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Keishi Ohara - One of the best experts on this subject based on the ideXlab platform.
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correlation among singlet oxygen quenching free radical scavenging and excited state intramolecular proton transfer activities in hydroxyflavones anthocyanidins and 1 Hydroxyanthraquinones
Journal of Physical Chemistry A, 2017Co-Authors: Shin-ichi Nagaoka, Yuki Bandoh, Umpei Nagashima, Keishi OharaAbstract:Singlet-oxygen (1O2) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-Hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1O2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1O2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1O2 quenching and free-radical scaven...
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Correlation among Singlet-Oxygen Quenching, Free-Radical Scavenging, and Excited-State Intramolecular-Proton-Transfer Activities in Hydroxyflavones, Anthocyanidins, and 1‑Hydroxyanthraquinones
2017Co-Authors: Shin-ichi Nagaoka, Yuki Bandoh, Umpei Nagashima, Keishi OharaAbstract:Singlet-oxygen (1O2) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-Hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1O2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1O2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1O2 quenching and free-radical scavenging activities negatively correlate to the ESIPT activity. A catechol structure at B-ring is another factor that enhances the free-radical scavenging in hydroxyflavones. In contrast to these hydroxyflavones, 1-Hydroxyanthraquinones having an electron-donating OH substituent adjacent to the O–H---OC moiety susceptible to ESIPT do not show a simple correlation between their 1O2 quenching and ESIPT activities, because the OH substitution modulates these reactions
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correlation between excited state intramolecular proton transfer and singlet oxygen quenching activities in 1 acylamino anthraquinones
Journal of Physical Chemistry B, 2015Co-Authors: Shin-ichi Nagaoka, Keishi Ohara, Hikaru Endo, Umpei NagashimaAbstract:Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen (1O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their 1O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with 1O2. Intramolecularly hydrogen-bonded Hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way.
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Correlation between Excited-State Intramolecular Proton-Transfer and Singlet-Oxygen Quenching Activities in 1‑(Acylamino)anthraquinones
2015Co-Authors: Shin-ichi Nagaoka, Keishi Ohara, Hikaru Endo, Umpei NagashimaAbstract:Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen (1O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their 1O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with 1O2. Intramolecularly hydrogen-bonded Hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way
Shin-ichi Nagaoka - One of the best experts on this subject based on the ideXlab platform.
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correlation among singlet oxygen quenching free radical scavenging and excited state intramolecular proton transfer activities in hydroxyflavones anthocyanidins and 1 Hydroxyanthraquinones
Journal of Physical Chemistry A, 2017Co-Authors: Shin-ichi Nagaoka, Yuki Bandoh, Umpei Nagashima, Keishi OharaAbstract:Singlet-oxygen (1O2) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-Hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1O2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1O2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1O2 quenching and free-radical scaven...
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Correlation among Singlet-Oxygen Quenching, Free-Radical Scavenging, and Excited-State Intramolecular-Proton-Transfer Activities in Hydroxyflavones, Anthocyanidins, and 1‑Hydroxyanthraquinones
2017Co-Authors: Shin-ichi Nagaoka, Yuki Bandoh, Umpei Nagashima, Keishi OharaAbstract:Singlet-oxygen (1O2) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-Hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1O2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1O2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1O2 quenching and free-radical scavenging activities negatively correlate to the ESIPT activity. A catechol structure at B-ring is another factor that enhances the free-radical scavenging in hydroxyflavones. In contrast to these hydroxyflavones, 1-Hydroxyanthraquinones having an electron-donating OH substituent adjacent to the O–H---OC moiety susceptible to ESIPT do not show a simple correlation between their 1O2 quenching and ESIPT activities, because the OH substitution modulates these reactions
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correlation between excited state intramolecular proton transfer and singlet oxygen quenching activities in 1 acylamino anthraquinones
Journal of Physical Chemistry B, 2015Co-Authors: Shin-ichi Nagaoka, Keishi Ohara, Hikaru Endo, Umpei NagashimaAbstract:Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen (1O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their 1O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with 1O2. Intramolecularly hydrogen-bonded Hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way.
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Correlation between Excited-State Intramolecular Proton-Transfer and Singlet-Oxygen Quenching Activities in 1‑(Acylamino)anthraquinones
2015Co-Authors: Shin-ichi Nagaoka, Keishi Ohara, Hikaru Endo, Umpei NagashimaAbstract:Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen (1O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their 1O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with 1O2. Intramolecularly hydrogen-bonded Hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way
Umpei Nagashima - One of the best experts on this subject based on the ideXlab platform.
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correlation among singlet oxygen quenching free radical scavenging and excited state intramolecular proton transfer activities in hydroxyflavones anthocyanidins and 1 Hydroxyanthraquinones
Journal of Physical Chemistry A, 2017Co-Authors: Shin-ichi Nagaoka, Yuki Bandoh, Umpei Nagashima, Keishi OharaAbstract:Singlet-oxygen (1O2) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-Hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1O2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1O2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1O2 quenching and free-radical scaven...
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Correlation among Singlet-Oxygen Quenching, Free-Radical Scavenging, and Excited-State Intramolecular-Proton-Transfer Activities in Hydroxyflavones, Anthocyanidins, and 1‑Hydroxyanthraquinones
2017Co-Authors: Shin-ichi Nagaoka, Yuki Bandoh, Umpei Nagashima, Keishi OharaAbstract:Singlet-oxygen (1O2) quenching, free-radical scavenging, and excited-state intramolecular proton-transfer (ESIPT) activities of hydroxyflavones, anthocyanidins, and 1-Hydroxyanthraquinones were studied by means of laser, stopped-flow, and steady-state spectroscopies. In hydroxyflavones and anthocyanidins, the 1O2 quenching activity positively correlates to the free-radical scavenging activity. The reason for this correlation can be understood by considering that an early step of each reaction involves electron transfer from the unfused phenyl ring (B-ring), which is singly bonded to the bicyclic chromen or chromenylium moiety (A- and C-rings). Substitution of an electron-donating OH group at B-ring enhances the electron transfer leading to activation of the 1O2 quenching and free-radical scavenging. In 3-hydroxyflavones, the OH substitution at B-ring reduces the activity of ESIPT within C-ring, which can be explained in terms of the nodal-plane model. As a result, the 1O2 quenching and free-radical scavenging activities negatively correlate to the ESIPT activity. A catechol structure at B-ring is another factor that enhances the free-radical scavenging in hydroxyflavones. In contrast to these hydroxyflavones, 1-Hydroxyanthraquinones having an electron-donating OH substituent adjacent to the O–H---OC moiety susceptible to ESIPT do not show a simple correlation between their 1O2 quenching and ESIPT activities, because the OH substitution modulates these reactions
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correlation between excited state intramolecular proton transfer and singlet oxygen quenching activities in 1 acylamino anthraquinones
Journal of Physical Chemistry B, 2015Co-Authors: Shin-ichi Nagaoka, Keishi Ohara, Hikaru Endo, Umpei NagashimaAbstract:Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen (1O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their 1O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with 1O2. Intramolecularly hydrogen-bonded Hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way.
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Correlation between Excited-State Intramolecular Proton-Transfer and Singlet-Oxygen Quenching Activities in 1‑(Acylamino)anthraquinones
2015Co-Authors: Shin-ichi Nagaoka, Keishi Ohara, Hikaru Endo, Umpei NagashimaAbstract:Excited-state intramolecular proton-transfer (ESIPT) and singlet-oxygen (1O2) quenching activities of intramolecularly hydrogen-bonded 1-(acylamino)anthraquinones have been studied by means of static and laser spectroscopies. The ESIPT shows a substituent effect, which can be explained in terms of the nodal-plane model. The ESIPT activity positively and linearly correlates with their 1O2 quenching activity. The reason for this correlation can be understood by considering ESIPT-induced distortion of their ground-state potential surface and their encounter complex formation with 1O2. Intramolecularly hydrogen-bonded Hydroxyanthraquinones found in aloe also show a similar positive and linear correlation, which can be understood in the same way
Harold Corke - One of the best experts on this subject based on the ideXlab platform.
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antibacterial properties of polygonum cuspidatum roots and their major bioactive constituents
Food Chemistry, 2008Co-Authors: Bin Shan, J. D. Brooks, Harold CorkeAbstract:Abstract Antibacterial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of crude extract from Polygonum cuspidatum roots were assayed against five common foodborne bacteria ( Bacillus cereus , Listeria monocytogenes , Staphylococcus aureus , Escherichia coli , and Salmonella anatum ). The crude extract exhibited potent antibacterial properties. Major bioactive compounds in P. cuspidatum roots were identified as stilbenes (e.g., piceid, resveratroloside, and resveratrol) and Hydroxyanthraquinones (e.g., emodin, emodin-1- O -glucoside, and physcion) by LC–ESI-MS. Both stilbenes and hydroxyanthraquinoines greatly contributed to the antibacterial properties. Additionally, scanning electron microscopy was used to observe morphological changes of the bacteria treated with the crude extract and its major antibacterial components. Possible mechanisms of the antibacterial action were also discussed. This study suggests that the roots of P. cuspidatum and its antibacterial components may have potential for use as natural preservatives.
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antibacterial properties of polygonum cuspidatum roots and their major bioactive constituents
Food Chemistry, 2008Co-Authors: Bin Shan, J. D. Brooks, Harold CorkeAbstract:Abstract Antibacterial activity, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) of crude extract from Polygonum cuspidatum roots were assayed against five common foodborne bacteria ( Bacillus cereus , Listeria monocytogenes , Staphylococcus aureus , Escherichia coli , and Salmonella anatum ). The crude extract exhibited potent antibacterial properties. Major bioactive compounds in P. cuspidatum roots were identified as stilbenes (e.g., piceid, resveratroloside, and resveratrol) and Hydroxyanthraquinones (e.g., emodin, emodin-1- O -glucoside, and physcion) by LC–ESI-MS. Both stilbenes and hydroxyanthraquinoines greatly contributed to the antibacterial properties. Additionally, scanning electron microscopy was used to observe morphological changes of the bacteria treated with the crude extract and its major antibacterial components. Possible mechanisms of the antibacterial action were also discussed. This study suggests that the roots of P. cuspidatum and its antibacterial components may have potential for use as natural preservatives.
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antioxidant phenolic constituents in roots of rheum officinale and rubia cordifolia structure radical scavenging activity relationships
Journal of Agricultural and Food Chemistry, 2004Co-Authors: Yizhong Cai, Mei Sun, Jie Xing, Harold CorkeAbstract:The phenolic constituents in the roots of Rheum officinale and Rubia cordifolia were identified with the aid of high-performance liquid chromatography and liquid chromatography-mass spectrometry and by comparison with authentic standards. A total of 17 Hydroxyanthraquinones, gallic acid, and tannins were separated, and 14 of them were identified, being the main phenolic constituents present. Their antioxidant activity (Trolox equivalent antioxidant capacity) was evaluated using the improved 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt method. Hydroxyanthraquinones were the predominant antioxidant phenolic constituents in the roots of R. cordifolia, and tannins and gallic acid were the predominant antioxidant phenolic constituents in the roots of R. officinale. The structure-radical scavenging activity relationships of the tested Hydroxyanthraquinones were systematically demonstrated as follows: Hydroxy groups on one benzene ring of the anthraquinone structure were essential for Hydroxyanthraquinones to show activity, the ortho-dihydroxy structure in the hydroxyanthraquinone molecules could greatly enhance their radical scavenging effect, and glycosylation of the Hydroxyanthraquinones reduced activity.
Yoichiro Ito - One of the best experts on this subject based on the ideXlab platform.
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application of high speed counter current chromatography and preparative high performance liquid chromatography mode for rapid isolation of anthraquinones from morinda officinalis how
Separation and Purification Technology, 2009Co-Authors: Licai Zhu, Yong Liang, Xiaohong Wang, Huichun Xie, Tianyou Zhang, Yoichiro ItoAbstract:Abstract Five anthraquinones including alizarin-1-methylether, 1,2-dimethoxy-3-hydroxyanthraquinone, 1-hydroxy-3-hydroxymethylanthraquinone, rubiadin-1-methylether and anthragallol-2-methylether were isolated and purified by high-speed counter-current chromatography (HSCCC) and followed by preparative high-performance liquid chromatography (prep-HPLC) mode from Morinda officinalis How. n-Hexane–ethyl acetate–methanol–water (6:4:5:5, v/v/v/v) was employed as the two-phase solvent system in HSCCC. Consequently, partially purified fraction “1” (90.6 mg, containing alizarin-1-methylether and 1,2-dimethoxy-3-hydroxyanthraquinone), partially purified fraction “2” (52.5 mg, containing 1-hydroxy-3-hydroxymethylanthraquinone and rubiadin-1-methylether) and 19.8 mg anthragallol-2-methylether were obtained from 300 mg of the crude extract. Then the partially purified fractions were further separated by prep-HPLC, which recovered 54.9 mg alizarin-1-methylether, 10.2 mg 1,2-dimethoxy-3-hydroxyanthraquinone, 16.4 mg 1-hydroxy-3-hydroxymethylanthraquinone and 18.2 mg rubiadin-1-methylether. The purity of each compound was over 96%, as determined by HPLC. The structures of five anthraquinones were identified by MS and 1H NMR. It is the first report of discovering 1,2-dimethoxy-3-hydroxyanthraquinone from the plant of M. officinalis How. The results demonstrated that this separation mode can integrate the advantages of HSCCC and prep-HPLC to improve separation efficiency, and adopted method was a feasible, economical and efficient technique for rapid preparative isolation of complicated natural products.
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preparative isolation and purification of Hydroxyanthraquinones from rheum officinale baill by high speed counter current chromatography using ph modulated stepwise elution
Journal of Chromatography A, 1999Co-Authors: Fuquan Yang, Guilian Tian, Haifeng Cao, Qinhui Liu, Yoichiro ItoAbstract:Analytical and preparative high-speed counter-current chromatography was successfully used for the isolation and purification of Hydroxyanthraquinones from Rheum officinale Baill (Dahuang) using pH-modulated stepwise elution. Four major components including chrysophanol, emodin, physcion and aloe-emodin were isolated each at over 98% purity.
