Experimentally Determined Diagnostic Ions for Identification of Peptide Glycotopes.

The analysis of the structures of glycans present on glycoproteins is an essential component for determining glycoprotein function; however, detailed glycan structural assignment on glycopeptides from proteomics mass spectrometric data remains challenging. Glycoproteomic analysis by mass spectrometry currently can provide significant, yet incomplete, information about the glycans present, including the glycan monosaccharide composition and in some circumstances the site(s) of glycosylation. Advancements in mass spectrometric resolution, using high-mass accuracy instrumentation and tailored MS/MS fragmentation parameters, coupled with a dedicated definition of diagnostic fragmentation ions have enabled the determination of some glycan structural features, or glycotopes, expressed on glycopeptides. Here we present a collation of diagnostic glycan fragments produced by traditional positive-ion-mode reversed-phase LC-ESI MS/MS proteomic workflows and describe the specific fragmentation energy settings required to identify specific glycotopes presented on N- or O-linked glycopeptides in a typical proteomics MS/MS experiment.

In-depth characterization of cycloartane triterpenoids and discovery of species-specific markers from three Cimicifuga species guided by a strategy that integrates in-source fragment elimination, diagnostic ion recognition, and feature-based molecular networking.

Characterization studies of the plant metabolome are crucial for revealing plant physiology, developing functional foods, and controlling quality. Mass spectrometry-based metabolite profiling allows unprecedented qualitative coverage of complex biological extract composition. However, the electrospray ionization used in metabolite profiling generates multiple artifactual signals for a single analyte, which makes it challenging to filter out redundant signals and organize the signals corresponding to abundant constituents. This study proposed a strategy integrating in-source fragments elimination, diagnostic ions recognition, and feature-based molecular networking (ISFE-DIR-FBMN) to simultaneously characterize cycloartane triterpenoids (CTs) from three medicinal Cimicifuga species. The results showed that 63.1 % of the measured ions were redundant. A total of 184 CTs were annotated, with 27.1 % being reported for the first time. It presents a promising approach to assess the composition of natural extracts, thus facilitating new ingredient registrations or natural-extracts-based drug discovery campaigns. Besides, chemometrics analysis of the three Cimicifuga species identified 32 species-specific markers, highlighting significant differences among them. The valuable information can enhance the sustainable utilization and further development of Cimicifuga resources. The codes involved in ISFE-DIR-FBMN are freely available on GitHub (https://github.com/LHJ-Group/ISFE-DIR-FBMN.git).

Integration of diagnostic ions, molecular network and chemometrics to illustrate the chemical mechanism of Radix Astragali processed with honey.

Radix Astragali (RA) is one of the most frequently used traditional Chinese medicine (TCM) in China, and honey-processed RA (HRA) is its common processing product. Thus far, their comprehensive chemical differences are not well understood. In this work, an integrated approach using Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) combined with diagnostic ions, molecular network (MN) and chemometrics was established to profile their chemical characterizations and illustrate the chemical mechanism of RA processed with honey. A total of 226 compounds were tentatively identified including 50 flavonoid glycosides, 26 flavonoid aglycone, 56 saponins, 30 organic acids, 18 amino acids, 3 coumarins and 43 other compounds, of which 33 compounds were characterized according to MN. Their chemical differences were further investigated by integrating of multivariate statistical analysis, student's t-test analysis, linear regression analysis and MN. Consequently, multivariate statistical analysis showed that the raw and processed RA were different form each other. Besides, 33 different compounds were found to be significantly altered by student's t-test analysis. Apart from this, linear regression analysis indicated 42 and 120 compounds underwent the significant varieties. The potential chemical reactions induced by honey-processing, such as possible hydrolysis reactions and isomerization reactions, were speculated based on these variations coupled the areas changes of the nodes in MN. This study provided an efficient strategy to illustrate the chemical mechanism of TCM processing.

Enhanced LC-ESI-MS/MS Sensitivity by Cationic Derivatization of Organophosphorus Acids.

The chemical derivatization to enhance the signal intensity and signal-to-noise (S/N) of several organophosphorus (OP) acids in liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS) is illustrated. The OP class of compounds represents the environmental degradants of OP nerve agents and pesticides. N-(2-(bromomethyl)benzyl)-N,N-diethylethanaminium bromide (CAX-B) was utilized to derivatize a panel of eight acids consisting of five alkyl methylphosphonic acids (ethyl-, isopropyl-, isobutyl-, cyclohexyl-, and pinacolyl-methylphosphonic acid) along with three dialkylphosphate analogs (diethyl-, dibutyl-, and diethyl thio-phosphate). The derivatization reaction with CAX-B was conducted in acetonitrile in the presence of potassium carbonate at 70 °C for 1 h. The resulting acid derivatives were analyzed with an LC-Orbitrap-ESI-MS/MS, and their dissociation processes were investigated. It was found that the derivatization procedure increased the limits of identification (LOIs) by one to over two orders of magnitude from the range of 1 to 10 ng/mL for the intact OP-acids to the range of 0.02-0.2 ng/mL for the derivatized acids utilizing an LC-MS(QqQ) in MRM mode, regardless of the sample matrix (hair, concrete, or plant extracts). The interpretation of the corresponding ESI-MS/MS spectra for each type of derivatized sub-OP family revealed the formation of characteristic neutral losses and a characteristic ion for the organophosphorus core. This derivatization is beneficial and useful for screening and identifying target and "unknown" OP acids.

Rapid identification of stigmastane-type steroid saponins from Vernonia amygdalina leaf based on α-glucosidase inhibiting activity and molecular networking.

Steroid saponins are secondary metabolites with multiple medicinal values that are found in large quantities in natural medicines, especially Vernonia amygdalina, a famous nature medicine for the treatment of tonsillitis, diabetes, pneumonia. The current study was designed to combine molecular networking (MN) with diagnostic ions for rapid identification of Δ7,9(11) stigmastane-type saponins which were the α-glucosidase inhibitory active substances in V. amygdalina. First, the α-glucosidase inhibitory activities of five Δ7,9(11) stigmastane-type steroid saponins that were previously isolated were screened, which indicated that the Δ7,9(11) stigmastane-type steroid saponin was one of the active constituents responsible for ameliorating diabetes. Furthermore, a strategy was proposed to identify stigmastane-type steroid saponins and verify the plausibility of derived fragmentation pathways by applying MN, MolNetEnhancer and unsupervised substructure annotation (MS2LDA). Based on this strategy, other seven Δ7,9(11) stigmastane-type steroid saponins were identified from this plant. Our research provide scientific evidence for the antidiabetic potential of the steroid saponin-rich extract of V. amygdalina leaf.

Targeted discovery and characterization of secoiridoid glycosides from Jasminum pentaneurum Hand.-Mazz by ultra-performance liquid chromatography coupled with quadruple time-of-flight mass spectrometry based on diagnostic ion and neutral loss filtering strategy.

In this study, we proposed an integrated analytical strategy for the rapid and comprehensive discovery of a specific class of secoiridoid glycosides from a Yao medicine, Jasminum pentaneurum Hand.-Mazz. The strategy fully took advantage of the accuracy of ultra-performance liquid chromatography coupled with quadruple time-of-flight mass spectrometry, and the efficiency of diagnostic ion filtering and neutral loss filtering. Twenty-four secoiridoid glycosides, including three known ones and 21 unreported ones, were rapidly discovered and characterized based on the detail analysis of their mass spectrometry data. Particularly, 10-syringicoyl-ligustroside (18) was isolated under the guidance of mass spectrometry analysis. Its chemical structure was elucidated on the basis of extensive spectroscopic data analysis, and absolute configuration was further elucidated by comparison of its experimental and electronic circular dichroism spectra. Furthermore, the mass spectrometry data of 18 was analyzed and the corresponding results indicated that its fragment pathway was fully consistent with the applied diagnostic ion filtering and neutral loss filtering rules, and thus the precision and efficiency of the integrated strategy were validated. The result demonstrated that the proposed integrated strategy could serve as a rapid, accurate, and comprehensive targeted components discovery method to effectively screen out those ingredients of interest from the complex herbal medicines.

A database-guided integrated strategy for comprehensive chemical profiling of traditional Chinese medicine.

A comprehensive chemical profiling of traditional Chinese medicine is the basic issue for further pharmacological research and quality assessment. To facilitate chemical identification and potential components discovery, the present study proposed an integrated identification strategy guided by a self-built component database constructed from literatures to carry out the global profiling of complex matrixes. Lanqin Oral Liquid was applied as example to validate the feasibility of this strategy. Based on LQL Component Database containing 710 compounds, modified MDF windows was established to extract the interested analogues, isoquinoline alkaloids, flavonoids and iridoid glycosides, according to their regular integral masses and mass defect. For compounds with characteristic substructures, such as quinic acids, crocins and some glycoside derivatives, the associated neutral losses and diagnostic fragment ions were collected to assist in profiling. Directly matching the m/z or formulas in database was proposed to components with limited regularity of accurate masses and substructures, like indole alkaloids, sesquiterpenes and some nucleosides. Eventually, 170 ions of 1038 precursor ions were identified or temporarily deduced, including 59 alkaloids, 36 flavonoids, 48 terpenoids, 24 organic acids and their derivatives, 2 oligosaccharides, and 1 lignans. Among them, 52 putative compounds were confirmed by chemical standards. The results indicated that the database-oriented identification strategy could locate potential components quickly and eliminate interfering ions, which have the potential for in-depth analysis of compounds.

Insight into Isomeric Diversity of Glycated Amino Acids in Maillard Reaction Mixtures.

Maillard reactions generate a wide array of amino acid- and sugar-derived intermediates; the isomeric mixtures of glycated amino acids are of particular interest. Excluding stereoisomers, regioisomers, and various anomers, most amino acids can form two monoglycated and three N,N-diglycated isomers when reacted with sugars during the Maillard reaction. Using synthetic Schiff bases and Amadori compounds as standards, we have demonstrated that diagnostic ions obtained from MS/MS fragmentations in negative ionization mode can be used effectively for the discrimination between glucose-derived Schiff bases and their corresponding Amadori compounds in both mono- and diglycated forms. The utilization of these diagnostic ions and isotopic labeling in the glycine/glucose model system revealed that milling glucose/glycine mixtures for 30 min/30 Hz at ambient temperature produced monoglycated glycine in equal proportions of Amadori and Schiff base forms, whereas diglycated glycine was a mixture of the three isomers: Schiff-Schiff, Schiff-Amadori, or Amadori-Amadori in approximately equal molar proportions. The above results were further corroborated using a synthetic histidine Amadori product, N,N-difructosyl-ß-alanine, dipeptides, and ribose. Using mechanochemistry as a convenient synthetic tool in combination with MS/MS diagnostic ions, the isomeric diversity of the early stages of the Maillard reaction can be revealed.

Use of Diagnostic Ions for the Detection of Fentanyl Analogs in Human Matrices by LC-QTOF.

To combat the ongoing opioid epidemic, our laboratory has developed and evaluated an approach to detect fentanyl analogs in urine and plasma by screening LC-QTOF MS/MS spectra for ions that are diagnostic of the core fentanyl structure. MS/MS data from a training set of 142 fentanyl analogs were used to select the four product ions and six neutral losses that together provided the most complete coverage (97.2%) of the training set compounds. Furthermore, using the diagnostic ion screen against a set of 49 fentanyl analogs not in the training set resulted in 95.9% coverage of those compounds. With this approach, lower reportable limits for fentanyl and a subset of fentanyl-related compounds range from 0.25 to 2.5 ng/mL in urine and 0.5 to 5.0 ng/mL in plasma. This innovative processing method was applied to evaluate simulated exposure samples of remifentanil and carfentanil in water and their metabolites remifentanil acid and norcarfentanil in urine. This flexible approach enables a way to detect emerging fentanyl analogs in clinical samples.

Small Mass but Strong Information: Diagnostic Ions Provide Crucial Clues to Correctly Identify Histone Lysine Modifications.

(1) Background: The proteomic analysis of histones constitutes a delicate task due to the combination of two factors: slight variations in the amino acid sequences of variants and the multiplicity of post-translational modifications (PTMs), particularly those occurring on lysine residues. (2) Methods: To dissect the relationship between both aspects, we carefully evaluated PTM identification on lysine 27 from histone H3 (H3K27) and the artefactual chemical modifications that may lead to erroneous PTM determination. H3K27 is a particularly interesting example because it can bear a range of PTMs and it sits nearby residues 29 and 31 that vary between H3 sequence variants. We discuss how the retention times, neutral losses and immonium/diagnostic ions observed in the MS/MS spectra of peptides bearing modified lysines detectable in the low-mass region might help validate the identification of modified sequences. (3) Results: Diagnostic ions carry key information, thereby avoiding potential mis-identifications due to either isobaric PTM combinations or isobaric amino acid-PTM combinations. This also includes cases where chemical formylation or acetylation of peptide N-termini artefactually occurs during sample processing or simply in the timeframe of LC-MS/MS analysis. Finally, in the very subtle case of positional isomers possibly corresponding to a given mass of lysine modification, the immonium and diagnostic ions may allow the identification of the in vivo structure.

Systematically characterization of in vivo substances of Ziziphi Spinosae Semen in rats by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry analysis.

Ziziphi Spinosae Semen (ZSS), the seeds of Ziziphus jujuba var. spinosa, is widely used in China or other Asian countries for the treatment of insomnia and palpitation. In our previous work, chemical constituents in ZSS were profiled by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC/Q-TOF MS). Notably, characterization of substances in vivo was of great importance to reveal the therapy basis or mechanism in further work. Till now, there were few reports about in vivo substances' investigation of ZSS. In the present study, an integrated strategy contained represented compounds and diagnostic ions extraction was applied to characterize metabolism feature of ZSS in rats based on UHPLC/Q-TOF MS method. First, the metabolic information of four compounds (spinosin, isovitexin, jujuboside B, betulinic acid) featuring three representative chemical structures (flavonoids, saponins, terpenes) in ZSS was conducted, and their metabolism features were summarized, especially for flavonoid C-glycosides. Second, the absorbed compounds and representative compounds-related metabolites were quickly screened out; during this time, the diagnostic ions were sorted out. Last, with the help of diagnostic ions and summarized metabolic reactions, other metabolites were characterized. As a result, a total of 151 xenobiotics (58 prototypes and 93 metabolites) were identified or tentatively characterized in rats after ingestion of ZSS. Among them, 16 substances were presented in plasma, 114 in urine, 51 in bile, and 120 in feces, respectively. Hydrogenation, hydrolysis, and glucuronidation were the major metabolic reactions of ZSS in rats. The present study provided meaningful data for further pharmacological mechanism research or pharmacokinetics evaluation of ZSS.

Rapid and comprehensive profiling of α-glucosidase inhibitors in Buddleja Flos by ultrafiltration HPLC-QTOF-MS/MS with diagnostic ions filtering strategy.

Buddleja Flos is used as yellow rice colorant and a well-known traditional Chinese medicine. But its biochemical profiling is still lack due to complex matrix. Here, ultrafiltration high-performance liquid chromatograph-quadrupole time-of-flight tandem mass spectrometry (HPLC-QTOF-MS/MS) with diagnostic ions filtering strategy was proposed for rapid and comprehensive investigation of its α-glucosidase inhibitors. As a result, 33 bioactive compounds (13 phenylethanoid glycosides and 20 flavonoids) were successfully screened and identified. In addition, α-glucosidase inhibitory activities of twenty-two references were verified. Six flavonoid aglycones (4, 28, and 30-33) showed excellent α-glucosidase inhibitory activities (IC50, from 5.11 ± 0.85 to 32.49 ± 9.76 µg/mL), much higher than that of acarbose (IC50, 195.49 ± 10.05 µg/mL). Five flavonoid-monoglycosides (7, 12, 13, 20, and 22) presented moderate inhibitory activities with IC50 from 160.98 ± 23.19 to 249.37 ± 35.83 µg/mL. Results showcased the high efficiency of proposed strategy in profiling of bioactive compounds from natural products.

MS diagnostic model and rapid distinguishing of bioactive limonoids in fruits of Melia toosendan using solid-phase extraction coupled with LC-MS/MS.

INTRODUCTION: Melia toosendan Sieb. et Zucc. has been used as a Chinese folk medicine for roundworm treatment since ancient times. Many diverse limonoids have been isolated from Meliaceae plants, but it remains difficult to isolate and identify other limonoids because of their small natural concentrations. OBJECTIVE: This study was performed to overcome the difficulties associated with fast and accurate identification of limonoids and establish a reliable and sensitive method for the analysis of minor limonoids in M. toosendan fruits. METHODS: An efficient strategy for enrichment, detection, and identification of minor limonoids from M. toosendan fruits using solid-phase extraction with high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (SPE-HPLC-Q-TOF-MS/MS) was developed herein. RESULTS: Characteristic fragmentations and fragmentation ions containing trichilin-, nimbin-, and vilasinin-class limonoid skeletons were initially studied, and characteristic diagnostic ions involved retro Diels-Alder (RDA) reactions or homolytic cleavages, which were used to identify minor limonoids. In total, 13 limonoids, including four new ones, were identified. CONCLUSION: This is the first report on the analysis of M. toosendan fruits to identify limonoids. This novel analysis method may stimulate further research regarding the identification of limonoids in other plant species.

Semiochemicals containing lepidopteran sex pheromones: Wonderland for a natural product chemist.

Since the first identification of bombykol, sex pheromones of about 700 moth species have been elucidated. Additionally, field evaluations of synthetic pheromones and their related compounds have revealed the male attraction of another 1,300 species. These pheromones and attractants are listed on the web-sites, "Pheromone Database, Part I." Pheromone components are classified according to their chemical structures into two major groups (Types I and II) and miscellaneous. Based on our previous review published in 2004, studies reported during the last two decades are highlighted here to provide information on the structure characteristics of newly identified pheromones, current techniques for structure determination, new enantioselective syntheses of methyl-branched pheromones, and the progress of biosynthetic research. Besides the moth sex pheromones, various pheromones and allomones from many arthropod species have been uncovered. These semiochemicals are being collected in the "Pheromone Database, Part II." The chemical diversity provides a wonderland for natural product chemists.

Mechanochemical generation of Schiff bases and Amadori products and utilization of diagnostic MS/MS fragmentation patterns in negative ionization mode for their analysis.

The use of tandem mass spectrometry under positive ionization mode was previously developed as a tool for distinguishing isomeric Schiff bases and Amadori products. In this paper, similar diagnostic MS/MS fragmentation patterns were identified under negative ionization mode and was utilized to study the composition of mechanochemically generated Maillard reaction mixtures. The major diagnostic ion of the Schiff base was found to be a diose attached to the amino acid residue, while that of the Amadori compound was a triose. The structures of the diagnostic ions were confirmed through isotope labeling technique and elemental composition. Furthermore, application of this technique showed that ball milling of glucose with different amino acids almost exclusively results in the formation of a mixture of Schiff bases and Amadori compounds, and that amino acids with basic side chains generated more Schiff bases and those with acidic side chains generated more Amadori products.

Diagnostic MS/MS fragmentation patterns for the discrimination between Schiff bases and their Amadori or Heyns rearrangement products.

Schiff bases, the Amadori and Heyns rearrangement products are the most important isomeric intermediates involved in the early Maillard reaction; distinguishing between them by analytical mass spectroscopic techniques remains a challenge. Here we demonstrate that MS/MS fragmentation patterns can be used for the discrimination between glucose derived Schiff bases, Amadori, and Heyns compounds with glycine. An ESI-qTOF-MS system operated in the positive mode under both acidic and neutral conditions was employed to generate unique MS/MS fragmentation patterns of the molecules. Analysis of the MS data has indicated that acidic medium is suitable for generating characteristic and diagnostic ions. At high collision energy (20 eV), the spectrum of Schiff base was largely uninformative, whereas both Amadori and Heyns compounds undergo characteristic fragmentations with high diagnostic value. At low collision energy values (10eV), we observed formation of prominent diagnostic ions from the Schiff base precursor, as well as extensive dehydration reactions of all three molecules. Under acidic conditions, the diagnostic fragmentation pattern of the Amadori compound featured consecutive dehydration reactions. At higher values (20 eV) it underwent the α-fission at the carbonyl group and produced a prominent diagnostic ion [AA + H + CH2]+ at m/z 88. The Schiff base was found to preferentially undergo the retro-aldol degradation and produce diagnostic ions at m/z 118 [AA + H + diose]+ and m/z 140 [AA + Na + diose]+, together with their sugar complements at m/z 85 [tetrose + H-2H2O]+ and m/z 143 [tetrose + Na]+. In the case of Heyns compound, several diagnostic ions were also detected, including the ions at m/z 154 [M + H-2H2O-C2H4O2]+, m/z 170 [AA + Na + triose]+ and m/z 142 [AA + H + Furan]+.

Mass Spectrometric Determination of Protein Ubiquitination.

Mass spectrometric methods of determining protein ubiquitination are described. Characteristic mass shifts and fragment ions indicating ubiquitinated lysine residues in tryptic and gluC digests are discussed. When a ubiquitinated protein is enzymatically digested, a portion of the ubiquitin side chain remains attached to the modified lysine. This "tag" can be used to distinguish a ubiquitinated peptide from the unmodified version, and can be incorporated into automated database searching. Several tags are discussed, the GGK and LRGGK tags, resulting from complete and incomplete tryptic digestion of the protein, and the STLHLVLRLRGG tag from a gluC-digested protein.A ubiquitinated peptide has two N-termini-one from the original peptide and the other from the ubiquitin side chain. Thus, it is possible to have two series of b ions and y ions, the additional series is the one that includes fragments containing portions of the ubiquitin side chain, and any diagnostic ions for the modification must include portions of this side chain. Fragment ions involving any part of the "normal" peptide will vary in mass according to the peptide being modified and will therefore not be of general diagnostic use. These diagnostic ions, found through examination of the MS/MS spectra of model ubiquitinated tryptic and gluC peptides, have not previously been reported. These ions can be used to trigger precursor ion scanning in automated MS/MS data acquisition scanning modes.

Comprehensive chemical profiling of Yindan Xinnaotong soft capsule and its neuroprotective activity evaluation in vitro.

Discovering effective combinational components (ECCs) and quality control markers of TCMs is still facing challenges because the holistic healing system comprises hundreds of compounds. Here, taking Yindan Xinnaotong soft capsule (YDXNT), a TCMs preparation composed by 8 herbs, as a case, a strategy that integrated multiple chromatographic analysis and bioactivity assay was proposed for potential ECCs of neuroprotection discovery. Firstly, ultra-high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF MS) and gas chromatography-mass spectrometry (GC-MS) were applied for comprehensive profiling of the chemical constituents in YDXNT. Given the fact that the complex matrix interference makes it more difficult to identify potentially active compounds, we proposed a structure-diagnostic ions-oriented strategy to remove interference ions from the raw UHPLC-MS data. The proposed strategy consisted of different filtering methods, including diagnostic fragment ions filtering (DFIF), mass defect filtering (MDF) and neutral loss (NL). Using this strategy, a total of 124 compounds were rapidly identified. Among them, 62 non-volatile and 5 volatile constituents in 30 batches of YDXNT were quantified by UHPLC tandem triple quadrupole mass spectrometry (QQQ-MS) and GC-MS methods, respectively. In order to facilitate the quality control of YDXNT, candidate ECCs were selected based on the threshold setting of absolute -contents, and their neuroprotective effects were examined. Finally, a combination of 16 compounds, accounts for 2.80% (w/w) of original YDXNT, was identified as its potential ECCs, which could be considered for the improvement of quality standardization of YDXNT.

A Combined Chemical Derivatization/Mass Spectrometric Method for the Enhanced Detection and Relative Quantification of Protein Ubiquitination.

Mass spectrometry (MS) is a sensitive analytical technique with wide application across the sciences including for the detection of peptides and proteins in biological analysis. Ubiquitinated (Ub) proteins are typically analyzed by proteolytic digestion and subsequent chromatographic separation followed by MS detection of the resulting isopeptides. Here we describe a novel method which enables enhanced detection of this important posttranslational modification (PTM) by use of a simple chemical labeling strategy prior to Data-Independent Acquisition (DIA) using a SWATH-based acquisition approach on a suitable Quadrupole-Time-Of-Flight (Q-TOF) mass spectrometer.

Integrated strategy for identifying minor components in complex samples combining mass defect, diagnostic ions and neutral loss information based on ultra-performance liquid chromatography-high resolution mass spectrometry platform: Folium Artemisiae Argyi as a case study.

Ultra-performance liquid chromatography coupled to high-resolution mass spectrometry (UPLC-HRMS) has been used as a powerful tool to profile chemicals in traditional Chinese medicines. However, identification of potentially bioactive compounds is still a challenging work because of the large amount of information contained in the raw UPLC-HRMS data. Especially the ubiquitous matrix interference makes it more difficult to characterize the minor components. Therefore, rapid recognition and efficient extraction of the corresponding parent ions is critically important for identifying the attractive compounds in complex samples. Herein, we propose an integrated filtering strategy to remove un-related or interference MS1 ions from the raw UPLC-HRMS data, which helps to retain the MS features of the target components and expose the compounds of interest as effective as possible. The proposed strategy is based on the use of a combination of different filtering methods, including nitrogen rule, mass defect, and neutral loss/diagnostic fragment ions filtering. The strategy was validated by rapid screening and identification of 16 methoxylated flavonoids and 55 chlorogenic acids analogues from the raw UPLC-HRMS dataset of Folium Artemisiae Argyi. Particularly, successful detection of several minor components indicated that the integrated strategy has obvious advantages over individual filtering methods, and it can be used as a promising method for screening and identifying compounds from complex samples, such as herbal medicines.