Determination of berberine-upregulated endogenous short-chain fatty acids through derivatization by 2-bromoacetophenone

The chemical and biological characteristics of fatty acid esters of hydroxyl fatty acids

With the continuous advancements in detection methods and the exploration of unknown substances, an increasing number of bioactive compounds are being discovered. Fatty acid esters of hydroxyl fatty acids (FAHFAs), a class of endogenous lipids found in 2014, exhibit various physiological activities, such as improving glucose tolerance and insulin sensitivity, stimulating insulin secretion, and demonstrating broad anti-inflammatory effects. Moreover, some FAHFAs are closely linked to intestinal health and can serve as potential biomarkers for gut health. Various FAHFAs have been observed in food, including palmitic acid esters of hydroxy stearic acids (PAHSA), oleic acid esters of hydroxy stearic acids (OAHSA), linoleic acid esters of hydroxy linoleic acid (LAHLA). As a type of lipid regularly consumed in the daily diet, it is highly important to ascertain the types and quantities of FAHFAs present in the diet. This article, based on existing research, provides a review of the analysis methods for FAHFAs, particularly focusing on the separation of chiral isomers. It also summarizes the sources and contents of dietary FAHFAs, emphasizing their bioavailability and impact on the gut. Understanding the beneficial effects of these lipids in the diet can serve as a valuable reference for the development of specific functional foods.

Comparison of 3-nitrophenylhydrazine, O-benzyl hydroxylamine, and 2-picolylamine derivatizations for analysis of short-chain fatty acids through liquid chromatography coupled with tandem mass spectrometry

Short-chain fatty acids (SCFAs) are metabolites derived from gut microbiota and implicated in host homeostasis. Hence, the profiling SCFAs from biological samples plays an important role in revealing the interaction between gut microbiota and pathogens. Previous studies, liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with various derivatization strategies have been performed to obtain the SCFA profiles from biological samples. However, it is poor evidence to compare these derivatization regents and conditions. Thus, we present the evaluation of three major derivatization reagents, namely 3-nitrophenylhydrazine (3-NPH), O-benzylhydroxylamine (O-BHA), and 2-picolylamine (2-PA), for the analysis of eight SCFAs classified as C2-C5 isomers using LC-MS/MS. First, in a reversed-phase LC separation, 3-NPH showed good retention capacity. Although O-BHA derivatization showed higher sensitivity and good retention capacity than 2-PA, only 2-PA derivatization could successfully separate eight SCFAs. The matrix effects in human serum ranged 77.1-99.0% (RSD ≤ 3.4%, n = 6) for 3-NPH derivatives, 91.0-94.6% (RSD ≤ 5.4%, n = 6) for O-BHA derivatives, 81.6-99.5% (RSD ≤ 8.0%, n = 6) for 2-PA derivatives. These compared results showed each characteristic of 3-NPH, O-BHA, and 2-PA for SCFA derivatization based on LC-MS/MS approaches.

Recent Analytical Methodologies in Lipid Analysis

Lipids represent a large group of biomolecules that are responsible for various functions in organisms. Diseases such as diabetes, chronic inflammation, neurological disorders, or neurodegenerative and cardiovascular diseases can be caused by lipid imbalance. Due to the different stereochemical properties and composition of fatty acyl groups of molecules in most lipid classes, quantification of lipids and development of lipidomic analytical techniques are problematic. Identification of different lipid species from complex matrices is difficult, and therefore individual analytical steps, which include extraction, separation, and detection of lipids, must be chosen properly. This review critically documents recent strategies for lipid analysis from sample pretreatment to instrumental analysis and data interpretation published in the last five years (2019 to 2023). The advantages and disadvantages of various extraction methods are covered. The instrumental analysis step comprises methods for lipid identification and quantification. Mass spectrometry (MS) is the most used technique in lipid analysis, which can be performed by direct infusion MS approach or in combination with suitable separation techniques such as liquid chromatography or gas chromatography. Special attention is also given to the correct evaluation and interpretation of the data obtained from the lipid analyses. Only accurate, precise, robust and reliable analytical strategies are able to bring complex and useful lipidomic information, which may contribute to clarification of some diseases at the molecular level, and may be used as putative biomarkers and/or therapeutic targets.

Microbiome metabolite quantification methods enabling insights into human health and disease

Many of the health-associated impacts of the microbiome are mediated by its chemical activity, producing and modifying small molecules (metabolites). Thus, microbiome metabolite quantification has a central role in efforts to elucidate and measure microbiome function. In this review, we cover general considerations when designing experiments to quantify microbiome metabolites, including sample preparation, data acquisition and data processing, since these are critical to downstream data quality. We then discuss data analysis and experimental steps to demonstrate that a given metabolite feature is of microbial origin. We further discuss techniques used to quantify common microbial metabolites, including short-chain fatty acids (SCFA), secondary bile acids (BAs), tryptophan derivatives, N-acyl amides and trimethylamine N-oxide (TMAO). Lastly, we conclude with challenges and future directions for the field.

Mass Spectrometry-based Single-Cell Lipidomics: Advancements, Challenges, and the Path Forward

In the past decade, lipidomics, now recognized as standalone subdiscipline of metabolomics, has gained considerable attention. Due to its sensitivity and unparalleled versatility, mass spectrometry (MS) has emerged as the tool of choice for lipid identification and detection. Traditional MS-based lipidomics are performed on bulk cell samples. While informative, these bulk-scale cellular lipidome measurements mask cellular heterogeneity across seemingly homogeneous populations of cells. Unfortunately, single cell lipidomics methodology and analyses are considerably behind genomics, transcriptomics, and proteomics. Therefore, the cell-to-cell heterogeneity and related function remains largely unexplored for lipidomics. Herein, we review recent advances in MS-based single cell lipidomics. We also explore the root causes for the slow development of single-cell lipidomics techniques. We aim to provide insights on the pivotal knowledge gaps that have been neglected, prohibiting the propulsion of the single-cell lipidomics field forward, while also providing our perspective towards future methodologies that can pave a path forward.

Determination of short-chain fatty acids as putative biomarkers of cancer diseases by modern analytical strategies and tools: a review

Short-chain fatty acids (SCFAs) are the main metabolites produced by bacterial fermentation of non-digestible carbohydrates in the gastrointestinal tract. They can be seen as the major flow of carbon from the diet, through the microbiome to the host. SCFAs have been reported as important molecules responsible for the regulation of intestinal homeostasis. Moreover, these molecules have a significant impact on the immune system and are able to affect inflammation, cardiovascular diseases, diabetes type II, or oncological diseases. For this purpose, SCFAs could be used as putative biomarkers of various diseases, including cancer. A potential diagnostic value may be offered by analyzing SCFAs with the use of advanced analytical approaches such as gas chromatography (GC), liquid chromatography (LC), or capillary electrophoresis (CE) coupled with mass spectrometry (MS). The presented review summarizes the importance of analyzing SCFAs from clinical and analytical perspective. Current advances in the analysis of SCFAs focused on sample pretreatment, separation strategy, and detection methods are highlighted. Additionally, it also shows potential areas for the development of future diagnostic tools in oncology and other varieties of diseases based on targeted metabolite profiling.

Berberine for Adjunct/Alternative Treatment of Dyslipidemia: A Literature Review

Berberine (BBR) is an ancient plant popular in China and is used to treat dyslipidemia, among other cardiovascular and metabolic-related diseases. BBR has historically been regarded as having multiple benefits, with a few clinical trials indicating this fact. We searched PubMed, Embase, and Google Scholar with the following keywords: Berberidaceae, berberine, Berberis spp., dyslipidemia, atherosclerosis, and inflammation. We synthesized the information within the literature to provide an updated review of BBR, its potential, and its applicability in real-world medicine in the future. This review sought to evaluate the literature and advancement in BBR's efficacy regarding dyslipidemia, inflammation, and atherosclerosis.

Quantitative Analysis and Structural Elucidation of Fatty Acids by Isobaric Multiplex Labeling Reagents for Carbonyl-Containing Compound (SUGAR) Tags and m-CPBA Epoxidation

In this study, a novel analytical method was developed to investigate fatty acids (FAs) for relative quantification, carbon-carbon double-bond localization, and cis-/trans-geometry differentiation by isobaric multiplex labeling reagents for carbonyl-containing compound (SUGAR) tag conjugation and meta-chloroperoxybenzoic acid (m-CPBA) epoxidation. FAs are essential components of cells and have diverse functions in energy storage and as complex lipid constituents. It has been reported that FAs play different roles in various biological processes such as the functional development of the brain. The comprehensive characterization and quantification of FAs are crucial to further elucidate their biological roles. However, it is challenging to perform relative quantification and structural elucidation of FAs using integrated mass spectrometry (MS)-based methods. Recently, our group developed isobaric multiplex SUGAR tags for quantitative glycomics. Besides aldehyde/ketone groups on glycans, hydrazide groups also possess reactivity toward carboxylic acids on FAs. In this study, we extended SUGAR tag labeling with FAs for the quantitative analysis by liquid chromatography (LC)-MS/MS in the positive ion mode and applied this strategy for the comparative analysis of FAs hydrolyzed from oil samples. In addition, to comprehensively elucidate the structures of unsaturated FAs, epoxidation by m-CPBA was performed before SUGAR tag labeling to enable carbon-carbon double-bond localization. Moreover, the cis- and trans-geometries of carbon-carbon double bonds in multiple pairs of monounsaturated FAs could also be differentiated in higher-energy collisional dissociation (HCD)-MS/MS. This study developed a high-throughput comprehensive FA analysis platform, which could be widely applied and utilized in biological and clinical studies.

Liquid Chromatography-Mass Spectrometry (LC-MS) Derivatization-Based Methods for the Determination of Fatty Acids in Biological Samples

Fatty acids (FAs) play pleiotropic roles in living organisms, acting as signaling molecules and gene regulators. They are present in plants and foods and may affect human health by food ingestion. As a consequence, analytical methods for their determination in biological fluids, plants and foods have attracted high interest. Undoubtedly, mass spectrometry (MS) has become an indispensable technique for the analysis of FAs. Due to the inherent poor ionization efficiency of FAs, their chemical derivatization prior to analysis is often employed. Usually, the derivatization of the FA carboxyl group aims to charge reversal, allowing detection and quantification in positive ion mode, thus, resulting in an increase in sensitivity in determination. Another approach is the derivatization of the double bond of unsaturated FAs, which aims to identify the double bond location. The present review summarizes the various classes of reagents developed for FA derivatization and discusses their applications in the liquid chromatography-MS (LC-MS) analysis of FAs in various matrices, including plasma and feces. In addition, applications for the determination of eicosanoids and fatty acid esters of hydroxy fatty acids (FAHFAs) are discussed.

Berberine treats atherosclerosis via a vitamine-like effect down-regulating Choline-TMA-TMAO production pathway in gut microbiota

Trimethylamine-N-oxide (TMAO) derived from the gut microbiota is an atherogenic metabolite. This study investigates whether or not berberine (BBR) could reduce TMAO production in the gut microbiota and treat atherosclerosis. Effects of BBR on TMAO production in the gut microbiota, as well as on plaque development in atherosclerosis were investigated in the culture of animal intestinal bacterial, HFD-fed animals and atherosclerotic patients, respectively. We found that oral BBR in animals lowers TMAO biosynthesis in intestine through interacting with the enzyme/co-enzyme of choline-trimethylamine lyase (CutC) and flavin-containing monooxygenase (FMO) in the gut microbiota. This action was performed by BBR’s metabolite dihydroberberine (a reductive BBR by nitroreductase in the gut microbiota), via a vitamine-like effect down-regulating Choline-TMA-TMAO production pathway. Oral BBR decreased TMAO production in animal intestine, lowered blood TMAO and interrupted plaque formation in blood vessels in the HFD-fed hamsters. Moreover, 21 patients with atherosclerosis exhibited the average decrease of plaque score by 3.2% after oral BBR (0.5 g, bid) for 4 months (*P < 0.05, n = 21); whereas the plaque score in patients treated with rosuvastatin plus aspirin, or clopidogrel sulfate or ticagrelor (4 months, n = 12) increased by 1.9%. TMA and TMAO in patients decreased by 38 and 29% in faeces (*P < 0.05; *P < 0.05), and 37 and 35% in plasma (***P < 0.001; *P < 0.05), after 4 months on BBR. BBR might treat atherosclerotic plaque at least partially through decreasing TMAO in a mode of action similar to that of vitamins.

Optimization and validation of direct gas chromatography-mass spectrometry method for simultaneous quantification of ten short-chain fatty acids in rat feces

Short-chain fatty acids (SCFAs) play key roles in maintaining health and treating disease. Quantification of important fecal SCFAs is necessary to facilitate the clarification of their biological roles. However, the existing quantifying methods mainly depend on complicated precolumn derivatization, and/or are unable to determine formic acid, a SCFA commonly associated with toxicity. In this study, a direct gas chromatography-mass spectrometry (GC-MS) method for simultaneous quantification of ten SCFAs including formic acid in rat feces was developed. The approach was optimized in terms of chromatographic and spectrometric conditions as well as sample preparation. DB-FFAP capillary column with temperature programming was used to get baseline separation and symmetrical peak shape of SCFAs without precolumn derivatization in a relatively short running time (8 min). Multiple reaction monitoring (MRM) scan mode was employed to enhance the sensitivity and selectivity of SCFAs. Acidification with 50% HCl and immediate extraction with diethyl ether were utilized to achieve sample preparation of ten SCFAs from feces. Furthermore, the developed method was validated with wide linear range, high sensitivity and precision, low matrix effect and acceptable accuracy. The established method was successfully applied to compare the contents of fecal SCFAs between normal and immunosuppressed animal models.

Pharmacokinetics and Pharmacological Activities of Berberine in Diabetes Mellitus Treatment

Traditional Chinese medicine (TCM) has good clinical application prospects in diabetes treatment. In addition, TCM is less toxic and/or has fewer side effects and provides various therapeutic effects. Berberine (BBR) is isolated as the main component in many TCM kinds (e.g., Rhizoma Coptidis and Berberidis Cortex). Furthermore, BBR can reduce blood sugar and blood fat, alleviate inflammation, and improve the state of patients. Based on the recent study results of BBR in diabetes treatment, the BBR pharmacokinetics and mechanism on diabetes are mainly studied, and the specific molecular mechanism of related experimental BBR is systematically summarized and analyzed. Clinical studies have proved that BBR has a good therapeutic effect on diabetes, suggesting that BBR may be a promising drug candidate for diabetes. More detailed BBR mechanisms and pathways of BBR need to be studied further in depth, which will help understand the BBR pharmacology in diabetes treatment.

Multi-Pharmacology of Berberine in Atherosclerosis and Metabolic Diseases: Potential Contribution of Gut Microbiota

Atherosclerosis (AS), especially atherosclerotic cardiovascular diseases (ASCVDs), and metabolic diseases (such as diabetes, obesity, dyslipidemia, and nonalcoholic fatty liver disease) are major public health issues worldwide that seriously threaten human health. Exploring effective natural product-based drugs is a promising strategy for the treatment of AS and metabolic diseases. Berberine (BBR), an important isoquinoline alkaloid found in various medicinal plants, has been shown to have multiple pharmacological effects and therapeutic applications. In view of its low bioavailability, increasing evidence indicates that the gut microbiota may serve as a target for the multifunctional effects of BBR. Under the pathological conditions of AS and metabolic diseases, BBR improves intestinal barrier function and reduces inflammation induced by gut microbiota-derived lipopolysaccharide (LPS). Moreover, BBR reverses or induces structural and compositional alterations in the gut microbiota and regulates gut microbe-dependent metabolites as well as related downstream pathways; this improves glucose and lipid metabolism and energy homeostasis. These findings at least partly explain the effect of BBR on AS and metabolic diseases. In this review, we elaborate on the research progress of BBR and its mechanisms of action in the treatment of AS and metabolic diseases from the perspective of gut microbiota, to reveal the potential contribution of gut microbiota to the multifunctional biological effects of BBR.

The Association Between Intestinal Bacteria and Allergic Diseases-Cause or Consequence?

The incidence of allergic disorders has been increasing over the past few decades, especially in industrialized countries. Allergies can affect people of any age. The pathogenesis of allergic diseases is complex and involves genetic, epigenetic, and environmental factors, and the response to medication is very variable. For some patients, avoidance is the sole effective therapy, and only when the triggers are identifiable. In recent years, the intestinal microbiota has emerged as a significant contributor to the development of allergic diseases. However, the precise mechanisms related to the effects of the microbiome on the pathogenesis of allergic diseases are unknown. This review summarizes the recent association between allergic disorders and intestinal bacterial dysbiosis, describes the function of gut microbes in allergic disease development from both preclinical and clinical studies, discusses the factors that influence gut microbial diversity and advanced techniques used in microbial analysis. Ultimately, more studies are required to define the host-microbial relationship relevant to allergic disorders and amenable to new therapeutic interventions.

Determination and Application of Nineteen Monoamines in the Gut Microbiota Targeting Phenylalanine, Tryptophan, and Glutamic Acid Metabolic Pathways

It has been reported that monoamine neurotransmitters can be produced by gut microbiota, and that several related metabolites of amino acids in these pathways are associated with nervous system (NVS) diseases. Herein, we focused on three pathways, namely, phenylalanine (Phe), tryptophan (Trp), and glutamic acid (Glu), and established an underivatized liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the quantification of nineteen monoamine neurotransmitters and related metabolites in the gut microbiota. The neurotransmitters and related metabolites included Phe, tyrosine (Tyr), l-dopa (Dopa), dopamine (DA), 3-methoxytyramine, Trp, hydroxytryptophan, 5-hydroxytryptamine (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), kynurenine (KN), kynurenic acid (KYNA), melatonin, tryptamine (TA), indole-3-lactic acid (ILA), indole-3-acetic acid (IAA), indolyl-3-propionic acid (IPA), Glu, gamma-aminobutyric acid (GABA), and acetylcholine (Ach). A fluoro-phenyl bonded column was used for separation, and the mobile phase consisted of methanol:acetonitrile (1:1) and water, with 0.2% formic acid in both phases. The compounds exhibited symmetric peak shapes and sufficient sensitivity under a total analysis time of 8.5 min. The method was fully validated with acceptable linearity, accuracy, precision, matrix effect, extraction recovery, and stability. The results showed that neurotransmitters, such as Dopa, DA, 5-HT, GABA, and Ach, were present in the gut microbiota. The metabolic pathway of Trp was disordered under depression, with lower levels of 5-HT, 5-HIAA, KN, KYNA, TA, ILA, IAA, IPA, and Glu, and a higher ratio of KYNA/KN. In addition, some first-line NVS drugs, such as sertraline, imipramine, and chlorpromazine, showed regulatory potential on these pathways in the gut microbiota.

Dual derivatization strategy for the comprehensive quantification and double bond location characterization of fatty acids by ultra-high performance liquid chromatography-tandem mass spectrometry

Comprehensive analysis of fatty acids (FAs) has long been challenging due to their poor ionization efficiency, lack of characteristic fragment ions and difficulty of identifying C=C bond locations. In this study, a high coverage ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established for the quantification and C=C bond location characterization of FAs using two structural analogues, 2-hydrazinyl-4,6-dimethylpyrimidine (DMP) and 2-hydrazinylpyrimidine (DP), as dual derivatization reagents. DP-labeled FA standards were used as internal standards to reduced matrix effects, which guaranteed the accurate quantification of FAs. The derivatization yields of FAs were larger than 99% and the sensitivities were increased by 400-fold compared with non-derivatized FAs. Pretreatment and instrumental analysis of FAs can be completed in 20 minutes. Only 5 μL rat plasma can satisfy the quantification of 36 FAs with good linearity (r>0.99). Both intra-day and inter-day accuracies were in the range of 85-105%, and the precisions were less than 15%. The extraction recoveries were investigated to be in the range of 88-112%. No obvious matrix effects were observed for the derivatized FAs. In addition, the locations of C=C bonds in DMP-derivatized FAs could be identified by diagnostic fragment ions generated from 1,4-hydrogen elimination and allylic cleavage under low energy collision induced dissociation (CID). The new method was finally employed for FA profiling in plasma from rats with moxifloxacin-induced liver injury. Significant downregulation of butyric acid was observed in moxifloxacin treated model rats, which was believed to be related to the liver injury.

Derivatization procedures and their analytical performances for HPLC determination in bioanalysis

Derivatization, or chemical structure modification, is often used in bioanalysis performed by liquid chromatography technique in order to enhance detectability or to improve the chromatographic performance for the target analytes. The derivatization process is discussed according to the analytical procedure used to achieve the reaction between the reagent and the target compounds (containing hydroxyl, thiol, amino, carbonyl and carboxyl as the main functional groups involved in derivatization). Important procedures for derivatization used in bioanalysis are in situ or based on extraction processes (liquid-liquid, solid-phase and related techniques) applied to the biomatrix. In the review, chiral, isotope-labeling, hydrophobicity-tailored and post-column derivatizations are also included, based on representative publications in the literature during the last two decades. Examples of derivatization reagents and brief reaction conditions are included, together with some bioanalytical applications and performances (chromatographic conditions, detection limit, stability and sample biomatrix).

The role of gut microbiota (GM) and GM-related metabolites in diabetes and obesity. A review of analytical methods used to measure GM-related metabolites in fecal samples with a focus on metabolites' derivatization step

Disruption of gut microbiota (GM) composition is increasingly related to the pathogenesis of various metabolic diseases. Additionally, GM is responsible for the production and transformation of metabolites involved in the development of metabolic disorders, such as obesity and type 2 diabetes mellitus (T2DM). The current state of knowledge regarding the composition of GM and GM-related metabolites in relation to the progress and development of obesity and T2DM is presented in this review. To understand the relationships between GM-related metabolites and the development of metabolic disorders, their accurate qualitative and quantitative measurement in biological samples is needed. Feces represent a valuable biological matrix which composition may reflect the health status of the lower gastrointestinal tract and the whole organism. Mass spectrometry (MS), mainly in combination with gas chromatography (GC) or liquid chromatography (LC), is commonly used to measure fecal metabolites. However, profiling metabolites in such a complex matrix as feces is challenging from both analytical chemistry and biochemistry standpoints. Chemical derivatization is one of the most effective methods used to overcome these problems. In this review, we provide a comprehensive summary of the derivatization methods of GM-related metabolites prior to GC-MS or LC-MS analysis, which have been published in the last five years (2015-2020). Additionally, analytical methods used for the analysis of GM-related metabolites without the derivatization step are also presented.

A rapid and convenient derivatization method for quantitation of short-chain fatty acids in human feces by ultra-performance liquid chromatography/tandem mass spectrometry

RATIONALE

Short-chain fatty acids (SCFAs) are associated with intestinal microbiota and diseases in humans. SCFAs have a low response in mass spectrometry, and in order to increase sensitivity, reduce sample consumption, shorten analysis time, and simplify sample preparation steps, a derivatization method was developed.

METHODS

We converted seven SCFAs into amide derivatives with 4-aminomethylquinoline. The reaction occurred for 20 min at room temperature. The analytes were separated on a reversed-phase C18 column and quantitated in the positive ion electrospray ionization mode using multiple reaction monitoring. Acetic acid-d₄ was used as the stable-isotope-labeled surrogate analyte for acetic acid in the working solutions, while the other stable-isotope-labeled standards were used as internal standards (ISs).

RESULTS

Method validation showed that the intra-day and inter-day precision of quantitation for the seven SCFAs over the whole concentration range was ≤3.8% (n = 6). The quantitation accuracy ranged from 85.5% to 104.3% (n = 6). Most important, the collected feces were vortexed immediately with ethanol.

CONCLUSIONS

This study provides a new derivatization method for a precise, accurate, and rapid quantitation of SCFAs in human feces using ultra-performance liquid chromatography/tandem mass spectrometry. This method successfully determined the concentration of SCFAs in human feces and could assist in the exploration of intestinal microbiota and diseases.

Applying mass spectrometry-based assays to explore gut microbial metabolism and associations with disease

The workings of the gut microbiome have gained increasing interest in recent years through the mounting evidence that the microbiota plays an influential role in human health and disease. A principal focus of this research seeks to further understand the production of metabolic by-products produced by bacteria resident in the gut, and the subsequent interaction of these metabolites on host physiology and pathophysiology of disease. Gut bacterial metabolites of interest are predominately formed via metabolic breakdown of dietary compounds including choline and ʟ-carnitine (trimethylamine N-oxide), amino acids (phenol- and indole-containing uremic toxins) and non-digestible dietary fibers (short-chain fatty acids). Investigations have been accelerated through the application of mass spectrometry (MS)-based assays to quantitatively assess the concentration of these metabolites in laboratory- and animal-based experiments, as well as for direct circulating measurements in clinical research populations. This review seeks to explore the impact of these metabolites on disease, as well as to introduce the application of MS for those less accustomed to its use as a clinical tool, highlighting pertinent research related to its use for measurements of gut bacteria-mediated metabolites to further understand their associations with disease.

Assessment of gut microbiota fecal metabolites by chromatographic targeted approaches

Gut microbiota, the specific microbial community of the gastrointestinal tract, by means of the production of microbial metabolites provides the host with several functions affecting metabolic and immunological homeostasis. Insights into the intricate relationships between gut microbiota and the host require not only the understanding of its structure and function but also the measurement of effector molecules acting along the gut microbiota axis. This article reviews the literature on targeted chromatographic approaches in analysis of gut microbiota specific metabolites in feces as the most accessible biological matrix which can directly probe the connection between intestinal bacteria and the (patho)physiology of the holobiont. Together with a discussion on sample collection and preparation, the chromatographic methods targeted to determination of some classes of microbiota-derived metabolites (e.g., short-chain fatty acids, bile acids, low molecular masses amines and polyamines, vitamins, neurotransmitters and related compounds) are discussed and their main characteristics, summarized in Tables.