Serially coupled reversed phase-hydrophilic interaction liquid chromatography–tailored multiple reaction monitoring, a fit-for-purpose tool for large-scale targeted metabolomics of medicinal bile

Direct infusion-multiple reaction monitoring cubed (DI-MRM3) enables widely targeted bi-omics of Colla Corii Asini (Chinese name: Ejiao)

Food authenticity is extremely important and widely targeted bi-omics is a promising pipeline attributing to incorporating metabolomics and peptidomics. Colla Corii Asini (CCA, Ejiao) is one of the most popular tonic edible materials, with counterfeit and adulterated products being widespread. An attempt was devoted to develop a high-throughput and reliable DI-MRM3 program facilitating widely targeted bi-omics of CCA. Firstly, predictive MRM program captured metabolites and peptides in trypsin-digestive gelatins. After data alignment and structure annotation, primary parameters such as Q1 → Q3 → QLIT, CE, and EE were optimized for all 17 metabolites and 34 peptides by online ER-MS. Though a single run merely consumed 6.5 min, great selectivity was reached for each analyte. Statistical results showed that nine peptides contributed to distinguish CCA from other gelatins. After cross-validation with LC-MRM, DI-MRM3 was justified to be reproducible and high-throughput for widely targeted bi-omics of CCA, suggesting a meaningful tool for food authenticity.

Polarity-extended liquid chromatography-triple quadrupole mass spectrometry for simultaneous hydrophilic and hydrophobic metabolite analysis

Although various metabolomic methods have been reported in recent years, simultaneous detection of hydrophilic and hydrophobic metabolites in a single analysis remains a technical challenge. In this study, based on the combination of hydrophilic interaction liquid chromatography (HILIC) and reversed phase liquid chromatography (RPLC), an online two-dimensional liquid chromatography/triple quadrupole mass spectrometry method (2D-LC/TQMS) was developed for the simultaneous analysis of hydrophilic and hydrophobic metabolites of various biological samples. The method can measure 417 biologically important metabolites (e.g., amino acids and peptides, pyrimidines, purines, monosaccharides, fatty acids and conjugates, organic dicarboxylic acids, and others) with logP values ranging from -10.3 to 21.9. The metabolites are involved in a variety of metabolic pathways (e.g., purine metabolism, pyrimidine metabolism, tyrosine metabolism, galactose metabolism, gluconeogenesis, and TCA cycle). The developed method has good intra- and inter-day reproducibility (RSD of retention time <2%, RSD of peak area <30%), good linearity (R2 > 0.9) and wide linear range (from 0.0025 μg/mL to 5 μg/mL). The applicability of the method was tested using different biological samples (i.e., plasma, serum, urine, fecal, seminal plasma and liver) and it was found that 208 (out of 417) identical metabolites were detected in all biological samples. Furthermore, the metabolomic method was applied to a case/control study of urinary of bladder cancer. Thirty differential metabolites were identified that were involved in carbohydrate and amino acid metabolism.

Integrated strategy facilitates rapid in-depth chemome characterization of traditional Chinese medicine prescriptions: Shengbai oral liquid as a case

Chemome characterization is the prerequisite for either therapeutic mechanism clarification or quality control of traditional Chinese medicine prescriptions (TCMPs). Liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) currently serves as the most popular analytical tool; however, chemome characterization is still challenged by MS/MS spectral acquisition and post-acquisition data processing. Here, an integrated strategy was proposed for in-depth chemome clarification of Shengbai oral liquid (SBOL). Gas phase ion fractionation with staggered mass ranges was demonstrated to be the superior acquisition method regarding MS2 spectrum coverage in this study, and narrower mass range further advanced coverage. To facilitate information extraction, all ingredient materials were measured in parallel to form an in-house library, where each MS1 -MS2 item generated a square mass-to-charge ratio (m/z) frame to capture the tagged identity and each chemical family produced a pentagon frame for mass defect features to accomplish chemical analogs-targeted quasi-molecular ion extraction. Square m/z frame imprinting captured 355 identities, while mass defect frames extracted 275 compounds. Attributing to comprehensive MS2 spectrum acquisition and efficient data processing, 355 components were captured and tentatively identified, resulting in a clarified chemical composition for SBOL. Therefore, the proposed strategy should be meaningful for the chemome characterization of TCMPs.

Serially coupled column liquid chromatography: An alternative separation tool

Despite the rapid development of liquid chromatography (LC) in recent decades, it remains a challenge to achieve the desired chromatographic separation of complex matrices using a single column. Multi-column LC techniques, particularly serially coupled column LC (SCC-LC), have emerged as a promising solution to overcome this challenge. While more attention has been focused on heart-cutting or comprehensive two-dimensional LC, reviews specifically focusing on SCC-LC, which offers advantages in terms of precision and facile instrumentation, are scarce. Here, our concerns are devoted to the progress summary regarding the instrumentation and applications of SCC-LC. Emphasis is placed on column selection aiming to enlarge peak capacity, selectivity, or both through the optimization of combination types (e.g. RPLC-RPLC, -RPLC-HILIC, and achiral-chiral LC), connection devices (e.g. zero dead volume connector, tubing, and T-type connector), elution program (i.e. isocratic or gradient) and detectors (e.g. mass spectrometer, ultraviolet detector, and fluorescence detector). The application of SCC-LC in pharmaceutical, biological, environmental, and food fields is also reviewed, and future perspectives and potential directions for SCC-LC are discussed. We envision that the review can give meaningful information to analytical scientists when facing heavy chromatographic separation tasks for complicated matrices.

Enhanced profiling and quantification of ginsenosides from mountain-cultivated ginseng and comparison with garden-cultivated ginseng

Panax ginseng can be generally divided into mountain-cultivated ginseng (MCG) and garden-cultivated ginseng (GCG). The market price of MCG is significantly higher than that of GCG. However, the chemical compositions of MCG and the differences from GCG remained unclear. In this study, an integrated strategy combing an offline two-dimensional liquid chromatography separation, LTQ-orbitrap dual mode acquisition, and Q-trap full quantification/quasi-quantification was proposed to explore and compare the chemical compositions of MCG. Consequently, 559 ginsenosides were characterized, among which 437 ginsenosides were in-depth characterized with α-chain and β-chain annotated. Subsequently, enhanced quantification of 213 ginsenosides was conducted in 57 batches of MCG and GCG. Ginsenosides were found more abundant in MCG than GCG. In addition, 25-year-old MCG could be distinctly differentiated from 15/20-year-old MCG. This strategy facilitated the enhanced profiling and comparison of ginsenosides, improved the quality control tactics of MCG and provided a reference approach for other ginseng related products.

Identification of the Authenticity and Geographical Origin of Bear Bile Powder by Using High Performance Liquid Chromatography - Charged Aerosol Detector Fingerprints Combined with Chemometrics

Bear bile powder (BBP) is a rare animal-derived traditional Chinese medicine, and it has been widely used to treat visual disorders and hepatobiliary diseases in East Asia. However, there is still a lack of reliable quality control methods for BBP. This study was designed to establish a comprehensive quality map of BBP based on bile acids. High-performance liquid chromatography coupled with charged aerosol detector (HPLC-CAD) was used for fingerprint establishment and quantitative analysis of BBP. The similarities of HPLC-CAD chromatograms for 50 batches of BBP were more than 0.95, while the similarities of reference chromatograms between 6 other animal bile and BBP were low than 0.7. Additionally, five bile acids in BBP, including tauroursodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, ursodesoxycholic acid, and chenodeoxycholic acid, were simultaneously quantified. This method has been validated with good regression as well as satisfactory precision, sensitivity, stability, repeatability, and accuracy. Using this method, the contents of five bile acids in BBP samples from five producing areas were determined and compared. Furthermore, Fisher linear discriminant analysis was performed to discriminate the geographic origins of BBP. The result demonstrated that HPLC-CAD fingerprint combined with multi-components quantification is an effective and reliable method for quality control of BBP, it could be a meaningful reference for the quality evaluation of medicinal bile.

Stepwise solid phase extraction integrated with chemical derivatization for all-in-one injection LC-MS/MS analysis of metabolome and lipidome

The metabolome and lipidome are critical components in illustrating biological processes and pathological mechanisms. Generally, two or more independent methods are required to analyze the two compound panels due to their distinct chemical properties and polarity differences. Here, a novel strategy integrating stepwise solid-phase extraction (SPE) and dansyl chemical derivatization was proposed for all-in-one injection LC-MS/MS analysis of serum metabolome and lipidome. In this workflow, a stepwise elution procedure was firstly optimized to separate the metabolome and lipidome fractions using an Ostro plate. Dansyl chemical derivatization was then applied to label amine/phenol, carboxyl, and carbonyl-containing sub-metabolomes. Our results demonstrated that the dansyl labeling could significantly improve chromatographic separation, enhance the MS response, and overcome the matrix effect of co-eluting lipids. Ultimately, an all-in-one injection LC-MS/MS method measuring 256 lipids (covering 20 subclasses) and 212 metabolites (including amino acids, bile acids, fatty acids, acylcarnitines, indole derivatives, ketones and aldehydes, nucleic acid metabolism, polyamines, etc.) was established. This method was applied to investigate the metabolic changes in cisplatin-induced nephrotoxicity in rats and the results were compared with previous untargeted metabolomics. The presented strategy could predominantly improve the analytical coverage and throughput and can be of great use in discovering reliable potential biomarkers in various applications.

Integrated strategy for widely targeted metabolome characterization of Peucedani Radix

Herbal medicines (HMs) are widely recognized as extremely complicated matrices, resulting in a great challenge for the existing analytical approaches to characterize the widely targeted metabolome. The primary obstacles include high-level structural diversity, broad concentration range, large polarity span, insufficient authentic compounds and frequent occurrences of isomers, even enantiomers. Here, we aimed to propose an integrated strategy being able to circumvent the technical barriers, and a well-known HM namely Peucedani Radix was employed to illustrate and justify the applicability. Regarding qualitative analysis, the hydrophilic metabolites were detected with HILIC-predictive multiple-reaction monitoring mode, and structurally identified by matching predefined identities with authentic compounds or information archived in relevant databases. After RPLC-MS/MS measurement, full collision energy ramp-MS² spectrum in combination with quantum structural calculation was applied to confirmatively identify those less polar components, mainly angular-type pyranocoumarins (APs). For quantitative analysis, achiral-chiral RPLC/HILIC was configured for chromatographic separations because the analytes spanned a large polarity range and involved many enantiomers. A quasi-content concept was employed for comprehensively relative quantitation through constructing a so-called universal metabolome standard (UMS) sample and building calibration curves by assaying serial diluted UMS solutions. Consequently, high-confidence structural annotation and relatively quantitative analysis were achieved for 103 compounds, in total. After multivariate statistical analysis, some APs, e.g., (3'S)-praeruptorin A, (3'S)-praeruptorin B, (3'S)-praeruptorin E, as well as several primary metabolites were screened out as the prominent contributors for inter-batch variations. Together, current study shows a promising strategy enabling widely targeted metabolomics of, but not limited to, HMs.

Simultaneous Analysis of the Metabolome and Lipidome Using Polarity Partition Two-Dimensional Liquid Chromatography-Mass Spectrometry

Comprehensive metabolic profiling is a considerable challenge for systems biology since the metabolites in biological samples have significant polarity differences. A heart-cutting two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) method-based polarity partition was established to analyze both the metabolome and lipidome in a single run. Based on the polarity partition strategy, metabolites with high polarity were retained and separated by one-dimensional hydrophilic chromatography, while low- and medium-polarity lipids were collected into a sample loop and injected into two-dimensional reversed-phase chromatography for separation. A simple online dilution strategy realized the online coupling of the 2D-LC-MS, which effectively solved band broadening and peak distortion caused by solvent incompatibility. Moreover, a dual gradient elution procedure was introduced to further broaden the coverage of low-polarity lipids. The metabolites' log P values, which this 2D-LC-MS method could analyze, ranged from -8.79 to 26.86. The feasibility of the 2D-LC-MS system was demonstrated by simultaneous analysis of the metabolome and lipidome in rat plasma related to depression. A total of 319 metabolites were determined within 40 min, including organic acids, nucleosides, carbohydrate derivatives, amino acids, lipids, and other organic compounds. Finally, 44 depression-related differential metabolites were screened. Compared with conventional LC-MS-based methods, the 2D-LC method covered over 99% of features obtained by two conventional methods. In addition, the selectivity and resolution of the hydrophilic metabolites were improved, and the matrix effects of the hydrophobic metabolites were reduced in the developed method. The results indicated that the established 2D-LC system is a powerful tool for comprehensive metabolomics studies.

Online pressurized liquid extraction enables directly chemical analysis of herbal medicines: A mini review

Extraction is responsible for transferring components from solid materials into solvent. Tedious extraction procedures are usually involved in liquid chromatography-based chemical analysis of herbal medicines (HMs), resulting in extensive consumptions of organic solvents, time, energy, and materials, as well as the significant chemical degradation risks for those labile compounds. Fortunately, an emerging online pressurized liquid extraction (OLE, also known as online liquid extraction) technique has been developed for the achievement of directly chemical analysis for solid matrices in recent years, and in a short period, this versatile technique has been widely applied for the chemical analysis of HMs. In the present mini-review, we aim to briefly summarize the principles, the instrumentation, along with the application progress of this robust and flexible extraction technique in the latest six years, and the emerging challenges and future prospects are discussed as well. Special attention is paid onto the hyphenation of the versatile OLE module with LC-MS instrument. The described information is expected to introduce a promising OLE approach and to provide the guidance for the achievement of directly chemical analysis of, but not limited to, HMs.

Simultaneous quantitative assays of 15 ginsenosides from 119 batches of ginseng samples representing 12 traditional Chinese medicines by ultra-high performance liquid chromatography coupled with charged aerosol detector

Despite the extensive consumption of ginseng, precise quality control of different ginseng products is highly challenging due to the containing of ginsenosides in common for different Panax species or different parts (e.g. root, leaf, and flower) of a same species. Herein we performed a comparative investigation of diverse ginseng products by simultaneously assaying 15 saponins (notoginsenoside R1, ginsenosides Rg1, -Re, -Rf, -Ra2, -Rb1, -Rc, -Ro, -Rb2, -Rb3, -Rd, 20(R)-ginsenoside Rg3, 24(R)-pseudoginsenoside F11, chikusetsusaponins IV, and -IVa) using an ultra-high-performance liquid chromatography/charged aerosol detector (UHPLC-CAD) approach. Twelve Panax-derived ginseng products (involving P. ginseng root, P. quinquefolius root, P. notoginseng root, Red ginseng, P. ginseng leaf, P. quinquefolius leaf, P. notoginseng leaf, P. ginseng flower, P. quinquefolius flower, P. notoginseng flower, P. japonicus root, and P. japonicus var. major root) were considered. Benefiting from the condition optimization, the baseline resolution of 15 ginsenosides was achieved on a CORTECS UPLC Shield RP18 column. This method was validated as specific, precise (0.81-1.94% intra-day variation; 0.86-2.35% inter-day variation), and accurate (recovery: 90.73-107.5%), with good linearity (R² > 0.999), high sensitivity (limit of detection: 0.02-0.21 μg; limit of quantitation: 0.04-0.42 μg) and sample stability (1.49-4.74%). Its application to 119 batches of ginseng samples unveiled vital information enabling the authentication of these different ginseng products. Detection of ginsenosides by CAD exhibited superiority over UV in sensitivity and the ability to monitor chromophore-free structures. Large-scale comparative studies by quantifying multiple markers provide methodological reference to the precise quality control of herbal medicine.

Liquid Chromatography-Mass Spectrometry for Clinical Metabolomics: An Overview

Metabolomics is a discipline that offers a comprehensive analysis of metabolites in biological samples. In the last decades, the notable evolution in liquid chromatography and mass spectrometry technologies has driven an exponential progress in LC-MS-based metabolomics. Targeted and untargeted metabolomics strategies are important tools in health and medical science, especially in the study of disease-related biomarkers, drug discovery and development, toxicology, diet, physical exercise, and precision medicine. Clinical and biological problems can now be understood in terms of metabolic phenotyping. This overview highlights the current approaches to LC-MS-based metabolomics analysis and its applications in the clinical research.

[Analysis of chemical components of Chinese medicine Ligustici Radix by achiral-chiral liquid chromatography-predictive multiple reaction monitoring]

Ligustici Radix (Chinese name: maoqianhu) consists of the dried roots of Ligusticum brachylobum Franch., which is mainly distributed in the Yunnan and Sichuan provinces. This herbal medicine has been primarily used for the treatment of cough in traditional Chinese medicine. Ligustici Radix is rich in coumarin derivatives. Interestingly, enantiomers and diastereomers are widely used for these coumarins, thus posing a great challenge for in-depth chemical profile characterization. In the present study, a new analytical platform, achiral-chiral liquid chromatography-tandem mass spectrometry (achiral-chiral LC-MS/MS) was configured to profile the chemical composition of Ligustici Radix. Because achiral and chiral columns were serially coupled, especially enantiomers, both chemically and enantiomerically selective separations could be accomplished simultaneously. The newly configured achiral-chiral LC-MS/MS platform did not require any electronic valve; hence, it could overcome the drawbacks of heart-cutting achiral-chiral two-dimensional LC, i. e., sophisticated instrumentation and limited reproducibility due to the use of electronic valve(s) and the undesired retention time shift across different analytical runs. Some available candidates for chemically selective or enantiomerically selective separation were assayed; then, Capcell core RP-C₁₈ column that was packed with core-shell type particles, and AD-RH column embedding amylose coated particles were employed the achiral and the chiral columns, respectively. The narrow-bore core-shell RP-C₁₈ column served as the front tool to achieve efficient chemoselective separation of coumarin analogs, and enantioselective enantiomers were obtained by using a wide-bore AD-RH chiral column. The predictive multiple reaction monitoring (predictive MRM) mode allowed for the sensitive detection of potential components, and an enhanced product ion (EPI) scan, which was a unique function of Qtrap-MS, was programmed to record the MS² spectra for all captured signals and thus aid structural annotation. Online energy-resolved mass spectrometry (online ER-MS) was introduced to pursue the suitable collision energy for each compound; in particular, inferior collision energy instead of the optimal one was utilized to suppress the response of the primary components such as praeruptorin A, B and pteryxin. The criteria to judge enantiomers or not included identical quantitative and qualitative precursor-to-product ion transitions, identical quantitative versus qualitative responses, and longer retention times from achiral-chiral LC over single-column achiral LC. As a result, a total of sixty components were observed and structurally identified. In particular, enantiomerically selective separations were achieved for eight enantiomers, cis-khellactone (CKL), qianhucoumarin G (QC-G), pteryxin (Pte), praeruptorin A (PA), cis-3'-isovaleryl-4'-acetylkhellactone (IAK), praeruptorin B (PB), praeruptorin E (PE), and cis-3',4'-diisovalerylkhellactone (DIK). Notably, none of the enantiomers were present as racemates; instead, the proportion of one enantiomer in each pair was greater than the other. Achiral-chiral LC-predictive MRM is a feasible choice for the quantitative and qualitative analyses of Ligustici Radix as well as other herbal medicines characterized by enantiomers and diastereomers.

Configuration of the ion exchange chromatography, hydrophilic interaction chromatography, and reversed-phase chromatography as off-line three-dimensional chromatography coupled with high-resolution quadrupole-Orbitrap mass spectrometry for the multicomponent characterization of Uncaria sessilifructus

Herbs represent complex chemical systems involving various primary and secondary metabolites that are featured by large spans of acid-base property, polarity, molecular mass, and content, etc., which thus poses great challenges to characterize the metabolites contained. Here, the combination of multiple-mechanism chromatography coupled with improved data-dependent-MS² acquisition (DDA-MS²) is presented as a strategy to support the deep metabolites characterization. Targeting Uncaria sessilifructus, a reputable medicinal herb containing alkaloids and triterpenic acids (TAs) as the main pharmacologically bioactive ingredients, a three-dimensional liquid chromatography (3D-LC) system was established by integrating ion exchange chromatography, hydrophilic interaction chromatography, and reversed-phase chromatography (IEC-HILIC-RPC). The first-dimensional chromatography, configuring a PhenoSphere SCX column eluted by methanol/20 mM ammonium acetate-0.05% formic acid in water, could well fractionate the total extract into two fractions (unretained ingredients and alkaloids). The subsequent HILIC using an XAmide column and RPC by a CSH Phenyl-Hexyl column achieved the sufficient resolution of the total TAs and total alkaloids, respectively. A polarity-switching precursor ions list-including DDA approach by Q-Orbitrap-MS enabled the high-efficiency, coverage-enhanced identification of alkaloids and TAs. This 3D-LC/Q-Orbitrap-MS system was validated as precise (RSD < 5% for intra-day/inter-day precision), Up to 308 components were separated from U. sessilifructus, and 128 thereof (including 85 alkaloids, 29 TAs, and 14 others) were identified or tentatively characterized, exhibiting superiority over the conventional one-dimensional LC/MS. Conclusively, 3D-LC/MS in an off-line mode can facilitate the flexible configuration of multiple chromatography to accomplish the fit-for-purpose characterization of the metabolites from an herbal extract or a biosample.

Pharmacokinetics/pharmacometabolomics-pharmacodynamics reveals the synergistic mechanism of a multicomponent herbal formula, Baoyuan decoction against cardiac hypertrophy

Multicomponent herbal formulas (MCHFs) have earned a wide reputation for their definite efficacy in preventing or treating chronic complex diseases. However, holistic elucidation of the causal relationship between the bioavailable ingredients of MCHFs and their multitarget interactions is very challenging. To solve this problem, pharmacokinetics/pharmacometabolomics-pharmacodynamics (PK/PM-PD) combined with a multivariate biological correlation-network strategy was developed and applied to a classic MCHF, Baoyuan decoction (BYD), to clarify its active components and synergistic mechanism against cardiac hypertrophy (CH). First, multiple plasma metabolic biomarkers for β-adrenergic agonist-induced CH rats were identified by using untargeted metabolomic profiling, and then, these CH-associated endogenous metabolites and the absorbed BYD-compounds in plasma at different treatment stages after oral administration of BYD were analyzed by using targeted PK and PM. Second, the dynamic relationship of BYD-related compounds and CH-associated endogenous metabolites and signaling pathways was built by using multivariate and bioinformatic correlation analysis. Finally, metabolic-related PD indicators were predicted and further verified by biological tests. The results demonstrated that the bioavailable BYD-compounds, such as saponins and flavonoids, presented differentiated and distinctive metabolic features and showed positive or negative correlations with various CH-altered metabolites and PD-indicators related to gut microbiota metabolism, amino acid metabolism, lipid metabolism, energy homeostasis, and oxidative stress at different treatment stages. This study provides a novel strategy for investigating the dynamic interaction between BYD and the biosystem, providing unique insight for disclosing the active components and synergistic mechanisms of BYD against CH, which also supplies a reference for other MCHF related research.

Liquid chromatography-three-dimensional mass spectrometry enables confirmative structural annotation of cistanoside F metabolites in rat

Clarification the existence forms, including prototype and metabolite(s) is the prerequisite for understanding in-depth the therapeutic mechanisms of a given agent, particularly when oral administration. However, it is still a long distance for unambiguous structural identification of metabolites even employing the cutting-edge MS/MS technique, and the determinant obstacle is produced by its inherent isomer-blind disadvantage. To tackle with this drawback, online energy-resolved mass spectrometry (online ER-MS) was introduced to enable isomeric discrimination after that high-resolution MS/MS provided empirical molecular formula as well as substructures. In-depth metabolic characterization of cistanoside F (CF), an effective natural product, was conducted as a proof-of-concept for the new strategy namely three-dimensional MS that was configured by MS¹, MS² and online ER-MS as 1st, 2nd, and 3rd dimensions, respectively. Sensitive metabolite detection was assisted by predictive multiple-reaction monitoring function on Qtrap-MS, and the empirical formulas of all metabolites were calculated from the quasi-molecular ions yielded from IT-TOF-MS. Subsequently, substructures of each metabolite were constructed by combining the calculated element compositions and the well-defined mass fragmentation pathways. Finally, online ER-MS was responsible to generate optimal collision energies for bonds-of-interest, and enabled rational selection among candidate structures. A total of thirteen metabolites were detected and confirmatively identified in rat after oral treatment of CF using LC-3D MS. Acyl-migration, hydrolysis and sulfation played key roles for the metabolic fate of CF. More importantly, LC-3D MS is an eligible tool to achieve confidence-enhanced structural annotation of metabolites in biological matrices because of the unique isomeric differentiation ability from online ER-MS.

Online energy-resolved MS boosts the potential of LC-MS towards metabolite characterization of salidroside and tyrosol

Although currently serving as the workhorse for metabolite characterization, one of the most challenging tasks for LC-MS is isomeric differentiation because isomers frequently yield identical quasi-molecular ions and fragmented ion species. Our previous studies have demonstrated that online energy-resolved MS (ER-MS) is an orthogonal technique for MS/MS experiments to facilitate isomeric identification. Herein, attempts were made for the in-depth characterization of the metabolic profiles of an effective natural product named salidroside (SA) in rats using LC coupled with three-dimensional mass spectrometry (LC-3D MS) that was configured by MS¹, MS² and online ER-MS as 1^st, 2^nd, and 3^rd dimensions, respectively. Moreover, the metabolism characterization of its aglycone, namely, tyrosol (Try) was conducted in parallel to aid in proposing metabolic pathways. High-resolution MS¹ and MS² spectra were acquired by IT-TOF-MS, and subsequent data processing provided theoretical formula and sub-structures for each metabolite. Subsequently, online ER-MS was conducted for precursor > product ion transitions-of-interest to offer linkage information among the sub-structures via building breakdown graphs. As a result, ten (M1-10) and nine (M1, M2, and M5-11) metabolites were detected in SA- and Tyr-administrated biological samples, respectively, and their structures were qualitatively identified. Crucial metabolism occurred for either component. SA initially underwent hydrolysis to produce Tyr, and subsequently hydroxylation, oxidation, glucuronidation, and sulfation were observed as the primary metabolic pathways. To summarize, the metabolic fate of SA was understood in depth, and Tyr, as the hydrolytic product, was responsible for the occurrences of most metabolites (M1, M2, and M5-10). More importantly, identification confidences of the metabolites were significantly advanced by LC-3D MS, suggesting that it is eligible to serve as an integral part of the analyst's toolbox.

Confirmative Structural Annotation for Metabolites of (R)-7,3'-Dihydroxy-4'-methoxy-8-methylflavane, A Natural Sweet Taste Modulator, by Liquid Chromatography-Three-Dimensional Mass Spectrometry

Flavonoids occupy the largest family of natural products and possess a broad spectrum of health benefits. Their metabolites are sometimes the truly effective molecules in vivo. It is still challenging, however, to unambiguously identify flavonoid metabolites using conventional LC-MS/MS. Herein, we aimed to pursue auxiliary structural clues to m/z values in both MS¹ and MS² spectra through LC coupled to three-dimensional MS (LC-3D MS). MS¹, as the first dimension, was in charge of suggesting theoretical molecular formulas, MS², the as second dimension, was responsible for offering substructures, and exactly, online energy-resolved MS (ER-MS), as the third dimension, provided optimal collision energies (OCEs) that reflected the linkage manners among the substructures. Metabolic characterization of a natural sweet taste modulator, namely, (R)-7,3'-dihydroxy-4'-methoxy-8-methylflavane (DHMMF), was conducted as a proof-of-concept. Extensive efforts, such as full MS¹ and MS² scans on IT-TOF-MS and predictive selected-reaction monitoring mode on Qtrap-MS, were made for in-depth metabolite mining. Seventeen metabolites (M1-M17) were captured from DHMMF-treated biological samples, including 17 (M1-M17), 10 (M4-M9, M11, M13, M14, and M16), and 2 (M5 and M10) metabolites from urine, plasma, and feces, respectively. Their structures were configured by integrating MS¹, MS², and OCE information. Except M10, all metabolites were new compounds. LC-MS/MS-guided chromatographic purification yielded three glucuronyl-conjugated metabolites (M5, M8, and M11), and NMR spectroscopic assays consolidated the structures transmitted from LC-3D MS. Demethylation, glucuronidation, and sulfation occurred as the primary metabolic pathways of DHMMF. Above all, LC-3D MS bridged LC-MS/MS from putatively structural annotation toward confidence-enhanced identification, beyond the metabolite characterization of flavonoids.

Analytical techniques for metabolomic studies: a review

Metabolomics is the comprehensive study of small-molecule metabolites. Obtaining a wide coverage of the metabolome is challenging because of the broad range of physicochemical properties of the small molecules. To study the compounds of interest spectroscopic (NMR), spectrometric (MS) and separation techniques (LC, GC, supercritical fluid chromatography, CE) are used. The choice for a given technique is influenced by the sample matrix, the concentration and properties of the metabolites, and the amount of sample. This review discusses the most commonly used analytical techniques for metabolomic studies, including their advantages, drawbacks and some applications.

Profiling and identification of aqueous extract of Cordyceps sinensis by ultra-high performance liquid chromatography tandem quadrupole-orbitrap mass spectrometry

Characterization of aqueous extract in traditional Chinese medicine (TCM) is challenging due to the poor retention of the analytes on conventional C₁₈ columns. This study presents a systematic characterization method based on a rapid chromatographic separation (8 min) on a polar-modified C₁₈ (Waters Cortecs T3) column of aqueous extract of Cordyceps sinensis. UHPLC-HRMS method was used to profile components in both untargeted and targeted manners by full MS/PIL/dd-MS² acquisition approach. The components were identified or tentatively identified by reference standards comparison, fragmentation rules elucidation and available databases search. A total of 91 components, including 10 nucleobases, 20 nucleosides, 39 dipeptides, 18 amino acids and derivatives and 4 other components, were characterized from the aqueous extract of C. sinensis. And this was the first time to systematically report the presence of nucleosides and dipeptides in C. sinensis, especially for modified nucleosides. The chemical basis inquiry of this work would be beneficial to mechanism exploration and quality control of C. sinensis and related products. Meanwhile, this work also provided an effective solution for characterization of aqueous extract in TCM.

Integrated approach for confidence-enhanced quantitative analysis of herbal medicines, Cistanche salsa as a case

Although far away from perfect, it is practical to assess the quality of a given herbal medicine (HM) through simultaneous determination of a panel of components. However, the confidences of the quantitative outcomes from LC-MS/MS platform risk several technical barriers, such as chemical degradation, polarity range, concentration span, and identity misrecognition. Herein, we made an attempt to circumvent these obstacles by integrating several fit-for-purpose techniques, including online extraction (OLE), serially coupled reversed phase LC-hydrophilic interaction liquid chromatography (RPLC-HILIC), tailored multiple reaction monitoring (MRM), and relative response vs. collision energy curve (RRCEC) matching. Confidence-enhanced quantitative analysis of Cistanche salsa (Csa), a well-known psammophytic species and tonic herbal medicine, was conducted as a proof-of-concept. OLE module was deployed to prohibit chemical degradation, in particular E/Z-configuration transformation for phenylethanoid glycosides. Satisfactory retention took place for each analyte regardless of polarity because of successive passing through RPLC and HILIC columns. Optimum parameters for the minor components, at the meanwhile of inferior ones for the abundant ingredients, ensured the locations of all contents in the linear ranges. The unequivocal assignment of the captured signals was achieved by matching retention times, ion transitions, and more importantly, RRCECs between authentic compounds and suspect peaks. Diverse validation assays demonstrated the newly developed method to be reliable. Particularly, the distribution of mannitol rather than galactitol was disclosed although these isomers showed identical retention time and ion transitions. The contents of 21 compounds-of-interest were definitively determined in Csa as well as two analogous species, and the quantitative patterns exerted great variations among not only different species but different Csa samples. Together, the fortification of OLE-RPLC-HILIC-tailored MRM with RRCEC matching could fully address the demands from confidence-enhanced quantitative analysis of HMs.

A full solution for multi-component quantification-oriented quality assessment of herbal medicines, Chinese agarwood as a case

The quality of herbal medicines (HMs) is the prerequisite for their pronounced therapeutic outcomes in clinic, and multi-component (also known as quality markers, Q-markers) quantification has been widely emphasized as a viable means for quality evaluation. Because of the chemical diversity, the quality control practices are extensively dampened by four principal technical bottlenecks, including the lack of authentic compounds, large polarity span, extensive concentration range, and signal misrecognition for those potential Q-markers. An attempt to promote the potential of LC-MS/MS is made herein to cope with those obstacles and Chinese agarwood was employed as a case study. Firstly, a home-made fraction collector was introduced to automatically fragment the entire extract into a panel of fractions-of-interest. Secondly, quantitative ¹H-NMR was deployed to offset the LC-MS/MS potential towards in-depth chemical profiling each fraction, and those well-defined fractions were then pooled and combined with some accessible authentic compounds to generate the pseudo-mixed standard solution. Thirdly, serial improvements were conducted for LC-MS/MS measurements. Reversed phase LC and hydrophilic interaction LC were serially coupled in respond to the large polarity window, and online parameter optimization, response tailoring, as well as RRCEC (relative response vs. collision energy curve) matching were integrated in MS/MS domain to advance the quantitative confidences. Simultaneous determination was conducted for 26 components, in total, in Chinese agarwood after method validation. In particular, authentic compound-free quantification was achieved for eight 2-(2-phenylethyl)chromone derivatives. Above all, the strategy is a promising solution to completely tackle with the technical barriers toward Q-marker quantification-oriented quality control of Chinese agarwood, as well as other HMs.