Xing-Long Chen

LC-MS Guided Isolation of (+/-)-Sweriledugenin A, a Pair of Enantiomeric Lactones, from Swertia leducii

(±)-Sweriledugenin A, a pair of novel enantiomeric lactones, were isolated from Swertia leducii under the guidance of LC-MS investigation. The enantiomeric separation was achieved by HPLC on a chiral column. Their structures were determined by extensive NMR spectra, X-ray, and quantum calculations. (+)-Sweriledugenin A and (-)-sweriledugenin A showed activities inhibiting HBV DNA replication with the IC50 values of 36.86 and 26.55 μM on the HepG 2.2.15 cell line in vitro.

Bioactivity-guided isolation of anti-hepatitis B virus active sesquiterpenoids from the traditional Chinese medicine: Rhizomes of Cyperus rotundus

ETHNOPHARMACOLOGICAL RELEVANCEnThe rhizome of Cyperus rotundus (C. rotundus) is a well-known traditional Chinese medicine to cure hepatitis in many formulae, but the active components responsible for hepatitis have not been elucidated. According to our bioassay on HepG2.2.15 cell line in vitro, the ethanol extract of C. rotundus demonstrated potent anti-HBV activity. This current study was designed to isolate and identify the anti-HBV active constituents from the rhizomes of C. rotundus.nnnMATERIAL AND METHODSnBioactivity and LC-MS guided fractionation on the extract of C. rotundus using various chromatographic techniques including open-column, Sephadex LH-20 and semi-preparative high performance liquid chromatography led to the isolation and identification of thirty-seven sesquiterpenoids. Structural elucidation of the isolates was carried out by extensive spectroscopic analyses (UV, IR, HRMS, 1D- and 2D -NMR). The anti-HBV activity and cytotoxicity were evaluated on the HBV-transfected HepG2.2.15 cell line in vitro. The cytotoxicity effects of the isolates were assessed by a MTT assay. The secretions of HBsAg and HBeAg in the culture medium were detected by ELISA method, and the load of HBV DNA was quantified by real-time fluorescent PCR technique.nnnRESULTSnFive new patchoulane-type sesquiterpenoids, namely cyperene-3, 8-dione (1), 14-hydroxy cyperotundone (2), 14-acetoxy cyperotundone (3), 3β-hydroxycyperenoic acid (4) and sugetriol-3, 9-diacetate (5), along with 32 known sesquiterpenoids were isolated from the active fractions of C. rotundus. Compounds 2 and 3 were the first cyperotundone-type sesquiterpenoids with a hydroxyl group at C-14 position. Nine eudesmane-type sesquiterpenoids (15-21 and 23-24) significantly inhibited the HBV DNA replication with IC50 values of 42.7±5.9, 22.5±1.9, 13.2±1.2, 10.1±0.7, 14.1±1.1, 15.3±2.7, 13.8±0.9, 19.7±2.1 and 11.9±0.6 μM, respectively, of which, compounds 17, 21, 23 and 24 possessed high SI values of 250.4, 125.5,>259.6 and 127.5, respectively. Two patchoulane-type sesquiterpenoids (4 and 7) effectively suppressed the secretion of HBsAg in a dose-dependent manner with IC50 values of 46.6±14.3 (SI=31.0) and 77.2±13.0 (SI=1.7) μM, respectively. Compounds 2, 8, 12, 15, 17 and 25 possessed moderate activities against HBeAg secretion with IC50 values of 162.5±18.9 (SI=13.3), 399.2±90.0 (SI=10.6), 274.7±70.8 (SI=5.2), 313.9±87.5 (SI=7.2), 334.0±70.4 (SI=9.9) and 285.3±20.9 (SI=15.5) μM, respectively.nnnCONCLUSIONSnThis is the first study to reveal the anti-HBV constituents of C. rotundus, demonstrating that the eudesmane-type sesquiterpenoids might contribute to the anti-HBV activity of the rhizomes of C. rotundus.

Three new anti-HBV active constituents from the traditional Chinese herb of Yin-Chen (Artemisia scoparia).

ETHNOPHARMACOLOGICAL RELEVANCEnYin-Chen is a famous traditional Chinese medicine (TCM) in China for the treatment of acute and chronic hepatitis. Two species, namely Artemisia scoparia and Artemisia capillaris, are documented in Chinese Pharmacopoeia as the authentic resources for Yin-Chen. Previous investigation has proved that chlorogenic acid analogs and phenolic acids are two main types of the anti-HBV active constituents of A. capillaris. However, there is no investigation concerned with the anti-HBV components of A. scoparia.nnnAIM OF THE STUDYnThe aim of the present study is to recognize the new anti-HBV constituents of A. scoparia by detailed LCMS analyses.nnnMATERIALS AND METHODSnLCMS and bioassay-guided fractionation on the active part of A. scoparia led to the isolation of three new compounds. Their structures were determined by detailed spectroscopic analyses. Anti-HBV assay involving inhibition on HBsAg and HBeAg secretions and HBV DNA replication were performed in virto on HepG 2.2.15 cell line.nnnRESULTSnThe 90% ethanol extract of A. scoparia was revealed with anti-HBV activity for the first time, which was further separated into several fractions by column chromatography. Fr. D-4 was revealed with the highest anti-HBV activity, from which three new compounds including one unusual 4-pyridone glucoside (1) and two polyacetylene glucosides (2-3) were isolated under the guidance of LCMS analyses. Compounds 1-3 exhibited activity against the secretions of HBsAg and HBeAg, and HBV DNA replication. In particular, compounds 2 and 3 inhibited HBV DNA replication with IC50 values of 0.07 ± 0.04 and 0.012 ± 0.05 mM, with SI values of 23.6 and 17.1, respectively. Based on the MS/MS experiment, the fragmentation pathways of 1 in both positive and negative modes, and 2 and 3 in negative mode were proposed. The ion pairs of 388-208 (positive) and 432-206 (negative) for 1, 503-341 (negative) for 2, and 503-203 (negative) for 3, could be recognized as their respective diagnostic ions.nnnCONCLUSIONSnThe first time investigation on the anti-HBV constituents of A. scoparia yielded three new active compounds, which will provide valuable information for understanding the ethnopharmacological usage of Yin-Chen, as well as the chemical difference with A. capillaris.

Catalytic Asymmetric Total Synthesis of (+)- and (−)-Paeoveitol via a Hetero-Diels–Alder Reaction

The first catalytic asymmetric total synthesis of (+)- and (-)-paeoveitol has been accomplished in 42% overall yield via a biomimetic hetero-Diels-Alder reaction. The chiral phosphoric acid catalyzed hetero-Diels-Alder reaction showed excellent diastereo- and enantioselectivity (>99:1 dr and 90% ee); two rings and three stereocenters were constructed in a single step to produce (-)-paeoveitol on a scale of 452 mg. This strategy enabled us to selectively synthesize both paeoveitol enantiomers from the same substrates by simply changing the enantiomer of the catalyst.

A fragmentation study on four C19-diterpenoid alkaloids by electrospray ionization ion-trap time-of-flight tandem mass spectrometry

High-resolution electrospray ionization ion-trap time-of-flight tandem mass spectrometry (HR-ESI-IT-TOF-MSn) in positive-ion mode was used to determine the accurate masses and fragmentation pathways of four C19-diterpenoid alkaloids, aconitine (1), yunnaconitine (2), crassicauline A (3), and benzoylmesaconine (4). The [M+H]+ ions of compounds 1–4 were readily observed in conventional single-stage mass spectrometry. Based on the MS1–6 analyses, detailed fragmentation rules of the four compounds were proposed. The neutral losses of AcOH, MeOH, H2O, CO, C2H4, PhCOOH and p-OMePhCOOH segments were the characteristic eliminations from the precursor ions due to the presence of acetyl, methoxyl, hydroxyl, N-ethyl, benzoyl and p-methoxyl-benzoyl units in the structures. Benefited from the high resolution of the mass analyzer, the loss of 28 Da corresponding to CO or CH4 segment in product ions was unambiguously distinguished. The losing sequence of the main substituent groups was summarized as: C(8)-acetyl>C(16)-methotyl>C(15)-hydroxyl>C(6)-methoxyl>C(1)-methoxyl/C(3)-hydroxyl>C(18)-methoxyl>>C(13)-hydroxyl. The sequential loss of (16)-methoxyl moiety and CO (generating from enol–ketone tautomerism) groups could be recognized as the characteristic eliminations for the compounds with C(16)-methoxyl and C(15)-hydroxyl groups simultaneously. The application of HR-ESI-IT-TOF-MSn technique to investigate the fragmentation of C19-diterpenoid alkaloids provided useful information to understand their fragmentation behaviors.

LC–MS guided isolation of ent-kaurane diterpenoids from Nouelia insignis

The preliminary LC-MS investigation on the stems of Nouelia insignis manifested the existence of diterpenoids. As a result, 15 ent-kaurane diterpenoids, including 7 new glycosides (nouelosides A-G, 1-7), were isolated under the direction of LC-MS analysis. The new compounds were determined by extensive spectroscopic analysis including HRESIMS, 1D and 2D NMR data and chemical methods. Compounds 6 and 15 with the exo-methylene cyclopentanone functional group exhibited obvious nitric oxide production inhibitory activity with IC50 values of 3.84±0.20 and 3.19±0.25μM.

New C 16 -noriridals and formyl-monocycloiridals from the rhizomes of Iris pseudoacorus

Four new C16-noriridals (1-4) and two reported C16-noriridals (5-6), together with two new formyl-monocycloiridals (7-8) and three known monocycloiridals (9-11) were isolated from the rhizomes of Iris pseudoacorus. Irispseudoacorins A-D (1-4) and iridojaponals A-B (5-6) were C16-noriridals which shared a 6/5/7 tricyclic ring system (1-2, 5-6) or 6/5 tricyclic ring system (3-4). The formyl-monocycloiridals (7-8) were detected in the crude extracts of I. pseudoacorus by LC-MS analysis which suggested they were originated from natural sources rather than artificial products during the isolation. Their structures were determined by UV, IR, extensive NMR spectra and X-ray diffraction analyses. The known monocycloiridals 9-10 displayed pronounced cytotoxic effects against five human tumor cell lines. The IC50 values of 9 were ranging from 12.63 to 24.69μM.

Bioassay-guided isolation of saikosaponins with agonistic activity on 5-hydroxytryptamine 2C receptor from Bupleurum chinense and their potential use for the treatment of obesity

5-Hydroxytryptamine 2C (5-HT2C) receptor is one of the major targets of anti-obesity agents, due to its role in regulation of appetite. In the present study, the 70% EtOH extract of the roots of Bupleurum chinense was revealed to have agonistic activity on 5-HT2C receptor, and the subsequent bioassay-guided isolation led to identification of several saikosaponins as the active constituents with 5-HT2C receptor agonistic activity in vitro and anti-obesity activity in vivo. The new compound, 22-oxosaikosaponin d (1), was determined by extensive spectroscopic analyses (HR-ESI-MS, IR, and 1D and 2D NMR). The primary structure-activity relationship study suggested that the intramolecular ether bond between C-13 and C-28 and the number of sugars at C-3 position were closely related to the 5-HT2C receptor agonistic activity. Saikosaponin a (3), the main saponin in B. chinense, showed obviously agonistic activity on 5-HT2C receptor with an EC50 value of 21.08 ± 0.33 μmol·L-1in vitro and could reduce food intake by 39.1% and 69.2%, and weight gain by 13.6% and 16.4%, respectively, at 3.0 and 6.0 mg·kg-1in vivo. This investigation provided valuable information for the potential use of B. chinense as anti-obesity agent.

Bioactivity-guided synthesis of tropine derivatives as new agonists for melatonin receptors

Twenty-three tropine derivatives as new melatonin receptor (MT1 and MT2) agonists were synthesized and evaluated on HEK293 cells in vitro. Derivatives 1f, 1i, 1j, 1m–1s and 1t exhibited increased agonisting activities on MT1 and MT2 receptors compared to the substrate tropine. Particularly, compound 1r showed significant agonistic activities on MT1 and MT2 receptors with EC50 values of 0.20 and 0.24 mM, respectively. The preliminary structure–activity relationships (SARs) of tropine derivatives were summarized for further investigation on melatonin receptor agonists.

Productivity and K-supplying power change by an eight-season potash application in different patterns on two paddy soils

Abstract An eight-season rice–wheat rotation field experiment was conducted on two paddy soils in Siyang County and Liyang City of Jiangsu Province, respectively, to study the influence of different potash application patterns on crop yields and K-supplying power of the soils. The potash application patterns were: 216 kg K 2 O ha −1 in the rice season and no K in the wheat season; 216 kg K 2 O ha −1 in the wheat season and no K in the rice season; and 108 kg K 2 O ha −1 in each season. The results show that potash application significantly increased the crop yield, and that the benefit from potash application followed the order: potash only applied in rice>splitting application in each season>potash applied only in wheat>CK. Soil tests indicated that the K-supplying power of the soils was in the reverse order after eight cropping-season harvests, suggesting that potash application priority be given to the rice season and that the application rate should be increased to get more benefit and to maintain soil K fertility.