Direct Infusion-Three-Dimensional-Mass Spectrometry Enables Rapid Chemome Comparison among Herbal Medicines

Identifying isomers in Chinese traditional medicine via density functional theory and ion fragmentation simulation software QCxMS

In the realm of electrospray ionization mass spectrometry (ESI-MS), distinguishing among isomers poses a significant challenge due to the minimal spectral differences that often arise from their subtle structural differences. This makes the accurate identification of these compounds through solely experimental spectra a daunting task. Computational chemistry has emerged as a pivotal tool in bridging the gap between experimental observations and theoretical understanding. This study used the MS fragmentation simulation software, QCxMS, to model the spectra of five groups of isomers, encompassing 11 compounds, found in the traditional Chinese medicine, Zhishi Xiebai Guizhi Decoction. By comparing the spectra predicted through computational methods with those derived from Ultra-high performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS) experiments, it was observed that, following the optimization of simulation parameters, QCxMS was capable of generating reliable spectra for all examined compounds. Notably, the data calculated under both GFN1-xTB and GFN2-xTB levels exhibited no significant discrepancies. Further analysis enabled the identification of the principal fragments of the 11 compounds from the theoretical data, facilitating the deduction of their fragmentation pathways. The Density Functional Theory (DFT) method was subsequently applied to compute the primary fragmentation energies of these compounds. The findings revealed a congruence between the energy data calculated using both thermodynamic and kinetic approaches and the observed fragment abundance of the isomers. This alignment providing a more precise theoretical framework for understanding the mechanisms underlying the generation of fragment ion differences among isomers.

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.

Metabolite identification of salvianolic acid A in rat using post collision-induced dissociation energy-resolved mass spectrometry

BACKGROUND

As one of the most famous natural products, salvianolic acid A (SAA) is undergoing clinical trials for the treatments of angina pectoris and coronary heart disorders. However, the in vivo metabolites of SAA have only been tentatively identified, leading to a barrier for precise therapeutical drug monitoring.

METHODS

Ultra-high performance liquid chromatography coupled with quadrupole time of flight tandem mass spectrometry (UPLC-Qtof-MS/MS) was firstly employed to acquire high-resolution MS1 and MS2 spectra for all metabolites. Through paying special attention onto the features of ester bond dissociation, metabolism sites were restricted at certain regions. To further determine the metabolism site, such as the monomethylated products (M23, M25, and M26), post collision-induced dissociation energy-resolved mass spectrometry (post-CID ER-MS) was proposed through programming progressive exciting energies to the second collision chamber of hybrid triple quadrupole-linear ion trap mass spectrometry (Qtrap-MS) device.

RESULTS

After SAA oral administration, 29 metabolites (M1-M29), including five, thirteen, and sixteen ones in rat plasma, urine, and feces, respectively, were detected in rats. The metabolism route was initially determined by applying well-defined mass fragmentation pathways to those HR-m/z values of precursor and fragment ions. Metabolism site was limited to SAF- or DSS-unit based on the fragmentation patterns of ester functional group. Through matching the dissociation trajectories of concerned 1st-generation fragment ions with expected decomposition product anions using post-CID ER-MS strategy, M23 and M25 were unequivocally assigned as 3'-methyl-SAA and 3''-methyl-SAA, and M26 was identified as 2-methyl-SAA or 3-methyl-SAA. Hydrolysis, methylation, glucuronidation, sulfation, and oxidation were the primary metabolism channels being responsible for the metabolites' generation.

CONCLUSION

Together, the metabolism regions and sites of SAA metabolites were sequentially identified based on the ester bond dissociation features and post-CID ER-MS strategy. Importantly, the present study provided a promising way to elevate the structural identification confidence of natural products and metabolites.

Two-dimensional code enables visibly mapping herbal medicine chemome: an application in Ganoderma lucidum

BACKGROUND

Chemical profile provides the pronounced evidence for herbal medicine (HM) authentication; however, the chemome is extremely sophisticated. Fortunately, two-dimensional (2D) code, as a quick response means, is conceptually able to store abundant information, exactly fulfilling the chemical information storage demands of HMs.

METHODS

We here attempted to denote both MS[Formula: see text] and MS[Formula: see text] dataset of HM with a single 2D-code chart. Measurement of Ganoderma lucidum that is one of the most famous HMs with LC-MS/MS was employed to illustrate the "coding-decoding" workflow for the conversion amongst MS/MS dataset, 2D-code, and chemical profile, and to evaluate the applicability as well. After data acquisition, and m/z value of each deprotonated molecular signal was divided into integer and decimal portions, corresponding to x and y coordinates of 2D-plot, respectively. On the other side, m/z values of all its fragment ions were exactly assigned to serial x values sharing an identical y value being equal to the precursor ion. 2D-code was thereafter produced by plotting these defined dots at a 2D-chart. Regarding a given 2D-code map, the entire chart (x coordinate: 0-600; y coordinate: 0-600) was fragmented into two regions by the line of y=x. MS[Formula: see text] spectral signals always located below the line, whereas all fragment ions lay at the left zone. After extracting information from the edges of each square frame, m/z values of both precursor ion and fragment ions could be harvested and putatively deciphered to a compound through applying some empirical mass fragmentation rules.

RESULTS

The entire code of Ganoderma lucidum fruit bodies therefore corresponded exactly to a compound set. The elution program, even the employment of direct infusion, couldn't significantly impact the code, and dramatical differences occurred between different species and amongst different parts of Ganoderma lucidum as well. Not only ganoderic acid cluster but also certain primary metabolites served as the diagnostic compounds towards species differentiation.

CONCLUSION

2D-code might be a meaningful, practical visual way for rapid HM recognition because it is convenient to achieve the conversion amongst MS/MS dataset, 2D-barcode plot, and the chemome.

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.

Direct infusion electrospray ionization-ion mobility-mass spectrometry for rapid metabolite marker discovery of medicinal Phellodendron Bark

Ion-mobility mass spectrometry (IM-MS) currently serves as a powerful tool for the structural identification of numerous biological compounds and small molecules. In this work, rapid metabolomic analysis of closely-related herbal medicines by direct injection ion mobility-quadrupole time-of-flight mass spectrometry (DI-IM-QTOF MS) was established. Phellodendron chinense Bark (PC) and Phellodendron amurense Bark (PA) were studied as a case. Thirty-three batches of PC and twenty-two batches of PA have been directly injected in electrospray ionization-IM-QTOF MS in positive mode. Without chromatographic separation, each run was completed within 3 min. After data alignment and statistical analysis, a total of seven chemical markers were found (p-value < 0.05, VIP > 1.00). Among them, the ion m/z 342.17 and m/z 356.18 present a single peak in the drift spectrum, respectively, but their drift time has a certain deviation compared with the pure substance of known compounds. In addition, the MS/MS spectra also confirmed that the single peak includes two chemical isomers. To investigate the composition ratio of individual isomers, the calibration curves of relative drift time (rDT) based on the standard superposition method were established, which were found to fit the least square regression. The ion [M]⁺m/z 342.17 was recognized consisting of magnoflorine (MAG) and phellodendrine (PHE), and their composition ratio in PA and PC samples was calculated. The results were compared with those obtained by the HPLC quantitative method, which produced equivalent quantification results. Our DI-IM-QTOF MS methodology provides an additional methodology for the relative quantification of unresolved isomers in drift tube IM-MS and offers DI-IM-QTOF MS based metabolomics.

In-depth characterization of nitrogen heterocycles of petroleum by liquid chromatography-energy-resolved high resolution tandem mass spectrometry

With the increased attention to processing heavy crude oils, a detailed description of chemical composition is critical for the petroleum refining industry. The current analytical technique such as ultrahigh resolution mass spectrometry has been successfully applied for the molecular level characterization of complex petroleum fractions. But the structural characterization of heavy petroleum feedstock is still a great challenge. In this study, a novel in-depth characterization method of nitrogen heterocycles (N-heterocycles) in heavy petroleum mixtures was proposed by online liquid chromatography coupled with electrospray ionization high resolution energy-resolved mass spectrometry. A series of typical basic aromatic, neutral aromatic and naphtheno-aromatic nitrogen heterocyclic model compounds were synthesized to investigate energy-resolved fragmentation behaviors in high energy collision-induced dissociation at 10-100 eV. Energy-dependent fragmentation pathways were elucidated. Notably, characteristic double bond equivalent (DBE) versus carbon number distributions of N₁ ions and all CH ions were discovered, which were closely related to their core structure. Then a workflow to assign core structures of alkyl-substituted N-heterocycles in petroleum was proposed and validated. The developed method was applied to investigate the structural isomers in feed and product vacuum gas oil (VGO) fractions. Core structural differences in feed VGO and subtle structural variations between feed and product VGOs were recognized. This work can distinguish structural isomers of N-heterocycles with the subtle difference in their core structure in heavy petroleum fractions based on global energy dimensional fragmentation characteristics.

Unsupervised methods in LC-MS data treatment: Application for potential chemotaxonomic markers search

The combination of Liquid Chromatography and Mass Spectrometry (LC-MS) is commonly used to determine and characterize biologically active compounds because of its high resolution and sensitivity. In this work we explore the interpretation of LC-MS data using multivariate statistical analysis algorithms to extract useful chemical information and identify clusters of similar samples. Samples of leaves from 19 plants belonging to the Apiaceae family were analyzed in unified LC conditions by high- and low-resolution mass spectrometry in a wide range scan mode. LC-MS data preprocessing was performed followed by statistical analysis using tensor decomposition in the form of Parallel Factor Analysis (PARAFAC); matrix factorization following tensor unfolding with principal component analysis (PCA), independent component analysis (ICA), non-negative matrix factorization (NMF); or unsupervised feature selection (UFS). The optimal number of components for each of these methods were found and results were compared using four different metrics: silhouette score, Davies-Bouldin index, computational time, number of noisy components. It was found that PCA, ICA and UFS give the best results across the majority of the criteria for both low- and high-resolution data. An algorithm for biomarker signal selection is suggested and 23 potential chemotaxonomic markers were tentatively identified using MS² data. Dendrograms constructed by the methods were compared to the molecular phylogenic tree by calculating pixel-wise mean square error (MSE). Therefore, the suggested approach can support chemotaxonomic studies and yield valuable chemical information for biomarker discovery.

Full Collision Energy Ramp-MS2 Spectrum in Structural Analysis Relying on MS/MS

Albeit frequently being overlooked, MS² spectrum variation against collision energy (CE) implies auxiliary structural clues for m/z values. Online energy-resolved MS (ER-MS) provides the opportunity to acquire the trajectory of ion intensity against CE for any fragment ion of interest, thus exactly offering the desired momentum to empower the conventional MS² spectrum at a certain CE forward to a full-CE ramp MS² spectrum (FCER-MS²). Efforts were made here to construct an FCER-MS² spectrum and to evaluate its potential toward structural analysis. Flavonoids were employed as a proof of concept. MS² spectra of 76 compounds were recorded by LC-Q-Exactive-MS, and online ER-MS was subsequently programmed using LC-Qtrap-MS to build a breakdown graph for each obvious fragment ion. After defining the greatest value amongst all regressive apices as 100%, the normalized breakdown graphs comprised an FCER-MS² spectrum for each compound. The FCER-MS² spectrum contained the MS² spectrum at any CE as well as optimal CE (OCE) and maximal relative ion intensity (RII_max) of each fragment ion. Except the pronounced isomeric discrimination potential, either OCE or RII_max reflected certain structural properties, such as aglycone, glycosidic bond, and hydroxy, methoxy, and glycosyl substituents. These rules were subsequently applied for flavonoid-focused characterization of a famous herbal medicine, namely Scutellariae Radix, and high-level structural annotation was accomplished for 75 flavonoids. Above all, the FCER-MS² spectrum includes m/z, OCEs, and RII_max features, thus facilitating confidence-advanced structural analysis.

A pseudotargeted method based on sequential window acquisition of all theoretical spectra mass spectrometry acquisition and its application in quality assessment of traditional Chinese medicine preparation-Yuanhu Zhitong tablet

Quality control plays a key role in the application of Chinese materia medica, especially in the preparation of traditional Chinese medicine. A pseudotargeted analysis method using an ultra-high-performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry that was operated in the sequential window acquisition of all theoretical spectra mode was proposed to explore the chemical markers of traditional Chinese medicine preparation. Full-scan-based untargeted analysis was applied to extract the target ions. After data preprocessing, 302 target ions were extracted and used for the subsequent sequential window acquisition of all theoretical spectra analyses. The established sequential window acquisition of all theoretical spectra-based pseudotargeted approaches exhibited good repeatability and a wide linear range. The established method was successfully applied to discover analytical markers for the Yuanhu Zhitong tablet. After multivariate statistical analysis, 94 potential markers were identified. Ten markers were annotated by matching accurate m/z and product ion information obtained from previous reports. It is clearly indicated that the pseudotargeted analysis could make a great contribution to the quality assessment of traditional Chinese medicine preparation as a newly emerging technique.

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.

[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.

Direct infusion-tandem mass spectrometry combining with data mining strategies enables rapid chemome characterization of medicinal plants: A case study of Polygala tenuifolia

Data-independent MS² spectrum acquisition after fragmenting the precursor ion cohort with 1 Da bin, termed as MS/MS^{ALL ®}, offers an opportunity to achieve rapid chemome characterization when being coupled with direct infusion (DI). Some post-acquisition data processing strategies, such as mass defect filtering (MDF), diagnostic fragment ion filtering (DFIF), and neutral loss filtering (NLF), facilitate data extraction from massive dataset, and moreover, molecular weight (MW) imprinting allows rapid capturing those reported components. Here, DI-MS/MS^{ALL ®} was employed to acquire cubic spectral dataset, and the strategies such as MW imprinting, MDF, DFIF, and NLF, were subsequently applied to filter the structural information. The integrated pipeline was utilized for the chemome characterization of Polygala tenuifolia, a famous edible medicinal plant. To aid information filtering, an in-house chemical library was built by comprehensively collecting structural information from some available databases. A single analytical run was completed within 5 min. For MS¹ spectrum processing, MW imprinting was firstly applied to capture the compounds in the chemical library, and "five-point" MDF frames were employed to pursue saponins, oligosaccharide esters, and xanthones. Regarding MS² spectral plot, DFIF and NLF were deployed to search information-of-interest. Structural identification was accomplished by carefully correlating precursor ions and MS² spectra, applying the well-defined mass cracking rules, and referring to literature information as well as available databases. A total of 109 compounds, mainly saponins (40 ones), oligosaccharide esters (29 ones), and xanthones (19 ones), were captured and structurally annotated. MS¹ spectra were also implemented for chemome comparison between Polygala tenuifolia and several similar plants belonging to Polygala genus, resulting in the observation of significant inter- and intra-species differences. Above all, DI-MS/MS^{ALL ®} is a promising choice for high-throughput chemome profiling of, but not limited to, medicinal plants, in particular when being integrated with post-acquisition data processing strategies.

Classification-based strategies to simplify complex traditional Chinese medicine (TCM) researches through liquid chromatography-mass spectrometry in the last decade (2011-2020): Theory, technical route and difficulty

The difficulty of traditional Chinese medicine (TCM) researches lies in the complexity of components, metabolites, and bioactivities. For a long time, there has been a lack of connections among the three parts, which is not conducive to the systematic elucidation of TCM effectiveness. To overcome this problem, a classification-based methodology for simplifying TCM researches was refined from literature in the past 10 years (2011-2020). The theoretical basis of this methodology is set theory, and its core concept is classification. Its starting point is that "although TCM may contain hundreds of compounds, the vast majority of these compounds are structurally similar". The methodology is composed by research strategies for components, metabolites and bioactivities of TCM, which are the three main parts of the review. Technical route, key steps and difficulty are introduced in each part. Two perspectives are highlighted in this review: set theory is a theoretical basis for all strategies from a conceptual perspective, and liquid chromatography-mass spectrometry (LC-MS) is a common tool for all strategies from a technical perspective. The significance of these strategies is to simplify complex TCM researches, integrate isolated TCM researches, and build a bridge between traditional medicines and modern medicines. Potential research hotspots in the future, such as discovery of bioactive ingredients from TCM metabolites, are also discussed. The classification-based methodology is a summary of research experience in the past 10 years. We believe it will definitely provide support and reference for the following TCM researches.

Shotgun chemome characterization of Artemisia rupestris L. Using direct infusion-MS/MSALL

In comparison of liquid chromatography, direct infusion is a superior choice to achieve high-throughput measurements. The specificity and selectivity of tandem mass spectrometry (MS/MS) actually result in a so-called MS separation potential when chemical characterization of herbal medicines. Here, a MS/MS^ALL program was introduced to promote DI-MS/MS to be an eligible tool for shotgun chemome characterization of Artemisia rupestris L. that is currently drawing worldwide interests because of the promising antiviral activity. After MS¹ spectral acquisition for the crude extract, the gas phase fractionation concept enabled the precursor ion cohort sequentially entered the collision cell with a stepped unit mass window (step-size as 1 Da) to generate MS² spectra, thus generating a unique property integrating the advantages of both data-dependent and data-independent acquisition manners. Even though being free of chromatographic separation, spectrometric separations were accomplished for by MS/MS^ALL program unless the components shared identical nominal molecular weights. Extensive efforts such as the correlations of MS¹ signals with MS² spectra, structural annotations of fragment ion species, information retrieval in some accessible databases, and referring to the literature data, were devoted for chemical characterization, and as a result, 44 compounds, in total, were structurally identified from 50% aqueous methanol exact of A. rupestris, including 8 caffeoyl quinic acid derivatives, 13 flavonoids, 15 monomeric and dimeric sesquiterpenoids, 4 fatty acids, 2 penylpropanoids, along with 2 other compounds. However, isomers were assigned as an isomeric mixture because their precursor ions always co-existed in a single mass window. Above all, DI-MS/MS^ALL provides an alternative tool for chemome characterization of herbal medicines, in particular when the great measurement workload for a large sample cohort, attributing to the high-throughput advantage.

Simultaneous determination of eight tryptic peptides in musk using high-performance liquid chromatography coupled with tandem mass spectrometry

In comparison of herbal medicines, less attention has been paid onto animal medicines, partially attributing to the protein-enriched property. Particularly, it is still challenging to conduct quality evaluation for the animal medicines because of the lack of a fit-for-purpose analytical tool. Herein, an attempt was made to propose a workflow allowing the quality assessment of animal medicines by LC-MS/MS, and musk that is one of the most precious traditional Chinese medicines was employed as a representative case for utility illustration. After the extraction of protein from musk with a well-defined protocol, tryptic digestion was conducted to hydrolyze proteins into peptides, and the peptide-enriched sample was subjected to nanoLC-Orbitrap MS measurement. The tandem mass spectral dataset was retrieved in Human Swiss-Prot FASTA database, and the sequences together with the sources of 733 tryptic peptides, in total, were annotated. Because of the abundant distributions, eight peptides were chosen as the analytes for quantitative measurements, and their quantitative MS parameters, such as ion transitions and collision energies, were rapid optimized in an authentic compound-free manner using online energy-resolved MS (ER-MS). On the other side, the annotated peptides were structurally consolidated via synthesizing reference peptides. When the synthetic peptides were applied for parameter optimization with the authentic compound-dependent manner, the values were almost identical with those from online ER-MS measurements. After being validated with diverse assays, the developed method was applied for the simultaneous determination of eight peptides in 28 batches of musk samples, including captive (C1-C18) and wild ones (W1-W10). Significant differences took place for the content patterns of concerned tryptic peptides between the captive and wild musk samples. Trace distributions occurred for DVDAAYMNK in most batches. Captive samples were rich of QSLEASLAETEGR, TLLDIDNTR, and EVATNSELVQSGK, whereas wild samples were able to accumulate YLGYLEQLLR. Together, the present study provided a meaningful approach for the quality evaluation of musk, as well as other peptide-enriched animal medicines, even if the absences of authentic peptides.

Assessment of variation of inline cartridge extraction mass spectra

Recently, mass-spectrometry methods show its utility in tumor boundary location. The effect of differences between research and clinical protocols such as low- and high-resolution measurements and sample storage have to be understood and taken into account to transfer methods from bench to bedside. In this study, we demonstrate a simple way to compare mass spectra obtained by different experimental protocols, assess its quality, and check for the presence of outliers and batch effect in the dataset. We compare the mass spectra of both fresh and frozen-thawed astrocytic brain tumor samples obtained with the inline cartridge extraction prior to electrospray ionization. Our results reveal the importance of both positive and negative ion mode mass spectrometry for getting reliable information about sample diversity. We show that positive mode highlights the difference between protocols of mass spectra measurement, such as fresh and frozen-thawed samples, whereas negative mode better characterizes the histological difference between samples. We also show how the use of similarity spectrum matrix helps to identify the proper choice of the measurement parameters, so data collection would be kept reliable, and analysis would be correct and meaningful.