaminophen degradation. We showed that the reaction occurs in a natural Arctic lake matrix (nitrite and acetaminophen spiked). Considering that the freezing phenomenon is common in the natural environment, our research provides a possible scenario for the freezing chemistry of nitrite and pharmaceuticals in environmental chemistry.

Suspect Screening of Lupin-Produced Phytotoxins in Environmental Samples

Phytotoxins, the secondary metabolites synthesized by plants, are now recognized as a new category of environmental micropollutants. So far, only a limited number of phytotoxins have been detected and reported in terrestrial and aquatic environments, partially due to the analytical challenge involved. In this article, a robust, reliable, and efficient approach, namely Source Supported Suspect Screening (4S), is introduced for high-throughput analysis of phytotoxins from their plant origin to the downstream environmental compartments. The approach was established on an ultrahigh-performance liquid chromatography–electrospray ionization–quadrupole‑time‑of‑flight-mass spectrometry (UHPLC–ESI-QTOF-MS) analytical platform where optimal sample preparation and chromatographic conditions were investigated and a new suspect screening protocol was suggested.

Study of Ultrahigh-Performance Liquid Chromatography Electrospray Ionization Q-Orbitrap Mass Spectrometry and Various Extraction Methods for Fingerprinting and Identification of Molecular Authenticity Markers in Apple and Grape Juices

Study of Ultrahigh-Performance Liquid Chromatography Electrospray Ionization Q-Orbitrap Mass Spectrometry and Various Extraction Methods for Fingerprinting and Identification of Molecular Authenticity Markers in Apple and Grape Juices

Associations between low-dose triclosan exposure and semen quality in a Chinese population

BackgroundThe antimicrobial agent triclosan (TCS) has attracted much attention worldwide because of its pervasive existence in the human body and environment. TCS exposure has been reported to be associated with decreased male reproductive function. However, few studies have investigated these associations in humans. ObjectiveTo examine the relationship between TCS in urine and male semen quality. MethodsA total of 406 men from a reproductive clinic were enrolled in this study. Urinary TCS concentrations were determined by ultra-high performance liquid chromatography–electrospray ionization tandem mass spectrometry. Sixteen semen parameters were assessed according to the guidelines of World Health Organization (WHO), including parameters for volume, count, motility, and motion. We used multivariate linear regression models and restricted cubic splines to estimate the linear and non-linear associations between TCS exposure and semen parameters, respectively. Logistical regression models were further applied to explore the associations with abnormal semen quality. ResultsTCS was detected in 74.6% of urine specimens. The monotonous trend of TCS tertiles and continuous TCS levels with all semen quality parameters were not observed in multivariate linear regression models (p > 0.05). However, compared with those in the lowest tertile, subjects in the second tertile showed significantly higher linearity and wobble (p < 0.05), indicating potential effects on sperm motion. In the models using restricted cubic splines with 3–5 knots, there were no significant non-linear associations between TCS exposure and any semen quality parameter. In addition, TCS tertiles were not associated with the risk of abnormal semen quality (i.e., count and motility) in the logistical regression models. ConclusionOur results revealed that low-level TCS exposure may have limited (none or modest) effects on male semen quality, potentially inducing some fluctuations. Further mechanistic studies on low levels of exposure are needed.

Analytical Strategies for LC-MS-Based Untargeted and Targeted Metabolomics Approaches Reveal the Entomological Origins of Honey.

A comprehensive liquid chromatography-mass spectrometry (LC-MS)-based metabolomics approach was developed to discriminate honey harvested from Apis mellifera ligustica Spinola (A. mellifera) and Apis cerana cerana Fabricius (A. cerana). Based on an untargeted strategy, ultrahigh-performance liquid chromatography electrospray ionization quadrupole orbitrap high-resolution mass spectrometry (UPLC Q-Orbitrap) was combined with chemometrics techniques to screen and identify tentative markers from A. mellifera and A. cerana honey. In targeted metabolomics analysis, a sensitive method of solid-phase extraction followed by ultrahigh-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry (UPLC-MS/MS) was established for quantifying three markers, and the results showed that 3-amino-2-naphthoic acid and methyl indole-3-acetate could be considered markers of A. cerana honey, as they were present in higher amounts in A. cerana honey than in A. mellifera honey, whereas kynurenic acid was determined to be a marker of A. mellifera honey. This work highlights critical information for the authentication of A. cerana and A. mellifera honey.

Simultaneous Analyses of 5 Omega Fatty Acids on Dried Serum Spot using Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

Omega fatty acids play an important role as biomarkers of chronic inflammatory diseases such as asthma, chronic obstructive pulmonary disease, rheumatoid arthritis, and inflammatory bowel disease. The purpose of our study was to develop a new analytical method for the detection of omega fatty acids from dried serum spots. We developed an ultrahigh performance liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS)-based method in the multiple reaction monitoring (MRM) mode with negative ionization. The detected MRM transitions for five omega fatty acids are as follow: α-linolenic acid (m/z=277.20→277.20), eicosapentaenoic acid (m/z=301.10→257.30), docosahexaenoic acid (m/z=327.00→283.15), arachidonic acid (m/z=303.20→259.25), and docosapentaenoic acid (m/z= 329.10→285.25). The calibration curve showed an excellent linearity within 0.1-2.5 μg/mL range (R2=0.9947~0.9994). The analytical methods howed excellent sensitivity (LOD: 0.005-0.01 μg/mL, LOQ: 0.03-0.1 μg/mL), which would allow for the targeted analyses of omega fatty acids. The recoveries of the omega fatty acid from the dried serum spots were 92.6%- 110.4% (RSD: ±0.2%-9.6%) and the retention time was within 5 min. This improved method offers rapid and sensitive quantification of omega fatty acids on dried serum spots using a small volume of serum and is expected to be applied to various biological specimens.

Metabolome and Transcriptome Integration Reveals Insights Into Flavor Formation of 'Crimson' Watermelon Flesh During Fruit Development.

Metabolites have been reported as the main factor that influences the fruit flavor of watermelon. But the comprehensive study on the dynamics of metabolites during the development of watermelon fruit is not up-to-date. In this study, metabolome and transcriptome datasets of ‘Crimson’ watermelon fruit at four key developmental stages were generated. A total of 517 metabolites were detected by ultrahigh-performance liquid chromatography–electrospray ionization–tandem mass spectrometry and gas chromatography–solid-phase microextraction–mass spectrometry. Meanwhile, by K-means clustering analysis, the total differentially expressed genes were clustered in six classes. Integrating transcriptome and metabolome data revealed similar expression trends of sugars and genes involved in the glycolytic pathway, providing molecular insights into the formation of taste during fruit development. Furthermore, through coexpression analysis, we identified five differentially expressed ADH (alcohol dehydrogenase) genes (Cla97C01G013600, Cla97C05G089700, Cla97C01G001290, Cla97C05G095170, and Cla97C06G118330), which were found to be closely related to C9 alcohols/aldehydes, providing information for the formation of fruit aroma. Our findings establish a metabolic profile during watermelon fruit development and provide insights into flavor formation.

High-Resolution Metabolomics of 50 Neurotransmitters and Tryptophan Metabolites in Feces, Serum, and Brain Tissues Using UHPLC-ESI-Q Exactive Mass Spectrometry

Recent evidence indicates that tryptophan metabolites and neurotransmitters are potential mediators of the microbiome–gut–brain interaction. Here, a high-resolution ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) assay was developed and validated for quantifying 50 neurotransmitters, tryptophan metabolites, and bacterial indole derivatives in mouse serum, feces, and brain. The lower limit of quantitation for the 50 compounds ranged from 0.5 to 100 nmol/L, and sample preparation procedures were adapted for individual compounds to allow quantitation within linearity of the assay with a correlation coefficient >0.99. Reproducibility was tested by intra- and interday precision and accuracy of analysis: intra- and interday precision at the lower limit of quantitation was less than 20% for all compounds, with over two-thirds of the compounds achieving an interday precision below 10%, while the interday accuracy at the lower limit of quantitation ranged from 82.3 to 128.0% for all compounds. The analyte recovery was assessed based on sample-spiked stable-isotope-labeling standards, illustrating a need to consider matrix-specific recovery discrepancies when performing interorgan comparison. Carryover was evaluated by intermittent solvent blank injection. The assay was successfully applied to determining the concentration profiles of neurotransmitter and tryptophan metabolites in serum, feces, and brain of conventionally raised specific pathogen-free (SPF) C57BL/6 mice. Our method may serve as a useful analytical resource for investigating the roles of tryptophan metabolism and neurotransmitter signaling in host–microbiota interaction.