Development of a High-Coverage Quantitative Metabolome Analysis Method Using Four-Channel Chemical Isotope Labeling LC-MS for Analyzing High-Salt Fermented Food

High-coverage identification of hydroxyl compounds based on pyridine derivatization-assisted liquid chromatography mass spectrometry

Hydroxyl compounds are widely present in plants and play essential roles in plant growth and development. High-coverage detection of hydroxyl compounds is crucial for understanding the physiological processes of plants. Despite the prevalence of chemical derivatization-assisted liquid chromatography-high resolution mass spectrometry (CD-LC-HRMS) in high-coverage detection of compounds with diverse functional groups, the confident identification of these compounds after derivatization remains a significant challenge. Herein, a novel method was developed for the identification of pyridine (PY)-derivatized hydroxyl compounds by comparing the MS/MS similarity of derivatized and corresponding underivatized compounds. Fragmentation rules of standards were summarized, and theoretical calculations have demonstrated the MS/MS similarity of PY-derivatized hydroxyl compounds with their underivatized counterparts. The effectiveness of the developed method was demonstrated by identifying PY-derivatized authentic standards. A total of 90 hydroxyl compounds were putatively identified in maize using the proposed method. This method can significantly enhance ionization efficiency with minimal impact on the quality of the MS/MS spectra, enabling the effective utilization of mass spectra databases for the identification of hydroxyl compounds.

Serum metabolomics reveals the effectiveness of human placental mesenchymal stem cell therapy for Crohn's disease

Mesenchymal stem cell (MSC) therapy offers a promising cure for Crohn's disease (CD), however, its therapeutic effects vary significantly due to individual differences. Therefore, identifying easily detectable biomarkers is essential to assess the efficacy of MSC therapy. In this study, SAMP1/Yit mice were used as a model of CD, which develop spontaneous chronic ileitis, closely resembling the characteristics present in CD patients. Serum metabolic alterations during treatment were analyzed, through the application of differential 12C-/13C-dansylation labeling liquid chromatography-mass spectrometry. Based on the significant differences and time-varying trends of serum amine/phenol-containing metabolites abundance between the control group, the model group, and the treatment group, four serum biomarkers were ultimately screened for evaluating the efficacy of MSC treatment for CD, namely 4-hydroxyphenylpyruvate, 4-hydroxyphenylacetaldehyde, caffeate, and N-acetyltryptamine, whose abundances both increased in the serum of CD model mice and decreased after MSC treatment. These metabolic alterations were associated with tyrosine metabolism, which was validated by the dysregulation of related enzymes. The discovery of biomarkers may help to improve the targeting and effectiveness of treatment and provide innovative prospects for the clinical application of MSC for CD.

Chemical Composition of Commercial Cannabis

Cannabis is widely used for medicinal and recreational purposes. As a result, there is increased interest in its chemical components and their physiological effects. However, current information on cannabis chemistry is often outdated or scattered across many books and journals. To address this issue, we used modern metabolomics techniques and modern bioinformatics techniques to compile a comprehensive list of >6000 chemical constituents in commercial cannabis. The metabolomics methods included a combination of high- and low-resolution liquid chromatography-mass spectrometry (MS), gas chromatography-MS, and inductively coupled plasma-MS. The bioinformatics methods included computer-aided text mining and computational genome-scale metabolic inference. This information, along with detailed compound descriptions, physicochemical data, known physiological effects, protein targets, and referential compound spectra, has been made available through a publicly accessible database called the Cannabis Compound Database (https://cannabisdatabase.ca). Such a centralized, open-access resource should prove to be quite useful for the cannabis community.

Challenges and recent advances in quantitative mass spectrometry-based metabolomics

The field of metabolomics has gained tremendous interest in recent years. Whether the goal is to discover biomarkers related to certain pathologies or to better understand the impact of a drug or contaminant, numerous studies have demonstrated how crucial it is to understand variations in metabolism. Detailed knowledge of metabolic variabilities can lead to more effective treatments, as well as faster or less invasive diagnostics. Exploratory approaches are often employed in metabolomics, using relative quantitation to look at perturbations between groups of samples. Most metabolomics studies have been based on metabolite profiling using relative quantitation, with very few studies using an approach for absolute quantitation. Using accurate quantitation facilitates the comparison between different studies, as well as enabling longitudinal studies. In this review, we discuss the most widely used techniques for quantitative metabolomics using mass spectrometry (MS). Various aspects will be addressed, such as the use of external and/or internal standards, derivatization techniques, in vivo isotopic labelling, or quantitative MS imaging. The principles, as well as the associated limitations and challenges, will be described for each approach.

Profiling and annotation of carbonyl compounds in Baijiu Daqu by chlorine isotope labeling-assisted ultrahigh-performance liquid chromatography-high resolution mass spectrometry

Carbonyl compounds are among the most important flavor substances that affect the taste of Baijiu. However, high coverage analysis of carbonyl compounds is obstructed due to the poor ionization efficiency of these compounds. Here we report a chlorine isotope labeling-assisted ultrahigh-performance liquid chromatography-high resolution mass spectrometry-based method (CIL-UHPLCHRMS) for profiling and annotation of carbonyl compounds in sauce flavored-Baijiu Daqu. 4-Chloro-2-hydrazinylpyridine was demonstrated to be a good labeling reagent that could achieve highly sensitive profiling and high-coverage screening of carbonyl compounds in the absence of heavy isotope labeling reagents. In the analysis of eight carbonyl standards representing different carbonyl categories, l-(-)-fucose, 2-carboxybenzaldehyde, 2-hydroxyacetophenone and heptan-2-one could be ionized only after labeling and MS signals were significantly increased for other 4 standards with an enhancement factor ranging from 181-fold for 3-methoxysalicylaldehyde to 3141-fold for tridecan-2-one. The annotation was achieved based on multidimensional information including MS1, predicted t_R, in silico MS/MS and manually annotated fragments. In total, 487 carbonyl compounds were detected in Baijiu Daqu, among which, 314 (64.5%) of them were positively or putatively identified. The outcome of the linearity (with a linear range of 2, 3 orders of magnitude), precision (less than 10%), and limit of detection (varied from 0.07 to 0.10 nM) indicated that the method was adequate for profiling carbonyl compounds in complex biological samples. The established method was successfully applied to study carbonyl compounds in Baijiu Daqu with different colors and different seasons. Taken collectively, the present work provides an effective, simple and economic strategy for comprehensive analysis of carbonyl compounds in complex matrix samples.

Enhanced Identification of Ginsenosides Simultaneously from Seven Panax Herbal Extracts by Data-Dependent Acquisition Including a Preferred Precursor Ions List Derived from an In-House Programmed Virtual Library

Data-dependent acquisition (DDA) is widely utilized for metabolite identification in natural product research and food science, which, however, can suffer from low coverage. A potential solution to improve DDA coverage is to include the precursor ions list (PIL). Here, we aimed to construct a PIL-containing DDA strategy based on an in-house library of ginsenosides (VLG) and identify ginsenosides simultaneously from seven Panax herbal extracts. VLG, combined with mass defect filtering, could efficiently screen the ginsenoside precursors and elaborate the separate PIL involved in DDA for each ginseng extract. Consequently, we could characterize 500 ginsenosides, including 176 ones with unknown masses. Using the Panax ginseng extract, the superiority of this strategy was embodied in targeting more known ginsenoside masses and newly acquiring the MS² spectra of 13 components. Conclusively, knowledge-based large-scale molecular prediction and PIL-DDA can represent a powerful targeted/untargeted strategy beneficial to novel natural compound discovery.