Publications by authors named "Yun-bao Liu"

The metabolites from the endophytic fungus Talaromyces malicola hosted in the gastrointestinal tract of the arthropods Armadillidium vulgare were investigated, and six undescribed fusicoccane diterpenoids, talarmalnoids A-F (1-6), along with three known analogs were isolated. Talarmalnoid C (3) was an unprecedented fusicoccane diterpenoid with two sugar units, i.e.

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The secondary metabolites of the endophytic fungus Talaromyces malicola hosted in the arthropod Armadillidium vulgare were separated by silica gel column chromatography, gel column chromatography, and semi-preparative high-performance liquid chromatography. Eleven compounds(1-11) were obtained from the ethyl acetate fraction of the fermentation broth of T. malicola, and their structures were identified by NMR, HR-ESI-MS, UV, IR, and ECD.

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One previously undescribed xanthanolide sesquiterpene dimer pungiolide P (1), possessing an unprecedented scaffold with a 5/7/5/7/5 ring system skeleton and its intermediate pungiolide Q (2), ten xanthanolide sesquiterpenes (3-12), two eudesmene sesquiterpene derivatives (13-14), one phenylpropionic acid derivative (15), together with eleven known compounds (16-26) were obtained from the fruits of Xanthium italicum Moretti. A possible biosynthetic pathway for pungiolide P (1) was also proposed, which was supported by its bio-synthetic intermediate (2). Compounds 1, 4-5, 18-21, and 25 exhibited cytotoxic activity against a variety of human cancer cell lines.

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A newly discovered trihydroxynaphthalenone derivative, epoxynaphthalenone () involving the condensation of ortho-hydroxyl groups into an epoxy structure, and a novel pyrone metabolite characterized as pyroneaceacid (), were extracted from , an endophytic fungus residing in . The structures of these compounds were elucidated through a comprehensive analysis of their NMR and HRESIMS data. The determination of absolute configurations was accomplished using electronic circular dichroism (ECD) calculations and CD spectra.

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Article Synopsis
  • Sesquiterpene synthases (STPSs) are enzymes that create diverse hydrocarbons through carbocation-driven reactions, with deprotonation-reprotonation processes contributing significantly to this diversity.
  • Research focused on two STPSs, AhCS and AhIS, showing they produce different compounds by selectively protonating at different positions of germacrene A (GA).
  • Structural analyses and site-directed mutagenesis identified specific active site residues that control regioselectivity, allowing researchers to successfully interchange the functions of AhCS and AhIS, paving the way for designing STPSs with varied structural outputs.
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The present study investigated the chemical constituents from the leaves of Craibiodendron yunnanense. The compounds were isolated and purified from the leaves of C. yunnanense by a combination of various chromatographic techniques including column chromatography over polyamide, silica gel, Sephadex LH-20, and reversed-phase HPLC.

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The metabolites from the endophytic fungus Muyocopron laterale hosted in the medicinal plant Tylophora ovata were investigated, and five undescribed xanthones, muyocoxanthones O-S, along with seven known compounds were isolated. Their structures were elucidated by HR-ESI-MS, NMR, and ECD calculations. Compounds were evaluated for their anti-cardiomyocyte oxidative damage activity using a model of oxidative damage induced by cell hypoxia incubation.

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One new taraxastane-type triterpenoid, three new grayanane-type diterpenoids (, and 12 known compounds () were isolated from the leaves of W. W. Smith.

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Six undescribed meleagrin analogues, isomeleagrin, meleagrin F, meleagrin G, methylmeleagrin G, isomethylmeleagrin G and meleagrin H, were isolated from the endophytic fungus Penicillium commune, which was obtained from the fresh leaves of a toxic medicinal plant, Tylophora ovata. The structures of these analogues were elucidated through extensive spectroscopic data analysis, and their absolute configurations were characterized by calculated electronic circular dichroism (ECD). Structurally, meleagrin F features an undescribed skeleton with an aniline moiety, which is linked to meleagrin through a C-C bond at C8-C26.

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Two new sydowic acid derivatives, a pair of enantiomers, involving (+)-sydowiccal () and (-)-sydowiccal (), a new sulfonyl metabolite of 2-methoxy-5-methyl-3-(methylsulfonyl)phenol (), as well as three known sydowic acid derivatives, were isolated from , an endophytic fungus of . The structures of these new compounds were elucidated by analyzing their NMR and HRESIMS data, and the absolute configurations of enantiomers were determined on the basis of the CD spectrum. Three new metabolites showed weak anti-inflammation on nitric oxide (NO) production in LPS-induced RAW 264.

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One undescribed diterpenoid illisimonone A, four undescribed sesquiterpenes named (±)-simonones A, simonterpenoids A and B, and two undescribed lignans, illisimonins A and B, along with five known compounds were isolated from the fruits of Illicium simonsii. Their structures were elucidated by extensive spectroscopic data. The absolute configuration of illisimonone A was determined by single-crystal X-ray diffraction analysis.

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Six new secondary metabolites, including two new nor-triterpenes ( and ), one new sesquiterpene (), two new -pyrone derivatives ( and ), and one new natural product () along with two known compounds ( and ) were isolated from an endophytic fungus obtained from a toxic medicinal plant . Their structures were elucidated by spectroscopic data analyses, while their absolute configurations were determined by CD and X-ray diffraction analyses. The anti-inflammatory activities of these compounds were evaluated.

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Twelve new dimeric tetrahydroxanthones, muyocoxanthones A-L (-), were isolated from the endophytic fungus, . Their structures were characterized on the basis of the interpretation of NMR and HRESIMS data. The absolute configurations of - and were unambiguously determined by ECD spectrum data and single-crystal X-ray diffraction analysis.

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A pair of new lignans [(+)- and (-)- ] and three new compounds (), together with a known compound , were isolated from the fruits of Moretti. The structures of these compounds were determined on the basis of spectroscopic analysis, particularly HR-ESI-MS and 1 D and 2 D NMR. Compounds and showed antinociceptive effects in an acetic acid-induced writhing test in mice with the writhe inhibition rates of 80.

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The construction of libraries of stereoisomers of natural products serves as an important approach to investigating the correlation between the stereostructure and biological activity. However, the total synthesis and isomerzation of polycyclic scaffolds with multiple chrial centers are rare. Spirooliganin (), a new skeleton natural product isolated from the plant , was structurally characterized by comprehensive analysis of NMR spectroscopic data and ECD which revealed an unprecedented 5-6-6-6-7 polycyclic framework with six chiral centers.

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Thirty new pentacyclic triterpenoids, including five oleanane-type (1-5), twenty-three ursane-type (9-23, 26-33) and two taraxerane-type (24 and 25), along with fourteen known triterpenoids, were isolated from the stems and branches of Enkianthus chinensis. Their structures were elucidated by extensive spectroscopic analyses, X-ray crystallographic data and electronic circular dichroism (ECD) techniques. Sixteen compounds (1-5, 9-13, 20, 22, 32, 34-36) bearing a gem-hydroxymethyl group at C-4 represent rare examples of pentacyclic triterpenoids.

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Seventeen new prenylated C-C derivatives, namely, illifargeins A-M (1-13), including three pairs of enantiomers (1, 5, and 12) and one norillifargeal A (14), together with eight known analogues (15-22), were isolated from the stems and leaves of Illicium fargesii. The structures of the new compounds were elucidated using spectroscopic data (UV, IR, 1D and 2D NMR, and HRESIMS). Their absolute configurations were determined by using experimental and calculated ECD data analysis, as well as a modified Mosher's method.

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Three new alkaloids (-) were isolated from the rhizomes of . The structures and configurations were established by extensive spectroscopic analyses, including 1D, 2D NMR, and ECD. [Formula: see text].

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Article Synopsis
  • - Eight compounds were isolated from the endophytic fungus Talaromyces purpurogenus using various column chromatographic techniques, including two new compounds (1 and 2).
  • - The structures of the isolated compounds were determined through techniques like NMR, MS, CD, and optical rotation.
  • - The anti-diabetic activities of these compounds were assessed, revealing that compound 1 displayed moderate inhibitory activity against XOD with a 69.9% inhibition rate at a concentration of 10 μmol·L~(-1).
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Six new nonadride derivatives (-) and three new spirocyclic anhydride derivatives (-) were isolated from the endophytic fungus obtained from fresh leaves of the toxic medicinal plant The structures of these compounds were determined by spectroscopic analyses including 1D and 2D NMR, HRESIMS, and ECD techniques. Maleic anhydride derivatives - were evaluated for their anti-inflammatory activities. Compound showed significant inhibitory activity against NO production in LPS-induced RAW264.

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Eight new cadinene-sesquiterpenes (1-8), one eudesmane-sesquiterpene (9), and three known compounds (10-13) were isolated from an endophytic fungus, Aspergillus flavus, which was isolated from a toxic medicinal plant, Tylophora ovata. Their structures were elucidated by interpretation of spectroscopic data, and absolute configurations determined according to the specific rotation and electron circular dichroism methods. Compounds 4-8, 11, and 12 exhibited latent hepatic protection effects at 10 μM, and compound 12 selectively inhibited the proliferation of MCF-7 breast cancer cells with an IC values of 2.

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Six new glycosides (1-6), together with three known ones, were isolated from the twigs and leaves of Rhododendron latoucheae. Their structures were elucidated based on the spectroscopic data, including infrared spectrometry, mass spectrometry, and nuclear magnetic resonance experiments, along with Mosher's method. In addition, all compounds were tested their antiviral (herpes simplex virus-1 and influenza A/95-359) activities.

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Two new azafluoranthene alkaloids (1 and 2), and a new phytoecdysone (3), were isolated from the stems of Cyclea barbata Miers, together with six known compounds (4-9). Their structures were elucidated by spectroscopic data analysis and comparison with published data. This is the first report of azafluoranthene alkaloids (1 and 2) and phytoecdysones (3, 8, and 9) from Cyclea genus.

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Three new megastigmane glucosides (1-3) and two new monoterpenes (4-5), together with 14 related known compounds (6-19) were isolated from the twigs and leaves of Lyonia ovalifolia. The structures of the new compounds were determined by extensive MS, NMR, CD experiments and chemical methods. Compounds 2, 6, and 18 displayed potent antiviral activity against Coxsackie B3, with IC values between 6.

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In our on-going study to investigate components with analgesic activity, eight new grayanane diterpenoids, epoxypieristoxins A-H (1-8), along with one known compound (9) were isolated from the roots of Pieris formosa. Their structures with absolute configurations were characterized by a series of spectroscopic methods and X-ray diffraction. Notably, compounds 1-5 represented the first example of natural grayanane diterpenoids possessed a 10,14-epoxy group.

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