Collision-induced dissociation of 40 flavonoid aglycones and differentiation of the common flavonoid subtypes using electrospray ionization ion-trap tandem mass spectrometry and quadrupole time-of-flight mass spectrometry

Differentiation of isomeric chalcone and dihydroflavone using liquid chromatography coupled with hydrogen-deuterium exchange tandem mass spectrometry (HDX-MS/MS): An application for flavonoids-focused characterization of Snow chrysanthemum

Although the co-occurrences of isomeric chalcones and dihydroflavones widely appear in medicinal plants, the differentiation of such isomerism seldom succeeds using MS/MS, attributing to totally identical MS/MS spectra. Here, efforts were paid to pursue an eligible tool allowing to address the technical challenge. Being inspired by that one more proton signal is observed in 1H NMR spectrum of isoliquiritigenin than liquiritigenin when employing DMSO‑d6 as solvent, hydrogen-deuterium exchange (HDX)-MS/MS was evaluated towards differentiating isomeric chalcones and dihydroflavones through replacing H2O with D2O to prepare the mobile phase. As a result, differences were observed for either MS1 or MS2 spectrum when comparing two pairs of isomers, such as liquiritigenin vs. isoliquiritigenin and liquiritin vs. isoliquiritin, because the isomeric precursor and fragment ion species owned different amounts of hydroxyl protons and those reactive protons could be partially or completely substituted by deuterium protons at the exposure in D2O to result in n × 1.006 mass increments. Moreover, utmost four hydrogen/deuterium exchanges occurred for a single glucosyl moiety. Thereafter, HDX-MS/MS was applied to characterize the flavonoids of Snow chrysanthemum, a precious edible herbal medicine that is rich in isomeric chalcones and dihydroflavones. Through paying special attention to the deuterium labeling styles of (de)protonated molecules as well as those featured fragment ions, five pairs of isomeric chalcones and dihydroflavones were confirmatively differentiated, in addition to that 28 flavonoids were structurally annotated by applying those well-defined mass fragmentation rules. Hence, this study offered an in-depth insight towards the flavonoids-focused characterization of Snow chrysanthemum, and more importantly, HDX-MS/MS is a superior tool to differentiate, but not limited to, isomeric chalcones and dihydroflavones.

Liquid chromatography-mass spectrometry-based strategy for systematic profiling of chemical components and associated quantitative analysis of quality markers in Qi-Wei-Tong-Bi oral liquid

Qi-Wei-Tong-Bi oral liquid (QWTB), a famous Chinese medicine preparation composed of seven crude drugs has a good therapeutic effect on rheumatoid arthritis and is widely used in China. However, its chemical composition and quality control have not been comprehensively and systematically investigated. In this study, high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was employed for its chemical profiling. As a result, 100 components were chemically characterized. Additionally, high-performance liquid chromatography coupled with a quadrupole linear ion trap mass spectrometry method was developed to simultaneously quantify nine bioactive components (hyperoside, ononin, quercetin, sinomenine, magnoflorine, gallic acid, protocatechuic acid, monotropein, and cyclo-(Pro-Tyr)) in multiple-reaction monitoring mode. After successful validation in terms of linearity, precision, repeatability, and recovery, the assay method was applied for the determination of 10 batches of QWTB. The results showed that QWTB was enriched in sinomenine and magnoflorine with the highest amount up to hundreds or even thousands of µg/mL, while quercetin, ononin, cyclo-(Pro-Tyr), and hyperoside were much lower with the lowest content below 10 µg/mL. This study work would help to reveal the chemical profiling and provide a valuable and reliable approach for quality evaluation and even pharmacodynamic material basis studies of QWTB.

Assessment of the effect of drying on Brassica greens via a multiplex approach based on LC-QTOF-MS/MS, molecular networking, and chemometrics along with their antioxidant and anticancer activities

Turnip (Brassica rapa var rapa L.) leaves are a rich source of versatile bioactive phytochemicals with great potential in the food and herbal industries. However, the effect of drying on its constituents has never been studied before. Hereto, three drying techniques were compared, namely, lyophilization (LY), vacuum oven (VO), and shade drying (SD). Chemical profiling utilizing liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS) combined with chemometrics showed the different impacts of the drying methods on the phytochemical composition of the alcoholic leaf extracts. Unsupervised principal component analysis (PCA) and supervised partial least squares-discriminant analysis (PLS-DA) of the LC-QTOF-MS/MS data showed distinct distant clustering across the three drying techniques. Loading plots and VIP scores demonstrated that sinapic acid, isorhamnetin glycosides, and sinapoyl malate were key markers for LY samples. Meanwhile, oxygenated and polyunsaturated fatty acids were characteristic for SD samples and oxygenated polyunsaturated fatty acids and verbascoside were characteristic for VO samples. LY resulted in the highest total phenolics (TP) and total flavonoid (TF) contents followed by SD and VO. LY and SD samples had much higher antioxidant activity than VO measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), and iron metal chelation assays. According to the anticancer activity, the drying methods were ranked in descending order as SD > LY ≫ VO when tested against colon, breast, liver, and lung cancer cell lines. Among the identified compounds, flavonoids and omega-3 fatty acids were key metabolites responsible for the anticancer activity as revealed by partial least squares (PLS) regression and correlation analyses. In conclusion, compared to LY, SD projected out as a cost-effective drying method without compromising the phytochemical and biological activities of Brassica greens. The current findings lay the foundation for further studies concerned with the valorization of Brassica greens.

Rapid classification and identification of chemical components in three different Zanthoxylum species by ultra-high-performance-liquid chromatography quadrupole-orbitrap-mass spectrometry

Zanthoxylum, as a medicinal and edible herbal medicine, has a long history and complex chemical composition. There are many varieties of Zanthoxylum, and there are differences in composition between varieties. In this study, a rapid classification and identification method for the main components of Zanthoxylum was established using ultra-high-performance-liquid chromatography quadrupole-orbitrap-mass spectrometry. The components of Shandong Zanthoxylum bungeanum, Wudu Zanthoxylum bungeanum, and Zanthoxylum schinifolium were identified by studying the characteristic fragmentations and neutral losses of characteristic components. A total of 48 common components and 24 different components were identified and the fragmentation patterns of the main components, such as flavonoids, alkaloids, and organic acids were summarized. These findings provided a reference for the study of pharmacodynamic substance basis and quality control of different varieties of Zanthoxylum.

Two Multidimensional Chromatography/High-Resolution Mass Spectrometry Approaches Enabling the In-Depth Metabolite Characterization Simultaneously from Three Glycyrrhiza Species: Method Development, Comparison, and Integration

Two offline multidimensional chromatography/high-resolution mass spectrometry systems (method 1: fractionation and online two-dimensional liquid chromatography, 2D-LC; method 2: fractionation and offline 2D-LC) were established to characterize the metabolites simultaneously from three Glycyrrhiza species. Ion exchange chromatography in the first-dimensional (1D) separation was well fractionated between the acidic (mainly triterpenoids) and weakly acidic components (flavonoids). These obtained subsamples got sophisticated separation by the second (2D) and third dimension (3D) of chromatography either by online reversed-phase chromatography × reversed-phase chromatography (RPC × RPC) or offline hydrophilic interaction chromatography × RPC (HILIC × RPC). Orthogonality for the 2D/3D separations reached 0.73 for method 1 and 0.81 for method 2, respectively. We could characterize 1097 compounds from three Glycyrrhiza species based on an in-house library and 33 reference standards, involving 618 by method 1 and 668 by method 2, respectively. They exhibited a differentiated performance and complementarity in identifying the multiple subclasses of Glycyrrhiza components.

Systematical targeted multicomponent characterization and comparison of Arnebiae Radix and its three confusing species by offline two-dimensional liquid chromatography/LTQ-Orbitrap mass spectrometry

Arnebiae Radix, commonly known as "Zicao," can be easily confused with other compounding species, posing challenges for its clinical use. Here, we developed a comprehensive strategy to systematically characterize the diverse components across Arnebiae Radix and its three confusing species. First, an offline two-dimensional liquid chromatography (2D-LC) system integrating hydrophilic interaction chromatography (HILIC) and reverse phase (RP) separations was established, enabling effective separation and detection of more trace constituents. Second, a polygonal mass defect filtering (MDF) workflow was implemented to screen target ions and generate a precursor ion list (PIL) to guide multistage mass (MSn) data acquisition. Third, a three-step characterization strategy utilizing diagnostic ions and neutral losses was developed for rapid determination of molecular formulas, structure classes, and compound identification. This approach enabled systematic characterization of Arnebiae Radix and its three confusing species, with 437 components characterized including 112 shikonins, 22 shikonfurans, 144 phenolic acids, 131 glycosides, 18 flavonoids, and 10 other compounds. Additionally, 361, 230, 340, and 328 components were identified from RZC, YZC, DZC, and ZZC, respectively, with 142 common components and 30 characteristic components that may serve as potential markers for distinguishing the four species. In summary, this is the first comprehensive characterization and comparison of the phytochemical profiles of Arnebiae Radix and its three confusing species, advancing our understanding of this herbal medicine for quality control.

An efficient approach addressing the chemical complexity of Jiawei Fangji Huangqi decoction by integrating ultra-high-performance liquid chromatography/ion mobility-quadrupole time-of-flight mass spectrometry and intelligent data processing workflows

A challenge in the quality control of traditional Chinese medicine is the systematic multicomponent characterization of the compound formulae. Jiawei Fangji Huangqi, a modified form of Fangji Huangqi, is a prescription comprising seven herbal medicines. To address the chemical complexity of the Jiawei Fangji Huangqi decoction, we integrated ion mobility-quadrupole time-of-flight high-definition MSE coupled to ultra-high-performance liquid chromatography and intelligent data processing workflows available in the UNIFI software package. Good chromatographic separation was achieved on CORTECS UPLC T3 column within 52 min, and high-accuracy MS2 data were acquired using high-definition MSE in the negative and positive modes. A chemical library of 1250 compounds was created and incorporated into the UNIFI software to enable automatic peak annotation of the high-definition MSE data. We identified or tentatively characterize 430 compounds in the Jiawei Fangji Huangqi decoction. The potential superiority of high-definition MSE over conventional MS data acquisition approaches was revealed in its spectral quality (MS2 ), differentiation of isomers, separation of coeluting compounds, and target mass coverage. The multiple components of the Jiawei Fangji Huangqi decoction were elucidated, offering insight into its improved pharmacological action compared with that of the Fangji Huangqi formula.

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.

MS/MS fingerprint comparison between adjacent generations enables substructure identification: Flavonoid glycosides as cases

MS/MS spectrum matching currently serves as a favored means to identify the concerned metabolites attributing to the accessibility of several famous databases. However, the rule that takes the entire structure into account frequently leads to "0 hit" when inquiring MS/MS (usually MS2) spectrum in the databases. Conjugation plays an important role for the high-level structural diversity of metabolites in all organisms, and a given conjugate usually consists of two or more substructures. If MS3 spectra participate in database retrieval, the structural annotation potential of those databases should be dramatically expanded via identifying substructures. Attributing to the ubiquitous distribution pattern, flavonoid glycosides were deployed as the representative family to justify whether the primary fragment ion termed as Y0+, resulted from neutral loss of glycosyl residue(s), generated identical MS3 spectrum with MS2 spectrum of the aglycone cation namely [A+H]+. Because of owning unique ability to measure MS/MS spectrum with the exactly desired exciting energy, linear ion trap chamber of Qtrap-MS was responsible for generating the desired MS3 and MS2 spectra. When taking both m/z and ion intensity features into consideration, the findings included: 1) glycosides sharing identical aglycones produced the same MS3 spectra for Y0+; 2) different MS3 spectra for Y0+ occurred amongst glycosides bearing distinct, even isomeric, aglycones; 3) isomeric aglycones generated different MS2 spectra; and 4) MS3 spectra for Y0+ agreed with MS2 spectra of [A+H]+ when comparing paired glycoside and aglycone. Together, fingerprint comparison between MS3 and MS2 spectra could structurally annotate the substructures and further advance MS/MS spectrum matching towards the identification of, but not limited to, aglycones for flavonoid glycosides.

Rationalising the retro-Diels-Alder fragmentation pattern of viscutins using electrospray interface-tandem mass spectrometry coupled to theoretical modelling

RATIONALE

Although mass spectrometry (MS) is a powerful tool in structural elucidation of unknown flavonoids based on their unique fragmentation patterns, proposing the correct fragmentation mechanism is still a challenge from tandem mass spectrometry data only. In recent years, computational tools such as molecular networking and MS2LDA have played a major role in the identification of structurally related compounds through an in-depth survey of their fragmentation patterns.

METHODS

Therefore, in this study, three viscutin molecules in Viscum combreticola Engl. crude extracts were characterised using ultra-high-performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry and MS2LDA, a computational tool. Ion-trap mass spectrometry and density functional theoretical modelling were used as confirmatory tools to rationalise the unique fragmentation patterns observed for these molecules.

RESULTS

Here, MS2LDA revealed the presence of a unique Mass2Motif in all the three viscutin molecules at m/z 137, which was confirmed to be a ^1,3 A^- RDA (retro-Diels-Alder) fragmentation product using liquid chromatography-ion-trap mass spectrometry and density functional theoretical modelling. Moreover, MS2LDA proved to be useful in differentiating this spectral feature that was specific to viscutin molecules in the presence of other isobaric ions at m/z 137 occurring in compounds in other molecular families.

CONCLUSION

Therefore, the results of the current study showed that computational tools such as MS2LDA are essential in uncovering some gas-phase fragmentation reactions of molecules in MS and that theoretical modelling is a powerful tool in rationalising these reactions in metabolite identification.

Phytochemical analysis for ten Peruvian Mentheae (Lamiaceae) by liquid chromatography associated with high resolution mass spectrometry

The profile of secondary metabolites in ten members of tribe Mentheae (Nepetoideae, Lamiaceae) from Peru by liquid chromatography associated with high resolution mass spectrometry, is presented. Salvianolic acids and their precursors were found, particularly rosmarinic acid, caffeic acid ester derivatives, as well as a diversity of free and glycosylated flavonoids as main substances. At all, 111 structures were tentatively identified.

Comment on Villalva et al. Antioxidant, Anti-Inflammatory, and Antibacterial Properties of an Achillea millefolium L. Extract and Its Fractions Obtained by Supercritical Anti-Solvent Fractionation against Helicobacter pylori. Antioxidants 2022, 11, 1849

Villalva et al. evaluated the potential utility of an Achillea millefolium (yarrow) extract in the control of H. pylori infection. The agar-well diffusions bioassay was applied to determine the antimicrobial activity of yarrow extracts. The supercritical anti-solvent fractionation process of yarrow extract was made to give two different fractions with polar phenolic compounds and monoterpenes and sesquiterpenes, respectively. Phenolic compounds were identified by HPLC-ESIMS by using the accurate masses of [M-H]^- ions and the characteristic product ions. However, some of the reported product ions seem to be disputable, as described below.

Comprehensive profiling of chemical composition of Gleditsiae spina using ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

RATIONALE

Gleditsiae spina (GS) is an important herb used in traditional and folk medicinal systems of East Asian countries for its various medicinal properties. In China, it has been traditionally used through the centuries for its anticancer, detoxication, detumescence, apocenosis, and antiparasitic effects. Although some of its ingredients have been isolated and identified, most active constituents remain unknown. Past research mostly exploited nuclear magnetic resonance for the identification of compounds, which is suitable for monomers only. Moreover, the extraction and isolation procedures for obtaining purified molecules are time consuming. Therefore, establishing an efficient approach will assist in rapid discovery of the potential active ingredients of GS. The present study aimed to identify the chemical constituents in GS by a data analysis strategy using ultra-high-performance liquid chromatography combined with quadrupole time-of-flight tandem mass spectrometry.

METHODS

First, the theoretical formula of the candidate compound was calculated using the accurate mass of the precursor/adduct ions. Second, the compounds were classified by the diagnostic ions from the MS/MS data. Third, characteristic ion filtering was used to identify the structures. Finally, the diverse skeletons and substitutions were further identified through the neutral loss in the GS.

RESULTS

A total of 277 compounds were identified in GS, comprising 169 flavonoids, 70 lignans, and 38 other compounds. At least 43 potential new compounds were represented.

CONCLUSIONS

This experiment devised an efficient and systematic method for detecting complex compounds and provided a foundation for future research into bioactive ingredients and quality control of GS.

Protonated Forms of Naringenin and Naringenin Chalcone: Proteiform Bioactive Species Elucidated by IRMPD Spectroscopy, IMS, CID-MS, and Computational Approaches

Naringenin (Nar) and its structural isomer, naringenin chalcone (ChNar), are two natural phytophenols with beneficial health effects belonging to the flavonoids family. A direct discrimination and structural characterization of the protonated forms of Nar and ChNar, delivered into the gas phase by electrospray ionization (ESI), was performed by mass spectrometry-based methods. In this study, we exploit a combination of electrospray ionization coupled to (high-resolution) mass spectrometry (HR-MS), collision-induced dissociation (CID) measurements, IR multiple-photon dissociation (IRMPD) action spectroscopy, density functional theory (DFT) calculations, and ion mobility-mass spectrometry (IMS). While IMS and variable collision-energy CID experiments hardly differentiate the two isomers, IRMPD spectroscopy appears to be an efficient method to distinguish naringenin from its related chalcone. In particular, the spectral range between 1400 and 1700 cm^-1 is highly specific in discriminating between the two protonated isomers. Selected vibrational signatures in the IRMPD spectra have allowed us to identify the nature of the metabolite present in methanolic extracts of commercial tomatoes and grapefruits. Furthermore, comparisons between experimental IRMPD and calculated IR spectra have clarified the geometries adopted by the two protonated isomers, allowing a conformational analysis of the probed species.

Chemical profiling and identification of Radix Cudramiae and their metabolites in rats using an ultra-high-performance liquid chromatography method coupled with time-of-flight tandem mass spectrometry

Radix Cudramiae, known as "Chuan-Po-Shi" in China, is a herbal medicine widely used in the southwest of the country, especially applied by the Miao and Zhuang nationalities for the treatment of liver diseases, such as acute liver injury and liver fibrosis. As a kind of ethnomedicine, the report on its chemical analysis was still blank, which restricted its clinical application. Therefore, this paper aimed to illustrate the chemical characteristics of Radix Cudramiae. A rapid analytical strategy based on ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry was developed to profile the natural small-molecular compounds in Radix Cudramiae, as well as the related prototypes and their metabolites in rats after drug administration. As a result, a total of 74 compounds were detected in the aqueous exact of Radix Cudramiae. In vivo, 45 chemicals including 16 prototypes and 29 metabolites in rat serum, along with 35 chemicals including 17 prototypes and 18 metabolites in rat liver, were screened out and identified. For the first time, the chemical constituents of Radix Cudramiae and their metabolic characteristics were discovered. It was hoped that this work would be beneficial for the safe and effective application of Radix Cudramiae in a clinic.

Magnetic/Zeolitic Imidazolate Framework-67 Nanocomposite for Magnetic Solid-Phase Extraction of Five Flavonoid Components from Chinese Herb Dicranopteris pedata

A magnetically functionalized Fe₃O₄@ZIF-67 metal-organic framework (MOF) was prepared by electrostatic self-assembly using magnetic Fe₃O₄ nanoparticles as the core and ZIF-67 as the shell. The composite was characterized by electron microscopy, X-ray diffraction, Fourier- transform infrared spectroscopy, and Brunauer-Emmett-Teller measurements. Magnetic solid-phase extraction (MSPE) was performed on five flavonoids from Dicranopteris pedata using Fe₃O₄@ZIF-67 as an adsorbent. The developed MSPE method was combined with high-performance liquid chromatography-ultraviolet detection to preconcentrate and separate five flavonoids (rutin, quercitrin, kaempferol-3-O-α-L-rhamnoside, quercetin, and kaempferol) from Dicranopteris pedata. The factors affecting the extraction, such as the amount of Fe₃O₄@ZIF-67 adsorbent, salt ion concentration in the sample solution, vortex time, type and amount of desorbing solvent, concentration of formic acid to acidify the desorbing solvent, and acetonitrile ratio, were optimized. The developed method showed good linearity over the concentration range of 1.09-70.0 μg∙mL^-1 for the five flavonoids, with R² values between 0.9901 and 0.9945. The limits of detection and average recoveries for the five flavonoids were in the ranges of 39.5-56.2 ng∙mL^-1 and 92.2-100.7%, respectively. The method presented herein is simple, efficient, and sensitive; it can be used for enrichment analysis of the five flavonoids in Dicranopteris pedata.

Identification of Chemical Constituents in Zhizhu Pills Based on UPLC-QTOF-MSE

Background

Zhizhu pills (ZZP) are a traditional Chinese medicine (TCM) prescription, mainly used for clinically treating digestive diseases such as functional dyspepsia, constipation, and peptic ulcer. However, the chemical constituents of ZZP have rarely been reported.

Objective

To establish an ultrahigh-performance liquid chromatography-quadrupole time of flight-mass spectrometry (UPLC-QTOF-MSE) method for the identification of chemical constituents in ZZP, including individual herbs and a complicated Chinese medicinal formula.

Methods

The extracts of ZZP and its individual herb samples were analyzed by a UPLC-QTOF-MSE method on an ACQUITY UPLC HSS T3 column (100 × 2.1 mm id, 1.8 μm particle size) using a gradient elution of 0.1% formic acid in acetonitrile - 0.1% formic acid water (v/v) at a constant flow rate of 0.4 mL/min. With the MSE technique, both precursor ion and fragmentation information of compounds can be simultaneously acquired by alternating between low and high collision energy during a single chromatographic run. The data were analyzed on UNIFI.

Results

A total of 154 compounds, including 67 flavonoids, 17 coumarins, 11 terpenoids, 10 alkaloids, six limonoids, six sequiterpene lactones, and 37 other components, were ultimately identified based on accurate masses and fragmentation patterns in ZZP and its individual herbs.

Conclusions

This paper summarized fragmentation patterns of flavonoids, sequiterpene lactones, alkaloids, coumarins, and limonoids. A rapid, accurate, and comprehensive UPLC-QTOF-MSE method has been developed for the identification of chemical compounds and applied to simultaneously evaluate the quality and effectiveness of ZZP.

Highlights

A total of 154 compounds were ultimately identified in ZZP and its individual herbs by UPLC-QTOF-MSE; the fragmentation patterns of flavonoids, sequiterpene lactones, alkaloids, coumarins, and limonoids in ZZP and its individual herbs are summarized.

Structure-based identification and pathway elucidation of flavonoids in Camptotheca acuminate

Flavonoid metabolism in Camptotheca acuminate remained an untapped area for years. A tandem MS approach was used and focused on the mining and characterizing of flavonoids in mature C. acuminate. Fifteen new flavonoids and forty-three known flavonoids, including fifteen flavone analogs, sixteen flavonol analogs, seven flavanone analogs, six chalcone analogs, four xanthone analogs, ten flavane analogs were mined and identified based on their MS/MS fragments. Fifty-three of them were firstly characterized in C. acuminate. Eight biosynthetic precursors for these flavonoids were also identified. We constructed a specific metabolic map for flavonoids according to their relative contents in the flowers, fruits, stems, and leaves of C. acuminate. Furthermore, the most probable genes involved in chalcone biosynthesis, flavonoid hydroxylation, methylation, and glycosylation were further mined and fished in the gene reservoir of C. acuminate according to their conserved domains and co-expression analysis. These findings enable us to acquire a better understanding of versatile flavonoid metabolism in C. acuminate.

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 targeted prenylation analysis by a combination of IT-MS and HR-MS: Identification of prenyl number, configuration, and position in different subclasses of (iso)flavonoids

Prenylated (iso)flavonoids are potent bioactive compounds found in the Fabaceae family. Analysis and quantification of this type of phytochemicals is challenging due to their large structural diversity. In this study, the fragmentation of prenylated (iso)flavonoids was investigated using electrospray ionization ion trap mass spectrometry (ESI-IT-MSⁿ) with fragmentation by collision induced dissociation (CID) in combination and Orbitrap-MS (ESI-FT-MS²) with fragmentation by higher energy C-trap dissociation (HCD). With this combination of IT-MSⁿ and high resolution MS (FT-MSⁿ), it was possible to determine the fragmentation pathways and characteristic spectral features of different subclasses of prenylated (iso)flavonoid standards, as well as characteristic fragmentations and neutral losses of different prenyl configurations. Based on our findings, a decision guideline was developed to (i) identify (iso)flavonoid backbones, (ii) annotate prenyl number, (iii) configuration, and (iv) position of unknown prenylated (iso)flavonoids, in complex plant extracts. In this guideline, structural characteristics were identified based on: (i) UV absorbance of the compound, (ii) mass-to-charge (m/z) ratio of the parent compound; (iii) ratio of relative abundances between neutral losses 42 and 56 u in MSⁿ; (iv) retro-Diels-Alder (RDA) fragments, neutral losses 54 and 68 u, and the ratio [M+H-C₄H₈]⁺/[M+H]⁺. Using this guideline, 196 prenylated (iso)flavonoids were annotated in a Glycyrrhiza glabra root extract. In total, 75 skeletons were single prenylated, 104 were double prenylated, and for merely 17 skeletons prenyl number could not unambiguously be annotated. Our prenylation guideline allows rapid screening for identification of prenylated (iso)flavonoids, including prenyl number, configuration, and position, in complex plant extracts. This guideline supports research on these bioactive compounds in the areas of plant metabolomics and natural products.

Comprehensive multicomponent characterization and fingerprinting analysis of Lanqin Oral Liquid by ultra-high-performance liquid chromatography coupled with ion mobility-quadrupole time-of-flight mass spectrometry

Comprehensive characterization of the chemical constituents of Chinese patent medicine poses a great challenge due to the frustrating complexity resulting from superposition of multiple drugs. Lanqin Oral Liquid is a five-component Chinese patent medicine widely applied to treat pharyngeal inflammation in clinic. Here, we streamline a universal three-dimensional separation approach to efficiently identify the multicomponents from Lanqin Oral Liquid by ultra-high-performance liquid chromatography/ion mobility quadrupole time-of-flight mass spectrometry and UNIFI/in-house library-driven automatic peak annotation. Because of the systematic optimization, the use of an HSS T3 column enabled good separation of the multiple components within 42 min, while high-definition MS^E in both the negative and positive modes could characterize more classes of herbal components, thus providing the retention, collision cross-section, and MS information for each component. Benefiting from the ion mobility separation, cleaner MS¹ and MS² spectra were acquired. Aided by comparison and analysis of the fragmentation pathways of 49 reference compounds, we could characterize 175 compounds from Lanqin Oral Liquid. A validated high-performance liquid chromatography fingerprinting approach unveiled good similarity (0.985-1.000) among 22 batches of commercial samples. Conclusively, we demonstrated a practical solution to elucidating the chemical composition of Chinese patent medicines, with the potential of popularization.

De novo biosynthesis of garbanzol and fustin in Streptomyces albus based on a potential flavanone 3-hydroxylase with 2-hydroxylase side activity

Flavonoids are important plant secondary metabolites, which were shown to have antioxidant, anti-inflammatory or antiviral activities. Heterologous production of flavonoids in engineered microbial cell factories is an interesting alternative to their purification from plant material representing the natural source. The use of engineered bacteria allows to produce specific compounds, independent of soil, climatic or other plant-associated production parameters. The initial objective of this study was to achieve an engineered production of two interesting flavanonols, garbanzol and fustin, using Streptomyces albus as the production host. Unexpectedly, the engineered strain produced several flavones and flavonols in the absence of the additional expression of a flavone synthase (FNS) or flavonol synthase (FLS) gene. It turned out that the heterologous flavanone 3-hydroxylase (F3H) has a 2-hydroxylase side activity, which explains the observed production of 7,4'-dihydroxyflavone, resokaempferol, kaempferol and apigenin, as well as the biosynthesis of the extremely rare 2-hydroxylated intermediates 2-hydroxyliquiritigenin, 2-hydroxynaringenin and probably licodione. Other related metabolites, such as quercetin, dihydroquercetin and eriodictyol, have also been detected in culture extracts of this recombinant strain. Hence, the enzymatic versatility of S. albus can be conveniently exploited for the heterologous production of a large diversity of plant metabolites of the flavonoid family.

A Novel Chinese Honey from Amorpha fruticosa L.: Nutritional Composition and Antioxidant Capacity In Vitro

False indigo (Amorpha fruticosa L., A. fruticosa) is the preferred tree indigenous for windbreak and sand control in Northwest China, while information on nutritional and bioactive characteristics of its honey is rare. Herein, 12 honey of Amorpha fruticosa L. (AFH) were sampled in Northwest China and the nutritional composition was determined. Sixteen mineral element and ten dominant polyphenols content were identified and quantified by ICP-MS (Inductively coupled plasma mass spectrometry) and HPLC-QTOF-MS (High performance liquid chromatography-Quadrupole time-of-flight mass spectrometry), respectively. Moreover, AFH demonstrated high levels of DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging activity (IC50 100.41 ± 15.35 mg/mL), ferric reducing antioxidant power (2.04 ± 0.29 µmol FeSO4·7H2O/g), and ferrous ion-chelating activity (82.56 ± 16.01 mg Na2EDTA/kg), which were significantly associated with total phenolic contents (270.07 ± 27.15 mg GA/kg) and ascorbic acid contents (213.69 ± 27.87 mg/kg). The cell model verified that AFH exhibited dose-dependent preventive effects on pBR322 plasmid DNA and mouse lymphocyte DNA damage in response to oxidative stress. Taken together, our findings provide evidence for the future application of AFH as a potential antioxidant dietary in food industry.

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.

MS-based metabolite analysis of two licorice chalcones in mice plasma, bile, feces, and urine after oral administration

Isoliquiritigenin (ILG) and isoliquiritin (ILQ), two kinds of major flavonoids in licorice, are biological active substances with antioxidant, anti-inflammatory, and tumor-suppressive effects. However, their in vivo metabolites, possible material basis of this two licorice chalcones for the treatment of diseases, have not been studied completely. To determine the metabolism of ILG and ILQ, after oral administration of 100 mg/kg/day of these compounds for consecutive 8 days, the metabolites of these two licorice chalcones in mice plasma, urine, feces, and bile were determined using liquid chromatography coupled with quadrupole/time-of-flight mass spectrometry in this study. The structures of those metabolites were tentatively identified according to their fragment pathways, accurate masses, characteristic product ions, metabolism law, and reference standards-matching. As a result, a total of 25 and 29 metabolites of ILG and ILQ were identified, respectively. Seven main metabolic pathways, oxidation and reduction, deglycosylation and glycosylation, dehydroxylation and hydroxylation, demethoxylation and methoxylation, acetylation, glucuronidation, and sulfation, were summarized to tentatively explain how the metabolites were biologically transformed. These results provide the important information on the metabolism of ILG and ILQ, which may be helpful for the further research of their pharmacological mechanism.

Metabolic profiling of mice plasma, bile, urine and feces after oral administration of two licorice flavonones

ETHNOPHARMACOLOGICAL RELEVANCE

Licorice is an ancient food and medicinal plant. Liquiritigenin and liquiritin, two kinds of major flavonoes in licorice, are effective substances used as antioxidant, anti-inflammatory and tumor-suppressive food, cosmetics or medicines. However, their in vivo metabolites have not been fully explored.

AIM OF STUDY

To clarify the metabolism of liquiritigenin and liquiritin in mice.

MATERIALS AND METHODS

In this study, we developed a liquid chromatography coupled with quadrupole/time-of-flight mass spectrometry approach to determine the metabolites in mice plasma, bile, urine and feces after oral administration of liquiritigenin or liquiritin. The structures of those metabolites were tentatively identified according to their fragment pathways, accurate masses, characteristic product ions, metabolism laws or reference standard matching.

RESULTS

A total of 26 and 24 metabolites of liquiritigenin or liquiritin were respectively identified. The products related with apigenin, luteolin or quercetin were the major metabolites of liquiritigenin or liquiritin in mice. Seven main metabolic pathways including (de)hydrogenation, (de)hydroxylation, (de)glycosylation, (de)methoxylation, acetylation, glucuronidation and sulfation were summarized to tentatively explain their biotransformation.

CONCLUSION

This study not only can provide the evidence for in vivo metabolites and pharmacokinetic mechanism of liquiritigenin and liquiritin, but also may lay the foundation for further development and utilization of liquiritigenin, liquiritin and then licorice.

Application of multiple chemical and biological approaches for quality assessment of Carthamus tinctorius L. (safflower) by determining both the primary and secondary metabolites

BACKGROUND

The florets of Carthamus tinctorius L. (safflower) serve as the source of a reputable herbal medicine targeting gynecological diseases. Conventional investigations regarding the quality control of safflower, however, mainly focused on the secondary metabolites with primary metabolites ignored.

PURPOSE

To holistically evaluate the quality difference of safflower samples collected from five different producing regions by multiple chemical and biological approaches with both the primary and secondary metabolites considered.

METHODS

A precursor ions list-triggered data-dependent MS² approach was established by ultra-high performance liquid chromatography/Q-Orbitrap mass spectrometry (UHPLC/Q-Orbitrap MS) to comprehensively identify the secondary metabolites from safflower. Primary metabolites were identified by various 1D and 2D nuclear magnetic resonance (NMR) experiments. Similarity evaluation and quantitative assays of all the characterized primary metabolites and a quinochalcone C-glycoside (QCG) marker, hydroxysafflor yellow A (HSYA), were performed by quantitative ¹H NMR (qNMR) using an external standard method. Multiple in vitro models with respect to the antioxidant, anti-platelet aggregation, and antioxidant stress injury effects, were assayed to determine the efficacy differences.

RESULTS

Totally thirteen primary metabolites (including one nucleoside, two sugars, five organic alkali/acids, and five amino acids) and 135 secondary metabolites (97 QCGs and 38 flavonoids) could be identified or tentatively characterized from safflower. Good chemical consistency was observed between the commercial safflower samples and a standard safflower sample, with similarity varying in the range of 0.95‒0.99. The results from qNMR-oriented quantitative experiments (thirteen primary metabolites and HSYA) and biological assays indicated the quality of safflower samples from Xinjiang (XJ-2 and XJ-4), Hunan (HuN-1 and HuN-2), and Sichuan (SC), was comparable to the standard safflower sample.

CONCLUSION

The integration of multiple chemical (using two analytical platforms, UHPLC/Q-Orbitrap MS and NMR) and biological (four in vitro models) approaches by determining both the primary and secondary metabolites demonstrated a powerful strategy that could facilitate the holistic quality evaluation of traditional Chinese medicine.

Phytochemical analysis of Vietnamese propolis produced by the stingless bee Lisotrigona cacciae

Propolis produced by the stingless bee Lisotrigona cacciae was studied for the first time. Using different chromatographic procedures, a total of eighteen constituents (phenols and triterpenes) were isolated, among which flavane 1, homoisoflavanes 2-4, and xanthones 5 and 6 were new for propolis. Propolis extract was also characterized by gas chromatography/mass spectrometry and other fifteen constituents were identified. The xanthone α-mangostin (8) demonstrated significant activity against Staphylococcus aureus with MIC and MBC 0.31 μg/ml, followed by 7,4'-dihydroxy-5-methoxy-8-methylflavane (1) with MIC 78 μg/ml and MBC 156 μg/ml. 10,11- Dihydroxydracaenone C (4), a component bearing ortho-hydroxyl groups, was the only compound displaying radical scavenging ability. Triple botanical origin of the sample was defined, consisting of Dracaena cochinchinensis, Cratoxylum cochinchinense and Mangifera indica. D. cochinchinensis is a new resin source of propolis.

Mushroom Tyrosinase-Based Enzyme Inhibition Assays Are Not Suitable for Bioactivity-Guided Fractionation of Extracts

Tyrosinase (Tyr) catalyzes the rate-limiting step of melanogenesis in human skin and is thus the main target for treating pigmentation disorders today. This has led to an increased research interest in Tyr inhibitors during the last decades, with a frequent focus on polyphenols. In the early stages of drug discovery, it is typical to avoid the high costs of human Tyr by using the more economic mushroom tyrosinase (mh-Tyr). Since some polyphenols are accepted as substrates by mh-Tyr, the present study aimed to more generally investigate this enzyme's specificity toward polyphenols and to discuss its significance in the context of bioactivity-guided fractionation. Mh-Tyr substrates can change the sample color during an inhibition assay, leading to unreliable inhibition constants or to the discontinuation of a bioactivity-guided fractionation campaign. A data set of 56 natural products was investigated and classified into assay interferers (AIs) and noninterferers, using a spectrophotometric and an LC-ESIHRMS assay. Based on these experimental findings, structure-activity relationships defining AIs were deduced and implemented into an in silico tool that will allow for rapid prescreening in the future. We anticipate that these results will aid in the search for new Tyr inhibitors and contribute to the understanding of this enzyme, as well as its optimal use in pharmacological research.

Signals of diagnostic ions in the product ion spectra of [M - H]- ions of methoxylated flavonoids

RATIONALE

The main feature of the fragmentation of [M - H]^- ions of methoxylated flavonoids is the loss of methyl radical (formation of the [M - H - CH₃ ]^-• product ion). Subsequent decomposition of [M - H - CH₃ ]^-• product ions may be useful for identification of a given compound by HPLC/MS. This paper describes how the selected diagnostic fragment ions can be useful during HPLC/MS(-) analysis of methoxylated flavonoids.

METHODS

Product ion spectra (ESI-CID-MS/MS spectra) of [M - H]^- ions of 17 methoxylated flavonoids (flavones, isoflavones and flavonols) were obtained with a Q-TOF mass spectrometer. Full scan mass spectra (ESI-MS) were obtained with a single quadrupole type of instrument.

RESULTS

A number of product ions were recognized as useful from the point of view of structural elucidation. In most cases they were diagnostic product ions, formed as a result of C ring breaking.

CONCLUSIONS

The most important conclusions drawn from this study are: the product ion at m/z 132 indicates that the analysed compound is an isoflavone; the product ion at m/z 117 indicates the presence of one hydroxy group at ring B or at the 3-position; biochanin A and prunetin can be differentiated by their 'in-source' fragmentation, by the relative abundances of product ions at m/z 195, 183 and 167; loss of mass 102 from the [M - H - CH₃ ]^-• ion indicates that ring B is not substituted and there is no hydroxy group at the 3-position; and rhamnetin can be detected using three diagnostic product ions, namely at m/z 121, 165 and 193.

Systematic Profiling of the Multicomponents and Authentication of Erzhi Pill by UHPLC/Q-Orbitrap-MS Oriented Rapid Polarity-Switching Data-Dependent Acquisition and Selective Monitoring of the Chemical Markers Deduced from Fingerprint Analysis

The analytical platform UHPLC/Q-Orbitrap-MS offers a solution to quality investigation of TCM with high definiteness. Using Erzhi Pill (EZP) as a case, we developed UHPLC/Q-Orbitrap-MS based approaches to achieve systematic multicomponent identification and rapid authentication. Comprehensive multicomponent characterization of EZP was performed by negative/positive switching data-dependent high-energy collision-induced dissociation-MS² (HCD-MS²) after 25 min chromatographic separation. By reference compounds comparison, elemental composition analysis, fragmentation pathways interpretation, and retrieval of an in-house library, 366 compounds were separated and detected from EZP, and 96 thereof were structurally characterized. The fingerprints of two component drugs (Ligustri Lucidi Fructus, LLF; Ecliptae Herba, EH) for EZP were analyzed under the same LC-MS condition by full scan in negative mode. In combination with currently available pharmacological reports, eight compounds were deduced as the ‘identity markers’ of EZP. Selective ion monitoring (SIM) of eight marker compounds was conducted to authenticate six batches of EZP samples. Both LLF and EH could be detected from all EZP samples by analyzing the SIM spectra, which could indicate their authenticity. Conclusively, UHPLC/Q-Orbitrap-MS by rapid polarity switching could greatly expand the potency of untargeted profiling with high efficiency, and SIM of multiple chemical markers rendered a practical approach enabling the authentication of TCM formulae.

Simultaneously targeted and untargeted multicomponent characterization of Erzhi Pill by offline two-dimensional liquid chromatography/quadrupole-Orbitrap mass spectrometry

Large-scale targeted and untargeted metabolites characterization can be achieved by feat of different liquid chromatography/mass spectrometry (LC-MS) platforms by multiple MS experiments or using data-independent acquisition followed by precursor-product ions matching based on certain algorithms. The resulting insufficiency in efficiency and availability greatly restricts the applicability of these strategies in large-scale profiling and identification of various metabolites. A strategy simultaneously enabling both the targeted and untargeted metabolites characterization is established on a Q Exactive hybrid quadrupole-Orbitrap mass spectrometer, by integrating precursor ions list-triggered data-dependent MS² acquisition (PIL/dd-MS²) of the targeted components and using the "If idle-pick others" (IIPO) function to induce untargeted metabolites fragmentation. A compounds-specific mass defect filter (MDF) algorithm is proposed as a method to generate the PIL. As a proof of concept, this strategy coupled with offline two-dimensional liquid chromatography (2D-LC) was applied to identify the multicomponents of a traditional Chinese medicine formula Erzhi Pill (EZP). A rigid MDF vehicle was elaborated by orthogonal screening of the integer mass and integer mass-dependent dynamic mass defects considering a variation of 20 ppm. The Full MS/dd-MS² method enabling PIL and IIPO exhibited better performance than Full MS/dd-MS² and Targeted SIM/dd-MS² (selected ion monitoring) in respect of the sensitivity in identifying the targeted components and the ability to characterize more untargeted ones. As a consequence, 270 components were separated from EZP, and 146 thereof were selectively characterized. In conclusion, it is a practical, multifaced strategy facilitating the in-depth metabolites profiling and characterization of complex herbal and biological samples.

Towards better quality criteria of European honeydew honey: Phenolic profile and antioxidant capacity

Concerning the particular nutritive value of honeydew honey compared to blossom honey, and small number of studies defining botanical origin of honeydew honey, comprehensive analysis of phenolic profile of 64 honeydew honey samples of specific botanical origin was performed. Two advanced techniques of liquid chromatography hyphenated with mass spectrometry were used for identification of a total of 52 compounds and quantification of 25 of them. Pattern recognition analysis applied on data on phenolic compounds content confirmed that quercetin, naringenin, caffeoylquinic acid, hydroxyphenylacetic acid, apigenin and genistein, could be considered as potential markers of botanical origin of honeydew honey. Spectroscopic and electrochemical approaches were applied for the evaluation of the antioxidant capacity. Quercus sps. samples, Quercus frainetto and Quercus ilex, showed high biological activity and specific chemical composition. Additionally, cyclic voltammetry profiles were used for characterization and natural clustering of honeydew honey for the first time.

A Combined LC-MS Metabolomics- and 16S rRNA Sequencing Platform to Assess Interactions between Herbal Medicinal Products and Human Gut Bacteria in Vitro: a Pilot Study on Willow Bark Extract

Herbal preparations are complex mixtures of natural products, many of which are able to reach the distal gut due to low oral bioavailability. There, they can influence the microbial communities, and can be metabolized into potentially absorbable bioactive compounds by the intestinal bacteria. This aspect has often been disregarded when searching for the active principles of medicinal plants and herbal medicinal products. The aim of this study was to establish an interdisciplinary platform to unravel interactions of herbal medicine and intestinal microbiota, using a combined LC-MS metabolomics and 16S rRNA microbiome sequencing approach. Willow bark extract (WBE), a herbal medicinal product with a long history of traditional use and a well-established anti-inflammatory activity, was incubated with human fecal suspension under anoxic conditions. Samples were taken after 0.5, 4, and 24 h of incubation. Microbiome analyses revealed that incubation with WBE had a marked effect on microbial community composition and functions. For example, the proportion of Bacteroides sp. was clearly enhanced when the fecal sample used in this study was incubated with WBE. LC-MS analysis showed that WBE constituents were readily metabolized by fecal bacteria. Numerous microbial metabolites could be annotated, allowing the construction of putative microbial degradation pathways for the main groups of WBE constituents. We suggest that studies of this type help to increase the knowledge on bioactive principles of medicinal plants, since gut microbial metabolites might have been underestimated as a source of bioactive compounds in the past.

Cytotoxicity mechanisms in melanoma cells and UPLC-QTOF/MS2 chemical characterization of two Brazilian stingless bee propolis: Uncommon presence of piperidinic alkaloids

The present study characterized propolis extracts produced by Scaptotrigona bipunctata (Tubuna) and Melipona quadrifasciata (Mandaçaia) by LC-MS/MS; their cytotoxicity as well as the mechanism of action in a melanoma cellular model were also assessed. The chemical characterization performed by UPLC-ESI-QTOF/MS² analysis revealed uncommon presence of piperidinic alkaloids in Tubuna's propolis extract together with C-glycopyranoside flavonoids. Mandaçaia's propolis collected in the same area rather presented terpenoids and flavonoids. Regarding the mechanism of cytotoxicity, propolis extracts increased the accumulation of reactive oxygen species (ROS), reduced the potential of mitochondrial membrane, induced a decrease in the proteins Bcl-2 and AKT-3 levels, and decreased melanoma cells' migration and invasion. Both propolis extracts induced apoptosis while only Mandaçaia's propolis extract induced cell cycle arrest in G2/M.

An enhanced targeted identification strategy for the selective identification of flavonoid O-glycosides from Carthamus tinctorius by integrating offline two-dimensional liquid chromatography/linear ion-trap-Orbitrap mass spectrometry, high-resolution diagnostic product ions/neutral loss filtering and liquid chromatography-solid phase extraction-nuclear magnetic resonance

Targeted identification of potentially bioactive molecules from herbal medicines is often stymied by the insufficient chromatographic separation, ubiquitous matrix interference, and pervasive isomerism. An enhanced targeted identification strategy is presented and validated by the selective identification of flavonoid O-glycosides (FOGs) from Carthamus tinctorius. It consists of four steps: (i) enhanced separation and detection by offline two-dimensional liquid chromatography/LTQ-Orbitrap MS (offline 2D-LC/LTQ-Orbitrap MS) using collision-induced dissociation (CID) and high-energy C-trap dissociation (HCD); (ii) improved identification of the major aglycones by acid hydrolysis and LC-SPE-NMR; (iii) simplified spectral elucidation by high-resolution diagnostic product ions/neutral loss filtering; and (iv) more convincing structural identification by matching an in-house library. An offline 2D-LC system configuring an Acchrom XAmide column and a BEH Shield RP-18 UPLC^® column enabled much better separation of the easily co-eluting components. Combined use of CID and HCD could produce complementary fragmentation information. The intensity ratios of the aglycone ion species ([Y₀-H]^-/Y₀^- and [Y₀-2H]^-/Y₀^-) in the HCD-MS² spectra were found diagnostic for discriminating the aglycone subtypes and characterizing the glycosylation patterns. Five aglycone structures (kaempferol, 6-hydroxykaempferol, 6-methoxykaempferol, carthamidin, and isocarthamidin) were identified based on the ¹H-NMR data recorded by LC-SPE-NMR. Of the 107 characterized flavonoids, 80 FOGs were first reported from C. tinctorius. Unknown aglycones, pentose, and novel acyl substituents were discovered. A new compound thereof was isolated and fully identified, which could partially validate the MS-oriented identification. This integral strategy can improve the potency, efficiency, and accuracy in the detection of new compounds from medicinal herbs and other natural sources.

Characterization of 2,3-diarylxanthones by electrospray mass spectrometry: gas-phase chemistry versus known antioxidant activity properties

RATIONALE

Xanthones (XH) are a class of heterocyclic compounds widely distributed in nature that hold numerous noteworthy biological and antioxidant activities. Therefore, it is of utmost importance to achieve relevant detailed structural information to understand and assist prediction of their biological properties. The potential relationship between radical-mediated xanthone chemistry in the gas phase and their promising antioxidant activities has not been previously explored.

METHODS

Protonated xanthones XH1-9 were generated in the gas phase by electrospray ionization (ESI) and the main fragmentation pathways of the protonated XH1-9 formed due to collision-induced dissociation (CID) were investigated.

RESULTS

In the CID-MS/MS spectra of [M+H](+) ions of XH1, XH2 and XH4 the product ions formed due to H2 O elimination corresponding to the base peak of the spectra. For the remaining six xanthones (XH3, XH5-9), showing the most promising biological profile, the product ion produced with the highest relative abundance (RA) corresponded to the one formed through concomitant loss of H2 O plus CO. Indicative of an inexistent or lower biological activity is the combined loss of CO plus O unique to the CID-MS/MS spectra of XH1, XH2, XH4, and XH5. The product ion formed by loss of 64 Da (concomitant loss of two molecules of H2 O plus CO) is only observed for xanthones containing a catechol unit (XH3 and XH6-9). This product ion has the highest RA for the most potent scavenger of reactive oxygen and nitrogen species XH9 that contains two of these catechol moieties.

CONCLUSIONS

A strong relationship between some of the biological activities of the studied 2,3-diarylxanthones and their ESI-MS/MS fragmentation spectra was found. The multivariate statistical analysis results suggest that the selected MS features are related to the important biological features. Copyright © 2016 John Wiley & Sons, Ltd.

Elucidation of the fragmentation pathways of a complex 3,7-O-glycosyl flavonol by CID, HCD, and PQD on an LTQ-Orbitrap Velos Pro hybrid mass spectrometer

The present study was designed to systematically investigate the ESI-MS(n) behavior of a complex 3, 7-O-glycosyl flavonol, kaempferol 3-O-α-L-[2,3-di-O-β-D-(6-E-p-coumaroyl)glucopyranosyl]-rhamnopyranosyl-7-O-α-L-rhamnopyranoside (KO) isolated from Epimedium wushanense, and to address the elimination priority among different glycosylation sites and different sugars/substituents. The direct-infusion ESI-MS(n) experiment of KO was performed on a hybrid LTQ-Orbitrap Velos Pro mass spectrometer in both negative and positive ion modes by three different fragmentation mechanisms (CID, HCD, and PQD). The CID, HCD, and PQD analyses of KO exhibited remarkable discrimination in respect of the scan range, richness, and distribution of product ions through the entire spectra. KO experienced different fragmentation pathways between two ionization modes: the negative mode CID of KO eliminated the glycosyl portions (priority: 7-sugar > 3-substituent and terminal substituents > inner sugar) and produced aglycone product ions at m/z 284.03/285.04; however, abundant sodium-adduct B(3)2 together with subsequent (i,j)X(3)0 cleavages were found characteristic for the positive mode CID-MS(n). The fragmentation pathways by CID for KO were proposed by analyzing the high accuracy ESI-MS(n) data. Complementary structural information of KO regarding the aglycone and glycosyl portions was obtained by analyzing the ESI-MS(n) data in both ionization modes. In conclusion, the LTQ-Orbitrap method facilitates highly reliable qualitative analysis of bioactive flavonoids with three alternative fragmentation modes.

Sensitive profiling of phenols, bile acids, sterols, and eicosanoids in mammalian urine by large volume direct injection-online solid phase extraction-ultra high performance liquid chromatography-polarity switching tandem mass spectrometry

A new sensitive LVDI-online SPE-UHPLC-psMS/MS method was developed and applied for simultaneous and direct determination of 28 constituents, including 10 BAs, 5 sterols, 8 eicosanoids and 8 phenolic compounds in mammalian urinary samples.

Selective and comprehensive characterization of the quinochalcone C-glycoside homologs in Carthamus tinctorius L. by offline comprehensive two-dimensional liquid chromatography/LTQ-Orbitrap MS coupled with versatile data mining strategies

An offline 2D LC/LTQ-Orbitrap MS approach and versatile data mining techniques were developed to characterize new QCGs from C. tinctorius.

An integrated strategy for the systematic characterization and discovery of new indole alkaloids from Uncaria rhynchophylla by UHPLC/DAD/LTQ-Orbitrap-MS

The exploration of new chemical entities from herbal medicines may provide candidates for the in silico screening of drug leads. However, this significant work is hindered by the presence of multiple classes of plant metabolites and many re-discovered structures. This study presents an integrated strategy that uses ultrahigh-performance liquid chromatography/linear ion-trap quadrupole/Orbitrap mass spectrometry (UHPLC/LTQ-Orbitrap-MS) coupled with in-house library data for the systematic characterization and discovery of new potentially bioactive molecules. Exploration of the indole alkaloids from Uncaria rhynchophylla (UR) is presented as a model study. Initially, the primary characterization of alkaloids was achieved using mass defect filtering and neutral loss filtering. Subsequently, phytochemical isolation obtained 14 alkaloid compounds as reference standards, including a new one identified as 16,17-dihydro-O-demethylhirsuteine by NMR analyses. The direct-infusion fragmentation behaviors of these isolated alkaloids were studied to provide diagnostic structural information facilitating the rapid differentiation and characterization of four different alkaloid subtypes. Ultimately, after combining the experimental results with a survey of an in-house library containing 129 alkaloids isolated from the Uncaria genus, a total of 92 alkaloids (60 free alkaloids and 32 alkaloid O-glycosides) were identified or tentatively characterized, 56 of which are potential new alkaloids for the Uncaria genus. Hydroxylation on ring A, broad variations in the C-15 side chain, new N-oxides, and numerous O-glycosides, represent the novel features of the newly discovered indole alkaloid structures. These results greatly expand our knowledge of UR chemistry and are useful for the computational screening of potentially bioactive molecules from indole alkaloids. Graphical Abstract A four-step integrated strategy for the systematic characterization and efficient discovery of new indole alkaloids from Uncaria rhynchophylla.