Ruihong Feng

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

AbstractThe 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 AbstractA four-step integrated strategy for the systematic characterization and efficient discovery of new indole alkaloids from Uncaria rhynchophylla

Neolignanamides, Lignanamides, and Other Phenolic Compounds from the Root Bark of Lycium chinense

Seven new neolignanamides (1-7), including two pairs of cis- and trans-isomers, and a new lignanamide (8) were isolated from the EtOAc-soluble fraction of an EtOH extract of the root bark of Lycium chinense, together with 22 known phenolic compounds (9-30), four of which were obtained from the genus Lycium for the first time. Compounds 5, 6, and 7 are unusual dimers having a rare connection mode between the two cinnamic acid amide units, while compounds 6, 7, and 8 are the first naturally occurring dimers derived from two dissimilar cinnamic acid amides. The cinnamic acid amides, neolignanamides, and lignanamides possess moderate radical-scavenging activity against the DPPH (2,2-diphenyl-1-picrylhydrazyl) and superoxide radicals.

Simultaneous determination of 24 constituents in Cortex Lycii using high-performance liquid chromatography-triple quadrupole mass spectrometry.

A fast high-performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) tandem mass spectrometry method was developed to determine 24 components including 11 phenolic compounds, 9 phenolic amides, and 4 cyclic peptides in Cortex Lycii. The analytes were quantified by a triple quadrupole instrument in multiple reaction monitoring (MRM) mode. The fragmentation patterns of phenolic amides and cyclic peptides using ESI and collision-induced dissociation (CID) techniques are reported. This assay method was validated with respect to linearity (r(2)>0.9920), precision, repeatability, and accuracy (recovery rate between 93.0 and 105.9% with RSD<4.4%). The analytical results of 28 batches of Cortex Lycii indicated that cyclic peptides and phenolic amides were not only the abundant constituents, but also the characteristic components for Cortex Lycii to distinguish from the adulterants. Principle component analysis (PCA) was used to discriminate samples from different geographical regions of China, and cyclic peptides were considered to be the chemical markers responsible for the classification. The systematic and integrated assessment of Cortex Lycii provides sufficient evidence for the establishment of the quality standard.

Phenanthrenes, 9,10-dihydrophenanthrenes, bibenzyls with their derivatives, and malate or tartrate benzyl ester glucosides from tubers of Cremastra appendiculata

Eleven previously unknown compounds and 23 known compounds, including 20 phenanthrene or 9,10-dihydrophenanthrene derivatives, five bibenzyls, seven malate or tartrate benzyl ester glucosides, adenosine and gastrodin were isolated from tubers of Cremastra appendiculata. Among the obtained compounds, two are the first isolated dimers with one phenanthrene or bibenzyl unit connected to C-3 of 2,3,4,5-tetrahydro-phenanthro[2,1-b]furan moiety. In addition, 33 of these compounds were evaluated in vitro for their cytotoxic activity against two cancer cell lines. Among the compounds examined, one compound showed moderate cytotoxic activity, while five showed weak cytotoxic activity against the A549 cell line.

Rapid preparative isolation of a new phenylpropanoid glycoside and four minor compounds from Sparganium stoloniferum using high-speed counter-current chromatography as a fractionation tool.

A rapid high-speed counter-current chromatography (HSCCC) method was used to isolate five minor compounds from rhizome of Sparganium stoloniferum namely San Leng in Chinese, including two phenylpropanoid glycosides, sparganiaside A (1) and 1-O-feruloyl-3-p-coumaroylglycerol (2), and three aromatic acids, vanillic acid (3), p-hydroxylcinnamic acid (4), and p-hydroxybenzoic acid (5), of which, compound 1 was a new one. Five compounds were preparatively enriched at top efficiency by one-step HSCCC operation in the isolation procedure. A suitable solvent system composed of chloroform-methanol-water (4:3.5:1.8, v/v/v) was used. And the operation time was less than 4 h. The purities of compounds (1-5) in the enriched fractions were determined to be 75.8%, 66.3%, 90.6%, 79.9%, and 98.2%, respectively. The mean recoveries of the five compounds were 84.8%, 87.3%, 81.8%, 90.3%, and 92.7%, respectively. Compounds 1-4 were further purified by semi-preparative high-performance liquid chromatography (HPLC). This is the first report on the use of HSCCC as a fractionation tool for preparative isolation of minor compounds from S. stoloniferum. The method was proved to be rapid, convenient, high yield, and low cost. HSCCC was shown to be a quick and effective tool in isolation of natural products even though the compounds were not abundant.

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.

Anti-inflammatory Diterpenoids from the Root Bark of Acanthopanax gracilistylus

Five new ent-pimarane (1-3, 7, and 8) and three new ent-kaurane diterpenoids (4-6) and a new oleanane triterpene acid (9), together with 22 known compounds, were isolated from the root bark of the medicinal herb Acanthopanax gracilistylus. The structures of 1-9 were established based on the interpretation of high-resolution MS and 1D- and 2D-NMR data. The absolute configurations of 7 and 11 were determined by single-crystal X-ray diffraction and electronic circular dichroism analysis. Compounds 7 and 8 represent rare naturally occurring structures based on the devinyl ent-pimarane skeleton. Compounds 3, 10, 14, 16, and 17 exhibited potent inhibitory effects on the release of interleukin-1β (IL-1β), interleukin-8 (IL-8), and tumor necrosis factor (TNF-α) in lipopolysaccharide-stimulated peripheral blood mononuclear cells.

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 efficient and target-oriented sample enrichment method for preparative separation of minor alkaloids by pH-zone-refining counter-current chromatography

An efficient and target-oriented sample enrichment method was established to increase the content of the minor alkaloids in crude extract by using the corresponding two-phase solvent system applied in pH-zone-refining counter-current chromatography. The enrichment and separation of seven minor indole alkaloids from Uncaria rhynchophylla (Miq.) Miq. ex Havil(UR) were selected as an example to show the advantage of this method. An optimized two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (3:7:1:9, v/v) was used in this study, where triethylamine (TEA) as the retainer and hydrochloric acid (HCl) as the eluter were added at the equimolar of 10mM. Crude alkaloids of UR dissolved in the corresponding upper phase (containing 10mM TEA) were extracted twice with lower phase (containing 10mM TEA) and lower phase (containing 10mM HCl), respectively, the second lower phase extract was subjected to pH-zone-refining CCC separation after alkalization and desalination. Finally, from 10g of crude alkaloids, 4g of refined alkaloids was obtained and the total content of seven target indole alkaloids was increased from 4.64% to 15.78%. Seven indole alkaloids, including 54mg isocorynoxeine, 21mg corynoxeine, 46mg isorhynchophylline, 35mg rhynchophylline, 65mg hirsutine, 51mg hirsuteine and 27mg geissoschizine methylether were all simultaneously separated from 2.5g of refined alkaloids, with the purity of 86.4%, 97.5%, 90.3%, 92.1%, 98.5%, 92.3%, and 92.8%, respectively. The total content and purities of the seven minor indole alkaloids were tested by HPLC and their chemical structures were elucidated by ESI-HRMS and (1)H NMR.

Venenum Bufonis induces rat neuroinflammation by activiating NF-κB pathway and attenuation of BDNF

ETHNOPHARMACOLOGICAL RELEVANCE Venenum Bufonis (VB), also called toad venom, has been widely used in clinic as a cardiotonic, anohyne and antineoplastic agents both in China and other Asian countries. However, its neurotoxicity and cardiotoxicity limit its wide clinical application. Compared with extensive attention attracted with cardiotoxicity, the toxic effect of VB on Central Nervous System (CNS) is much less studied. AIM OF THE RESEARCH This study was performed to examine the neurotoxicity caused by VB on Sprague Dawley (SD) rats, then to clarify the mechanism in vivo by investigating its action on the neuroinflammation which possibly attributed to the activation of nuclear factor κB (NF-κB) pathway and the attenuation of brain-derived neurotrophic factor (BDNF). MATERIALS AND METHODS Rats administrated with 0.5% carboxymethyl cellulose sodium salt (CMC-Na) aqueous solution and VB (100mg/kg, 200mg/kg and 400mg/kg) were sacrificed at 2h, 4h, 6h, 8h, 24h and 48h. The brain level of neurotransmitters and their corresponding receptors, pro-inflammatory cytokines, BDNF/TrkB and NF-κB pathway-related proteins were examined, respectively. RESULTS VB administration induced severe neurologic damage and neuroinflammation, as indicated by the disordered 5-hydroxytryptamine (5-HT), dopamine (DA) and their corresponding receptors, together with the over production of inflammatory cytokines including interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). VB also notably promoted the expression of p-NF-κBp65, p-IκBα, p-IKKα and p-IKKβ and down-regulated the expression of BDNF and TrkB. CONCLUSION This study demonstrates that VB triggers neurotoxicity which probably is induced by neuroinflammation via activating of NF-κB pathway and attenuating the expression of BDNF.