Changliang Yao

A green protocol for efficient discovery of novel natural compounds: characterization of new ginsenosides from the stems and leaves of Panax ginseng as a case study.

Exploration of new natural compounds is of vital significance for drug discovery and development. The conventional approaches by systematic phytochemical isolation are low-efficiency and consume masses of organic solvent. This study presents an integrated strategy that combines offline comprehensive two-dimensional liquid chromatography, hybrid linear ion-trap/Orbitrap mass spectrometry, and NMR analysis (2D LC/LTQ-Orbitrap-MS/NMR), aimed to establish a green protocol for the efficient discovery of new natural molecules. A comprehensive chemical analysis of the total ginsenosides of stems and leaves of Panax ginseng (SLP), a cardiovascular disease medicine, was performed following this strategy. An offline 2D LC system was constructed with an orthogonality of 0.79 and a practical peak capacity of 11,000. The much greener UHPLC separation and LTQ-Orbitrap-MS detection by data-dependent high-energy C-trap dissociation (HCD)/dynamic exclusion were employed for separation and characterization of ginsenosides from thirteen fractionated SLP samples. Consequently, a total of 646 ginsenosides were characterized, and 427 have not been isolated from the genus of Panax L. The ginsenosides identified from SLP exhibited distinct sapogenin diversity and molecular isomerism. NMR analysis was finally employed to verify and offer complementary structural information to MS-oriented characterization. The established 2D LC/LTQ-Orbitrap-MS/NMR approach outperforms the conventional approaches in respect of significantly improved efficiency, much less use of drug materials and organic solvent. The integrated strategy enables a deep investigation on the therapeutic basis of an herbal medicine, and facilitates new compounds discovery in an efficient and environmentally friendly manner as well.

Method development and application of offline two-dimensional liquid chromatography/quadrupole time-of-flight mass spectrometry-fast data directed analysis for comprehensive characterization of the saponins from Xueshuantong Injection.

Xueshuantong Injection (XSTI), derived from Notoginseng total saponins, is a popular traditional Chinese medicine injection for the treatment of thrombus-resultant diseases. Current knowledge on its therapeutic basis is limited to five major saponins, whereas those minor ones are rarely investigated. We herein develop an offline two-dimensional liquid chromatography/quadrupole time-of-flight mass spectrometry-fast data directed analysis (offline 2D LC/QTOF-Fast DDA) approach to systematically characterize the saponins contained in XSTI. Key parameters affecting chromatographic separation in 2D LC (including stationary phase, mobile phase, column temperature, and gradient elution program) and the detection by QTOF MS (involving spray voltage, cone voltage, and ramp collision energy) were optimized in sequence. The configured offline 2D LC system showed an orthogonality of 0.84 and a theoretical peak capacity of 8976. Total saponins in XSTI were fractionated into eleven samples by the first-dimensional hydrophilic interaction chromatography, which were further analyzed by reversed-phase UHPLC/QTOF-Fast DDA in negative ion mode. The fragmentation features evidenced from 36 saponin reference standards, high-accuracy MS and Fast-DDA-MS(2) data, elemental composition (C<80, H<120, O<50), double-bond equivalent (DBE 5-15), and searching an in-house library of Panax notoginseng, were simultaneously utilized for structural elucidation. Ultimately, 148 saponins were separated and characterized, and 80 have not been isolated from P. notoginseng. An in-depth depiction of the chemical composition of XSTI was achieved. The results obtained would benefit better understanding of the therapeutic basis and significant promotion on the quality standard of XSTI as well as other homologous products.

Supercritical fluid chromatography for separation and preparation of tautomeric 7-epimeric spiro oxindole alkaloids from Uncaria macrophylla.

HIGHLIGHTSSFC was used to separate and isolate two pairs of 7‐epimers of SOAs.Acetonitrile stabilized two pairs of epimers and was used as modifier in SFC.Two achiral UPC2 methods were established on the Torus 1‐AA and Diol columns.Preparative SFC enabled isolation of four SOA compounds with the purity >95%.SFC provides a solution to preparation of high‐purity reference standards. ABSTRACT Increasing challenge arising from configurational interconversion in aqueous solvent renders it rather difficult to isolate high‐purity tautomeric reference standards and thus largely hinders the holistic quality control of traditional Chinese medicine (TCM). Spiro oxindole alkaloids (SOAs), as the markers for the medicinal Uncaria herbs, can easily isomerize in polar or aqueous solvent via a retro‐Mannich reaction. In the present study, supercritical fluid chromatography (SFC) is utilized to separate and isolate two pairs of 7‐epimeric SOAs, including rhynchophylline (R) and isorhynchophylline (IR), corynoxine (C) and corynoxine B (CB), from Uncaria macrophylla. Initially, the solvent that can stabilize SOA epimers was systematically screened, and acetonitrile was used to dissolve and as the modifier in SFC. Then, key parameters of ultra‐high performance SFC (ultra‐performance convergence chromatography, UPC2), comprising stationary phase, additive in modifier, column temperature, ABPR pressure, and flow rate, were optimized in sequence. Two isocratic UPC2 methods were developed on the achiral Torus 1‐AA and Torus Diol columns, suitable for UV and MS detection, respectively. MCI gel column chromatography fractionated the U. macrophylla extract into two mixtures (R/IR and C/CB). Preparative SFC, using a Viridis Prep Silica 2‐EP OBD column and acetonitrile‐0.2% diethylamine in CO2 as the mobile phase, was finally employed for compound purification. As a result, the purity of four SOA compounds was all higher than 95%. Different from reversed‐phase HPLC, SFC, by use of water‐free mobile phase (inert CO2 and aprotic modifier), provides a solution to rapid analysis and isolation of tautomeric reference standards for quality control of TCM.

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

Quinochalcone C-glycosides (QCGs) are a series of pharmacologically bioactive components chemotaxonomic for Carthamus tinctorius L. The low abundance and ubiquitous interference from flavonoid O-glycosides (FOGs) frequently hinder the systematic exposure and characterization of these QCG homologs. We herein present an offline comprehensive two-dimensional liquid chromatography/linear ion-trap quadrupole/Orbitrap mass spectrometry (2D LC/LTQ-Orbitrap MS) approach coupled with versatile data mining strategies, to systematically characterize the QCGs from C. tinctorius. Initially, an offline 2D LC system, with an orthogonality of 71% and a theoretical peak capacity of 7654, was established by combining an Acchrom XAmide column and a BEH Shield RP-18 column. Subsequently, the water extract of C. tinctorius was separated by first dimensional hydrophilic interaction liquid chromatography (HILIC) yielding twelve fractions, which were further analyzed by reversed-phase ultra-high performance liquid chromatography/LTQ-Orbitrap MS using high energy C-trap dissociation (HCD) and collision-induced dissociation (CID) in the negative ion mode. The characteristic product ion filtering of m/z 119.05 (C8H7O−) in the HCD spectra, ring double bond equivalent (RDB 10–30), characteristic UV absorption around 405 nm, preferred 0,2X0 cleavage for C-glycosides, and diagnostic product ions analysis, were simultaneously employed for the structural elucidation of QCGs. Ultimately, 163 QCQ homologs were putatively characterized, and 149 are potential new ones. Particularly, nine dimers of QCG-FOG have not been previously reported. The obtained results have greatly expanded the knowledge on the structural diversity of QCGs, demonstrating the potency of the offline comprehensive 2D LC/LTQ-Orbitrap MS approach in separation and characterization of minor herbal components.

New triterpenic acids from Uncaria rhynchophylla: chemistry, NO-inhibitory activity, and tandem mass spectrometric analysis.

Five new oleanane and ursane type triterpenes, namely uncarinic acids F-J (1-5), together with six known triterpenic acids (6-11) were isolated from the stems and hooks of Uncaria rhynchophylla. Structure elucidation of 1-5 was based on the integrated analyses of high-resolution MS data, 1D ((1)H NMR, (13)C NMR, DEPT) and 2D (HSQC, HMBC, ROESY) NMR spectra. Compounds 4, 10, and 11 exhibited weak inhibitory effects on LPS-induced NO production in RAW264.7 cells (with IC50 1.48, 7.01, and 1.89 μM, respectively) with dexamethasone (IC50 0.04 μM) and quercetin (IC50 0.86 μM) as the positive controls. 19-OH substituted oleanane triterpenic acids (1, 2, 5, 8) were prone to eliminate CH2O3, whereas those ursane-type encompassing 19-OH (3, 6, 7, 9, 4) were featured by preferred cleavage of H2O while performing the negative collision-induced MS/MS fragmentation on an LTQ/Orbitrap mass spectrometer.

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.

UHPLC-Q-TOF-MS-based metabolomics approach to compare the saponin compositions of Xueshuantong injection and Xuesaitong injection.

Various traditional Chinese medicine preparations developed from Notoginseng total saponins, including Xueshuantong injection and Xuesaitong injection, are extensively used in China to treat cardiocerebrovascular diseases. However, the difference of their saponin compositions remains unknown. An ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry based metabolomics approach was developed to probe the saponin discrimination between Xueshuantong and Xuesaitong and the related factors by large sample analysis. A highly efficient chromatographic separation was achieved on an HSS T3 column within 20 min with the holistic metabolites information recorded in the negative MSE mode. A six-step data pretreatment procedure mainly based on Progenesis QI and mass defect filtering was established. Pattern recognition chemometrics was used to discover the potential saponin markers. The saponin composition of Wuzhou Xueshuantong showed distinct discrimination from the other products. Wuzhou Xueshuantong contains more abundant protopanaxatriol-type noto-R1 , Rg1 , Re, and protopanaxadiol-type Rb1 , but less Rd and other low-polarity protopanaxadiol-type ginsenosides. These differences could not directly correlate to the use of different parts of Panax notoginseng, but possibly to the different preparation techniques employed by different manufacturers. These results are beneficial to the establishment of pharmacopoeia standards and the assessment of the efficacy and adverse drug reactions for these homologous products.

Mass defect filtering-oriented classification and precursor ions list-triggered high-resolution mass spectrometry analysis for the discovery of indole alkaloids from Uncaria sinensis

Discovery of new natural compounds is becoming increasingly challenging because of the interference from those known and abundant components. The aim of this study is to report a dereplication strategy, by integrating mass defect filtering (MDF)-oriented novelty classification and precursor ions list (PIL)-triggered high-resolution mass spectrometry analysis, and to validate it by discovering new indole alkaloids from the medicinal herb Uncaria sinensis. Rapid chromatographic separation was achieved on a Kinetex® EVO C18 column (<16min). An in-house MDF algorithm, developed based on the informed phytochemistry information and molecular design, could more exactly screen the target alkaloids and divide them into three novelty levels: Known (KN), Unknown-but-Predicted (UP), and Unexpected (UN). A hybrid data acquisition method, namely PIL-triggered collision-induced dissociation-MS2 and high-energy C-trap dissociation-MS3 with dynamic exclusion on a linear ion trap/Orbitrap mass spectrometer, facilitated the acquisition of diverse product ions sufficient for the structural elucidation of both indole alkaloids and the N-oxides. Ultimately, 158 potentially new alkaloids, including 10 UP and 108 UN, were rapidly characterized from the stem, leaf, and flower of U. sinensis. Two new alkaloid compounds thereof were successfully isolated and identified by 1D and 2D NMR analyses. The varied ring E and novel alkaloid-acylquinic acid conjugates were first reported from the whole Uncaria genus. Conclusively, it is a practical chemical dereplication strategy that can enhance the efficiency and has the potential to be a routine approach for the discovery of new natural compounds.

New monoterpenoid oxindole alkaloid derivatives from the stems of Uncaria hirsuta Havil. and their cytotoxicity and tandem mass spectrometric fragmentation

Four new alkaloids, comprising three 3-oxo-3,7-seco-oxindole alkaloids (hirsutanine D-F, 1-3) and one oxindole alkaloid N-oxide (uncarine B N-oxide, 4), together with four known heteroyohimbine-type oxindole alkaloids, were isolated from the stems of Uncaria hirsuta Havil. Structures of 1-4 were elucidated by extensive NMR and HR-ESIMS data analyses. Compound 3 is the first 3-oxo-3,7-seco-oxindole alkaloid with ring B opened and degraded isolated from the Uncaria genus. Compounds 1-3 exhibited slight inhibition effect on the proliferation of the breast cancer cell MDA-MB-231. The positive mode collision-induced dissociation of the 3-oxo-3,7-seco-oxindole alkaloids (1-3) was featured by the β-cleavage and α-cleavage of the amido bond, while the N-oxide (4) showed characteristic neutral eliminations of ·OH and H2O.

A strategy for establishment of practical identification methods for Chinese patent medicine from systematic multi-component characterization to selective ion monitoring of chemical markers: Shuxiong tablet as a case study

Authentication of Chinese patent medicine (CPM) is more challenging than that of a single herbal medicine due to the increasing complexity in the chemical matrix. A strategy from systematic multi-component characterization to selective ion monitoring of chemical markers (SMC-SIM) is presented and applied to authenticate Shuxiong tablet (SXT) as a case study. First, an ultra-performance liquid chromatography/quadrupole time-of-flight-Fast DDA (UPLC/QTOF-Fast DDA) approach was developed to comprehensively profile and characterize multi-components in SXT. Second, chemical markers were established using a home-made SXT sample. The SIM method for detection of these markers was initially established on an advanced QTOF mass spectrometer, and then transferred onto an easily accessible single quadrupole QDa detector. Third, the UPLC/QDa-SIM method was used to authenticate commercial SXT samples. Consequently, 250 compounds were characterized, and 73 of them were identified by comparison with reference standards. Two UPLC-SIM methods enabling the monitoring of eleven chemical markers (including five saponins for Notoginseng Radix et Rhizoma, two quinochalcone C-glycosides and a flavonoid O-glycoside for Carthami Flos, one phenolic acid and two phthalides for Chuanxiong Rhizoma), were developed on QTOF and QDa, respectively. Twelve batches of commercial SXT samples were identified by the UPLC/QDa-SIM method. Despite the lower sensitivity, the QDa-SIM method by simple sample preparation achieved similar authentication results, and was more easily generalized in practice than the QTOF-SIM method. In conclusion, targeted monitoring of multiple chemical markers was proven as feasible in comprehensive identification of CPM, and the SMC-SIM strategy enabled establishment of practical quality control methods for CPM that contains a complex chemical matrix.