The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Hong-xi Xu - One of the best experts on this subject based on the ideXlab platform.
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Characterization of polyprenylated Xanthones in Garcinia xipshuanbannaensis using liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry
Journal of Chromatography A, 2008Co-Authors: Yan Zhou, Quan Bin Han, Jing-zheng Song, Chun Feng Qiao, Hong-xi XuAbstract:A reliable and sensitive on-line high-performance liquid chromatography (HPLC) coupled with electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS/MS) method has been optimized and established for the analysis of polyprenylated Xanthones in the plant Garcinia xipshuanbannaensis. Collision induced MS/MS techniques were used to fragment the precursor molecular ions and MS/MS/MS techniques based on cone voltage fragmentation were used to further break down the resulting product ions sequentially. It was found that Retro-Diels-Alder rearrangement occurred from the xanthone skeleton in the MS/MS/MS process and produced characteristic fragment ions, which are useful for differentiating some positional isomers containing the prenyl unit on the A ring or B ring. Complementary fragmentation information, for instance the successive loss of prenyl residues, is also valuable for the identification of this class of Xanthones. Under optimized HPLC-MS/MS/MS method, a total of 15 prenylated Xanthones could be separated within 10 min. This method also provided information about the molecular formula of a precursor molecule and its fragments, which could be used for dereplication of known or likely new prenylated Xanthones in Garcinia plants before the purification and structural elucidation process. ?? 2008 Elsevier B.V. All rights reserved.
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Analysis of caged Xanthones from the resin of Garcinia hanburyi using ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry
Analytica Chimica Acta, 2008Co-Authors: Yan Zhou, Quan Bin Han, Song Lin Li, Jing-zheng Song, Chun Feng Qiao, Li-sheng Ding, Xin Liu, Jing Yang, Hong-xi XuAbstract:On-line ultra high-performance liquid chromatography (UHPLC) coupled with electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS/MS) has been developed for the analysis of a series of caged Xanthones in the resin of Garcinia hanburyi. The fragmentation of protonated molecular ions for 12 known cadged Xanthones was carried out using low-energy collision-induced electrospray ionization tandem mass spectrometry. It was found that Retro-Diels-Alder rearrangement occurred in the CID processes and produced the characteristic fragment ions, which are especially valuable for the identification of this class of Xanthones. The fragmentation differential between some cis-, trans-isomers was uncovered. Computation methods were utilized to rationalize the observed MS behaviors. On-line UHPLC-ESI-MS/MS/MS method has proved to be rapid and efficient in that within 6 min, 15 caged scaffold Xanthones, including three pairs of epimers and four pairs of isomers in gamboges, were effectively separated and identified. Among them, two known, namely isogambogenin (13) and isomorellinol (14) and one likely new caged Garcinia Xanthones from the Garcinia hanburyi were tentatively characterized based on the tandem mass spectra of known ones. ?? 2008 Elsevier B.V. All rights reserved.
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two new Xanthones isolated from the stem bark of garcinia lancilimba
Chemical & Pharmaceutical Bulletin, 2007Co-Authors: Nianyun Yang, Jing-zheng Song, Chun Feng Qiao, Shilin Chen, Dajian Yang, Hong-xi XuAbstract:Two new Xanthones, 1,5,6-trihydroxy-6′,6′-dimethyl-2H-pyrano(2′,3′:3,4)-2-(3-methylbut-2-enyl)xanthone (1) and 1,6,7-trihydroxy-6′,6′-dimethyl-2H-pyrano(2′,3′:3,2)-4-(3-methylbut-2-enyl)xanthone (2), have been isolated from the stem bark of Garcinia lancilimba (Guttiferae), together with six known Xanthones. Their structures were identified on the basis of extensive spectral evidence including detailed 2D NMR and HR-MS data. Two new compounds showed moderate inhibitory effect on human breast cancer MDA-MB-435S cell line.
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cytotoxic polyprenylated Xanthones from the resin of garcinia hanburyi
Chemical & Pharmaceutical Bulletin, 2006Co-Authors: Yulin Wang, Jing-zheng Song, Chun Feng Qiao, Shilin Chen, Dajian Yang, Ling Yang, Lijia Xu, Hong-xi XuAbstract:Thirteen Xanthones (1—13) were isolated from the resin of Garcinia hanburyi. Among them, two new compounds (namely gaudichaudic acid, and isogambogenic acid, 1, 2), and one new natural product (deoxygaudichaudione A, 3) were identified on the basis of extensive spectral evidence including detailed 2D NMR data. Ten of these Xanthones were tested for their cytotoxicities against human leukemia K562 (K562/S) and doxorubicin-resistant K562 (K562/R) cell lines, and showed similar inhibitory effects on both cell lines, suggesting that this group of polyprenylated Xanthones might not be multidrug resistance (MDR) substrates.
Walter C. Taylor - One of the best experts on this subject based on the ideXlab platform.
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tetraoxygenated Xanthones from the fruits of garcinia cowa
Phytochemistry, 2006Co-Authors: Kanda Panthong, Wipapan Pongcharoen, Souwalak Phongpaichit, Walter C. TaylorAbstract:Tetraoxygenated Xanthones, cowaXanthones A-E, together with 10 previously reported tetraoxygenated Xanthones, were isolated from the crude hexane extract of the fruits of Garcinia cowa. Cowaxanthone B has previously been reported as a synthetic xanthone. Their structures were elucidated by analysis of spectroscopic data, especially by 1D and 2D NMR. The antibacterial activities of the isolated compounds were also evaluated.
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prenylated Xanthones as potential antiplasmodial substances
Planta Medica, 2006Co-Authors: Wilawan Mahabusarakam, Kunnika Kuaha, Prapon Wilairat, Walter C. TaylorAbstract:Mangostin, the major xanthone of Garcinia mangostana, and a series of synthetic derivatives were investigated for their in vitro antiplasmodial activity against Plasmodium falciparum. Mangostin itself showed moderate activity, but prenylated Xanthones containing alkylamino functional groups exhibited quite potent antiplasmodial activity. Some structure-activity relationships are proposed.
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Xanthone derivatives from Cratoxylum cochinchinense roots
Phytochemistry, 2005Co-Authors: Wilawan Mahabusarakam, W. Nuangnaowarat, Walter C. TaylorAbstract:Abstract Two Xanthones and two caged-prenylated Xanthones, named cochinchinones A–D, respectively, and a synthetically known caged-prenylated xanthone, together with seven known compounds were isolated from the roots of Cratoxylum cochinchinense (Lour.) Blume. Their structures were assigned on the basis of analyses of spectroscopic data. Some of the compounds exhibited effective antioxidative properties.
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Xanthones from garcinia cowa roxb latex
Phytochemistry, 2005Co-Authors: Wilawan Mahabusarakam, P Chairerk, Walter C. TaylorAbstract:Abstract Five Xanthones named cowagarcinone A–E and six previously reported Xanthones were isolated from the latex of Garcinia cowa Roxb. Their structures were determined on the basis of spectroscopic analysis. The crude latex and the isolated compounds were investigated for their radical scavenging activities.
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Xanthones of Garcinia cowa.
Planta Medica, 1994Co-Authors: Pornpipat Na Pattalung, Weera Thongtheeraparp, Pichaet Wiriyachitra, Walter C. TaylorAbstract:Five Xanthones have been isolated from Garcinia cowa Roxb. (Guttiferae): cowanin (1), cowanol (2), cowaxanthone (3), 1,3,6-trihydroxy-7-methoxy- 2-5-bis(3-methyl-2-butenyl)xanthone (4), and norcowanin (5). The structures were assigned by spectroscopic studies. Xanthones 2 and 3 showed moderate antimicrobial activity against Staphylococcus aureus.
Ki Hun Park - One of the best experts on this subject based on the ideXlab platform.
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α glucosidase inhibition and antihyperglycemic activity of prenylated Xanthones from garcinia mangostana
Phytochemistry, 2011Co-Authors: Marcus J Curtislong, Sunin Jung, Ki Hun ParkAbstract:Abstract An ethanol extract of the fruit case of Garcinia mangostan , whose most abundant chemical species are Xanthones, showed potent α-glucosidase inhibitory activity (IC 50 = 3.2 μg/ml). A series of isolated Xanthones ( 1 – 16 ) demonstrated modest to high inhibition of α-glucosidase with IC 50 values of 1.5–63.5 μM. In particular, one hitherto unknown xanthone 16 has a very rare 2-oxoethyl group on C-8. Kinetic enzymatic assays with a p -nitrophenyl glucopyranoside indicated that one of them, compound ( 9) exhibited the highest activity ( K i = 1.4 μM) and mixed inhibition. Using, a physiologically relevant substrate, maltose, as substrate, many compounds ( 6 , 9 , 14 , and 15 ) also showed potent inhibition which ranged between 17.5 and 53.5 μM and thus compared favorably with deoxynojirimycin (IC 50 = 68.8 μM). Finally, the actual pharmacological potential of the ethanol extract was demonstrated by showing that it could elicit reduction of postprandial blood glucose levels. Furthermore, the most active α-glucosidase inhibitors ( 6 , 9 , and 14 ) were proven to be present in high quantities in the native seedcase by a HPLC chromatogram.
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Xanthones from cudrania tricuspidata displaying potent α glucosidase inhibition
Bioorganic & Medicinal Chemistry Letters, 2007Co-Authors: Marcus J Curtislong, Taesook Jeong, Ki Hun ParkAbstract:Abstract We have proven that Xanthones 1 – 8 isolated from the root of C. tricuspidata possess highly potent αα-glucosidase inhibition properties. Compound 1 was identified as a new isoprenylated tetrahydroxy xanthone, 1,3,6,7-tetrahydroxy-2-(3-methylbut-2-enyl)-8-(2-methylbut-3-en-2-yl)-9H-xanthen-9-one ( 1 ). These are the first natural Xanthones documented to exhibit such inhibition. The IC 50 values of compounds 1 – 8 inhibiting α-glucosidase activity were determined to be up to 16.2 μM. Mechanistic analysis showed the Xanthones 1 – 8 exhibited full mixed inhibition.
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antioxidant and cytotoxic activities of Xanthones from cudrania tricuspidata
Bioorganic & Medicinal Chemistry Letters, 2005Co-Authors: Taesook Jeong, Ki Hun ParkAbstract:Abstract The new catecholic xanthone, 1,3,7-trihydroxy-4-(1,1-dimethyl-2-propenyl)-5,6-(2,2-dimethylchromeno)-xanthone ( 1 ), was isolated from the root bark of Cudrania tricuspidata together with seven known Xanthones. The structures were fully characterized by analysis of physical and spectral (UV, IR, mass, and NMR) data. Relationships between the structural characteristics of Xanthones and their antioxidant activities (DPPH, superoxide, and hydroxyl radical) were studied. Among the range of catecholic Xanthones, 6,7-dihydroxyl Xanthones ( 3 – 8 ) exhibited a strong scavenging effect on the DPPH radical. When one of the catecholic hydroxyl groups was protected as in compounds 1 and 2 , DPPH radical scavenging activity was markedly decreased (IC 50 > 200 μM). DPPH activities were consistent with electrochemical response by cyclic voltammetry. Interestingly, compounds ( 1 , 2 ) which had the weak activities on DPPH, exhibited both potent superoxide and hydroxyl radical scavenging activities. The strong activity on the hydroxyl radical of compounds ( 1 , 2 ) could be rationalized by their chelating effect with iron (Fe 2+ ) due to a redshift of its complex. The catecholic Xanthones ( 3 – 8 ), being able to convert quinone methide intermediate, showed potent cytotoxicities against human cancer cell lines (HT-29, HL-60, SK-OV3, AGS, and A549). In particular, compounds 3 , 6 , and 7 had strong cytotoxic activities against AGS (LD 50
Yan Zhou - One of the best experts on this subject based on the ideXlab platform.
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Characterization of polyprenylated Xanthones in Garcinia xipshuanbannaensis using liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry
Journal of Chromatography A, 2008Co-Authors: Yan Zhou, Quan Bin Han, Jing-zheng Song, Chun Feng Qiao, Hong-xi XuAbstract:A reliable and sensitive on-line high-performance liquid chromatography (HPLC) coupled with electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS/MS) method has been optimized and established for the analysis of polyprenylated Xanthones in the plant Garcinia xipshuanbannaensis. Collision induced MS/MS techniques were used to fragment the precursor molecular ions and MS/MS/MS techniques based on cone voltage fragmentation were used to further break down the resulting product ions sequentially. It was found that Retro-Diels-Alder rearrangement occurred from the xanthone skeleton in the MS/MS/MS process and produced characteristic fragment ions, which are useful for differentiating some positional isomers containing the prenyl unit on the A ring or B ring. Complementary fragmentation information, for instance the successive loss of prenyl residues, is also valuable for the identification of this class of Xanthones. Under optimized HPLC-MS/MS/MS method, a total of 15 prenylated Xanthones could be separated within 10 min. This method also provided information about the molecular formula of a precursor molecule and its fragments, which could be used for dereplication of known or likely new prenylated Xanthones in Garcinia plants before the purification and structural elucidation process. ?? 2008 Elsevier B.V. All rights reserved.
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Analysis of caged Xanthones from the resin of Garcinia hanburyi using ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry
Analytica Chimica Acta, 2008Co-Authors: Yan Zhou, Quan Bin Han, Song Lin Li, Jing-zheng Song, Chun Feng Qiao, Li-sheng Ding, Xin Liu, Jing Yang, Hong-xi XuAbstract:On-line ultra high-performance liquid chromatography (UHPLC) coupled with electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS/MS) has been developed for the analysis of a series of caged Xanthones in the resin of Garcinia hanburyi. The fragmentation of protonated molecular ions for 12 known cadged Xanthones was carried out using low-energy collision-induced electrospray ionization tandem mass spectrometry. It was found that Retro-Diels-Alder rearrangement occurred in the CID processes and produced the characteristic fragment ions, which are especially valuable for the identification of this class of Xanthones. The fragmentation differential between some cis-, trans-isomers was uncovered. Computation methods were utilized to rationalize the observed MS behaviors. On-line UHPLC-ESI-MS/MS/MS method has proved to be rapid and efficient in that within 6 min, 15 caged scaffold Xanthones, including three pairs of epimers and four pairs of isomers in gamboges, were effectively separated and identified. Among them, two known, namely isogambogenin (13) and isomorellinol (14) and one likely new caged Garcinia Xanthones from the Garcinia hanburyi were tentatively characterized based on the tandem mass spectra of known ones. ?? 2008 Elsevier B.V. All rights reserved.
Stephen F Martin - One of the best experts on this subject based on the ideXlab platform.
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concise approach to 1 4 dioxygenated Xanthones via novel application of the moore rearrangement
Tetrahedron, 2012Co-Authors: Alexander L Nichols, Patricia Zhang, Stephen F MartinAbstract:The rapid synthesis of 1,4-dioxygenated Xanthones and related natural products employing the Moore rearrangement as a key transformation has been developed. The approach features an acetylide stitching step to unite a substituted squaric acid with a protected hydroxy benzaldehyde derivative to provide a key intermediate that undergoes facile Moore rearrangement to deliver a hydroxymethyl aryl quinone. Subsequent oxidation, hydroxy group deprotection and cyclization then affords highly functionalized Xanthones. The utility of the approach was demonstrated by its application to a concise and efficient synthesis of the naturally-occurring xanthone 1. The structure of a natural product that had been named dulcisxanthone C was also corrected to that of the xanthone 1.
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general and expedient synthesis of 1 4 dioxygenated Xanthones
Organic Letters, 2011Co-Authors: Alexander L Nichols, Patricia Zhang, Stephen F MartinAbstract:A facile entry to 1,4-dioxygenated Xanthones having a variety of substitution patterns and substituents was developed that features a novel application of the Moore cyclization using substrates that were readily assembled in a highly convergent fashion by an acetylide stitching process. The practical utility of the methodology was demonstrated by an efficient synthesis of a naturally occurring xanthone and correction of the structure of dulcisxanthone C.
